#65: Winged Wonders: Uncovering the Secrets of Bats with Wildlife Ecologist Dr. Dave Johnston – Nature's Archive
Summary
Are you ready to uncover the mysterious world of bats? Join us on an exciting journey as we explore the secrets of these enigmatic creatures with renowned wildlife ecologist and bat expert, Dr. Dave Johnston. Hailing all the way from Costa Rica, Dr. Johnston will guide us through the incredible diversity of bats, from tiny dragonfly-sized species to those with wingspans as large as eagles.
But that’s just the beginning! We’ll discover astonishing bat behaviors, from echolocation to singing bats to altruistic behavior. With so many different species filling various niches worldwide, we’ll learn about the challenges bats face, from urbanization to wind turbines and the devastating white-nose syndrome. So, buckle up and get ready to unravel the mysteries of these extraordinary creatures on this captivating episode with Dr. Dave Johnston.
You can find some of Dr. Johnston’s work on research gate.
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Links To Topics Discussed
People and Organizations
Bat Conservation International
Brock Fenton – Bat Biologist
High frequency hearing test – the YouTube video I mentioned
North American Society for Bat Research (nasbr.org)
Books and Other Things
Note: links to books are affiliate links
Bats of British Columbia by Cori Lausen, Mark Brigham, et al. 2022
A Miscellany of Bats. M. Brock Fenton and Jens Rydell. 2023.
Credits
Emily Smith provided editing assistance for this episode.
The following music was used for this media project:
Music: Spellbound by Brian Holtz Music
Free download: https://filmmusic.io/song/9616-spellbound
License (CC BY 4.0): https://filmmusic.io/standard-license
Artist website: https://brianholtzmusic.com
Transcript
Transcripts are automatically created, and are about 95% accurate. Apologies for any errors.
[00:00:00] Michael Hawk: Dr. Johnston, thank you so much for joining me today, all the way from Costa Rica.
[00:00:04] Dave Johnston: It’s my pleasure, Michael. It’s this is a great place. There are a lot of interesting biologists here, as well as other scientists. But I’m happy to be here .
[00:00:14] Michael Hawk: Yeah, this is a discussion long in the making. I’ve been wanting to do a well as ep of a dive as we can do in an hour or so, , but, a ep dive into bats and, you’ve come highly recommend. Really excited about where this conversation’s gonna go today. So, Before we get full on into bats maybe you can tell me a little bit about, where you grew up and how you got connected to nature in the first place.
[00:00:41] Dave Johnston: I was lucky enough to grow up along a creek. This is Saratoga Creek, and we lived right at what I call the angle of repose. That’s where a mountain stops eroding and starts a valley. so we had plants and animals from the upper watershed and also the lower watershed. I’m saying that because there is a lot of diversity there and among many other things, I saw a mountain lion in our creek when I was a youngster, as well as we had lots of red-legged frogs and things that you just don’t see now.
[00:01:19] That gave me a playground 24 7. I love the creek. I think I was about eight or nine years old when I became a member of the Youth Science Institute.
[00:01:31] My mentor was Larry Moitozo, wonderful person, and I was so enriched by his teachings and his thinking
[00:01:42] Michael Hawk: And for those who are maybe not familiar with Saratoga Creek and Ysi and these things, these are in the South Bay of the San Francisco Bay area of California. Having, seeing things like mountain lions and red-legged frogs, which are now, highly endangered, at the time did you recognize these as special creatures or was it oh, just another day on Saratoga.
[00:02:06] Dave Johnston: the red-legged frogs, the Western Pond Turtles. Those are just another day on Saratoga Creek, the mountain lion. Anytime you see a mountain lion, it’s special. Normally they see you first. I think of the four or five mountain lions that I’ve seen up close, every one of them saw me first. But to stair one in the eye, even for a moment, is special anytime you get to do that.
[00:02:38] But I’ve watched both as a youngster and then as an adult, I’ve watched enormous changes in our biological flo and fauna. It’s disturbing and it’s hard to see within a short span of time. But as those generations stack up, no one generation understands the. Magnitu of the changes that are going on really all over the world.
[00:03:08] And when I think of insects as a kid, we used to have huge polyphemus moths. There were so many insects, so many butterflies in moths , and now there’s, a parity of insects. It’s a strange phenomenon that is occurring again all around the world. And there’s a lot of different layers of this. One is just urbanization, which I consider a serious threat to a lot of sensitive species, and we can get into a little bit later.
[00:03:41] Michael Hawk: Yeah, and I don’t know if you knew this, and my listeners have probably heard me talk about this, but I recently started a new conservation organization called Jumpstart Nature, and the primary goal, Is to empower people to make a difference for nature. But in orderto do that, people need to understand what is happening in front of us and educating about things like shifting baseline syndrome that you talked about, this multi-generational loss of information.
[00:04:05] And then the clines in these foundational species, foundational insects that so many things rely on, including bats as we’ll talk about, like these are core tenets to what we’re gonna be doing with Jumpstart Nature.
[00:04:16] Dave Johnston: That’s great. I’m glad to hear that. And glad you mentioned shifting baseline syndrome because it is so pervasive. A and people are unaware. There is actually a population of Jaguars in California that probably reached up to the o Monterey County. And that area down around the transverse range.
[00:04:39] But, I think we’ve totally lost sight of that and many mammals.
[00:04:44] Michael Hawk: I didn’t know that. I didn’t know there used to be Jaguars here. So that’s something I’ll have to go look into now. So let’s transition then to how did you get connected to bats then?
[00:04:54] Dave Johnston: I think the first bat that I took notice of was in South Central California, and I was a stunt at Cal Poly San Los Obispo. My professor was Aaron Roost, who’s absolutely wonderful , inspiring, and I owe him the reason that I’m primarily a mammologist. Anyway, I was climbing up some cliffs in Avala beach found a cave, went into that cave, and got up pretty close to a California Myotis, but it was so tiny.
[00:05:28] When I started reading about bats, then I thought, wow, this bat can do so many things in total darkness. But it wasn’t until many years later after I had a whole career with Youth Science Institute as their director for about 16 years that I took a one day workshop from Brock Fenton, who is certainly one of the world’s foremost bat biologist he gave a one day seminar in beautiful downtown Burbank, California of all places. But he was so enthusiastic and inspiring that I took a workshop from him the following summer. Applied to a PhD program in Toronto and the rest is history.
[00:06:19] Michael Hawk: You touched on this tiny California myotis that you found in the cliff, and maybe for perspective for the listeners, you said it’s tiny and I saw one of these one time, at least I believe it’s what it was, and it didn’t look much bigger to me than say, one of the very large dragon flies. Like perhaps about that size.
[00:06:38] Is that about right?
[00:06:39] Dave Johnston: That’s about right there. If you can imagine your little finger is gonna make up like about maybe one and a half digits or one digit of your little finger making up the body, and then a wing that is no greater than the distance of your palm hand opened up. And they weigh about three and a half grams.
[00:07:05] They are really tiny. They’re not the smallest bat in the world. The smallest bat in the world is actually the Bumblebee bat, and it’s about two grams. I think it was the mid seventies that they were actually discovered by science and only after someone who had noticed moths apparently, at least as the story as I’ve heard it, one of these moths got hit by a vehicle in Capmandu, and when they looked down, it was not a moth, but a bat.
[00:07:39] And so some of the smallest bats then look for all the world like hawkmoth or something like that.
[00:07:46] Michael Hawk: That’s pretty crazy to think about and perhaps a good lead in to let’s talk about bats in general a little bit. How would you scribe a bat to someone who is perhaps totally ignorant of what a bat is?
