USGS Outstanding in the Field, Episode 10, Bats
Welcome to the USGS Ecosystems Mission Area Outstanding in the Field podcast series that tells stories about our science, our adventures, and our efforts to better understand fish and wildlife and the ecosystems that support them. In this episode we head to southern Florida to learn about one of North America’s most misunderstood - yet threatened - mammals: bats.
[Intro music fades out]
Narrator: Welcome, and thanks for listening to another episode of Outstanding in the Field, the U.S. Geological Survey’s podcast series produced by the Ecosystems Mission Area. This series highlights our fun, fascinating, and policy-informing fieldwork studying species and ecosystems across the country. I’m Marisa Lubeck.
[sounds of walking in the forest.]
Narrator: Today, we head to southern Florida to learn about one of North America’s most misunderstood - yet threatened - mammals: bats. Just as the movie Jaws terrified generations of beachgoers, Bram Stoker’s novel Dracula solidified the public’s perception of bats as dangerous creatures of the night that only wanted to drink blood. They may be night-dwelling animals, but bats are better viewed as invaluable members of the animal kingdom, and ecological and economic assets world-wide. These winged mammals help pollinate and disperse seeds and act as pest control, feeding on problematic insects that would otherwise destroy our crops. In fact, the USGS contributed to a study showing that insect-eating bats provide pest-control services that save the U.S. agriculture industry over $3.7 billion per year. That’s billion, with a “b!”
However, many bat populations in North America are threatened by habitat loss, degraded water quality, and disease. USGS scientists, like Dr. Laura D’Acunto, an ecologist at the USGS Wetland and Aquatic Research Center, study bats to better understand what they need to survive and flourish, as well as their ecological value to humans.
Laura: When I held a bat in my hand for the first time, I basically fell in love. And from that moment, it snowballed, into me pursuing any kind of research opportunity with bats that I could.
Narrator: Laura is leading an effort to guide the management and recovery of the most endangered bat species in Florida, the Florida Bonneted Bat. Their research is critical because the Florida bonneted bat, like so many other bat species, is at risk due to a number of threats.
Laura: Bats across the world are mainly threatened from habitat fragmentation or habitat destruction so either their foraging grounds are disturbed or degradaded or their roosting habitat, so where they sleep at night, could be degradaded as well.
Narrator: Diseases like white nose syndrome have devastated wild bat populations. Degraded water quality and an increasing presence of harmful chemicals in their environments are also impacting bats throughout North America.
Laura: Pollution from either pesticides or um other chemicals that get into the water um can really impact them because they’re insect eaters and so something called bioaccumulation happens where insects will get exposed to lots of chemicals um and then the bats will eat those insects full of chemicals and that impacts their health.
Narrator: Colonies of insect eating bats, like the Florida bonneted bat, can consume hundreds of thousands of insects over the course of a year, many of which are considered crop and forest pests. Decreasing bat populations in southern Florida could have severe impacts to the local economy, where agriculture plays a large role. The Florida bonneted bat has experienced significant population declines and is listed under the Endangered Species Act as federally endangered. It’s considered one of North America’s most endangered mammals.
Laura: When a species gets listed as federally endangered um a lot of things get triggered and start happening. Um one of those things is called a recovery plan.
Narrator: A recovery plan documents the current status, threats, and suggested methods for recovering a species to a healthy and stable size. The U.S. Fish and Wildlife Service is responsible for implementing the Endangered Species Act, but they work with partners, including the USGS, to ensure effective management actions are taken to conserve species and their habitat. Successful recovery plans can lead to an endangered species being downlisted or even removed from the Endangered Species Act. However, the recovery of a species can be a complicated process.
Laura: The issue with the Florida bonneted bat is that we just we don't have a lot of information um on their populations, um on their habitat requirements, on even um their home range or their population range in south Florida. Um so this project with the USGS partnering with the U.S. Fish and Wildlife Service is trying to gather up all the data that we have on Florida bonneted bats um and organizing it in a way that can facilitate um us coming up with some more concrete plans um for a recovery plan of the species.
Narrator: The Florida bonneted bat population is thought to be limited in range and small in size, making Laura’s efforts to consolidate all of the state’s data on the protected species even more important. The species is only found in a few southern counties in Florida, and though many bat species either hibernate or migrate with changing seasons, some, such as the Florida Bonneted Bat, do neither. While some bat populations around the world can include thousands of bats, colonies of the Florida bonneted bat are much smaller. Sometimes only 20 to 40 individuals find shelter in abandoned tree cavities, barrel tile roofs, or artificial bat houses. Like most bats, the Florida bonneted bat is nocturnal, only emerging at night to feed, and uses a strategy called echolocation to help move around in the dark.
Laura: So most bats in the world and pretty much all bats in North America are echolocating bats which means they emit these high frequency noises to help them locate and navigate through their environment. Um and so those sounds that they emit, most are too high for humans to hear, will bounce off of objects and allow them to identify the texture and the shape of their surroundings and allow them to move through the world. Um, and that doesn’t mean that their eyesight is poor. Their eyesight is actually pretty good. It’s just easier to echolocate um as a nocturnal mammal.
[Florida bonneted bat call.]
Narrator: The Florida bonneted bat happens to have a low echolocation frequency which makes it audible to most humans, and its body size and shape allow it to fly high and fast. These qualities make for interesting, but sometimes challenging, fieldwork. Roxanne Pourshoushtari, a contractor to the USGS and member of Laura’s research team, explains:
Roxanne: You're gonna have to set up special equipment, because obviously its difficult to catch them. This is their element.
