Transcripts of Interviews
Pit Tagging Bats
Tim Carter, Ph.D
The Indiana bat is a federally endangered species. Currently, there are somewhere around 400,000 animals left. In the 1960's there were over 880,000. So, we've lost half of the population. The Indiana bat, as we know it, uses caves or mines during the winter months for hibernation. But then during the summer months they leave those caves or mines and they head out into the forest. When I started there were lots of holes in the natural history of the Indiana bat that we, just frankly, did not know. We didn't know much about where they foraged. We didn't know a whole lot about where they roost in the summertime. We don't know much about where they eat, those kinds of simple questions which you'd be surprised, everybody thinks we know a lot about all the wildlife and there's quite a few animals, especially the bats, that we know very little about. And it's very hard to manage a forest and to try to save this endangered species when you don't even know what it eats. And that's one of the things that's really difficult. You've got a nocturnal animal that flies exceptionally fast and covers large areas. They're very hard to monitor. They're very hard to try to census and get an idea of how many animals are we looking at. So even just figuring out how many Indiana bats there are here is very difficult. And that's one of the aspects of this project here in Atterbury that we've been working on, is trying to figure out a way to estimate populations.
We're experimenting with a relatively new technology called pit tags. It's a little tiny passive integrated transponder, it's what PIT tag stands for, that you inject under the skin. And then when you pass a reader over it, it works kind of like a bar code at a grocery store, when you pass the reader over it, it will activate that little chip which transmits a unique signal and you get a number back. And you can say okay this is bat number-- and you've got a big long ten digit number.
So there's potential for maybe finding these guys in the hibernacula and starting to figure out where their summer grounds are versus their winter grounds. There's potential for finding them during migration. There's lots of potential for this kind of marking technique, for long-term marking of these animals. And then hopefully once we've done that and accomplished that, we can really start to figure out what practices as land managers are helping and hurting these animals. Does it matter if we timber harvest? You know, was that really bad for the animals? And at this point, we're just kind of making guesses. We really don't know and it'd be really good to try to really pin that down and say yes this is good for them and no this is bad for them.
William Pearson Ph.D
What I like about cave fishes are their adaptations and how they changed through time to become adapted to the underground environment. They’re definitely case selected animals. Meaning that they live a long time. They don’t reproduce very much. They live in a fairly protected environment. They don’t have any natural predators. They are the top carnivore of their system. And so they’re sort of like the little tigers of the streams in caves. And they live to be, for sure, 30 years old and might live to be 60 or 70 years old. They are blind, of course, that doesn’t hurt them in the cave. Well, there are eye sockets in the skull that are still there. Apparently it’s hard to change the shape of your bones relative to the shape of your soft body parts through evolutionary time. But it may look like its regressing to us but the loss of a functioning organ like an eye is really not anything more than evolution to meet a different environment. And so it’s really just evolution in a different direction.
Levels of Cave Adaptation
Caves are really good places to study evolutionary biology because they are limited environments. There are several different levels of cave adaptation, is how we describe in cave ecology. And one level, for example, might be a trogloxene that will go and use the cave for part of the time but then come back out to the surface. It can’t spend its entire life cycle in a cave. And then the next level up of cave adaptation is a troglophile. And troglophiles can spend their whole life in a cave, for example a cave salamander. But they don’t need to spend their life in a cave. In other words, they could also live under rotting logs or under rocks on the surface, just in places that are dark and humid and cool. And then of course, the highest level of cave adaptation is troglobite. And troglobites are fully cave adapted organisms. They cannot survive outside of the cave, they’re obligatory to be in the cave. And those are the ones that we think of as the typical, really extreme cave livers that have, a lot of times, no eyes left at all and no pigment and they tend to have these really slowed down life history strategies.
Hoosier National Forest
The Hoosier National Forest is in southern Indiana. Ah, it’s probably one of the smallest national forests in the United States. And it’s just in a huge karst region. So you had tons of sink holes. You have lots of caves and sinking streams. And cave environments are completely dependent on sources that are coming in from the surface for all the organisms that live in there.
