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How much does a bat survey cost?

Fri, 05 Jun 2026 00:37:31 GMT

If your project may require a bat survey, one of the first questions you're asking is also one of the hardest to find a straight answer to: what is this going to cost?

The honest answer is that there's no single price — and any firm that quotes you a flat rate before understanding your project is guessing. A bat survey isn't a fixed product; it's a scope of fieldwork whose size is largely dictated by federal and state regulations, the characteristics of your site, and the timing of your project. Two projects on neighboring parcels can carry very different survey costs.

That doesn't mean you're left in the dark. The factors that drive bat survey cost are well-defined, and once you understand them, you can budget realistically and avoid the two most expensive surprises in this process: an under-scoped survey that fails agency review, and a missed survey window that delays your project by a full year.

Here's what actually determines the cost of a bat survey.

Cost Driver #1: The Acreage of Suitable Habitat

The single biggest factor is how much suitable bat habitat your project may affect. Under the USFWS Range-wide survey guidelines, the required level of effort — the number of survey sites, net nights, or detector deployments — scales with the acreage of suitable habitat within your project area.

A small site with limited wooded habitat requires far less survey effort than a large, heavily forested project corridor. Linear projects like pipelines, transmission lines, and roadways are scoped differently again, because the survey has to cover suitable habitat along the entire length of the disturbance, not just a single site.

This is why the first question any qualified biologist asks isn't "what's your budget" — it's "how much suitable habitat are we dealing with." Reducing the acreage of impact, where your project design allows, is often the most direct way to reduce survey cost.

Cost Driver #2: Which Survey Methods Are Required

"Bat survey" is an umbrella term for several different methods, each with its own cost structure:

Habitat assessment is the lowest-cost first step — a biologist evaluates whether suitable habitat is even present. In some cases, documenting the absence of suitable habitat can eliminate the need for any further survey, which is the cheapest outcome available to you.
Acoustic surveys deploy ultrasonic detectors to record bat calls. Equipment-based and relatively efficient to deploy, but the cost includes the critical, labor-intensive step of manual data vetting (more on that below).
Mist-net surveys require trained, federally permitted biologists in the field at night over multiple net nights, making them more labor-intensive than acoustics.
Radio telemetry, emergence surveys, and hibernaculum assessments add cost when a project requires tracking captured bats to roosts or evaluating winter habitat.

Most projects use a combination, and the required mix is usually set by your USFWS Field Office — not chosen freely. A project that can be cleared with a habitat assessment costs a fraction of one that requires a full season of mist-netting plus telemetry.

Cost Driver #3: Manual Acoustic Data Vetting

If your survey involves acoustics, be aware that the recording is only half the job. Automated classification software produces a first-pass species identification, but for federally listed species, that output isn't sufficient on its own — the call data must be manually vetted by qualified biologists to produce defensible results.

This matters for cost in two directions. Skimping on vetting is a false economy: a false-positive misidentification can trigger unnecessary and expensive conservation measures, while a missed detection can expose you to liability. Proper manual vetting is a real line item, but it's the step that makes your data hold up under agency review — which is the entire point of doing the survey.

Cost Driver #4: Timing and Survey Windows

This is the factor that most often turns a manageable cost into an expensive one — not because the survey itself costs more, but because of when you engage.

Active-season bat surveys can only be conducted during a narrow summer window, which varies by state and USFWS Field Office. If a survey requirement is identified after that window has closed, your project waits until the next season — often a full year. That delay carries its own costs in financing, scheduling, and contractual penalties that can dwarf the price of the survey.

Engaging a biologist early — during due diligence or preliminary design — is the most reliable way to control both your survey cost and your overall project timeline. Early engagement also preserves options, like adjusting project design to reduce survey scope, that disappear once the schedule is locked.

Cost Driver #5: Location, Access, and Coordination

Finally, practical and regulatory geography affects cost:

Travel and access to remote or difficult sites adds field time and expense.
The specific USFWS Field Office and state agency involved set their own requirements, which can change the level of effort.
The complexity of consultation — whether your project clears informally or requires formal Section 7 review and documentation — affects the reporting and coordination effort.

How to Budget for a Bat Survey

Putting it together, the most useful way to think about cost is as a range that depends on where your project lands across these drivers:

Lowest cost: a habitat assessment that documents no suitable habitat, clearing your project without further survey.
Moderate cost: an acoustic survey with manual vetting vs. a mist-net survey on a modestly sized site are often similar in cost.
Higher cost: multi-method surveys — mist-netting, acoustics, and telemetry — across large or forested project areas, with formal consultation support.

The best way to get a meaningful estimate is a short conversation about your project's location, size, and timeline. At Volant EcoServices, we scope every project to the minimum defensible level of effort — enough to satisfy USFWS and state agencies, without paying for survey nights your project doesn't need.

This article is general information, not regulatory or legal advice. Survey requirements and costs vary by project and jurisdiction; confirm requirements with your USFWS Field Office or a qualified biologist.

Why Potential Bat Hibernacula Surveys Matter — and When Your Project Needs One

Wed, 27 May 2026 19:07:43 GMT

Most land development and infrastructure projects are designed with summer in mind — trees cleared, ground broken, construction underway between spring and fall. For ESA compliance, that means bat surveys focused on summer roosting habitat are usually the first thing on the checklist. But a second category of bat survey obligation exists that is entirely separate from summer P/A surveys, operates on a different seasonal calendar, and can catch projects off guard when it appears: the potential bat hibernaculum survey.

If your project is anywhere near a cave, abandoned mine, tunnel, rock outcropping, sinkhole, or similar subsurface feature, this article explains what the 2026 USFWS Range-wide Indiana Bat and Northern Long-Eared Bat Survey Guidelines require, when a hibernaculum survey is triggered, what the survey process involves, and what happens if a target species is confirmed at the site.

What is a bat hibernaculum?

A hibernaculum — plural hibernacula — is a thermally stable underground or enclosed feature that bats use for extended periods of torpor during winter. For the three target species under the 2026 guidelines , hibernacula are not an incidental habitat type. They are essential survival infrastructure, and the loss or disturbance of a hibernaculum can affect entire colonies.

Indiana bat, northern long-eared bat, and tricolored bat have been documented using caves, sinkholes, rock fissures, and other karst features, as well as anthropogenic features such as mines and tunnels as winter hibernation habitat.

The target species do not all use the same types of hibernacula, and this distinction matters for assessment purposes. Tricolored bats often use a much wider variety of hibernacula and warmer microclimates than would traditionally be considered suitable for Indiana bats and northern long-eared bats. Additionally, northern long-eared bats and tricolored bats have the potential to use smaller cave-like features such as rock shelters, outcrops, and talus formations. Coordination with the local USFWS Field Office is specifically recommended in the guidelines to ensure that TCB habitat assessments appropriately account for this broader range of suitable features.

Bridges and culverts represent a separate but related category — they can function as bat roost sites and are addressed under their own assessment and survey protocols in the 2026 Guidelines. This post focuses on underground and cave-like features.

When does a project trigger a hibernaculum assessment?

Project proponents are responsible for evaluating whether any potentially suitable hibernacula exist within a proposed project area. This obligation is built into the initial project screening process and applies regardless of whether summer bat surveys have already been completed. A negative summer P/A survey does not substitute for a hibernaculum assessment, and the two are treated as independent requirements under the guidelines.

Potential hibernacula surveys are in addition to any summer or year-round active season surveys that may be required for a proposed project.

The types of projects most likely to trigger a potential hibernacula assessment include anything involving ground disturbance, blasting, demolition, water table changes, or obstruction of access near subsurface features — including mining operations, quarrying, tunneling, road construction through karst terrain, utility installation in areas with known cave systems, and demolition or rehabilitation of structures built over or adjacent to underground features.

Step one: desktop analysis and initial field reconnaissance

Before any field work is conducted at a potential hibernaculum, the 2026 guidelines require a two-stage initial assessment process.

After coordinating with the local USFWS Field Office and appropriate state natural resource agency, a desktop analysis and initial field reconnaissance should be completed by individuals with a natural resource degree or equivalent work experience and an in-depth understanding of cave and karst topography and/or surface features associated with underground mines.

For all projects, a USFWS-approved field survey of all land within 0.5 miles of the edge of the project footprint — where access can be obtained — and documentation of all known caves and abandoned mines within 3 miles of the outside edge of the project footprint should be conducted. If caves or abandoned mines are found, further detail about the known or estimated underground extent should be provided to the USFWS Field Office, including minimum and maximum depth of features and where those features are located on a map.

Documentation for this stage draws from a range of sources: literature searches, maps from local cave survey groups or grottos, review of aerial photography and topographic maps, previous mining records, forest inventories, and previous species survey reports.

What makes a feature unsuitable — and what doesn't

Not every underground opening requires a full hibernaculum assessment and survey. The 2026 guidelines identify specific physical conditions under which an opening can be deemed unsuitable and dismissed from further consideration. However, these thresholds are specific and should not be applied loosely.

In general, underground openings can be deemed unsuitable as a potential hibernaculum and dismissed from further assessment and surveys if:

there is only one horizontal opening and it is less than 6 inches (15.2 cm) in diameter;
vertical shafts are less than 1 foot (0.3 m) in diameter;
the passage or opening extends a short distance — less than 50 feet (15.2 m) — with no visible evidence of bats or associated physical features such as visible fissures or crevices that bats can access;
openings are prone to flooding, collapsed shut and completely sealed, or otherwise inaccessible to bats; or openings have occurred recently — within the past 12 months — due to human activity or subsidence, with written documentation verifying this determination.