[00:07:59] Dave Johnston: First of all, it’s a mammal, and some people don’t realize that bats are mammals. They think well, they’re kind of weird birds, but no, they are mammals. They have mammary glands. They give live birth to young, and they have hair. But bats are very special mammals. They’ve evolved for probably the last 60 plus million years ago.
[00:08:21] And so just at the end of the dinosaur era bats were evolving. In fact, there are a few bat fossils that are very much like today’s bats. Remarkably. So for all these years, bats have had a chance to go through what we call adaptive radiation, where they fill many habitats and many niches Uniquely bats are the only mammals that have powered flight.
[00:08:50] A few other mammals, including some of the flying squirrels can gli very efficiently, but they don’t have powered lift. Another, not completely unique. The fact about bats is that many of them echolocate to communicate, to find their food and to orient that is, find their way through space.
[00:09:12] Some people say navigate, it’s not necessarily navigation for a long period, but just to orient and navigate through space. They have some very unique prey food among mammals. So like many of the other mammals, they eat a lot of insects, but they also eat fruit. In the case of the mega chiroptera or the flying foxes, many of them feed on nectar.
[00:09:42] They feed on pollen. Some of the phylo stomoths , that is the bats that. Have leaf noses that have gone through this incredible adaptive radiation here in Central America. In addition to eating fruit and nectar, they also eat pollen and there are three species that drink blood. They are completely obligates to getting a blood meal and they are extremely specialized.
[00:10:11] Their diversity is just amazing. We can talk about that as our story develops here. But I would say that many people have a lot of misconceptions falsehoods about bats, and that still worries me.
[00:10:26] Michael Hawk: Yeah, I want to vote some time to some of the myths and myth busting, so to speak before we wrap up today for.
[00:10:34] Dave Johnston: I wanna just mention their name because in most languages they’re considered some kind of mouse. It’s a flower mouse or flying mouse. In German, it’s murciélago or mouse of the sky. In Spanish, and I probably can’t pronounce this right, but chauve souris in French, which means bald mouse. So the word bats is unique among languages.
[00:11:05] It’s one of the very few languages that doesn’t inclu the word mouse in a name for bats. But that right away, you can see just looking at how various cultures call bat. By name right away. There’s a lot of kind of misinformation there. They are not related to ronts.
[00:11:26] Michael Hawk: Yeah, when you see one up close they’re definitely very unique, A lot of specialized anatomy. Those wings that you were talking about the myotis earlier and how long its wings were compared to its body size now that’s fairly typical. Correct. They have generally long unfurling wings.
[00:11:43] Dave Johnston: Yes. And there’s a wing ratio or flight ratio that varies according to the species and family for that matter. So on one hand you’ll get something like a pallid bat, which can hover I’ve seen them fly actually backwards, which is remarkable. That particular bat spends a lot of time on the ground eating crickets and so on.
[00:12:10] But it has a very. wide or very tall wing compared to its width, in other words it has a low wing re ratio so that, it’s almost as tall as it is wi, it’s slow, extremely maneuverable. And on the other end, you have something like a Mexican free tailed bat, a subspecies of our Brazilian free tailed bat, and they have very high wing ratios.
[00:12:38] In other words, they’re very wi and narrow. And here you have the fighter jet, right really fast. Probably an excessive 60 miles an hour, yet it doesn’t do very well on the ground. It can crawl pretty fast or pretty well, but it, once it’s ground, it takes a while for. Members of the free tailed bat, the Molossids to take off the ground.
[00:13:06] One very unique thing about these wings is that they retain their elasticity after they’re damaged. And when I was at Youth Science Institute one of the volunteers brought a bat in with a torn wing.
[00:13:22] a tear Almost a centimeter across . So it ma a hole. And we took it in, we fed it. and I would, I advise people do not touch bats or any wild animal because there is a risk of rabies. But nonetheless, having been vaccinated for rabies before, and by this time I was already studying bats anyway, my point being that the wing healed in three or four days.
[00:13:51] This tear had closed up and it was amazing. So there is virtually no scar tissue involved in the repair of that wing. And now since then, rmatologist have been studying this to try and figure out, okay, what can we learn about, skin that can repair itself to the point where it still retains its elasticity,
[00:14:12] Michael Hawk: So you didn’t have to do anything for that bat. It just, it healed.
[00:14:17] Dave Johnston: it healed on its own.
[00:14:18] Michael Hawk: So as we continue to set some guardrails, so to speak, around the diversity of bats, do you, you mentioned the, some of the mega bats the flying foxes, and how big do those bats get? Now that we know how small some of the like the Bumblebee bat , for example, is,
[00:14:36] Dave Johnston: The largest bat in the world is the gigantic flying fox. It’s found in Northern India along the Himalayan foothills. It has a wingspan of six feet, and it’s, I would say a body size of a small dog. It eats primarily fruit. I ask people, imagine seeing something that size flying around, in a park or something.
[00:15:03] I think that’d be spectacular.
[00:15:05] Michael Hawk: Yeah, the closest I’ve come to seeing anything like that is the flying foxes that they have in Australia. There are some, even some urban parks in Sydney that have colonies of flying foxes and that’s pretty amazing to see those ones, but they aren’t as big as the ones in India.
[00:15:20] Dave Johnston: No, but even so, it’s quite spectacular to see a tree full of, flying foxes that are, let’s say, have wingspans of three feet, because that’s still much larger than most people can imagine. In Central and South America, we have. Bat that has a three foot wingspan as well. The old name is the greater false vampire bat.
[00:15:44] It’s not a vampire at all. I think early biologists gave it that name because they were surprised or amazed at its size. But this is a serious carnivore and it often eats birds. Other bats and ronts, and I’ve caught them before. They’re very intense, just like a hawk or eagle is another top predator.
[00:16:10] But I have to say they are very gentle bats. That bat never attempted to bite or show any aggression at all. And I think that speaks to the fact that it’s normally a top predator and it doesn’t have much to worry about.
[00:16:26] Michael Hawk: How would you characterize where you would find bats in terms of geography or habitats? You know, as they’re distributed around the world?
[00:16:35] Dave Johnston: Bats are found in every continent except Antarctica. And given their long history, they’ve been able to exploit many habitats. , when you look at their lifecycle, they have several kinds of day roosts, and then they also have night roost, and then they’re also foraging. And so when we look at habitats, you can think of the habitat for the foraging bat and then the habitat for its day roost.
[00:17:06] They roost in a day, of course, in very seclud or secretive places so that they can sleep with some protection. But just in trees alone, bats will roost unr bark. In cavities, in the tree, in the bowls of a tree, let’s say the large redwoods that California has along its coast have in some cases, rotted out cavities that are huge.
[00:17:34] They might be four, five feet across maybe 10 to 20 feet high. And certain bats will use those cavernous habitats in these large trees. And then finally, there are a number of bats that use the foliage of the tree so that they hi among the leaves. And I’ve radio tracked red bats and hoary bats to the tree, and still couldn’t find the exact location of the bat, even though, okay, I know it’s in the foliage somewhere, but they’re extremely well camouflaged in many cases.
[00:18:14] That’s just the trees you can think of bats roosting as Cavity roosters, crevice roosters, like a crack in a rock, crack in a building, a crack in a bridge. And then there are cavernous roosters too. So cavernous roosters like caves of course, or mines or the insis of a building, or an attic or a barn.
[00:18:40] So again, there are many habitat types. Each species has, its own range that is, it’s found in certain locations .
