For my last installment of this theme, I’m going to tell you more about the bat work that we are doing in Yellowstone. There is more than the acoustic project in the Maple Fire and Buffalo Fire burn areas. Day and night, there is bat work to be done — from summer acoustic stations to bat capture!
Eight summer acoustic stations are scattered across northern Yellowstone, intently listening for these amazing creatures. The stations are comprised of an acoustic recorder, microphone, box with deep cycle battery, solar panel, and the various cables to connect everything together. If you recall, acoustic stations listen for the high frequency sounds that bats make to communicate with each other, navigate their environment, and forage for insects. With these recorded sounds, we can identify and confirm the presence of bat species within range of the station. Additionally, we can infer what the bats are doing — such as pursuing prey or just flying through the area. However, we cannot determine abundance from this data. For all we know, a bat may simply be flying past the station multiple times. We certainly should not count these detections as multiple individuals. Maintaining these stations is quite easy. Most of the time, a short hike is all that is needed to swap memory cards. Less often, we may have to repair a station that was damaged or replace a battery. Over time, we are recording the natural history of bat presence and activity in northern Yellowstone.
In addition to acoustic stations, we also perform emergence counts and have reason to go into bat roosts. An emergence count is exactly what it sounds like. We count bats coming out of their daytime roosts. The roosts that we focus on are certain buildings in the park. In the evening, just before twilight, we position ourselves around the building and wait for the bats to come out. We use tally counters to aid our data collection. When the bats are no longer exiting, we wait a little while longer before concluding the count. As a daytime activity, we sometimes have reason to go inside an attic where these bats are roosting. We always wear a respirator before entering these enclosed areas. While inside, we may take a count of the bats we see, look for deceased individuals, or preform maintenance on equipment.
Although we gather interesting and important data from the acoustic stations, in my opinion, capturing a bat is much more interesting. First of all, it happens at night. At least for me, I always feel like I’m getting away with something that I shouldn’t be doing. And second, you never know what you will find in the net. I’ve seen birds and squirrels and the occasional technician stuck in the net and I’ve heard of cars getting netted too. Imagine that! Sporadically, you get the cops called on you. Oh, that’s another story. That didn’t happen in Yellowstone. The best part, however, is getting to hold and work with a bat!
Bat capture in Yellowstone is very similar to capture elsewhere. We catch these flying mammals in the traditional way of mist netting. Before sundown, we deploy our nets in a strategic fashion. We try to utilize water bodies were bats quench their thirst after emerging from their daytime roost. Other times, we take advantage of flyways, such as old logging roads, that bats use to travel from one place to another. The reason is that bats are presumably concentrated in these locations and this increases our chance of success. To further up our odds, we deploy multiple nets at the location that we are netting.
Most of bat capture involves sitting a long time in the dark. Almost always, we bring chairs to make ourselves more comfortable. The time between net checks is often spent talking, reading, snacking, napping, and looking at our phones. About every fifteen minutes, we stop whatever we were doing, turn on our headlamps, and venture into the dark to check the nets. Most times, the nets are empty. On an unsuccessful night, the repetitiveness of these checks gets daunting. Nonetheless, we never know when something will be there. We don’t want a bat struggling in the net for too long.
The most exciting netting night at Yellowstone was the roost capture at Buffalo Ranch. Prior to this event, I never saw so many bats in a net. Our triple-high was positioned in front of the vent where the bats emerge. I was amazed by the agility of the little brown bat – most of them avoided the trap. Nonetheless, we managed to capture nearly sixty bats that night.
No matter how many times you do it, seeing a bat in the net is exciting! With gloved hands, we carefully extract the bat from the net. Sometimes this task is quick and easy; other times, it’s a struggle when the bat is tangled. Once removed, we place the individual in a material bag that can be tied closed. If we catch multiple bats, we string a rope between two trees and secure these occupied bags to the rope by a clothes pin. Placing a bat in a bag reduces stress on the individual and calms them down.
How we work up a bat depends on our protocols. These protocols may vary depending on the project. Almost always, the bats are weighed, sexed, have their forelimbs measured, and are examined for reproductive condition, life stage, and wing damage. Many times, a tissue sample is collected. A biopsy punch is used to procure a small sample from the thin membrane that makes a bat’s wing. In our case, we take one wing punch from both wings and the samples are used for genetic testing. This summer, we implanted PIT tags under the skin of female little brown bats. This procedure was done as a part of a graduate student’s research to determine how the bats are using summer roosts in Yellowstone. Sometimes we are interested in tracking bats and we will attach a transmitter on an individual’s back with surgical cement. These transmitters are usually only active for two week and about that time, the cement degrades and the transmitter falls off. Interestingly, back east, every bat got a wing band but this isn’t so in Yellowstone. Wing bands allow us to identify recaptured individuals. Through all of these procedures, the bat’s health is our priority over anything else.
Perhaps the most rewarding aspect of capture is releasing the bat. I’m continually amazed when I open my hand and let the bat take flight. They are the only mammals that are capable of true flight!
Some of the bats I worked with in Yellowstone
Towards the end of the night, bat activity wanes and our possibility of another capture is slim. At this time, we take down the nets, pack up our gear, and head out. This part doesn’t take long. However, depending on the location of the netting site, we may have a decent hike back to the truck. Once home, some of us stay up for a while and others, like me, try to get to sleep as quickly as possible. As a rule, we give ourselves ten hours before reporting back to work.
I hope that you enjoyed hearing about the work that I do in Yellowstone. Of course, if you have any questions or would like me to elaborate on something, just ask!