Any feature that does not clearly meet one of these exclusion criteria should be treated as potentially suitable and carried forward for a full habitat assessment.

The results of initial field assessments should be submitted to the USFWS Field Office and state regulatory partners for review and approval prior to proceeding. Field Office-approved results will remain valid for a minimum of five years.

Step two: habitat assessment of potentially suitable hibernacula

If the initial reconnaissance identifies one or more potentially suitable features, a formal habitat assessment is required before any surveys can be conducted or before any project work affecting the feature can proceed.

Habitat assessments should include all subterranean entrances or openings that will be directly or indirectly impacted by the proposed project. This would include caves, sinkholes, fissures, other karst features, and cave-like features such as rock shelters, outcrops, and talus slopes, as well as anthropogenic features such as mines and tunnels that are within the project site or that are otherwise connected — by physical passageway, airflow, or hydrologically — to any underground feature that will be directly or indirectly impacted by the proposed project.

The connectivity element is critical and often overlooked. A feature that appears to be outside the project footprint on a map may still require assessment if it is hydrologically or physically connected to a feature being disturbed. Physical descriptors required for each opening assessed, including dimensions, airflow, slope, internal conditions, and evidence of past flooding.

The results of a habitat assessment should be submitted to the USFWS Field Office and state regulatory partners for review and approval prior to proceeding, and FO-approved results will remain valid for a minimum of five years.

One important note: if suitable winter habitat is discovered as a result of a habitat assessment, do not alter, modify, or otherwise disturb entrances or internal passages of caves, mines, or other entrances to underground voids within the action area before completing a presence/probable absence survey.

Step three: the potential hibernaculum P/A survey

If the habitat assessment confirms that a feature is potentially suitable and the project will directly or indirectly impact it, a presence/probable absence survey is required . The 2026 guidelines provide two primary hibernaculum survey methods.

Winter internal survey

The acceptable survey window for winter internal surveys is January 1 through February 28, with the traditional survey window for known sites being January 15 through February 15.

Potential hibernacula that are deemed safe to enter should be entered and all accessible passages visually surveyed for the presence of Indiana bat and tricolored bat during hibernation. The use of direct internal surveys is not adequate for northern long-eared bat, due to the difficulty in visually detecting the species inside hibernacula where it typically roosts in deep cracks and crevices.

Working near and within abandoned mines and caves can be inherently dangerous due to potential hazards including ceiling collapse and presence of toxic gases. Surveyors must thoroughly assess their work sites for any known and potential health and safety hazards and must use appropriate personal protective equipment. The USFWS highly recommends that surveyors seek counsel from an occupational health and safety professional prior to working underground or under other potentially hazardous field conditions.

Only properly trained and qualified individuals with the appropriate federal and/or state permits and equipment should attempt internal P/A surveys. If the qualified biologist who completed the habitat assessment does not have the necessary experience or permits to complete internal survey work, then this portion of the project should be subcontracted to another individual or group that does.

Fall and spring emergence surveys

For sites where internal surveys are not feasible — due to safety concerns, inaccessibility, or site configuration — fall or spring emergence surveys using harp traps or mist nets at the cave or mine entrance are the alternative method.

The acceptable survey window for fall emergence surveys is September 15 through October 31. The acceptable survey window for spring emergence surveys is April 1 through April 21.

The level of effort required for each approach differs significantly.

For fall surveys: a minimum of one night of harp trap sampling per week for six weeks — six nights of sampling total — is required at each suitable entrance as determined by the habitat assessment. Each night of sampling should be separated by at least one week if weather conditions allow. Survey effort may be suspended if no bats of any species are captured after the first two nights of acceptable survey effort in the fall.

For spring surveys: a minimum of three nights of harp trap sampling per week for three weeks — nine nights of sampling total — is required at each suitable entrance. Due to the need to monitor weather conditions closely, each proposed spring mine or cave survey must be coordinated with the USFWS Field Office prior to surveying to ensure adequate survey results are achieved.

Harp traps are the preferred capture method for sampling entrances as they are less stressful on captured bats. Mist nets can also be deployed along corridors immediately adjacent to the entrance to increase survey effectiveness, but their use must be approved by the USFWS Field Office and appropriate state natural resource agency prior to initiation of survey.

The sampling period should begin at sunset and continue for at least five hours each night. A total of 30 hours of sampling for fall surveys and 45 hours for spring surveys should take place for a mine or cave survey to be approved.

What happens when a target species is confirmed

A confirmed detection of IBAT, NLEB, or TCB at a potential hibernaculum significantly changes the trajectory of a project.

Unless otherwise approved by the USFWS Field Office, the capture of an Indiana bat, northern long-eared bat, and/or tricolored bat during a fall or spring potential hibernacula survey requires that the applicant complete three additional nights of sampling per week for three consecutive weeks — nine additional nights of level of effort — to determine the relative significance of the hibernaculum and its associated underground workings. If the survey season ends prior to the completion of the required additional sampling, then sampling must be completed the following fall or spring.

If IBAT, NLEB, and/or TCB are captured during fall or spring surveys, notification to the local USFWS Field Office is required within 48 hours, and the sex and reproductive condition of the bat and GPS coordinates of the capture site must be provided.

From a project planning standpoint, a confirmed hibernaculum detection triggers a level of USFWS coordination that is substantially more involved than a summer P/A survey outcome. The significance of the hibernaculum — colony size, species composition, whether it represents a major or minor roosting site — will inform what conservation measures the USFWS requires before project work near the feature can proceed.

Personnel and permit requirements

At least one member of each survey crew must hold a valid USFWS Section 10(a)(1)(A) recovery permit as well as any applicable state agency permits that allow the qualified biologist to collect bats, including federally listed species. A qualified biologist must select and approve harp trap and mist-net sets, be physically present at each site throughout the survey period, and confirm all bat species identifications.

This permit requirement applies to fall and spring emergence surveys as well as internal surveys. Acoustic surveys conducted at a mine or cave entrance as a supplemental tool do not require a recovery permit, but acoustic collections at bridges or culverts should only be used as a supplement to a larger suite of structural survey approaches and cannot be used alone to determine species identification. The same logic applies at cave and mine entrances — acoustics alone at a hibernaculum entrance are not a substitute for harp trap sampling.

How hibernaculum surveys relate to summer surveys and project timelines

The seasonal timing of potential hibernacula surveys creates a planning challenge that is distinct from summer bat surveys. Summer P/A surveys occur between May 15 and August 15 in the hibernating range. Hibernacula surveys are conducted in winter (January–February for internal surveys) or during the narrow fall and spring emergence windows. A project that needs both survey types — because it involves tree clearing in suitable summer habitat and work near a potential hibernaculum — must plan for two separate survey windows that may span more than one calendar year.

Results of completed potential hibernacula surveys must be submitted to the appropriate USFWS Field Office prior to clearing or altering identified summer and winter bat habitat. The USFWS Field Office will review the results for the purposes of determining whether target species are occupying hibernacula in the project area and whether they may be adversely affected by any proposed actions.

For a project on a tight construction schedule, the worst-case scenario is discovering a potential hibernaculum during habitat assessment in the spring or summer of year one — after the spring emergence window has closed — and being unable to conduct a fall emergence survey until September at the earliest, with results not available for USFWS review until late fall or early winter. If a target species is confirmed, the additional nine-night survey requirement then pushes completion into the following year's spring window. Identifying potential hibernacula early — ideally during the initial desktop screening before any construction scheduling is finalized — is the only way to avoid this outcome.

What to do if your project area has subsurface features

The starting point is always the desktop analysis and initial field reconnaissance. If you are planning a project in karst topography, in areas with historical or active mining, in regions with known cave systems, or anywhere a subsurface feature could be present, the following steps should happen early in the project timeline — not after construction scheduling is locked.

Coordinate with your local USFWS Ecological Services Field Office through IPaC to determine whether any known hibernacula for the target species are documented near your project area. Commission a habitat assessment from a qualified biologist with specific experience in cave and karst topography assessment or underground mine assessment. Submit results to the USFWS Field Office for review before any work near the feature begins. If surveys are warranted, contact a permitted biologist well in advance of the fall survey window — September 15 arrival means your biologist needs to have an approved study plan before mid-September.

Do not disturb, modify, or block any entrance to a potentially suitable hibernaculum before the survey process is complete .

Volant EcoServices conducts potential bat hibernacula assessments and surveys across the eastern United States. Both co-founders, Mary Gilmore and Dan Cox, hold active USFWS Section 10(a)(1)(A) Recovery Permits for Indiana bat, northern long-eared bat, and gray bat — the federal authorization required to legally capture bats at cave and mine entrances during fall and spring emergence surveys. If your project involves subsurface features or karst terrain, contact us early. Learn about our hibernaculum survey services or contact us to discuss your project .

Bat Acoustic Data Vetting: What It Is and Why ESA Compliance Depends on It

Mon, 18 May 2026 23:20:02 GMT

If your project required an acoustic bat survey for ESA compliance , you may have received a report showing automated software outputs, species lists, and something called an MLE value. What you may not have been told is that automated software output alone is rarely the end of the story — and that in many cases, the 2026 USFWS Range-wide Indiana Bat and Northern Long-Eared Bat Survey Guidelines require something more: a process called qualitative analysis, or manual vetting.

Understanding what acoustic data vetting is, when it is required, and who is qualified to perform it can be the difference between a survey report that the USFWS accepts and one that gets sent back for more work — or worse, one that inadvertently establishes presence of a federally listed species without anyone noticing.