[00:18:51] Michael Hawk: So talking about the ranges of bats, why don’t we tie up some loose ends on the diversity and know that bats make up a large percentage of the total number of mammals. How many bat species might one find in the United States in North America or in California?
[00:19:08] Dave Johnston: Okay for California it’s about 25 or 26 species, and the United States and Canada, 47 species worldwide. As of January 27th, 2022, we had 1,456 species. That’s about a quarter of all mammals species in the world, but that’s remark. To have that many bats and it’s a group that we are still discovering many new species per year.
[00:19:43] Even down here in Costa Rica, I will likely work on one or two species that are very little unrstood In Costa Rica alone. There are over a hundred species of abouts here and this is a very tiny place.
[00:20:00] Michael Hawk: That’s incredible. And I guess it just shows all of the ways that they’ve been able to specialize on on prey, on roosting sites and so forth. When you talk about the number of bats in the United States, a question that came to my mind, like, when I think about birds I’m often comparing species richness , between birds and other taxa.
[00:20:20] There’s a definite difference in the species that exist in the Western US versus the eastern us. Do you see a similar type of dichotomy, , when it comes to bats in the United States?
[00:20:34] Dave Johnston: Absolutely. And there’s some interesting things that we’re learning that we’ve already learned about birds that is of migration. and the actual ranges of certain species and the increase in the range, or the crease in the range. In other words, some of these ranges are expanding and some of them are contracting just as some populations are dwindling or very threatened.
[00:21:03] Whereas a couple of bats in California are actually doing far better than they did pre colonization period, prior to 500 years ago. But taking these things one at a time. I think one reason bats are different on the east coast as opposed to the west coast is with the continental divi bat.
[00:21:27] Are not necessarily migratory, and those that are migratory probably have fewer, if any differences, like H bats are found on both sis of the continental divi. They migrate thousands of miles. Many of the ones in California I believe actually raise young in Central Canada, migrate all the way down to California.
[00:21:52] And we have a fairly good, robust population of hoary bats in the Bay Area in the winter. And I’ve found several hoary bats in Torper. It’s like a low level of hibernation, but they’ve dropped their temperature on tree trunk. And in January, February, I’ve observed several Hory bats and they’ll remain for a few days before they might move on or catch a meal and then go back into torper.
[00:22:21] So that’s a bat that’s pretty much the same on both sis. Enormous range. Another is Mexican free tailed bat does have two sub-species, but again, it’s very wispread, highly migratory, although their migrations are probably smaller and shorter than those of the hoary bats. And then you have things like, pallid bat that doesn’t move very much.
[00:22:48] This is a bat that again, eats scorpions and centipes and a few flying insects, but mostly ground dwelling arthropods. And I suspect that, they’re. Fairly big differences among the populations of pallid bats. And in California alone we have previously thought of two species. Then they combine the species and now people are thinking that there are really two species of pallid bats in California.
[00:23:18] One is almost half the size of the other one, the one along the Pacific coast. Antrozous pallidus, pacificus can get quite large up to 28 or 30 grams. And whereas the one in the sert as much tin, and I’ve seen them as small as 12 grams for an adult, which is, almost a third the size, but they’re regularly half the size of the Pacific one.
[00:23:47] And by the way, I consider the whole concept of species a human problem, right? Because the populations really are not mindful, they’re not cognizant of the fact that they’re evolving over time or that they’re separating from another population.
[00:24:05] It’s the humans who want to ci what’s a species and what’s not, and how do you fine a species? And this can get quite complex and as way beyond our discussion here. But bats like other organisms are fluid in their evolution and their populations. We have some bats that are expanding their population.
[00:24:30] Like the yellow bat Southern California because it’s primarily an obligate for fan palms. Washington is a native palm that occurs in our sert oasis, but we plant fan palms all over. Throughout the Bay Area, and much of California has introduced fan palms.
[00:24:54] Yellow bats are expanding the range. Why? Presumably because their habitat is increasing. They primarily moths, like many of the other members of the genus Lasiurus, so that’s Western Red Bat hoary, bat Western yellow bat or yellow bat, and they’re a number of yellow bats. , in the Southwest and throughout the Americas.
[00:25:20] In fact, on a trip to Peru Nancy Simmons from the American Museum of Natural History found a new species of yellow bat, and that was just two years ago. And then we have things like Mexican free retail bats that are also not just expanding the range so much, it’s increasing in numbers and it’s because they make use of anthropogenic structures.
[00:25:45] Michael Hawk: you read my mind. I wanted to ask you about that, so that, that’s great. So tell me.
[00:25:50] Dave Johnston: Okay, so there are two species in California that are greatly expanding their numbers and their. Yuma myotis, that forges primarily over flat water. They also forge in riparian situations, but their specialty really is forging over flat water. And if you look at California, as we velop bigger populations, .
[00:26:18] We need to store water. Why? Because we live in a xeric or dry environment. And so right away we’ve made these huge dams with flat water all over the state. That bat, which probably was not near as common, is just, going through these , increases in population because all of a suddenwe’ve increased the flat water and we’ve built concrete dams that provide day roosting habitat.
[00:26:46] And so they’re all set.
[00:26:48] Michael Hawk: I didn’t know this. This water association for the free tailed bats, I always, I think of the roosts that they have underneath bridges. Am I thinking of the same species or is that
[00:26:59] okay?
[00:27:01] Dave Johnston: . Those are the two species that are most commonly found in bridges over water.
[00:27:07] Michael Hawk: So that’s the two things I didn’t know that second part, the overwater part. I thought they just found a bridge that they liked and it’s okay, this is our roost now, but they need the water.
[00:27:16] Dave Johnston: They need the water, that species needs the water for a couple of reasons. One is to simply drink, but two, that’s their favorite habitat. And, I didn’t talk too much about. Foraging habitats, but there are specific foraging habitats. One is water, but you can even subdivi the water habitat by how far above the water the bat is foraging.
[00:27:43] For example, a yuma myotis forges very close to the water and will even glean insects off the water. When I was teaching at Santa Clara University, , we did a dietary study of Yuma Myotis on the Guadalupe River in Santa Clara County, and we found may fly larvae, which don’t fly right, and would’ve only been able to be picked up on the surface of the water.
[00:28:12] So they also glean and insects off the water, but they typically don’t forage. A lot higher than that when they’re forging against the water. I make the difference because if you observe the little brown bat, which also forages over water it forges about, let’s say 15 or 20 centimeters above the water.
[00:28:39] So it’s like a whole different little habitat. And if you see the both species, you can behaviorally , separate those out. Some bats will forage, let’s say within a meter of foliage. Some bats will glean insects off foliage. So they’ll katydids off branches. They’ll eat worms or caterpillars.
[00:29:03] So they’re a whole set of gleaners, which have a very unique and complex way of discerning the insects while they’re on the foliage with their echolocation. Other bats, like the Mexican free tailed bats are open aerial foragers, and so they can be up to 10,000 feet up or maybe even more, but they often move with migratory species of insects like corn, earworms and the like, but their space, imagine the jet fighter, right?
[00:29:38] Their space is this very open sky habitat, whereas many of the other bats are much more intimate.
[00:29:47] Michael Hawk: And I feel the gravitational pull of echolocation, you started talking about the gleaning behavior, which think is a good lead in to maybe. Give a quick overview of how does echo location work for a bat? What anatomy do they require? And maybe even more basic, sorry, lots of questions.
[00:30:06] But do all bats use echolocation?
