CEC Chats: Bats – To Survey or Not To Survey?

Listen to Ecological Sciences Principal Ryan Slack talk about what bat surveys are and how and why we conduct them. Ryan also explains the recent regulatory changes for the Northern long-eared, Indiana, and tricolored bats.

Podcast Transcript

Announcer: Welcome to CEC Explains — your deep dive into fascinating subjects from the worlds of engineering and the environment, brought to you by Civil & Environmental Consultants. And now, from our CEC studios around the nation, this is CEC Explains.

Ryan: Hi, I’m Ryan Slack. I work at Civil & Environmental Consultants. I’m a Principal here in the Indianapolis office, leading the Ecological group. Today, I’m going to talk about whether to survey or not to survey for bats. First, we’re going to talk about why we survey a little bit and that’s because several of the bats are endangered species at this point. One is the Indiana bat; it’s already endangered. The northern long-eared bat is listed as threatened and is proposed to be listed as endangered by the end of 2022, and the tricolored bat is not listed currently but is proposed to be listed by 2023. We’re going to call these three species the target species when we talk about surveying for bats during this talk.

All three of these species have different home ranges and differing life histories. So, those are things that go into where and why we would want to survey or not to survey. The home range of the Indiana bat is the smallest. It encompasses the Midwest and part of the South. The northern long-eared bat covers almost all of the eastern half of the United States and some of the northern states in the middle of the United States. And the tricolored bat pretty much ranges from the Rocky Mountain range east all the way to the east coast. The three species we’re focusing on today — Indiana bats, northern long-eared bats, and tricolored bats — are disappearing from the landscape for a number of reasons and different reasons. Indiana bats have been endangered since there was an Endangered Species Act of 1972. They were on a list before that. Indiana bats have always been endangered because of habitat loss and possibly pesticide use. We’re still not exactly sure why Indiana bats are endangered because they don’t seem to be recovering. With the things that come along with listing, helping their population, it has still only made it stabilize instead of continuing to drop.

Northern long-eared bats are currently listed as threatened on the Endangered Species Act. They are proposed to be listed as endangered, and the reason they’re listed at all is because of a disease called white-nose syndrome. Prior to white-nose syndrome being discovered in 2008, these bats were very common. The tricolored bats are in a similar boat; they are not listed currently but are now proposed to be listed as endangered for the same reason – white-nose syndrome. All of the bat species — all three target species that we are talking about today are also negatively impacted by wind energy. All bats are important, including the three listed species because they play an important role in controlling insect populations, especially agricultural pests and aquatic insects.

The reason we do bat surveys is typically driven by what’s called a federal nexus. The federal nexus is anytime that you have a federal connection to a project. Most of the time a federal nexus happens by either federal funding or a Waters of the U.S. permit, meaning you have some stream or wetland impacts that need to be permitted by the U.S. Army Corps of Engineers.

In general, the survey dates for the target species are May 15 to August 15 of each year. The reason we have trouble proposing on a project immediately when a client calls us is the approach that we need to take for that survey. It’s a very complicated, phased approach I’m going to try to simplify today.

It’s a phased approach that includes coordination with the U.S. Fish and Wildlife Service with habitat assessments, acoustic, mist netting, radio tracking, emergence, an outer-tier project which I’m not going to go into today, but that’s basically surveying in the outer tier of a known presence area of bats, and potential bat hibernacula surveys. These are all the different types of phases and surveys that we need to consider when looking at your project. As required by our federal permit, we propose a survey study plan that we coordinate with the Fish and Wildlife Service in regard to when to stop survey work at any point once an assumption or documentation of the targeted species occurs. Typically, negative presence/absence survey results are valid for a minimum of five years. U.S. Fish and Wildlife state-level coordination is important during the survey planning process. Surveys should only be conducted by a qualified biologist, which means a biologist that holds a recovery permit that authorizes the capture of bats for identification and handling of bats for measurements, photography, banding, and radio transmitter attachment.

So, let’s start into phases of the surveys and different steps. The first phase is the initial project screening, and in step one of phase one, we coordinate with the U.S. Fish and Wildlife Service. During this step, you may find that clearing trees in the winter months from October and November to the end of March when bats are hibernating underground may avoid having to conduct a survey for the target species. If this timing is not sufficient for your project, a survey becomes likely the only other option. Spring and fall use of hibernacula are the moments when bats go into hibernation or are coming out of hibernation. That’s typically at a cave or mine opening. When I refer to a known maternity colony or a roost, I’m typically referring to live or dead trees, sometimes snags, that bats have their young in and raise their young. It’s typically under the bark of a dead or alive tree.