This post explains the acoustic data analysis process from start to finish.

What acoustic bat surveys actually produce

When a bat biologist deploys ultrasonic detectors at a survey site, those detectors record echolocation calls throughout the night as bats fly through the detection zone. At the end of the survey period, what the biologist retrieves is a folder of audio files — typically full-spectrum WAV recordings — that may number in the hundreds or thousands depending on bat activity levels, survey duration, and site conditions.

Those files cannot simply be counted. Each one must be analyzed to determine whether it contains a bat call, whether it is of sufficient quality to be identified to species, and whether any of the recorded calls belong to a target species — Indiana bat (IBAT), northern long-eared bat (NLEB), or tricolored bat (TCB) — for ESA compliance purposes.

This analysis process involves two distinct stages under the 2026 guidelines: automated analysis using USFWS-approved software programs, followed — when warranted — by qualitative analysis, also referred to as visual vetting, in which a qualified biologist reviews the call files directly.

Stage one: automated analysis

The 2026 guidelines require surveyors to conduct automated acoustic analyses for all sites and all nights that were approved in the study plan. This is not optional. A survey that runs automated analysis only on nights when bats were active, or only on sites where the biologist expected detections, does not meet the standard.

Automated analysis runs each recorded file through a USFWS-approved software program that compares the statistical properties of the recorded call to a library of known calls. The program classifies each file to species and, when run at the site-night level (all files from a single detector location on a single night), produces a Maximum Likelihood Estimate — the MLE — which is a statistical measure of the probability that the target species is present at that site on that night.

The approved software programs — and their specific approved versions, settings, and recording formats — are listed on the USFWS Automated Acoustic Bat ID Software Programs webpage. Surveyors must use the most current approved software versions and the manufacturer's recommended settings for target species P/A surveys.

Candidate programs — those submitted for testing but not yet fully approved — are not approved for stand-alone use in P/A surveys, but may be used in conjunction with one or more approved programs.

One critical and often overlooked rule: surveyors are not permitted to switch programs from what was originally identified in their approved study plan. The software to be used must be named in the study plan submitted to the USFWS Field Office before field work begins.

When automated analysis is — and isn't — sufficient

This is the part of acoustic data analysis that is most frequently misunderstood. The MLE p-value from automated software is not a final determination of presence or absence on its own. The guidelines establish clear rules for how to interpret software output, and those rules create multiple scenarios in which qualitative analysis becomes required or strongly advisable.

If the approved software identifies one or more files as a target species and the MLE p-value is 0.05 or less, the surveyor may accept that result — presence is established at that site on that night — or may conduct qualitative analysis (i.e., manual vetting) to determine whether the result is a false positive.

If the software identifies one or more files as a target species but the MLE p-value is greater than 0.05, the guidelines direct the surveyor to either disregard the insignificant p-value and assume presence, or conduct qualitative analysis to determine if the result is a false negative.

This means that whenever a software program flags any file as a target species — regardless of the MLE p-value — the surveyor must either accept presence or conduct qualitative analysis. There is no scenario in which a low-confidence software flag can be silently dismissed without one of those two responses.

The USFWS notes that current versions of auto-ID software do not reliably provide an MLE p-value below 0.05 for rare target species when they are present in low numbers at the night level, specifically fewer than 15 files per site night. Regardless of the MLE value, if any files are identified as the target species, the surveyor must either assume presence and coordinate with the USFWS Field Office, or conduct qualitative analysis to confirm or reject presence.

The practical implication is significant: in low-activity situations — which are common for rare, federally listed species — automated software alone cannot reliably clear a site. Qualitative analysis is the mechanism that allows a surveyor to evaluate those flagged files and determine, based on expert review, whether they represent a genuine target species detection or a misclassification.

Stage two: qualitative analysis (manual vetting)

Qualitative analysis is the direct, file-by-file visual review of echolocation call recordings by a biologist with specialized expertise in bat acoustic identification. This is the "manual vetting" step, and it requires a different and more demanding skill set than deploying detectors or running automated software.

What vetting involves by software

The 2026 guidelines specify distinct vetting workflows depending on which approved software was used.

For IBAT and NLEB, when using Kaleidoscope Pro or BCID: the reviewer first examines all files labeled as IBAT and/or NLEB. If the target species is not confirmed at that step, the reviewer must then examine all other files in folders containing pulses with a characteristic frequency of 38 kHz or greater, including files in the NOID (no identification) folder.

For IBAT and NLEB, when using SonoBat: the reviewer examines files labeled as the target species in the "Spp Accp" (Species Accepted) column. If the species is not confirmed, the reviewer then examines files in the "~Spp" (Leaning Species) column — for example, MYSO, MYSO/other species, or LUSO. Files in the LUSO category could belong to either Indiana bat or little brown bat, and any files labeled LUSO should be treated as possible IBAT files.

For TCB, when using Kaleidoscope Pro or BCID: the reviewer first examines all files labeled as TCB, then reviews all other files containing pulses with characteristic frequency of 40 kHz or greater, including the NOID folder, if the target species is not confirmed in the initial review.

For TCB, when using SonoBat: the reviewer examines files in the "Spp Accp" column, then — if not confirmed — files in the "~Spp" column, such as PESU or LABO/PESU.

The standard for overturning software results

This is one of the most consequential aspects of the vetting process: it is the USFWS's preference that reviewers accept a target species auto-ID result unless the reviewer provides clear justification for why that sequence could not belong to the target species.

The burden is on the reviewer to justify a rejection — not on the software to justify its identification. A reviewer who dismisses a software flag without documented, call-level justification is not meeting the regulatory standard, and the USFWS Field Office may not accept the resulting report.

What vetting produces in the report

Qualitative analysis must include and present within a written report a comparison of the results of each acoustic ID program by site and night. The guidelines recommend providing a table that shows each species identification from the program, the suggested species ID from visual vetting, and the rationale for any changes.

If visual confirmation of the target species is achieved, presence is established and the surveyor must coordinate with the USFWS Field Office. If there is no visual confirmation of target species, no further summer or year-round active season surveys are recommended.

Who is qualified to perform qualitative analysis

This is the question that separates firms that can deliver a defensible report from those that cannot. The 2026 guidelines set specific qualification standards for the individuals who make final qualitative identification decisions.

Individuals qualified to conduct qualitative analysis of acoustic bat calls typically have: experience gathering known calls, which provides a valuable resource for understanding how bat calls change and the variation present in them; experience identifying bat calls recorded in numerous habitat types; familiarity with the species likely to be encountered within the project area; and multiple years of experience with qualitative ID skills that they have kept current. A resume or similar documentation must be submitted along with final acoustic survey reports for anyone making final qualitative identifications.

Acoustic survey reports submitted without this resume information will not be reviewed by the USFWS Field Office until the information is provided.

This is not a formality. It directly affects review timelines. Projects waiting on USFWS Field Office approval for a survey report — where tree clearing cannot proceed until that approval is received — face real schedule consequences if the report is returned for a missing resume or insufficient vetting documentation.

What the guidelines require in the final acoustic survey report

The 2026 guidelines include a detailed submission checklist for acoustic survey reports. Several items relate directly to the vetting process. Required report elements include:

the full name and resume of any individual conducting qualitative acoustic analyses;
the name of the service-approved and/or candidate software programs used, including versions and software settings;
acoustic analysis software program output and summary results by site by night, including number of calls detected, species composition, MLE results, and settings files;
discussion for any site-nights with zero bat calls;
and, if qualitative vetting was used, a detailed analysis and results of the qualitative analysis conducted on projects where a program identified target species presence as likely, including justification for rejecting any program MLE results.

All originally recorded data — whether zero-crossing or full-spectrum — must be maintained for a period of five years and made available to the USFWS Field Office upon request. Failure to provide data when requested may result in invalidation of survey results.

Why this matters for your report

A bat acoustic survey that produces no confirmed target species detections after both automated analysis and qualified manual vetting provides defensible probable absence documentation that, under the 2026 guidelines, is valid for a minimum of five years. That is the outcome that clears your project to proceed without species-specific conservation measures — and it depends entirely on the analysis being done correctly.

A survey where automated software flagged one or two files as a target species, and a biologist without documented acoustic expertise dismissed them without documented justification, does not produce that outcome. If the USFWS Field Office requests the raw data files and finds that potentially valid target species files were rejected without adequate rationale, the survey results may be invalidated — and the project may need to repeat the survey, missing the survey window.

The vetting step is where survey quality is either demonstrated or undermined.

Volant's approach to acoustic data analysis

At Volant EcoServices, all acoustic data is manually vetted by experienced, federally permitted biologists to ensure accurate species identification. This is our standard practice on every acoustic survey we conduct — not a premium add-on. Both co-founders, Mary Gilmore and Dan Cox, hold active USFWS Section 10(a)(1)(A) Recovery Permits for Indiana bat, northern long-eared bat, and gray bat, and both bring years of qualitative acoustic identification experience to the vetting process.

We also accept third-party data vetting requests. If your firm or agency has existing bat acoustic survey data collected by another surveyor and needs qualified manual vetting and a defensible analysis report, contact us to discuss your dataset and timeline.

Volant EcoServices conducts acoustic presence/absence surveys, full acoustic data analysis and qualitative vetting, and USFWS study plan coordination for state and federally listed bat species across the eastern United States. Learn about our bat survey services or contact us about your project or dataset .