[00:30:08] Dave Johnston: All really good questions, Michael. We’ll start out with how they do this and. , it’s in the larynx. There’s an apparatus that just as we make a sound with our larynx. Even fossilized bats have a certain process that vibrates to make these very high frequency sounds or ultrasounds.
[00:30:35] And youngsters can hear much higher than we can. But when I’m giving a talk to a group, if I jingle keys, the youngsters all can hear that quite well. And in fact, I’ll ask them if their baby brother or baby sister prefers real keys or those plastic ones. The babies always prefer the real ones, right?
[00:31:00] Because they make a lot of tingle sounds, these high frequencies that adults just can’t hear. Okay. How does echolocation work?
[00:31:09] Michael Hawk: I just, I want to interject something I,
[00:31:11] Dave Johnston: oh, yes.
[00:31:12] Michael Hawk: and I just went through this test. So yeah, I have two kids and we have a variety of age ranges. So I found a YouTube vio where they play a tone and slowly the tone gets higher and higher pitch, so you can identify when you stop hearing the tone and it matches exactly what you’re saying.
[00:31:32] It’s a fun thing to do, to see okay, how old am I from a high frequency
[00:31:37] Dave Johnston: yeah.
[00:31:37] Michael Hawk: so I’ll link to that in the show notes.
[00:31:39] Dave Johnston: So I can no longer often hear some of our lower frequency bats. I can hear spotted bat, I can usually hear Yuma, which is our largest Our largest California and US bat the great western or greater moths t bat. But sometimes I can’t hear where my stunts or colleagues can. It’s a little disturbing, so far getting olr beats the alternative.
[00:32:11] So it’s just something that we have to put up with. There are two bats by the way, that you can regularly hear with our human hearing. And one is, again, the western moths tiff bat and the other is a spotted bat. Okay. Getting back to specifically echolocation, that sound is either going through the mouth in many of our, vespertilionid bats or plain- nose bats.
[00:32:41] or through their nose, in the case of the leaf nose bats, which there’s a huge diversity here in central America. The leaf nose on these bats presumably helps shape the sound that’s emitted.
[00:32:58] And so you can, it’s like a choke perhaps of a gun or something like that. There are two groups of echolocation, but before we talk about that basically the sound goes out as this, very intense sound So loud that it’d be like a smoke tector alarm about one inch from your ear.
[00:33:21] What would that do to your ears or your hearing if you had a smoke tector alarm go off an inch away from your, every time you wanted to, find your way a around or look for an
[00:33:33] Michael Hawk: Yeah, I mean it would absolutely damage my hearing. I’m sure
[00:33:37] Dave Johnston: Absolutely it would. So bats have this very unique way of separating out their ear bones so that as that sound goes out, their ear bones disarticulate just for a split second while the sound goes out. And then after the sound goes out, the ear bones reconnect. Part of that sound hits an object in space.
[00:34:07] and then it bounces back. So in fact, it’s a form of sonar many people have ma a career out of studying the echolocation in bats, and we’re still learning a lot. But, when I first started learning about echolocation, I saw this as a very coarse sonar, something like, radar or something like that where you see a little blob or something.
[00:34:33] But now we know that it’s can be extremely fine tuned to the point where a big brown bat that has a echo echolocation call of about 20 or 20 plus kilohertz. That’s something that we cannot hear, but when it hits something about 20 feet away, let’s say six meters, they can discern a single human hair
[00:34:59] Michael Hawk: Oh man.
[00:35:00] Dave Johnston: that is precision.
[00:35:03] That is amazing. And if they can do that, I’m pretty sure that many bats can discern species of moth or insects that they’re looking for. And there’s so many games, if you will electronic games, war games, you could call them the electronic warfare between moths and other insects and bats.
[00:35:29] So they’re both evolving back and forth and it’s a evolutionary game of, upping one or the other and then developing defenses. And so this has been going on for, many tens of millions a years. So you can imagine how elaborate some of these schemes are. I’m gonna mention Doppler here too, because when a moth flies, it will have a certain wing beat.
[00:35:54] So when a bat. Sends out its echolocation, the pulse is going to hit that moth, and then the echo is going to have a certain shape. But not only that, as it sends out these pulses, when the moth is going forward, that sound will go down in pitch, but when the moth wings are coming back towards the bat, then that increases the pitch and the frequency goes up.
[00:36:27] So all of a sudden you have this doppler effect where it’ll make a certain pattern based on the wing beat of the moth, and in addition to the general shape of the moth and the wings and so on. These things get really elaborate.
[00:36:42] Michael Hawk: That’s fascinating. It’s as you’re scribing this, the way my brain is interpreting it is I’ve looked at sonograms before of bird calls, for example, and you can see in graphical form the frequency and the shape of the sound that’s been emitted. And in fact, when I edit the podcast, I’m often looking at at the podcast in that way.
[00:37:04] Dave Johnston: Oh, really? That’s
[00:37:06] Michael Hawk: yeah.
[00:37:06] So I could easily see a bat being specialized over millions of years interpreting things this way and being able to pick up on those subtle differences because I can look at one and, and see when somebody says, ah, or um, or, you know, whatever the case might be. So why not?
[00:37:20] Yeah. Why can’t the bat.
[00:37:22] Dave Johnston: Absolutely. I think you’d be really good at least fascinated by all the sonograms that, we look at and what bats are doing, and . We see some sonograms and we’re going like, what the heck? What is this? What’s going on here? You know, This is really like different, so now we’re getting more involved in what social calls look like and , what social calls mean, and that’s become a whole new area where people are focusing to try and learn, a bat language, if you will.
[00:37:55] I want to get back to the gleaning and open aerial foraging, because there are two, basic, very different ways of echolocating for insects. One is called CF calls, or constant frequency calls, and those usually are produced by bigger bats that forge in the open, and so they’re lower frequency. Why?
[00:38:22] Because they want the sound to go out for a farther distance, right? They’re flying really fast and they need to see that big, huge beetle from let’s say, a hundred meters away. And so they’ll pick up on that, but it’s not really high resolution. But they’ll zero in on it early on so that they can keep track of that.
[00:38:44] Those calls remain pretty much the same low frequency all the time, and I’ll just make a auditory sound. I could play back some that I found on the internet, but then, and they’re author, they have names, I haven’t asked any of these people if we could use them here today. So I’ll just mimic something using my own larynx.
[00:39:10] Beep beep, beep. Each time I sent out a call, it didn’t change in frequency very much. And again, those calls low frequency, long wave go out a long ways, low resolution, bigger bat. The other big group of bats, are called frequency modulated. They start out really high and then they go down low.
[00:39:38] And these are the bats that are much smaller. . They’re going to be eating smaller insects, so they need a much higher resolution and they don’t fly very fast. So you know they’re going to be very close to the insect before they actually tect it. Looking at almost an extreme case of this would be the little proboscis bat that starts at almost or about a hundred.
[00:40:06] Kilo herz and then drops down much lower let’s say drops down to 40 or something like that. And so these vests go
[00:40:19] something like that, but they, again, they start really high and then they drop down low. And this is to help separate out foliage from the actual prey that’s either in front of the foliage flying around or actually attached to it. One of the bats that’s in the Bay area. Frequently that forages not on foliage so much as near it is the California myo.
[00:40:47] And sometimes when California Myotis and Yuma my are found together. I can easily separate them in the field at night just by seeing where they forge. So a California, my typically forages about, let’s say a foot to two feet away from the edge of an oak tree foliage. So as they fly around that oak tree insects that are about to land on the oak or scared up or whatever, then are eaten by that.