One of our missions is to maintain viable populations of native species. And caves are certainly linked to that mission There are lots of species in caves that we know about. Certainly there are a lot that we don’t know about.
Bats are mammals, they have hair, feed their young milk but they're the only mammals that fly, that's what distinguishes them from everything else. There are some bats going way back in the fossil record but the earliest fossil bats are well-formed bats. So, from the fossil record we really can't tell anything about their evolution. However, from their structure, most people would think that they're probably from the shrew type ancestry.
It's the colonial bats that are in caves. Exactly why they hang upside down, we're not quite sure. This is one of the things that gets them up high, hanging upside down allows them to just drop and then fly out. Also, if there's something below them, a predator below them, they're in a position so that they can see something below them. And they wake up very fast, most hibernators wake up slowly.
In the fall, bats come into these cave and mine entrances in large numbers and we say they swarm. They come in and out at night and we think mostly what they do is pick up mates. They may also be on migratory routes.
We've been studying these populations for a long time, trying to determine where they come from, where they go, when they come, when they go, that sort of thing. And at what time of year, are there differences between the species? And we know really very little about them. Just recently we've been able to put radios on them. We follow these little radios and track the bats in flight to see where they're feeding. They eat loads and loads of farm pests. The Big Brown bat, about 80% of its food is a farm pest insects, that's one of the reasons that they're so valuable to us. Another thing, they are about the only predator around here that feeds on night flying insects. So this helps keep the balance of nature. Something's got to feed on those things and it happens to be bats.
Some of the bats make their summer colonies under sloughing bark of pretty much dead trees. And so, there are six species that have to have trees, have to have at least limited forest. Well, the biggest thing we can do for bats and for most other species is to set aside more land. A little piece of forest will do fine. Most bats don't feed too much way back in the forest, many of them feed along the edge of forests. We're losing about 101,000 acres per year to development, a lot of it is forest. We've got to stop doing that.Bats live a long, long time. The record that I know of in the Little Brown bat is 34 years. That's just phenomenal for an animal that size. A mouse or a shrew will live less than a year lots of times. Every species of bat that we have has a different life history, quite major differences. Most of them, all but three, kind of all look alike. One is red, one is kind of hoary color, it's called the Hoary bat, it looks like it's got hoar frost on it. And the third is the Silver Haired bat which is really a dark choc lately brown, almost black. The rest are pretty much brown bats. There are some differences between some of them in the teeth, there are some small differences in the ear, the length of the ears. No other mammal flies around, no other animal has echo-location and they are just plain darn interesting animals.
The majority of life on earth on the surface is driven by sunlight energy. And obviously in a cave you don't have that. So you lack one of the big energy drivers of an ecosystem.
So it becomes a very starved environment. For example if you took a grain of sugar and broke it up into a thousand parts and took one of those parts and put it in a liter of water, that's about how much energy is available for microorganisms in these environments.
When people think about a starved environment, they might think of something like the desert where there are very few species because there's just not enough energy to support the growth or life of these microorganisms. And that's what we expected to find in caves. But what we see is that that's true when you go into a system, as you get further away from the energy input at the entrance, you see a drop off in the number of species. But there is a threshold when all of a sudden you start to see the number of species and the diversity increase. And we think what's happening in these cave systems is that they've become so starved that there's a mutualism and that everybody kind of works together. And when you have them all work together, one organism brings in the energy, which drives another organism to bring in the nutrients which allows another organism to create the building blocks and the energy and the sugar for other organisms to grow. So you have this mutualistic interaction. And as a result, you have to have many species working together within the ecosystem to promote this, this life under extreme starvation. So we think that, you know, you've gone passed that analogy with the desert, you're way, way many orders of magnitude more starved than that. And when you get down to that extremely low level, you actually see the diversity start to rise again.
Microbes are so small that they can actually swim over time through the rock itself. When you think about, you know, a crawfish in a cave in Indiana, it may be confined to that cave its entire life because it can't move. Where the microbes can, you know, worm their way through a cave and pop up in another cave somewhere else because over geologic time, they've traversed that rock.