Skipping the Bat Survey: What ESA Liability Really Means for Developers

Fri, 08 May 2026 17:59:05 GMT

Tree clearing is one of the most common triggers for ESA liability on development projects in the eastern United States — and bats are at the center of it. Federally listed bat species with ranges covering most of the eastern half of the country have made bat surveys a standard part of the pre-construction compliance process for land developers, transportation agencies, utilities, and anyone else whose project involves removing trees or disturbing forest habitat.

What happens when that step gets skipped — whether intentionally or because no one flagged it early enough? The answer involves federal statute, stop work orders, financial penalties, and in some cases, consequences that can follow a project well past the point when the trees are already down.

This article explains the legal framework, the real project risks, and the pathway forward for projects in any stage of planning. It is written as general educational information and does not constitute legal advice. Readers with specific legal questions about their projects should consult a qualified environmental attorney.

The legal foundation: ESA Section 9

The Endangered Species Act of 1973 is the controlling federal statute. Section 9 of the ESA makes it unlawful for any person subject to the jurisdiction of the United States to take any endangered fish or wildlife species within the United States. The word "person" here is broad by design — it includes private citizens, corporations, state governments, and local government agencies. If you are a developer, contractor, utility operator, or transportation agency, you are a "person" under Section 9.

The ESA broadly defines "take" to include harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect. "Harm" extends beyond direct killing. Under USFWS regulations, harm includes significant habitat modification or degradation that actually kills or injures listed wildlife by significantly impairing essential behavioral patterns — including breeding, feeding, or sheltering. Tree clearing that destroys an occupied maternity roost during the summer roosting season is a textbook example of harm under this definition.

For the northern long-eared bat, all take occurring on or after March 31, 2023 is prohibited by Section 9 of the ESA, following that species' reclassification from threatened to endangered. The Indiana bat has carried full Section 9 protections since 1967. The tricolored bat, currently proposed for endangered listing, is moving toward the same framework.

Intent doesn't matter as much as you might think

This is the aspect of ESA liability that surprises project managers most. A developer doesn't need to know that a listed bat was roosting in the tree they cut down to face liability under Section 9. A knowing act only requires a general intent to commit the act impacting the species. A defendant need not know that the species is endangered or threatened, or intend to violate the ESA, to be held liable.

In other words: "I didn't know there were bats in those trees" is not a defense. The obligation to determine whether listed species are present — through IPaC screening, habitat assessment, and if necessary a bat survey — belongs to the project proponent. Skipping that process doesn't insulate you from liability; it removes the paper trail that would have demonstrated due diligence.

The penalties

ESA enforcement operates on two tracks — civil and criminal — and both can apply to a single violation.

Civil penalties

ESA Section 11(a)(1) authorizes the Secretary to assess a civil penalty of up to $25,000 for each knowing violation of the take prohibition (16 U.S.C. § 1540(a)(1)). The phrase "per violation" matters. If tree clearing destroys multiple roost trees, each instance of take may be counted separately. A project that clears 20 acres of occupied Indiana bat summer habitat without survey clearance is not facing a single violation — it is potentially facing dozens. The full text of Section 11 is available directly at fws.gov/laws/endangered-species-act/section-11 .

Criminal penalties

ESA Section 11(b)(1) provides that any person who knowingly violates any provision of the Act shall, upon conviction, be fined not more than $50,000 or imprisoned for not more than one year, or both (16 U.S.C. § 1540(b)(1)). Criminal prosecution is reserved for knowing violations and is handled by the Department of Justice, but the threshold for "knowing" is lower than most people assume — it requires only that the person intended to commit the act, not that they knew the species was listed or intended to violate the law.

Additional consequences

Penalties and fines are not the only exposure. All equipment, vehicles, and other means of transportation used to aid in the taking are subject to forfeiture after a person is convicted of a criminal violation. The federal government may also seek restitution for ESA violations or impose conditions of probation.

The ESA also gives the public the right to bring a citizen suit to enforce the statute's provisions. Under Section 11(g), citizens may file a civil suit to enjoin any person or organization alleged to be in violation of the ESA. Environmental organizations have used this provision actively. A stop work order from a federal agency is disruptive; a citizen suit filed by a conservation group is another layer of exposure entirely — one that can extend litigation well beyond the original project timeline.

The stop work order scenario

Federal penalties are one risk. The more immediate, day-to-day risk for most developers is the stop work order. USFWS coordinates regularly with the U.S. Army Corps of Engineers, state permitting agencies, and other federal action agencies. Projects that require a federal nexus — a Section 404 wetland permit, federal funding, a federal right-of-way — are subject to Section 7 consultation, which requires the federal agency involved to ensure the action is not likely to jeopardize a listed species.

These activities include any project that must obtain federal permits (e.g., USACE 404 permits), receives federal funding, or any other projects conducted by private, state, tribal, and local parties that may result in impacts to bat habitat — including timber harvest or tree clearing activities as part of land development and infrastructure projects.

If a project proceeds with tree clearing without completing required ESA coordination and a bat survey, and a federal agency subsequently becomes aware of it, the likely outcome is a demand to halt work pending consultation. For a project mid-grading or mid-clearing, that stop can mean carrying costs on heavy equipment, contractor holding fees, missed construction season windows, and financing exposure — all before a single penalty is assessed.

A couple of methods exist to avoid a total construction shutdown during the restricted season. The first is fairly obvious: plan to have all required permits in place and all trees cleared prior to April 1. If such a timeline is not feasible, a property owner can conduct a bat survey during the season to determine whether bats are actually living on the property. The survey window closes August 15. Projects that miss it must wait until the following year.

The specific tree clearing risk

Tree removal is the most direct threat when it involves trees suitable for roosting. Clearing vegetation can include crushing bats, flushing bats, noise, and chemical contaminants that may kill, wound, harm, or harass bats if they are present during the work.

Time-of-year restrictions (TOYRs) exist precisely because listed bat species are most vulnerable during the summer roosting season when maternity colonies are present and young-of-the-year are not yet volant. For Indiana bat, if your project is within a county where the federally endangered Indiana bat is known to hibernate or roost, project proponents must coordinate with the USFWS prior to clearing trees during any time of year. For NLEB, projects with a "May Affect" preliminary determination will need to coordinate further with the USFWS to determine what conservation measures may be necessary — likely including a TOYR on tree clearing during the summer occupancy season.

For most of the broader eastern U.S., the practical window for unrestricted tree clearing without bat survey clearance is limited to the winter inactive season. Tree clearing is generally not recommended between April 1 and September 30 each year due to the importance of forest habitats to listed bat species during the warmer months.

How to authorize incidental take the right way

The ESA does provide legal pathways for projects that will unavoidably impact listed bat species. Take itself is not impossible to authorize — but it must be authorized in advance, not retroactively.

For projects with a federal nexus, ESA Section 7 consultation with the USFWS is the standard pathway. The federal action agency consults with USFWS, a biological opinion is issued, and if incidental take is anticipated, an Incidental Take Statement provides authorization for a defined amount of take under specified terms and conditions. Compliance with those terms and conditions provides a legal shield against Section 9 liability for the authorized take.

For non-federal private projects where no federal nexus exists, ESA Section 10 Incidental Take Permits (ITPs) are available. An ITP requires the development of a Habitat Conservation Plan (HCP) demonstrating how the take will be minimized and mitigated. Once approved, the ITP authorizes a specific amount of incidental take and shields the permittee from penalties associated with a Section 9 violation, provided they comply fully with the terms of the approved HCP.

Both pathways require proactive coordination. Neither is available after the fact.

The practical path forward

The most common and cost-effective path for most development projects in the eastern U.S. is straightforward: run the project through IPaC, assess habitat, conduct a bat survey if one is warranted, and obtain a negative result that provides clearance for the project to proceed without ESA consultation. For projects with suitable habitat that yields negative P/A results, those results are valid for a minimum of five years from their completion, unless new information suggests otherwise. One season of survey investment protects the project — and future phases of the same property — for five years.

The bat survey is not the expensive part of an ESA compliance problem. The stop work order, the remediation, the missed survey window, the consultation process, and the legal exposure are the expensive parts. A survey conducted before ground disturbance begins resolves the question cleanly. A survey that never happened leaves the question open indefinitely.

What to verify before your project begins

Before breaking ground on any project involving tree clearing in the eastern United States:

Run the project through USFWS IPaC to generate an Official Species List. If Indiana bat, northern long-eared bat, or tricolored bat appear, determine your proximity to known occurrences and whether the inner-tier (presence assumed) or outer-tier (survey eligible) rules apply.
Commission a habitat assessment from a qualified biologist to evaluate tree quality, size, and roosting suitability within the project footprint.
If surveys are warranted, engage a permitted bat biologist early enough to submit a study plan and receive USFWS Field Office approval before the May 15 survey season opens (note: survey windows may vary by project location, and we suggest coordinating with the local USFWS FO) . Study plan approval can take up to 45–60 days for complex projects.
Do not plan tree clearing in suitable bat habitat between April 1 and September 30 without either a negative survey result on file or prior USFWS coordination authorizing the clearing.
Confirm that any biologist conducting mist-net capture surveys holds an active USFWS Section 10(a)(1)(A) Recovery Permit for the relevant species .

Volant EcoServices provides habitat assessments , acoustic presence/absence surveys , and mist-net surveys for Indiana bat, northern long-eared bat, gray bat, and tricolored bat across the eastern United States. Both co-founders, Mary Gilmore and Dan Cox, hold active USFWS Section 10(a)(1)(A) Recovery Permits for Indiana bat, northern long-eared bat, and gr ay bat — giving Volant the in-house capacity to take projects from initial IPaC screening through USFWS-approved field surveys and results reporting under one contract. Survey season opens May 15. Contact us to start planning your project .