[00:41:19] When a bat approaches the insect, it’ll produce what’s called a
[00:41:25] um, Feeding buzz. so it’ll go,
[00:41:31] it’s like a ping pong ball dropping. And so as the bat approaches the, that buzz is when the pulses are so close together that our ear just blends them together.
[00:41:47] Michael Hawk: and I assume that it picks up the pace as it’s getting close because it needs that higher resolution to keep track of exactly where that insect.
[00:41:55] Dave Johnston: I don’t think the resolution changes as it gets closer, per se. The pitch doesn’t change. The bat is trying to, Keep very close attention to where that insect goes as it’s trying to evade the bat. And mind you, these moths have many resources at their disposal to try and jam the bat, fake the bat out make them seem like different size by mimicking an echo back and all kinds of things like that.
[00:42:27] It’s fascinating. It, it’s really neat what they’ve learned now. And again I could talk all day just about this, moth and bat and katydid and bat interactions because it’s definitely electronic warfare, very sophisticated.
[00:42:43] I’ll just explain one little bat moth interaction. Some moths have two ears and one ear is activated when the bat is at some distance.
[00:42:56] When the moth hears the bat from the distance, it will fly in the opposite direction away from the bat. and this is just innate. It’s not something the moth has to learn, it just starts flying away. When the bat is much closer, the other ear is activated instead, and some will fly very erratically and very short pathways.
[00:43:24] And you know, you can imagine a moth that goes up four inches up, then five inches left, and then seven inches down and just keeps very erratically flying around. Yeah. A bat. Can’t al with that very well, and The, those bats are going to get, to react or to adapt evolutionarily, their wings are gonna get smaller and smaller.
[00:43:46] To be able to maneuver around this moth. It’s, playing some tricky business with them. I’ve released some moths in swarming areas that is areas with bats that are, boy meets girl sort of thing in the fall. Fascinating behavior, but also releasing moths in areas where I know there are a lot of bats, and sometimes the moth will just simply fold its wings, drop to the ground, and then crawl away they don’t risk flying.
[00:44:16] It’s a really interesting behavior, but, when that’s triggered then yeah, they don’t, they just don’t fly anymore. They just, okay, game over. I’m out here. So again, yeah, a lot going on there. And yes, we could talk for more than a day about all these interactions.
[00:44:34] Michael Hawk: Let’s tie up a few loose ends with the life history of bats or bats in general. And one thing that is curious, to me, there’s this huge range of size and it makes me think there’s probably also a high diversity in lifespan as well, is that.
[00:44:50] Dave Johnston: There is. But bats don’t follow this typical. Relationship between size and longevity in general, the larger the mammal, the longer it lives. Look at humans. Average lifespan is three quarters of a century, let’s say. And elephants, that long or longer shrews will live one or two years, tiny and very short-lived.
[00:45:17] But bats defy that and people are still working on why that is the case rather than, take off on some of those hypotheses. I’ll just tell you that there are some remarkable records out there. The oldest bat in the wild that’s been found was a Brandt’s bat, which is a Siberian bat and a Team from Europe was looking at the longevity of some of the bats in Siberia, and it is 41 years old.
[00:45:47] There are also some records in Europe and the United States. We have some myotis lucificus that, that are around 40 years. that’s a very tiny bat. It weighs about, let’s say eight or nine grams. Most bats live about 20 years old, or a little less than 20 years old.
[00:46:10] There are six bats in the world, including the one in Europe, and our myotis lucificus and Myotis brantii that live over 30 years. I can’t tell you why some live, let’s say 10 or 12 years and others are living over 30 years.
[00:46:30] Michael Hawk: It seems all over the map. So a lot of bats are communal as well, and they have social structures and there’s a lot of fascinating things there. Can you tell me a little bit about that? Like Are there solitary bats or are they all communal?
[00:46:46] Dave Johnston: No, I think that the perception is that bats tend to be colonial and very social. Some bats are not at all. One bat that’s quite solitary is the hoary bat. and I have observed what I would call antagonistic behavior between male hoary bats. This is on Hawaii. Doesn’t mean that they’re always antagonistic, but it would appear as though there might be territories going on there.
[00:47:17] Hoary bats will usually have one or two young, and they’re often in a neighborhood with other females, but they roost separately. So you might have one female in one tree and another female in that same tree or in another nearby tree. The same goes for our own Western red bat that we have in California.
[00:47:43] Western Red Bat, by the way, does not raise young in the Bay Area. It raises young along. Large river stems. So the Sacramento River, San Joaquin River, and usually in old growth, cottonwoods and old growth riparian areas, although appears to be adapting somewhat to, , some orchards like peach orchards and the like, but colonial bats.
[00:48:09] And we should make the difference between colonial and social bats that are living together aren’t necessarily social. So that’s just, something to keep in mind. Mexican free tailed bats live in very large aggregations in California. I’ve been monitoring and counting the bats in the Franklin Boulevard bridge near cosumnes River.
[00:48:38] The Nature Conservancy, preserve and our highest number, which was just a few years ago, was at about 168,500 bats. Wow. Talk about packed in tight. We have to count them by fives. There are so many, but we try and count each of those little groups, but they are three deep inside these cavities and then literally packed like sardines, they are just right up against each other. So they are highly social, highly colonial, and there are much larger colonies, if you will, in some of the caves in Texas, the well known YOLO bypass as you go into Sacramento has even larger numbers of bats than the Franklin Boulevard bridge. But it’s very difficult to count the bats there on the Yolo bypass, although Corky Quirk and others are doing their best to, monitor that.
[00:49:45] But the point being that species is very social and to the point where what’s interesting I’ll, I’ll give you two different kind of scenarios. Mexican free tailed bats and then vampire bats. Mexican free tailed bat mother will remember where she places her own baby and might fly through several chambers to get there.
[00:50:09] And then within that chamber start echolocating to try and find the baby. And then ultimately dropping down, smelling each baby until she finds her own baby. And as far as we know, will provide de milk for just her own baby among hundreds of thousands of bats. Whereas the social behavior of vampire bats is so really different.
[00:50:35] They are also colonize, they’re highly social, but they exercise this ritual where if a relative of a female goes without a meal, she can beg another of her kin in that colony for food and then that relative well, or can cough up a portion of her blood meal. For her comrade, if you will. And it’s a wonderful example of altruism and presumably then if you cough a part of your meal that may help you down the road when you also need a meal because you couldn’t find a dinner that night.
[00:51:18] I think for a long time people had assumed that, they had communal nurseries and things like that. No, I don’t think so. It may occur but it’s probably fairly rare. But they keep track of their own babies. They are, I think we’re only at the tip of the iceberg in terms of understanding relationships among bats within a colony.
[00:51:41] I do know that for pallid bats, which I’ve studied for years and years, not all comrades are equal. And there are some bats that’ll come into roost and they’ll call illicit callbacks. And a lot of times they’ll just move on until I think they find the right callback. And so they don’t all want to be together.
[00:52:05] They look out for specific individuals who would appear that they wanna roost next to. But again, this isn’t really studied well. I’ll mention another system, and that’s a lek and we’re only now finding leks and a lek, which is much better known in birds is a sexual process of.
[00:52:27] Advertising males advertise in a very specific location for females. very recently here in Costa Rica Bernal Rodriguez did a wonderful study on leking behavior in the wrinkled face bat, which is very strange looking bat. But the males congregate and they will call out to females who then start, looking and approaching each one of these males.