The other thing that microbes do is they're light enough they can actually float in air currents. So when a cave breathes out and blows air into the environment, the microbes can you know float around in the air and then get sucked into a cave somewhere else and then they flourish in that cave.
So every environment that we look at the microorganisms are the basis of all the ecosystems that form around them. So in caves, you know, they're responsible for mobilizing a lot of nutrients that you find in cave environments. When detritus gets washed in by floods, they're breaking it down and releasing energy for it. So they actually form the basis for nearly all the ecosystems that you will find in a cave.
Blind White Crayfish
Horton Hobbs, Ph.D
Crayfish are an old group. They've been around a long time. And one that has, pretty much, no eyes is an obligate, highly specialized organism. There are around 41, 42 species of blind, white crayfishes. They may look very spindly and very dainty and, and weak, but in reality these things are pretty tough. Out here the local streams will have crayfishes that live two and a half to three years maximum, that's their life history. But blind crayfishes kick it up to 50, 60, 70 years, or more. I think it's part of the adaptations that, you know, we think of some of these very elaborate traits that we begin to see appearing in obligate organisms, some of which include longevity. But loss of eyes, loss of pigments, those are really sort of characteristic things that occur across these major groups of organisms. So it's in response to moving underground into that type of environment.
To see an organism that has given up so much to live in this environment and altered everything that we think of as a classic surface form to show some of these derived traits that they have, that are so different from the surface things. And how they modify their life history. It's sort of this channeling of the speleo-environment that you end up producing organisms that have so many of these similar sorts of traits and I think a lot of it can be certainly traced back to the energetic problem.
You're looking at an environment that has limited energy. They have to make a little bit of food go a long way and anything organic. And so what we're talking about primarily in these caves would be leaves and sticks and acorns and walnuts and things like that. And they're getting something from eating that vegetative material, but where they're really gaining their energetic kick is from the microbial community. And it's sort of like the analogy of having a saltine cracker and you eat that and you get a little something, it tastes okay, and you get a little kick from it. But if you take a big slab of peanut butter and you go across it, and eat it then you're really getting the energy. You're really getting something for the effort. And in essence that's what happens. The microbial community that begins to coat and break down organic materials, that's the peanut butter and that's where they're getting the, the real kick.
Cave and Karst Ecology
Julian Lewis , Ph.D
The southern Indiana area is interesting from a cave biology standpoint because of the affect of the Ice Age glaciers. With each wave of glaciations you had bands of fauna that both came from the north and came from the tops of the Appalachian Mountains and dispersed widely over the eastern United States. Indiana is right on the very edge of the Pleistocene glaciations. At the time that the glaciers receded, these animals had a crisis to deal with. They had to do something to find a suitable habitat. One possibility is to go back to a high elevation. Another possibility is to migrate along with the glaciers as they receded. Another possibility was to find a cool moist habitat in the area to which they had come. And that in Indiana would be a cave.
The Hoosier National Forest takes in a broad swath of the Indiana karst. It has small areas where you'll have a band of caves formed in limestone separated by non-limestone ridges. And you have intense speciation occurring in these karst islands. And so you get a very large number of endemic species. The entire cave systems here and its fauna is a laboratory of evolution.
When you look at caves and karst and ground water. What you have is in fact not just cave that's, you know, a tube if you will that has bugs and worms and bats and salamanders and fish and things in it. It is a small cross section of a much larger environment. The trees that live on the surface are as much a part of the cave environment as the cave itself.
Karst in Indiana is under a full force attack, as humans encroach more and more on the natural environment. There's still a wide held belief that you can throw your pesticide in the sinkhole and that's the last you'll see of it. That's not the case. It will come back to bite you one way or another.
Pseudoscorpions aren't good to eat. They don't cost anything. No one will ever get rich on finding pseudoscorpions, but they're a small part of a much larger animal spectrum that, when you pull on any part of a food web that the whole thing's likely to go kaflooy.It's difficult to make a case for the importance of a springtail. But it's not difficult to make a case for the land management that goes into keeping the karst environment intact. And the indicator of that is; are the bugs and worms intact?