This article is provided for general educational purposes and does not constitute legal advice. Developers and project proponents with specific questions about ESA compliance or liability exposure should consult a qualified environmental attorney.

Sources: Endangered Species Act of 1973, as amended (16 U.S.C. §§ 1531–1544). U.S. Fish & Wildlife Service Section 9 and Section 11 statutory text. U.S. Fish & Wildlife Service. 2026. Range-wide Indiana Bat and Northern Long-Eared Bat Survey Guidelines . USFWS Region 3, Bloomington, MN. Ohio DNR Division of Wildlife State Bat Survey Guidance.

Acoustic vs. Mist-Net Bat Surveys: Which Method Does Your Project Need?

Tue, 14 Apr 2026 14:43:53 GMT

If you've been told your project requires a bat survey , the next question is usually: what kind? Not every bat survey is the same, and the method your project needs — acoustic monitoring, mist-netting, or a combination of both — depends on factors that are specific to your site, your project's footprint, and where you fall relative to known bat occurrences.

Choosing the wrong approach, or hi ring a firm that can only provide part of the picture, can mean redoing work, missing the survey window, or being sent back to the drawing board by your USFWS Field Office. This article breaks down both methods, explains how they work together under the 2026 USFWS Range-wide Bat Survey Guidelines, and helps you understand what your project actually needs before you make any commitments.

What both methods have in common

Whether a project uses acoustics , mist-netting , or both, the goal is the same: to establish the presence or probable absence (P/A) of one or more target species — the Indiana bat, northern long-eared bat (NLEB), and tricolored bat (TCB) — within the project area during the summer/year-round active season.

Both methods must be conducted by qualified biologists during the approved survey window (May 15 – August 15 for most of the eastern U.S.), must follow a USFWS-approved study plan, and must produce results that are reported to the coordinating Field Office regardless of outcome. The minimum prescribed level of survey effort cannot be completed in a single calendar night, regardless of which method is used. Planning around this multi-night minimum is one of the most common things project managers underestimate when they're scheduling bat survey work.

Acoustic bat surveys: how they work

Acoustic bat surveys use ultrasonic detectors placed at survey sites to record echolocation calls overnight. Trained biologists deploy detectors in locations that maximize detection probability — typically along forest edges, over water features, and near roost habitat — and retrieve them after the prescribed number of nights. The call files are then analyzed using USFWS-approved software programs (currently SonoBat and the latest approved version of Kaleidoscope Pro) to identify species based on call characteristics.

When acoustic surveys are sufficient on their own

If no high-frequency (HF) calls of 35 kHz or greater are detected during acoustic surveys, no mist-netting is required within that survey area, and probable absence for the target species can be established. For many projects with low-to-moderate habitat quality, an acoustic-only survey is a fully valid, more efficient path to P/A clearance.

Acoustic surveys are also the only practical option in some situations. Terrain, site access, dense vegetation, or the absence of suitable net placement locations can make mist-netting physically impractical. In those cases, the biologist should coordinate with the local Field Office before finalizing the study plan, since site-specific conditions that do not lend themselves to standard survey techniques require FO coordination prior to using alternative methods.

What acoustic surveys cannot do

A positive acoustic detection establishes probable presence — and that determination is final. Negative results from follow-up mist-netting at any level of effort do not refute a previously established positive acoustic result. Once the acoustic record shows a target species is active in your project area, presence is established and no amount of additional netting changes that outcome. The project then moves into consultation with the USFWS to determine minimization and mitigation measures.

It's also worth noting that North American Bat Monitoring Program (NABat) acoustic surveys are not adequate to confirm probable absence of target species for project-specific determinations, even though they may provide useful supporting context. If your project area has NABat data on file, that data can inform the study plan, but it does not substitute for a project-level acoustic P/A survey.

Mist-net bat surveys: how they work

Mist-netting involves setting ultra-fine nets across bat flight corridors — typically at gaps in vegetation, along stream corridors, or near known roost features — after dark. Bats flying through the area become briefly captured in the net. The biologist extracts each bat, identifies it by species, records morphological measurements, and may band it or attach a small radio transmitter depending on the study plan objectives. The bat is then released at the capture site.

The permit requirement

This is the most important practical distinction between the two methods. Because mist-netting results in the physical capture of listed bats, it constitutes "take" under the Endangered Species Act. Surveys involving physical capture and handling of federally listed species require an ESA Section 10(a)(1)(A) recovery permit, which authorizes capture for identification and handling for measurements, photography, banding, and radio transmitter attachment. Not every ecological consulting firm holds this permit. Before engaging any firm for mist-net surveys, confirm that the lead biologists have current, active recovery permits covering the specific species present in your project area.

Volant EcoServices' co-founders, Mary Gilmore and Dan Cox, both hold active USFWS Section 10(a)(1)(A) Recovery Permits for Indiana bat, northern long-eared bat, and gray bat. Having two permitted biologists on the same team provides meaningful operational flexibility — particularly for larger projects or tight scheduling windows where split crews may be needed simultaneously across a survey area.

When mist-netting is required

Mist-netting becomes required when acoustic surveys detect probable bat activity. If any HF calls are detected during acoustic Phase 2 surveys, mist-netting at the Phase 2 level of effort is then required within that survey unit. This is why the two methods are so frequently used together: acoustics efficiently screens the site, and netting is triggered only where the acoustic data indicates bat activity.

Mist-netting may also be the primary P/A method from the start, depending on site conditions, habitat quality, and USFWS Field Office preferences in your region. For high-quality Indiana bat habitat — mature forest patches with trees of 5-inch DBH or larger — your Field Office may require or recommend leading with netting rather than treating acoustics as the Phase 1 screen.

Federal guidance requires a minimum of two biologists — one permitted and one technician — present for every four net-sets being operated during a survey. Acoustic surveys cannot be completed in a single night and must be split across a minimum of two calendar nights under the range-wide guidance. Designing a study plan that satisfies USFWS requirements simultaneously starts with understanding these minimum staffing and timing constraints upfront.

The hybrid approach: how acoustic and mist-net surveys work together

Most larger projects — or projects in areas with high-quality bat habitat — use a phased approach that combines both methods. This is also the most defensible study design from a regulatory standpoint because it layers multiple lines of evidence into the P/A determination.

Under the 2026 guidelines, the general hybrid sequence works like this:

Acoustic screening. Detectors are deployed at survey sites across the project area for the required number of nights. Files are analyzed using USFWS-approved software.
If no HF calls are detected: Probable absence is established for that survey unit. No netting is required.
If HF calls are detected: Mist-netting is triggered at the Phase 2 level of effort at those locations.
If netting captures target species: Presence is confirmed. Depending on the study plan, radio-tracking may follow to locate roost trees and refine the area of occupancy for USFWS consultation.
If netting produces no captures: Probable absence is established for the netting phase — but only if the original acoustic results did not already establish probable presence . The study plan should be written carefully to make this sequence clear to the USFWS Field Office.

Any project study plan that includes use of both acoustics and mist-netting needs to be written clearly to avoid potential misunderstandings between the project proponent and the USFWS Field Office regarding which method is serving as the P/A method and what the outcomes of each phase mean. This is where having an experienced bat biologist who has written dozens of study plans — and has an existing working relationship with the local FO — makes a material difference.

How to decide what your project needs

A permitted bat biologist should make the final call on survey method after reviewing your project footprint, the habitat assessment, and your local USFWS Field Office's documented preferences. That said, here's a general framework:

Start with acoustics alone if:

The project area has low-to-moderate quality bat habitat (limited mature forest, fragmented cover)
Site access or physical conditions make mist-net placement impractical
The project is in the outer tier of a known occurrence buffer and the Field Office has indicated acoustic-only surveys are acceptable

Plan for mist-netting (or a hybrid) if:

The project area includes high-quality Indiana bat or NLEB roosting habitat (mature forest, riparian corridors)
The project is a large linear project (transmission line, road, pipeline) requiring survey across multiple habitat units
Prior acoustic or occurrence data in the vicinity suggests bat activity is likely
Your USFWS Field Office has historically required netting for projects of this type in this area
You need the most defensible P/A determination possible — for example, on a federally permitted project subject to Section 7 consultation

You will definitely need a permitted mist-net biologist if:

Any acoustic survey conducted on or near the project area has ever detected probable target species presence
The project is already within an inner-tier occurrence buffer and the USFWS FO is requiring capture data to inform minimization measures
Radio-tracking or roost tree identification is part of the scope

What to ask when hiring a bat survey firm

Before signing any contract for bat survey work, get clear answers to these questions:

Does the lead biologist hold an active USFWS Section 10(a)(1)(A) Recovery Permit for the relevant species? Confirm which species are covered — permits are species-specific. A firm permitted only for general wildlife surveys is not cleared to conduct mist-netting for Indiana bat or NLEB.

Has the firm worked with your specific USFWS Ecological Services Field Office before? Study plan review timelines and FO preferences vary significantly by region. A biologist with an established relationship with the FO serving your project area will move faster and hit fewer surprises.

Can the firm handle the full sequence — habitat assessment, study plan, acoustics, mist-netting, and results reporting — under one contract? Splitting these responsibilities across multiple vendors increases coordination risk and can create gaps in the reporting record.