[00:52:56] I’ve seen this in the greater noctule bat in Europe once, and it’s, just fantastic because these males would come out of their cavity and then sing, and the females come by and they listen and they ci, nah. Not good enough for me or Okay, you’re on, and that sort of thing. And typically the males that are in the middle are the most fit and they usually make the most right?
[00:53:24] Because females then are going back and forth and every time they go through the middle, then they may copulate
[00:53:30] Michael Hawk: these males are lined up and they’re all singing at the same time
[00:53:34] Dave Johnston: what I observed was that when a female passed by then a male would come out and sing. And I couldn’t tell you if the male was singing all the time or not, but I didn’t think so. But I really haven’t studied this in any great detail as others have. But leks are well known in the bird populations, and it’s only now that we’re finding a few situations in bats many bats are completely promiscuous.
[00:54:06] And this is what happens in swarming areas where a female will copulate with, presumably many males. In pallid bats. I’ve noticed that some females will visit very specific male Ruths in the winter, presumably for copulation. So it’s in, in pallid bats. It would appear as though the female is choosing the.
[00:54:30] Michael Hawk: So bats are, as you alluded to near the very beginning of this discussion, often misunderstood in a variety of ways. And I’d like to get into how that relates to the conservation of bats and what bats do in the environment, the benefits of bats and so forth. Why don’t we start there?
[00:54:46] If you’re making a case for bats to people, what do you tell.
[00:54:50] Dave Johnston: I think one of the big advantages or big good if you will for humans is that bats eat enormous amounts of insects. There are a number of statistics that I don’t have at my fingertips right now, but something about if you look at all the corn production in the world, if you have bats that are eating. Pests of corn, just corn alone per acre. I think it’s about seven or $8 that you’ll save if you have bats and anywhere in the world. That’s just this one little statistic. If you look at all the acres or hectares of corn in the world, that’s enormous. And I think you mentioned Michael, that in some circles bats probably save about 27 billion in agriculture benefits.
[00:55:43] In other words, in terms of pest control the same amount. Pest control that bats provide agricultural crops would cost about 27 billion. If you look at this at a worldwide basis, there are a number of papers. There’s a paper on Texas agriculture, a newer one out on California agriculture, but it’s enormous, the amount of insects that they eat every night.
[00:56:11] A lactating female will eat her weight every night, and, that’s a lot of bugs that really adds up. Another thing that, bats do that we’re not mindful of, is that they help pollinate, they help pollinate, thousands of different plants. And not only are they, I’m talking about all wild plants, of course they pollinate bananas and a number of fruits.
[00:56:40] That we rely on. More importantly, they pollinate many flowers in tropical areas.
[00:56:47] Michael Hawk: If I’m not mistaken, I think Are they critical for Saguaro Cactus
[00:56:52] Dave Johnston: Absolutely. Yeah.
[00:56:53] Michael Hawk: which is such an important plant in the Sonora desert.
[00:56:57] Dave Johnston: It’s a keystone species and they’re not exclusive. There are other things that can also pollinate the saguaro cactus, but the saguaro cactus is a keystone species and leptonictrous and a couple of nectar feeding bats pollinate that flower as well as pallid bats. pallid bats also will come in take a certain amount of nectar and they might even take a moth that’s visiting.
[00:57:25] The saguaro cactus. The really important thing and difference between birds and bats is that bats ingest the fruit and then they’re flying away very quickly. Whereas a bird usually roos in that tree and they stay in that tree for a long enough time that the seeds then that are eliminated, fall below the tree.
[00:57:50] And so birds are not particularly responsible for much dispersal, of, seeds. So bats are critical to, a lot of these plants
[00:58:00] Michael Hawk: I know, and I know there’s a lot of other great things bats do as well. And I am always a little torn when I hear the quantities of insects that they eat because at the same time I’m always really promoting that we need more insects, , so we need more insects so we can have more bats, and then the bats are gonna eat more insects.
[00:58:14] But that’s just part of the balance of nature.
[00:58:16] Dave Johnston: What we need most of all is balance. And lot of people I’m gonna bring up as we talk about conservation, I’m gonna bring up bat houses because I’m all in favor of them, one of the things that they do is they bring awareness, but there are many bat houses that go empty. And I worry about agencies and other well-meaning people who will destroy a habitat, let’s say.
[00:58:47] Or take down a tree and then put up a bat house. And then they don’t understand why the bats didn’t move into the bat house. And so I explain it like this. Imagine you have this wonderful mansion that you know is relatively warm. It has all the comforts of home, and somebody builds a drafty outhouse in your driveway and then stroys your mansion, and they expect you to move into this outhouse.
[00:59:22] typically the bats will just simply leave . There are a few species that take to bat houses regularly, but those are the most flexible of species. The species that typically need habitat the most. Usually don’t use bat houses. And I was, at one point at a conference, I noticed a woman who, was responsible for restoring about 20 miles of riparian habitat.
[00:59:51] And in order to accommodate the western red bat, she put up bat houses. That species does not use bat houses. They’re foliage roosters. And So if we can dive into some of the threats.
[01:00:07] Michael Hawk: For sure. Yeah. And that, I think that’s a good lead in, you’re talking about some habitat loss there as one of them. So what other ones are top of mind?
[01:00:15] Dave Johnston: Yeah, I think one of. Biggest threats to bats is actually habitat conversion and habitat loss. And what comes to mind first is urbanization. It’s a rather pervasive, development in our world because, the human population is only getting bigger and we don’t typically see the changes that are going on.
[01:00:44] But when I look at old records, I find some of the bats that are very sensitive, having been common in places like Los Angeles County or Santa Clara Valley and so on. And, they slowly wink out. And it’s hard to notice this. There’s a study, a acoustic study of San Francisco that detected hoary bats, Mexican free tailed bats, Yuma, my and maybe migratory little brown bat.
[01:01:18] I believe if you just go across the golden gate, you get about 16 species and presumably those 16 species would have occurred in San Francisco had it not been developed. But it’s hard to see this within just a single generation. It gets back to the shifting baseline syndrome.
[01:01:42] It’s hard to see the insidious. Nature of what urbanization does to plants and animals. One part of urbanization that we’re only now beginning to understand better is noise pollution and light pollution. And I’m horrified to see some posts that talk about you can help bats out by putting, more lights out because they attract moths and other insects and beetles, which is all true.
[01:02:13] And that will help the bats, that will help only the most flexible species that don’t mind the light.
[01:02:22] So
[01:02:23] Michael Hawk: That would be a very short-term and correct me if I’m wrong, but it seems like that would be very short-term thinking because having lights out is not long-term positive for the insects. It’s basically a trap
[01:02:34] Dave Johnston: Yes. Not good for the insects and okay for a couple of species they take advantage of it or a few species, but many species are lit phobic. And I’m realizing now that there are a lot of bats that avoid lights and it may disrupt their ability to forage. And they certainly become more vulnerable in areas where, let’s say you have a ravens and things like that, that are able to see in dim light.
[01:03:04] Why is it dim? In Los Angeles and other. Parts of urbanized areas, it may never really get dark. And there are plenty of flexible species out there like ravens that can take advantage of this. So all of this is part of habitat conversion. What I’ve noticed here in Monteverde Costa Rica is that about 30 years ago, people here decided that they need to replace habitat that had been taken.
[01:03:40] And so these people took seriously the whole problem of habitat conversion into, in this case Dairyland and, pastures. And they started replanting native trees. And there’s a lot of second growth that, you know, has exotic plants, but they had the right idea and it’s amazing what species have come back since they restored a lot of these forests.