[Night sounds with bat wings flapping overlay narration]
Narrator: The team sets up a series of tall nets called mist nets in strategic spots along wooded corridors before sunset, and waits for a bat to accidentally fly into one during its nightly commute. If a bat is caught, the team members wear thick, clean gloves to quickly and gently untangle the bat from the net. They then record information about the individual animal before it’s safely released.
Roxanne: And then you take certain measurements when you have the bat in hand, so this is different morphometrics such as weight or forearm length, different measurements of their physical features, as well as looking at their sex, their reproductive status, um and their age. You might take a small tissue sample, um from the wing membrane or you might tag the bats with a with a pit tag which is similar to a microchip for dogs and cats.
Narrator: Passive Integrated Transponders, or PIT tags, are one way researchers can identify an individual animal if it’s caught in the future, since it’s difficult to distinguish individual bats by external physical features. This information can help researchers better understand how bat populations change over time, which is critical information for recovery plans. Capturing the bats isn’t the only way to collect data, though. USGS researchers also collect data on the roosting habitat or bats’ echolocation signals.
Laura: We have this equipment called a bat detector and what is does is it can record high frequency noise from anything. And so, we you know go out to areas where we think the bats might be, and you set out the machine and the microphone and you leave it there um for either a night or several nights.
Narrator: The audio files collected in the field are downloaded to a software program which displays the bat calls visually in a form called spectrogram signatures. Just as a heart monitor graph shows the visualization of a heartbeat, spectrogram signatures visualize the frequency and duration of bat calls, with higher frequencies resulting in higher peaks on the Y axis of the graph and time tracked on the X axis.
[Scientists speaking with spectrogram audio in the background.]
Laura: Most echolocating bats have very specific spectrogram signatures so the shape of the call sometimes they look like little hockey sticks um and so that particular shape is unique to a particular species of bat um and some bats look similar and so you gotta do some measuring of the calls like the maximum frequency and the duration and looking at all those different parameters um but eventually you can get good enough at it that you can look at a spectrogram of a bat call and say "I know what species that is."
Roxanne: Florida bonneted bats are actually kind of neat in a way that it doesn’t really take as much practice to identify them over others because they are so much lower in frequency than other bats, because they can get below that 20 kilohertz frequency that is audible to human beings, so that helps make it easier to identify Florida bonneted bats with some confidence.
Narrator: Using this passive acoustic monitoring method can generate up to a terabyte of data, which is roughly 25,000 audio files or the equivalent of 25,000 photos on a modern smart phone. All of these files need to be categorized and identified, and that’s where Laura’s team comes in.
Laura: The USGS is really full of great statistical and software and data analysis people. It's known for scientists that can deal with big data problems with complicated data problems um and help get answers for their partners in other agencies.
Narrator: By collecting, organizing, and analyzing data on the Florida bonneted bat, Laura and the team are ensuring the U.S. Fish and Wildlife Service and other partners have the information they need to make effective decisions to conserve the species and its required habitat. Laura’s research efforts could help to refine the population range of the species or add to what we know about its habitat needs. This could help inform laws meant to protect the species during its birthing season, for example. Most bats give birth to only one or two babies, called pups, during summer months, and development on their habitat during this time is restricted. But the Florida bonneted bat consistently has babies outside of the normal range, which means development could potentially harm new pups.
Laura: Getting this data organized into a database will help the Fish and Wildlife Service do some higher level modeling in order to answer some of the questions.
Narrator: Want to help? There are plenty of things that you can do as an individual to help bats in your area.
Laura: It's always important to learn about the wildlife that exists in your backyard and listening to this podcast is probably the first start so great job, and if you want to do something you know more tangible, you could invest in bat boxes for your property, um there are different um colors and and different ways of setting them up that are specific to to different species. You could also plant native trees and other plants in your on your property um to attract the insects that bats like to eat.
Roxanne: Not using harmful chemicals on your property is also going to be huge. That bioaccumulation really does a lot of damage so trying to go for more natural things that you put into your property is also really important.
Narrator: While our USGS scientists are well-trained and equipped to safely handle wild bats, like all wildlife, it’s better to look, rather than touch, especially if, in the rare circumstance, you happen to come across one during the day.
Laura: If they’re acting strange by not you know hiding during the day, um and they’re out in the middle of the day, um on the ground, not looking too great, it’s probably best to leave it alone. Um if you’re really concerned for the animal’s wellbeing, you can call an animal control or a rehabber, a wildlife rehabber, um but you should not touch it or go near it yourself.
Roxanne: it is very important to protect them, plus they're awesome, so why not protect them?
[Narration with bat calls and ending music.]
Narrator: We couldn’t agree more.
For more information about USGS involvement in Florida bonneted bat research, please visit www.usgs.gov/warc.
This podcast is a product of the U.S. Geological Survey, Department of the Interior. Podcast artwork is by Jeffrey Kemp and our theme music is by the USGS’ own Marty Fitzpatrick. The Florida bonneted bat audio clips were provided by ZooMiami and the Miami Bat Lab. Special thanks goes to Dr. Laura D’Acunto and Roxanne Pourshoushtari from the USGS Wetland and Aquatic Research Center and the rest of the Outstanding in the Field podcast team including producer Suzanna Soileau. I’m Marisa Lubeck, thanks for listening.