What software is the firm using for acoustic analysis, and is it on the current USFWS-approved list? The approved software list is updated periodically; using an unlisted or outdated version can invalidate acoustic data.

Volant EcoServices provides the full scope of listed bat survey services across the eastern United States — habitat assessments, acoustic P/A surveys, mist-net surveys (both Dan Cox and Mary Gilmore hold active USFWS Recovery Permits for Indiana bat, northern long-eared bat, and gray bat), radio-tracking, and USFWS study plan coordination. Survey season opens May 15. Contact us to discuss your project .

Do I Need a Bat Survey? A Plain-Language Guide to Regulatory Compliance Bat Surveys

Fri, 03 Apr 2026 14:47:02 GMT

You're a project manager, a developer, a transportation agency contractor, or a utility company environmental coordinator. You've just received a comment letter from the U.S. Fish and Wildlife Service — or your environmental consultant has flagged a potential issue — and suddenly someone is telling you that you need a bat survey before your project can move forward.

If your first reaction w as "a bat survey? Why on earth do I need a bat survey?" — you're not alone. This is one of the most common questions we hear from new clients at Volant EcoServices. The short answer is that several bat species found across the eastern United States are federally protected under the Endangered Species Act, and projects that might affect their habitat — even indirectly — can trigger specific survey and compliance requirements before construction can begin.

This guide walks you through everything you need to know: who needs a bat survey, what triggers the requirement, when surveys have to happen, where they're conducted, and why the process exists in the first place. By the end, you'll have a clear picture of what's ahead and how to move through it efficiently.

Why Do Bats Have Federal Protection?

Before getting into the logistics, it helps to understand why bats matter from a regulatory standpoint. Three bat species found across the eastern United States are the primary drivers of bat survey requirements for development and infrastructure projects:

Indiana bat ( Myotis sodalis ) — Listed as federally endangered since 1967. Found across much of the eastern United States, the Indiana bat uses forested habitats for roosting and raising young in summer and hibernates in caves and mines during winter. White-nose syndrome — a devastating fungal disease — has caused population declines in recent decades.

Northern long-eared bat ( Myotis septentrionalis ) — Reclassified from threatened to federally endangered in 2023. The northern long-eared bat is particularly sensitive to white-nose syndrome and has experienced dramatic population declines. It uses a wide variety of forested habitats and hibernates in caves and mines.

Tricolored bat ( Perimyotis subflavus ) — Currently proposed as federally endangered. White-nose syndrome has caused estimated population declines of more than 90% in affected colonies, making this one of the most severely impacted bat species in North America.

All three species — Indiana bat, northern long-eared bat, and tricolored bat — depend on forested habitats for roosting, raising young, foraging, and commuting. When a project proposes to clear trees, demolish structures, or disturb caves, mines, bridges, or culverts near suitable habitat, the potential for harm to these species triggers the bat survey process.

Who Needs a Bat Survey?

The short answer: if your project involves a federal nexus and could affect suitable bat habitat, you very likely need to address bats as part of your environmental review process.

A federal nexus means your project involves one or more of the following:

Federal funding — FHWA, FRA, FTA, USDA, or any other federal agency money in the project budget
Federal permits — Section 404 Clean Water Act permits from the Army Corps of Engineers, NEPA review, or any other federal authorization
Federal land — work occurring on or adjacent to federal lands
Federal agency involvement — DOD installations, National Forest lands, Bureau of Land Management areas

If any of these apply, your project is subject to Section 7 of the Endangered Species Act — the provision that requires federal agencies to consult with the U.S. Fish and Wildlife Service to ensure their actions don't jeopardize listed species. Bat surveys are often a key component of that consultation process.

Common project types that trigger bat survey requirements include:

Highway expansion, bridge replacement, and road construction projects
Transmission line and pipeline corridors through forested habitat
Wind energy facility development
Natural gas and oil infrastructure in forested regions
Utility right-of-way clearing and vegetation management
Residential and commercial development involving significant tree clearing
Department of Defense installation management and construction
Timber harvesting and forest management on federal lands
Bridge and culvert rehabilitation or replacement

Even if your project doesn't have a direct federal nexus, state-level review processes in many eastern states may also trigger bat survey requirements. It's always worth confirming with your state's wildlife agency and your local USFWS Ecological Services Field Office early in the planning process.

What Triggers the Requirement — and What Are You Actually Being Asked to Do?

The bat survey requirement is triggered when your project has the potential to affect suitable habitat for Indiana bat, northern long-eared bat, and/or tricolored bat in the eastern United States. "Suitable habitat" generally means:

Forested or wooded areas containing trees at least 3–5 inches in diameter at breast height with features like exfoliating bark, cavities, crevices, or hollows that could serve as roost sites
Caves, mines, rock features, or tunnels that could serve as winter hibernacula
Bridges and culverts that meet minimum size criteria for bat roosting
Riparian corridors, woodland edges, and forest patches used for foraging and commuting

When USFWS determines that your project is within the range of one or more target species and involves suitable habitat, they will typically recommend — or require — that you complete a series of steps before project activities begin.

The general process works like this:

Step 1 — IPaC Review: Your consultant submits your project through the USFWS Information for Planning and Consultation (IPaC) website. IPaC generates an Official Species List identifying which listed species — including Indiana bat, northern long-eared bat, and/or tricolored bat — are potentially present in your project area. This step should happen as early as possible in your project planning.

Step 2 — Habitat Assessment: A qualified biologist visits your site - or conducts a desktop analysis - and evaluates whether suitable bat habitat is present within the project footprint. If no suitable habitat exists, no further surveys may be required. If suitable habitat is present, the assessment documents its type, quantity, and distribution — information that determines what surveys are needed and how much survey effort is required.

Step 3 — Study Plan Development: Your biologist develops a survey study plan describing the proposed survey methods, locations, personnel qualifications, schedule, and expected outcomes. This plan is submitted to the appropriate USFWS Field Office for review and approval before any fieldwork begins. This step takes time — plan for at least 15 business days for standard projects, and 45–60 days for energy projects or complex multi-state projects.

Step 4 — Conduct Surveys: Approved surveys are conducted during the appropriate survey window by qualified, federally permitted biologists. Survey types may include mist-netting , acoustic monitoring , or a combination of both. Hibernaculum surveys and bridge and culvert assessments may also be required depending on your project.

Step 5 — Report Results: Survey results — whether positive or negative — are submitted to the USFWS Field Office. Results inform whether Section 7 consultation is needed, what conservation measures apply, and whether your project can proceed as planned.

When Do Surveys Have to Happen? Survey Windows Explained

This is where a lot of first-time clients get caught off guard: bat surveys can only be conducted during specific windows of the year , and missing those windows means waiting until the following season. For projects with tight schedules, this can be a significant delay if survey planning doesn't start early enough.

Here are the key survey windows established by the USFWS Range-wide Indiana Bat and Northern Long-Eared Bat Survey Guidelines:

Summer Active Season Surveys (mist-netting and acoustic monitoring)

Survey window: May 15 – August 15 in the hibernating range (which covers most of the eastern United States)
Survey window: March 1 – October 15 in the year-round active range for northern long-eared bat and tricolored bat
These surveys are the most common requirement and are what most clients mean when they say "bat survey." They document whether listed bat species are using suitable forested habitat within or near your project area.

Hibernaculum Surveys (caves, mines, underground features)

Winter internal surveys: January 1 – February 28 (traditional window: January 15 – February 15)
Fall emergence surveys: September 15 – October 31
Spring emergence surveys: April 1 – April 21
These surveys are required when your project may affect caves, mines, or other underground features that could serve as winter bat roost sites.

Bridge & Culvert Surveys

Timing varies by project and should be coordinated with your local USFWS Field Office — surveys may be timed to the active season, the winter period, or both depending on the nature of the proposed impact.

The practical implication: If your project involves tree clearing and you're reading this in the spring, you need to act immediately. Study plan approval alone takes at least 15 business days, and surveys must be completed before August 15. If you're reading this in the fall or winter, you have time to plan before the summer survey season — use it. Projects that get their habitat assessments and study plans submitted early are projects that stay on schedule.

Where Are Surveys Conducted?

Bat surveys are conducted within and around your specific project area — not at a distant location or in a representative habitat somewhere else. Survey locations are designed to detect bats that are actually using the habitat your project proposes to impact.

The USFWS Guidelines establish a level of effort (LOE) requirement based on the acreage of suitable habitat your project will affect. The more suitable habitat impacted, the more survey effort required. For standard projects, the LOE is calculated based on 123-acre survey units — for every 123 acres of suitable habitat (or fraction thereof), a minimum number of mist-net nights or acoustic detector nights must be completed.

Survey locations must be within or immediately adjacent to your project footprint, placed in areas that give bats the best opportunity to be detected — forest edges, stream corridors, travel corridors, and water sources. All site locations must be documented with GPS coordinates and submitted as part of the survey study plan for USFWS approval.

Volant EcoServices serves clients across Ohio, Pennsylvania, Kentucky, West Virginia, Indiana, Virginia, and throughout the eastern United States — wherever your project is located, we can mobilize to your site.

What Happens If Bats Are Found?

If listed bat species are detected during surveys, it doesn't automatically mean your project is stopped. What it means is that USFWS must be notified within 48 hours and the consultation process moves to the next level.

For mist-net captures , our biologists immediately initiate radio telemetry to track the captured bat to its roost location. Roost data documents how the bat is using the project area and informs what conservation measures — tree clearing windows, buffer zones, avoidance measures — may be required.