[01:04:08] I’m going to mention a few other parts of this. Another really big one is global climate change, and certainly it looks like it’s getting drier and drier in western US, although I’m happy to hear that now we’re above average for rainfall, but we’ll see how that plays out to the end of the year.
[01:04:30] But bats need water and anytime that you go through a drought, I’ve noticed significant changes in some of the populations of roosts that I’ve counted. And so for example, After three years of drought at the Franklin Boulevard Bridge, we noticed a drought from 168,000 plus down to about 107,000. I’m not saying that there’s a direct relationship there, but over time, I think we’re going to see a correlation between numbers of bats and the number of drought years and so on.
[01:05:10] Here in Montever de something entirely different is going on, but it is also having an effect. And that is uh, I just looked at Richard Lava’s rain data and over the last 39 years, rain is consistently going up. There is a trend for more rain. . They already get over a hundred inches of rain a year now, and this is like a lot of rain.
[01:05:37] The bats are responding, so what’s interesting is we’re, it’s warmer here too, so we’re getting species that are moving up slope that never occurred here before and likewise, other species are dropping out. It is definitely changing here as it is in California for lots of reasons.
[01:05:59] It’s not just a direct temperature change, it’s all the things that are associated with global climate change.
[01:06:07] Michael Hawk: . Yeah. The disruption of climate patterns in general have far-reaching effects.
[01:06:12] Dave Johnston: Right and the posity of insects. There’s something else going on there that is likely associated with global climate change. And there’s a recent article that came out suggesting that it’s a change in the atmosphere that disrupts their lifecycle somehow.
[01:06:32] , the number of insects in California is much, much lower than it ever used to be, but it’s the same story all around the world. Little scary.
[01:06:42] Michael Hawk: Yeah. And not to go on too much of a tangent, but to that point I had the good fortune. To be able to do a little bit of travel for my last job to places like Iceland and Switzerland and Ireland and Australia, and a few others. And I always made a point to get out in nature when I talked to people to biologists, to whoever was taking me out in those locations.
[01:07:01] It’s, yeah, it was the same story everywhere, and it was very eye-opening to me that, it’s more than just an isolated.
[01:07:08] Dave Johnston: Yes, this is worldwide. It’s Central Valley, California. It’s Costa Rica, it’s Peru, it’s Thailand, and so on. So I think we’re just beginning to understand what’s going on there, and I know very little about that. But yes, certainly concerning pesticides are something I’m, going to mention here. It’s not well studied in bat.
[01:07:32] There is a researcher in Texas that worked somewhat, but that’s something that we could do a lot more with. And again, I think that some of the bat species that are more sensitive are going to drop out and we’re not going to know why
[01:07:48] and it’s hard to know what’s actually going on there. But you can’t help but to think that there is an effect there.
[01:07:56] Michael Hawk: Yeah, there’s so many threats to bats. I know there’s a couple other important ones and I’ve had listeners ask me about doing an episode on White Nose Syndrome. We’re not gonna do an episode here, but can you touch on that briefly?
[01:08:08] Dave Johnston: Oh yes. I think that’s important. Michael. White nose syndrome is of fungus. Basically grows in bats when they’re in hibernation and their immune system is pretty much turned off. So it’s heinous kind of thing, but the hypae actually start growing into the nasal cavities and, and other tissues as it feeds on the bat, literally while it’s alive.
[01:08:36] But this was probably in Europe for a long, long time. And those species have essentially evolved with white nose syndrome to the point where, there’s a certain amount of immunity. It’s interesting that they don’t have case with huge numbers of bats that some have suggested that may have be, cause of the fungus, but nonetheless, it was presumably.
[01:09:03] Transported on shoes or clothing into house cave in New York. And from there it spread as a spore on people’s clothing and boots and on the bats. And as I’ve said, several years ago. Whereas I think we need to be very careful about our equipment. We’re not going to stop this.
[01:09:25] This is going to work its way through North America where it’s cool and damp, and so it’s a cold loving fungus and it needs temperatures below 10 degrees. If you look at California, that limits much of the state to high parts of the Sierra Nevada. So the Sierra Nevada spine, if you will. and then also areas of the northeast part of California where it also gets very cold and remains cold much of the year in lava beds, national Park, you have ice caves.
[01:10:06] Those ice caves are ideal for nurturing this fungus and developing a problem. So those people have to be extremely careful about how they manage their caves. White nose syndrome has been discovered in very small amounts in three bats in Chester, which is in Northeast California. And it will presumably move bats migrate and we’re not going to be able to stop the migration.
[01:10:37] We can survey area and keep a handle on where it’s moving. But unfortunately, I think this will take out many bats to date. The prevailing thought is that about 6 million bats have been lost. Primarily bats that are most sensitive to this, the little brown bat and the Northern bat or Myotis.
[01:11:02] Sept entry analysis. So sad. It’s another case where there is some human wildlife interaction and you know, the bats essentially got their own pandemic in North America, . Some of our populations like. Little brown bat are probably down over 90% of their original population.
[01:11:26] So it’s part of the same problem. It’s a globalization problem, and bats are going to face more of these as well as humans and pandemics.
[01:11:38] Michael Hawk: It’s an interesting parallel and we see it in so many aspects of nature, including invasive insects, affecting trees, and so on and so forth.
[01:11:47] Dave Johnston: There’s so many stories there. I’ll give you just a short one on an invasive species that actually was introduced which, to even my delight, I enjoyed fishing as a kid in the Sierra Nevada, but as it turns out we’ve learned that some bats have to forge a lot harder and a lot longer in lakes with trout.
[01:12:10] These are introduced trout, and at first we thought that perhaps the bats just preferred these lakes with trout. And now it looks more like the bats just have to work a lot harder for the same amount of food because they are in fact competing with the trout who are eating some of the same prey and a lot of bats forged near water.
[01:12:34] very interesting story and in a way that we didn’t, first see, and we thought the bats would shun lakes with trout, but instead, no. Some of these bats spend more time on them, but they’re just less efficient.
[01:12:49] Michael Hawk: And we were talking a little bit about solar and wind energy and the nuance and trade-offs there. So how are these new industrial scale, solar and wind facilities affecting bat populations?
[01:13:02] Dave Johnston: Solar and wind are, very different. They present very different pressures on environments. A first take solar because it’s a little simpler when solar projects are built and they don’t disturb the land anymore than they have to. In other words, they don’t scrape, a meter of soil off before they put in their posts that have the solar panels.
[01:13:30] If the soil is left intact, I can’t say that those solar projects really harm bats significantly. There is an issue with solar power towers that is projects that. Radiator that heats up to about a thousand degrees. That then provide s molten salt or molten hot salt water that runs turbines when the turbines after they run through the turbines and they’re cooled the cooling fans.
[01:14:01] Sometime hit bats and bats go into these, the huge buildings that cool the, solution. And so there are a few bats lost there, and there are a few bats lost in the flux, but the worst of solar projects is when they remove the soil and therefore, it’s complete annihilation of that substrate, which then becomes the base of, their.
[01:14:27] Ecosystem, and I’m just saying that if they leave the soil mostly intact, bats can forge around solar panels without too much problem getting into wind. is far more complicated and we’re still trying to figure out the best way to keep wind and conserve bats. And unfortunately, as these towers have become much taller and larger, they have proportionately taken out many more bats than birds.
[01:15:01] When they were shorter, they took more birds. Now that they’re much taller, they take more bats.
[01:15:08] Michael Hawk: Wow. had, I had no idea that’s a message that has to get spread.