If known target species occurrences, such as known ruse trees, capture locations, forging locations, or hibernacula, or no known target species — summer, spring, fall, winter occurrences — occur, but they’re located within a known maternity colony home range, or a spring or fall zone of known hibernacula, or a project is within the range of the target species, we proceed to step two of phase one. In step two, we conduct a habitat assessment, which means we do a desktop or a field-based assessment to basically try to figure out if there are three-inch or greater trees on the project or not. That’s the entirety of step two. If no trees such as these exist, there are no further presence/absence surveys recommended at that point. If we do have trees like that, we move on to step three of phase one, and we assess for adverse effects to the target species.

Adverse effects to the target species are typically whether or not you’re going to clear trees on your site, and if you’re going to clear trees on your site, we typically need to move on to phase two. And that’s the big question of whether to conduct step four, mist netting, or step five, acoustic surveys. There are pros and cons to both of these approaches. It’s up to the surveyor — us — to determine whether the habitat on site is appropriate for the survey method chosen. Acoustics at the phase two level of effort may be used as a core screening tool for conducting subsequent mist netting. If netting is chosen as the preferred presence/absence method and a target species is captured, then the surveyors can immediately move from phase two to phase four, radio tracking, and we’ll talk about phase four in a little while.

Step four, if we decide to go with mist netting, we conduct the netting according to Regional Recovery Unit-based protocols. The regional protocols are the highest level of effort, and the most costly are in the Northeast in the Appalachian recovery units. There are two different types of projects that we can be looking at for levels of effort. There’s a linear type of project and nonlinear projects that are what we call area based. There are differing levels of effort for those two types of projects. One is on a per kilometer basis, and one is done on a per acre basis. The per kilometer or per acre basis on a linear or non-linear project gives us the level of effort in the survey protocol.

And the same thing happens in the regional recovery units of the Midwest and the Ozarks. This is the lowest level of effort and the least costly, same thing – linear and nonlinear, per kilometer or per acre basis. Then, if we’re just looking for northern long-eared bats, this is new guidance since they know they’re about to list that species as endangered. They have a medium level of effort that’s somewhere between the Northeast and the Appalachia and the Midwest and the Ozarks that’s range-wide for northern long-eared bats. And if you’ll recall, they’re most of the east and a lot of the northern states out to the Rockies, same linear and nonlinear things.  So, we would conduct a mist net survey, and if no bats are captured, there would be no further survey needed. If we capture the target species, we need to proceed to phase four.

Or in phase two, the big question about which way to survey is step five, an acoustic survey. That’s an or to the mist netting. If we choose step five, we have the same types of protocols, they’re linear or non-linear, and they’re on a per acre or per kilometer basis. There’s no regional difference between any acoustic surveys. I’ll go over some pros and cons of acoustics and mist netting. Acoustics is typically less costly is the pro. The cons are results are not conclusive. They can be inaccurate. They do not produce how many bats you’re hearing or seeing. They do not tell you the gender of the species, and you cannot locate the roost, which are all pretty important things if you find the target species.

So, you’ve completed your acoustic survey. Step six is to conduct what’s called an automated acoustic analysis. And we’re looking at anything that’s a high frequency or what’s called a myotis call. Myotis is the genus of the three species — of the target species we’re looking for. If the target species’ presence is considered unlikely after the automated step six, then no further summer surveys are recommended. If the target species’ presence is considered likely, we proceed to step seven for qualitative ID, or at any point during any of this we can assume presence. So, you could assume presence of those bats at this point and not even move on to step seven. Step seven would be to conduct a qualitative analysis of the bat calls from the acoustic survey. We will review all files visually instead of in the automated way of step six. If no visual confirmation of the target species occurs, then no further summer surveys are needed, but if visual confirmation of the target species occur, you can assume presence of the species and coordinate with the Fish and Wildlife Service, or you can assume presence and proceed to phase three.

Phase three takes you back to conducting a mist net survey. As we said, mist net surveys are costlier than acoustics, and they’re especially costly if you have to then turn around and do a mist net survey after you’ve done acoustics. So, you complete the mist net survey in the way that we described earlier, and if no target species are captured, you coordinate with the Fish and Wildlife Service field office. If the target species are captured, you proceed to phase four.

Phase four is conducting radio tracking. So, you’ve captured the bat, and you can put a radio transmitter on it and track it to its roost. And phase five is conducting potential hibernacula surveys. That’s the last phase of a project, but it’s also a phase that’s important and most likely will need to be done in addition to everything else that we just described. And basically, that’s looking for holes in the ground like caves and mine portals.

In talking about whether or not to survey for bats, it’s important to understand why we would survey for the species. First of all, in summary, it’s because the bats are listed is the reason we’re going to do these surveys, but what I tried to get across in my talk is the importance of knowing the critical pathways we have to go through to figure out even what type of survey to do for your projects. I hope you were able to get out of the talk that a lot of this hinges on whether you have trees to be cleared or not on your projects because all three of these bat species live in trees in the summer. So, a combination of these three species being listed on the Endangered Species Act and having a federal nexus in either the form of a wetland or stream permit or federal funding. These are what will push you to need to consider whether to survey or not to survey. I’d like to thank you for taking the time to listen to my podcast.

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