For acoustic detections , the confirmed presence of a listed species triggers coordination with the USFWS Field Office to determine appropriate next steps, which may include additional survey effort, project design modifications, or formal Section 7 consultation .

Formal Section 7 consultation results in a Biological Opinion from USFWS that describes the anticipated effects of your project on listed bat species and establishes Reasonable and Prudent Measures — specific conditions your project must follow to minimize impacts and avoid unauthorized take. These conditions commonly include seasonal tree clearing restrictions, work windows tied to the bat activity calendar, and monitoring requirements during construction.

The key point is that most projects that find listed bats can still move forward — they just move forward with specific conservation measures in place. The goal of the process is not to stop your project but to ensure it proceeds in a way that avoids, minimizes, or mitigates impacts to species that are genuinely imperiled.

What If No Bats Are Found?

If surveys are completed following USFWS Guidelines and no listed bat species are detected, you receive a probable absence determination — a defensible, agency-accepted finding that the listed species are probably not present in your project area under current conditions.

A negative survey result is valid for five years from the year the survey was conducted. This means you have a five-year window to complete your project without re-surveying, provided habitat conditions don't change significantly. If your project timeline extends beyond five years, coordinate with your local USFWS Field Office to determine whether updated surveys are needed.

Why Does This Process Exist? The Bigger Picture

It's worth taking a moment to understand why this regulatory framework exists — not just as compliance obligation, but as a reflection of a genuine conservation crisis.

White-nose syndrome has killed an estimated 6–7 million bats across North America since it was first detected in the United States in 2006. The northern long-eared bat alone has declined by more than 99% at some hibernacula. The tricolored bat has experienced colony declines exceeding 90% across much of its range. These are not abstract numbers — they represent a collapse of bat populations that may take a century to recover.

Bats provide enormous ecological and economic services. They consume billions of insects annually — including agricultural pests — reducing the need for pesticides and providing an estimated $3.7 billion per year in value to North American agriculture. Their loss has cascading effects on the ecosystems they're part of.

The bat survey and ESA compliance process exists because without it, routine development and infrastructure projects — individually small, cumulatively significant — would incrementally eliminate the roosting habitat, hibernation sites, and foraging corridors that these struggling species depend on to survive and recover. The regulatory framework is the mechanism through which society has decided to balance economic development with the obligation to protect species that cannot protect themselves.

At Volant EcoServices, we take that obligation seriously — not as a regulatory checkbox but as the reason we do this work. When we conduct a bat survey, we're not just helping you get a permit. We're contributing to the scientific record of where these species live, what habitats they depend on, and what conditions allow them to persist. That data matters, and it accumulates across thousands of surveys into a picture of population trends that informs conservation for decades.

How to Get Started

If you have a project that may require bat surveys, the most important thing you can do right now is start early . The survey windows are fixed. Study plan approval takes time. Projects that run into bat survey delays are almost always projects where the process wasn't started soon enough.

Here's your immediate action checklist:

Submit your project through IPaC at ipac.ecosphere.fws.gov to generate an Official Species List and determine which target species are in your project area
Contact your local USFWS Ecological Services Field Office to discuss your project and get preliminary direction on whether surveys are recommended
Engage a qualified bat survey firm — surveys for Indiana bat, northern long-eared bat, and tricolored bat must be conducted by biologists holding a valid USFWS Section 10(a)(1)(A) Recovery Permit for the applicable species
Submit your habitat assessment and study plan as early as possible — ideally well before the survey season begins

Volant EcoServices is a woman-owned ecological consulting firm based in Kent, Ohio. Our lead biologists hold a USFWS Recovery Permit for Indiana bat, northern long-eared bat, and gray bat, and our team is qualified to conduct the full range of bat surveys described in this guide — mist-netting , acoustic monitoring , hibernaculum surveys , bridge and culvert assessments , radio telemetry, emergence surveys, and bat acoustic data vetting .

Have questions about whether your project needs a bat survey, or ready to get the process started? Contact Volant EcoServices to speak with a federally permitted bat biologist about your project's survey needs across Ohio, Pennsylvania, Kentucky, West Virginia, Indiana, and the eastern United States. You can also reach us directly at (330) 541-5201 or info@volant.llc .

2026 USFWS Bat Survey Guidelines Released: What Changed and What It Means for Your Project

Fri, 20 Mar 2026 16:46:39 GMT

Today, the U.S. Fish and Wildlife Service (USFWS) released the 2026 version of the Range-wide Indiana Bat and Northern Long-Eared Bat Survey Guidelines — the foundational document governing presence/probable absence (P/A) survey methodology for the Indiana bat (Myotis sodalis), northern long-eared bat (Myotis septentrionalis), and tricolored bat (Perimyotis subflavus) across the eastern United States.

At Volant EcoServices, we base all of our bat survey methodology directly on these Guidelines — from mist-net surveys and acoustic monitoring to potential hibernacula surveys , fall/spring emergence surveys, bridge and culvert assessments, radio tracking, and emergence surveys. When the Guidelines change, the way we design and execute surveys changes with them. If you have an active project — or are planning one — here is what you need to know about the 2026 update.

What the USFWS Changed in 2026

The USFWS identified three primary changes in the 2026 Guidelines. Understanding each one helps project proponents and their consultants plan accordingly.

1. Streamlined Document Structure

The most immediately noticeable change is structural. The 2026 Guidelines document has been reduced by nearly half compared to previous versions. The USFWS explicitly states that this reduction was made to improve flow, clarity, and navigation — not to reduce the rigor of the survey requirements themselves.

What this means for your project: The core survey requirements — level of effort, survey windows, personnel qualifications, submission requirements — remain in place. The streamlined document should make it easier for project proponents and surveyors to locate relevant guidance quickly, but the underlying compliance expectations are unchanged. If you were planning surveys based on the 2024 Guidelines, coordinate with your local USFWS Ecological Services Field Office to confirm that your study plan aligns with the new 2026 version before submitting.

2. DNA Collection — New Instructions for Species Identification

One of the most substantive technical changes in the 2026 Guidelines is the formal inclusion of new instructions for DNA sample collection as a tool for species identification — specifically to reduce the need for wing biopsy punches, which are the most invasive of the DNA collection methods.

The 2026 Guidelines prioritize DNA collection methods in the following order, from most to least preferred:

Fecal collection — lowest risk of injury or additional stress; preferred when bats opportunistically defecate during processing or when feces can be collected below a known roost
Wing swabbing — second preferred method; provides adequate DNA while considered safe for the animal
Buccal swabs — less preferable due to potential for stress or injury during insertion
Wing biopsy punches — acceptable but least preferred; leaves a hole requiring healing and carries risk of tearing or infection

This hierarchy reflects a broader USFWS emphasis on minimizing stress and harm to listed bats during handling — particularly important for already-imperiled species like the Indiana bat and northern long-eared bat. The Guidelines note that fecal collection, wing swabbing, and buccal swabs can achieve approximately 95% efficacy for species identification, while wing biopsy punches reach approximately 98% — a relatively small difference that the USFWS has determined does not justify the additional invasiveness of biopsy collection as a first choice.

What this means for your project: If your survey captures a bat from the genus Myotis that cannot be readily identified to species in the field — a situation that arises most often with Indiana bat and little brown bat ( Myotis lucifugus ), which can be difficult to distinguish — DNA collection may be authorized or requested by the USFWS Field Office. Your survey team should be prepared to collect fecal or wing swab samples as the preferred methods. It is important to note that wing swabbing, buccal swabbing, and wing biopsy collection can only be conducted by individuals whose Section 10(a)(1)(A) Recovery Permit explicitly authorizes those activities. Collection of guano opportunistically, however, does not require a permit unless the bat is being held beyond the permitted 30-minute processing window.

At Volant EcoServices, our lead biologists Mary Gilmore and Dan Cox hold USFWS Recovery Permits for Indiana bat, northern long-eared bat, and gray bat, and our team is trained in appropriate handling and DNA collection procedures consistent with the updated Guidelines.

3. Western Species Identification — New Language for Western Myotis Species

The 2026 Guidelines include new language related to the identification of western Myotis bat species in portions of the NLEB and tricolored bat ranges that overlap with acoustically similar western species. This primarily affects surveys conducted in the western portions of these species' ranges — states such as Kansas, Nebraska, North Dakota, South Dakota, Montana, and Wyoming — where species like the long-eared myotis ( Myotis evotis ), western small-footed bat ( Myotis ciliolabrum ), and canyon bat ( Parastrellus hesperus ) can cause acoustic misidentification issues.

The 2026 FAQ confirms that for surveys in these western overlap zones, no acoustic software programs are currently approved as stand-alone tools. Surveyors must use two candidate programs and apply manual vetting protocols to confirm or reject species identifications.

What this means for your project: For the vast majority of Volant's clients in Ohio, Pennsylvania, Kentucky, West Virginia, Indiana, Virginia, and the broader eastern United States, this change has limited direct impact — the problematic western species overlap areas are outside your project geography. However, if you are working on a project in the range fringe states, this language is important. Coordinate with your local USFWS Field Office to confirm which software programs are approved and what manual vetting standards apply to your specific project location.

What Did Not Change in 2026

Given the scope of the document restructuring, it is worth being explicit about what the 2026 Guidelines did not change — because some of the most consequential requirements from recent years remain fully in effect.