[01:15:11] Dave Johnston: It is, It’s a problem worldwide It’s a problem. Throughout the Caribbean and Central America and you know, de
[01:15:21] more and more countries are looking towards renewable energy, particularly those countries that don’t have petroleum or oil resources like Costa Rica. In Costa Rica and in the Caribbean, like in the United States and Canada, it’s , primarily the open aerial foragers that get hit by the turbine. There are several conferences a year now that dedicate to wildlife and wind turbines and how we can keep the wind turbines and keep bats and birds and for bats, one of the recent.
[01:16:00] Movements to preventing bats from being hit was to produce high frequency sound blasters that are broad spectrum that in many cases, reduce the number of fatalities. They don’t prevent them a hundred percent, but they can significantly reduce them.
[01:16:22] But one of the problems is that as these turbines get bigger and bigger, the ultrasound broadcasters have to get bigger and bigger, and it takes a lot of energy to push. High frequency sounds out far enough to have an effect, and so it’s always been a catch game as the. Turbine blades get longer and the towers get higher.
[01:16:50] Then they’ve made more and more ultrasound broadcasters, and it’s still not anywhere near a hundred percent. And there’s some indication that it doesn’t conserve all species. It appears to help reduce the number of fatalities for hoary bats, which many of us are concerned about. One of the things we’re looking at is whether or not ultraviolet light might be an effective deterrent.
[01:17:19] One of the things I like about that is that. It’s not expensive. It goes, for a long ways. It’s not something that attenuates quickly, but a lot more work has to be done to see if this will help. I don’t think there’s any silver bullet. We need to look at all the possible ways to reduce that fatalities, because wind is here to stay.
[01:17:44] One of the things that I think has been overlooked is the spatial arrangement of the turbines in the West. I see situations where it would’ve helped if they located these turbines in a. Damaging way, we’ll say areas. In some cases, I’ve been able to predict when there have been high fatalities at certain turbines in other parts of the country and the world, this probably wouldn’t have any effect because for instance, in the Great Plains of Canada and the US, I think you’re not going to see patterns that are going to hold true year after year.
[01:18:24] So we need to keep working on this because I think wind is here to stay offshore. Turbines will be much, much less damaging to bat populations, and that’s probably a big part of the future.
[01:18:39] Michael Hawk: Lots of tra-offs to consider in all this as well. We were just talking about noise and light pollution and some of the solutions for the turbines is to introduce noise or light to keep the bats away at the same time. So it’s a interesting set of challenges that exist. There’s a project that you’re part of and working on that you wanted to highlight, so why don’t I just take things in a different orderthan I normally do?
[01:19:00] And can you tell me about team chiroptera?
[01:19:03] Dave Johnston: Thank you, Michael. Well, One of my concerns is that there are fewer and fewer young people who are interested in nature. I used to ask five year olds where hamburgers came from. I did this when I was a director at Youth Science Institute. About half or a little over half of those five year olds would say that they make it in the grocery store, or they didn’t know.
[01:19:32] Very few kids understood that hamburgers came from cows. They had completely lost this connection that when they eat a hamburger, it’s a ground up cow. And so there is this disconnect between our natural world, our natural resources, and what people think.
[01:19:54] And most concerning is that, I see less and less interest in science, and I’d like to do something that teaches kids and the population more about bats and also encourages using science.
[01:20:12] And I and a few others have developed what we call team chiroptera. And it takes about a year. We go into a middle school and we teach science through the study of bats. So the youngsters, usually seventh and eighth graders learn how to follow through with the scientific method. I give them or loan them bat detectors and they come up with their own hypothesis.
[01:20:40] They get their parents and families involved. and we go out and I show them what a real life bat looks like in the field. But in the end, these kids then are responsible for testing their hypothesis, usually with the use of bat detectors. And then I have them make a poster. And I have to do this with the full cooperation of the science teacher because they’re an important part of this.
[01:21:07] But it’s amazing what some of these kids have come up with after they make the poster. Then I have them submit that to a conference, scientific conference with professionals. And you should see these kids, they are so proud and so are their parents. And it’s a real lifetime experience. So I’ve done that in now on Maui with my staff there.
[01:21:33] And then also we had a project in Pacific Grove near Monterey. And now we’re working on a project in Belize and, Costa Rica here. It’s just a way that I can encourage science, have people learn more about bats, and ultimately get excited about doing science for lifetime. I wish I had a website that people could go to learn more about Team chiroptera, but I’m going to talk to some folks on Thursday of this week to see what we can get going.
[01:22:06] Michael Hawk: Let me know if you do get something going because I, we haven’t talked about the scheduling of, when this will be published, but it’ll probably be a couple months from now. Maybe you’ll have something by then. So look, so keep me posted
[01:22:17] Dave Johnston: maybe. I hope so.
[01:22:19] Michael Hawk: That sounds like an excellent initiative. And as I said, keep me up to date and I’ll make sure to share progress on that with with listeners. So just a another couple of quick questions for you before we bring this to a close. So for people who are interested in learning more about bats, do you have any resources, any books or.
[01:22:41] Documentaries or YouTube channels or whatever it might be that you wanna point people towards.
[01:22:47] Dave Johnston: Wow. The internet these days is so full of information. It’s just like totally amazing. I would encourage them to look at some of the nonprofits that are promoting conservation of bats. There are over a hundred conservation institutions in Europe alone in the us. We have some. We have one very large one, and that’s bat Conservation International, which is very well veloped locally in California.
[01:23:20] Here we have the California Bat working group. We have a website. There’s a website for the Western Bat Working Group and so on. There’s a lot of really good information out there. And if you want, I could make you a little list or something like that.
[01:23:36] Michael Hawk: If it’s no no hassle, certainly
[01:23:38] Dave Johnston: yeah, I can make a little list and I could also make a list of books. There are a number of recent books that are, fun, they’re fast, and there are a lot of books coming out now.
[01:23:49] Michael Hawk: Yeah. Sounds good. Dr. Johnston, it’s been a lot of fun talking with you today, and I wanted to ask you, before we come to a close, are there any other places where people could follow you or your work?
[01:24:00] Dave Johnston: Thanks for asking Michael. I’m hoping to set up a website while I’m down here in Costa Rica. I have a few really interesting projects that are developing and otherwise it’s fairly limited. I have some, I have some information about myself and a very few papers on the HT Harvey Associates website where I’m an adjunct associate and then also on research ga, but both of those are quite limited so, I hope to develop a new website that, will provide a lot more information and a lot more papers and reports and so on.
[01:24:41] Michael Hawk: Okay, look forward to that.
[01:24:43] Dave Johnston: I was just gonna say for our listeners out there, there are many places that you can see bats. I would recommend trying to get ahold of either a local bat biologist or a nonprofit and ask them where you could come out and watch bats emerge. And, in our own local church in Saratoga, in the South Bay there were people who brought out their lawn chairs and their chardonnays, and they would watch one of the large emergences in that little city regularly.
[01:25:18] And they do this at the YOLO bypass and so on. And so, I encourage you to go out there, bath seat when we eat. And so people often miss them foraging, but go outside some time at a football field or in your neighborhood about dusk and see if you can’t see a few bats.
[01:25:42] Michael Hawk: Yeah, I think that’s great advice. Dave, thank you so much for spending all this time. Your enthusiasm really shows we’ve covered so much more than I thought we’d be able to get to, and I really appreciate it. So thank you. I appreciate you and and what you’re doing for bats.
[01:25:55] Dave Johnston: Michael, thank you so much for the opportunity. It’s been my pleasure.
Nature's Archive Podcast 