Tricolored bat remains in scope. The 2026 Guidelines continue to include tricolored bat as a target species alongside Indiana bat and northern long-eared bat. The TCB-specific level of effort — using the NLEB LOE as the standard — remains in place. As the 2026 FAQ confirms, preliminary USFWS and USGS review indicates this LOE is sufficient to demonstrate P/A of tricolored bat throughout its range. The tricolored bat is currently proposed as federally endangered, and its inclusion in P/A survey planning remains essential for projects in suitable habitat.

Survey windows are unchanged. The summer survey season for the hibernating range remains May 15 – August 15. The year-round active survey season for NLEB and TCB remains March 1 – October 15. These windows govern when surveys must be completed to produce defensible presence/probable absence determinations.

Level of effort requirements are unchanged. The minimum survey LOE for mist-netting and acoustic surveys — the number of net-nights and detector-nights required per 123 acres of suitable habitat — remains the same as established in recent versions of the Guidelines. The combined acoustic and mist-netting approach remains available and is required for TCB surveys in areas outside the NLEB and IBAT range.

Study plan approval requirements remain in place. Surveyors are still required to receive prior, site-specific approval from the USFWS Field Office before conducting P/A surveys. Study plans should be submitted as early as possible — the Guidelines note that FOs can typically review and approve within 15 working days, but complex projects or energy projects can require 45–60 days. Plan accordingly.

Negative survey validity periods are unchanged. Negative P/A survey results remain valid for a minimum of five years from the year surveys are completed, assuming no significant habitat changes or new nearby detections. Negative bridge and culvert survey results remain valid for two years.

AudioMoth remains unacceptable. The 2026 Guidelines continue to explicitly exclude the AudioMoth detector (Open Acoustic Devices) from use in P/A surveys pending further refinement and testing. If your survey program uses AudioMoth as a primary detection tool, those results will not be accepted by the USFWS.

Acoustic Software — Check the Approved List Before Submitting Your Study Plan

The USFWS included a prominent reminder in the 2026 Guidelines update: review the approved acoustic software list before submitting your study plan for 2026 surveys. The approved software list is maintained separately from the Guidelines document and is updated as new programs and new versions are tested. The 2026 FAQ confirms that Kaleidoscope Pro versions using the approved 5.4.0 Bats of North America classifier and SonoBat 30 versions using approved Regional Pack classifiers remain acceptable for use.

At Volant EcoServices, our acoustic data vetting team stays current with approved software versions and classifier updates. All acoustic data we collect or vet is analyzed using the most current USFWS-approved programs and is manually reviewed by our federally permitted biologists to ensure defensible, agency-ready results.

What This Means If You Have a Project in 2026

If your project is in the planning stages and you have not yet conducted bat surveys, the 2026 Guidelines are the version that applies to your work this season. Here is what we recommend:

Start early. Study plan review and approval by the USFWS Field Office takes time. For standard projects, plan for at least 15 working days. For energy projects, complex linear projects, or multi-FO coordination, allow 45–60 days or more. Submitting early in the calendar year gives your project the best chance of completing surveys within the appropriate survey windows.

Use IPaC first. Submit your project through the USFWS Information for Planning and Consultation website (IPaC) to generate an official species list and determine which of the three target species — Indiana bat, northern long-eared bat, and/or tricolored bat — are within your project area. This step should happen before any survey planning begins.

Confirm your survey method is appropriate. The 2026 Guidelines allow mist-netting, acoustic surveys, or a combined approach for most projects. The combined approach continues to offer flexibility for projects with challenging survey conditions or limited high-quality mist-net locations. For TCB-only range projects, the acoustic or combined approach is required.

Coordinate on DNA collection if relevant. If your project involves capture of Myotis bats with ambiguous species identification, discuss DNA collection authorization and preferred methods with your USFWS Field Office ahead of time. Ensure your permitted biologist's recovery permit explicitly authorizes the collection methods that may be needed.

Have Questions About the 2026 Guidelines and Your Project?

Volant EcoServices follows the most current USFWS bat survey guidelines for all presence/probable absence surveys, acoustic monitoring, hibernaculum assessments, bridge and culvert surveys, radio tracking, and emergence surveys. Our team monitors guideline updates as they occur and ensures that every study plan we develop reflects current USFWS requirements.

If you have questions about how the 2026 Guidelines affect your specific project — whether you are a developer, transportation agency, utility company, or land manager — contact Volant EcoServices to speak with a federally permitted bat biologist. We serve clients across Ohio, Pennsylvania, Kentucky, West Virginia, Indiana, Virginia, and the broader eastern United States.

This post was written on the date of the 2026 Guidelines release, March 20, 2026. As with all regulatory guidance, project proponents should consult directly with their local USFWS Ecological Services Field Office for project-specific questions and study plan approval. The full 2026 Guidelines and associated FAQ are available at fws.gov .

Volant Volunteers at MAPS Stations to Support Avian Conservation

Thu, 25 Sep 2025 10:28:01 GMT

At Volant, our commitment to ecological stewardship goes beyond consulting—it’s a personal and professional passion. Recently, our co-founders took that commitment into the field by volunteering at Monitoring Avian Productivity and Survivorship (MAPS) stations, contributing to one of North America’s most important long-term bird monitoring programs.

Dan Cox participated at the MAPS station located at Shaker Village of Pleasant Hill in Kentucky , while Mary Gilmore volunteered at the station in Cuyahoga Valley National Park in Ohio. These experiences allowed us to engage directly with the science that informs conservation strategies and deepened our connection to the ecosystems we work to protect.

What Are MAPS Stations?

MAPS stations are part of a continent-wide network established by the Institute for Bird Populations (IBP). These stations operate during the breeding season and use standardized mist-netting and banding protocols to collect data on bird demographics—such as age, sex, and reproductive status. The goal is to monitor trends in avian productivity and survivorship, which are critical indicators of ecosystem health.

Why MAPS Matters

Birds are excellent bioindicators. Changes in their populations often reflect broader environmental shifts, including habitat loss, climate change, and pollution. MAPS data helps scientists and land managers understand these changes and develop informed conservation strategies. The program has been instrumental in identifying population declines and guiding habitat restoration efforts across North America.

Why Volant Participates

As ecologists, we rely on robust data to inform our work. Volunteering at MAPS stations allows us to contribute to the very datasets that shape conservation policy and practice. It also keeps us grounded in the fieldwork that underpins our consulting services. Participating in MAPS aligns with our mission to support science-based environmental solutions and gives us a chance to collaborate with other professionals and volunteers who share our passion for wildlife conservation.

Moreover, these experiences enrich our understanding of the landscapes we serve. Whether it’s the rolling hills of Kentucky or the forested valleys of Northeast Ohio, each MAPS station offers a unique glimpse into the local avian community and the broader ecological dynamics at play.

Looking Ahead

We’re proud to support MAPS and encourage others in the environmental sector to get involved. Whether through volunteering, funding, or simply spreading awareness, every contribution helps strengthen the scientific foundation of conservation.

Stay tuned for more field stories and insights from our team as we continue to engage with the ecosystems we serve—both professionally and personally.

Interested in long-term ecological monitoring or avian survey services for your property or project? Contact Volant EcoServices to discuss how our team can support your conservation goals across the eastern United States.

Could Bats Help Control the Spotted Lanternfly Invasion?

Thu, 03 Jul 2025 17:18:22 GMT

Bats vs Spotted Lanterfly

The spotted lanternfly ( Lycorma delicatula ) has become one of the most notorious invasive species threatening forests, agriculture, and ecosystems across the eastern United States. As this insect rapidly expands its range, land managers and researchers are urgently seeking natural solutions to control its spread.

A new study published in Forests (MDPI, 2023) offers a hopeful — and surprising — potential ally in the fight: bats.

The Spotted Lanternfly Problem

Originally from Asia, the spotted lanternfly was first detected in Pennsylvania in 2014 and has since spread across the Northeast and Mid-Atlantic. Its preferred host, the invasive tree of heaven ( Ailanthus altissima ), is common along roadsides, forest edges, and disturbed habitats — making containment especially difficult.

These insects cause extensive damage by feeding on sap from trees and plants, weakening them and leaving behind a sticky residue that promotes mold growth. The economic impacts are significant, affecting vineyards, orchards, timber, and even tourism.

Bats as Natural Pest Control

Recent research reviewed global studies on forest-dwelling bats and highlighted emerging evidence that some native bat species may be consuming spotted lanternflies.

This is promising news for several reasons:

Bats are voracious insect predators, capable of eating thousands of insects in a single night.
Utilizing native species for pest control reduces reliance on pesticides and promotes ecosystem balance.
Bats often forage along forest edges, roadsides, and near water — the same areas where spotted lanternflies tend to congregate.

While more targeted research is needed to fully understand the extent of bat predation on lanternflies, early findings suggest that enhancing bat habitat could be part of an integrated pest management strategy.

Supporting Bats, Supporting Forest Health

At Volant EcoServices, we specialize in bat research and habitat assessments. Protecting and enhancing bat populations isn’t just good for biodiversity — it may also provide tangible benefits in controlling invasive pests like the spotted lanternfly.

We assist clients with:

Acoustic monitoring to document bat activity
Roost surveys and habitat evaluations
Conservation planning that promotes healthy bat populations

As this research evolves, we’re optimistic about the role native wildlife can play in restoring balance to our forests.

Interested in learning more?

Read the full article here .

Interested in bat habitat assessments, acoustic monitoring, or conservation planning that supports healthy bat populations on your property or project site? Contact Volant EcoServices to speak with our team about bat survey and conservation services across Ohio, Pennsylvania, Kentucky, and the eastern United States.