As spring approaches, Oregon bats begin to take wing

Oregon is home to 15 bat species. As we approach warmer weather, bats hibernating in caves are beginning to wake up and those that migrated away are making their way back.

While bats can prey on fruit, fish and even blood, all of Oregon’s bats are on an insect-only diet, with many catching as many as 600 bugs an hour. Despite their role as pollinators and pest controls, a majority of these flying mammals in Oregon are classified as a state-sensitive species, meaning they are facing one or more threats to their population or habitat. Beth Ward is the Northwest Bat Hub Coordinator with the HERS Lab at Oregon State University Cascades. She joins us to share more on the bats residing in Oregon.

The following transcript was created by a computer and edited by a volunteer:

Dave Miller: From the Gert Boyle studio at OPB, this is Think Out Loud. I’m Dave Miller. We turn now to bats. With spring here and warmer weather hinting at arriving, the bats that hibernate in caves are starting to wake up. Those that migrate south for the winter are making their way back. Fifteen different bat species call Oregon home. So does Beth Ward. She is a Northwest Bat Hub Coordinator with the Human and Ecosystem Resilience and Sustainability or HERS Lab at the OSU Cascades Campus in Bend. Beth Ward, welcome.

Beth Ward: Thanks so much for having me.

Miller: So I mentioned that there are 15 bat species in Oregon. Can you give us a sense for just the diversity within that total?

Ward: Yeah. So we have a really wide ranging diversity of bat species here in Oregon and they range in many different habitats from the coast range all the way through the high desert, northern basin range of eastern Oregon. And they come in all different shapes and sizes and colors and different sizes of ears.

Miller: Well, you ended with ears, let’s start there, then. What do you mean by that? How big a variety of ear sizes are there?

Ward: Well, there’s a few species in Oregon that have quite large ear sizes, like spotted bats and pallid bats and Townsend’s big-eared bats. And they’re just much larger ears than some of our other species.

Miller: What are the reasons for having super large ears? I mean, the better to hear you with, I suppose. But what are they listening for?

Ward: Bats have really good hearing, but they also use echolocation to navigate and find insect prey. So, those big ears come in handy when they are producing their echolocation calls, which are sound waves that are typically above human hearing. But they produce these frequencies and those sound waves bounce off of objects in their environment such as prey, insects or trees, and then the sound returns to those bat’s ears which allows them to be really good at navigating and flying and catching those insects on wing.

Miller: So just to be clear here, a bat while it’s flying, it can make some kind of sound, many of which the frequency is too high for us to hear as humans. It could bounce off a flying mosquito and the bat could hear the resulting echo and know that it’s a mosquito and where it is and which direction it’s flying?

Ward: That’s exactly right.

Miller: Sort of boggles the mind. You mentioned the pallid bat and you also provided us with some of their calls. These are bats that make calls that we can hear. I’d love to hear but before we do, what should every Oregonian know about the pallid bat?

Ward: Pallid bats are really fascinating. They’re actually one of my favorite species here in Oregon. They’re very gregarious and as I mentioned, have large ears and a kind of little pig-like nose. And so pallid bats will, they have good hearing so they’re listening for prey, but they’re also echolocating to detect their prey. And they can actually attack prey on the ground. So, a lot of bat species are gleaning insects from foliage or capturing their insect prey on wing, but pallid bats will actually go to the ground. One interesting fun fact about pallid bats is that they have been shown to have an immunity to scorpion venom, which is one the arthropods that they’ll feed on.

Miller: So, the bats feed on scorpions, or the other way around?

Ward: Yeah, they also eat crickets and ants and other insects as well. But, yeah, one super interesting fact about pallid bats is they eat scorpions.

Miller: And they could be stung by them and have no ill effects, besides maybe a little bit of pain?

Ward: Correct, yeah.

Miller: You said that they’re gregarious. How do you know that?

Ward: They’re just social animals. They’ll roost collectively with other pallid bats. A lot of bat species are social and pallid bats in particular produce really interesting social calls that are audible to the human ear. So they’re producing those calls at a frequency low enough for us to hear in the evenings.

Miller: Let’s have a listen. So this is a pallid bat; and is what we’re about to hear, so this is not echolocating to find a tasty morsel to eat, but this is more to say hello?

Ward: Yes. Yeah, exactly.

Miller: Ok. Here it is.

[Bat sounds]

Miller: There were sort of two sounds there, there was the ongoing high pitch one and then the intermittent chirpy chirp. Are those both bats?

Ward: I believe one of those was an insect, but the pallid bats are calling out these little two calls at a time, and actually I couldn’t hear that super well on my end of things. So hopefully everyone else was.

Miller: Hopefully other people could hear it. It sounded good to me, but I’m in a very quiet room with good headphones on. You also gave us audio from another one, the spotted bat. What should we know about these critters?

Ward: So spotted bats are also super interesting species here and occur in the deserts of Eastern Oregon, typically near cliff and rock faces and rivers and they have really large ears and this beautiful black with white spotted pelage. And they’re just a really interesting species, they call it one of the lowest frequencies of all the bats that we have here. And actually the Northwest Bat Hub has a project that uses citizen scientist volunteers to perform listening surveys for spotted and pallid bats. So if folks are interested in volunteering for these surveys and wanna get involved, then please reach out to the Northwest Bat Hub. We’d love to get folks connected with our Audible Bats Project and we’ll plan on hosting group trainings for the project throughout the summer time. But surveys essentially consist of sitting out in the evening and listening for spotted and pallid bat calls and documenting them.

Miller: With what as the ultimate goal, why have people sit outside with notebooks listening for the calls?

Ward: Because they are calling at such a low frequency, they’re also really high flying bats as well, so they can be difficult to detect with more traditional methods of surveying. A lot of times we will use acoustic detectors, which are using a specialized microphone to record bat calls and then we analyze them on the back end. And each bat species has a different diagnostic call so you can actually look at those calls on your computer with some software to identify them. And those acoustic detectors are, they’re programmed in a way to be able to detect a wide range of frequencies. But also, there’s a number of bats that are calling at high frequencies, so the detector sensitivity and settings might be missing some of those spotted bat lower frequency calls. So the idea here is to supplement other survey methods by listening for those calls in order to help fill data gaps in the distributions of occurrence of this species throughout the state.

Miller: Let’s have a listen to the calls from the spotted bat.

[Bat calls]

Miller: So, both of these, if I’m not mistaken, are east of the Cascades. What’s a bat that folks, say, closer to the Portland Metro area or down the Willamette Valley, should be aware of?

Ward: Well, so you’re correct in that both of those species are typically found in our more desert environments, east of the Cascades. There has been some historical documentation of pallid bats in the Willamette Valley. But, those occurrences are few and far between. But yeah, in other regions of Oregon, certainly hoary bats, which are a migrating tree bat, would be a species to be tuned into on the western side of the Cascades.

They are a relatively large bat with this beautiful silver tipped hoary pelage, which is why they’re called the hoary bat. And they’re one of our migrating species which can be heavily impacted by wind energy development, actually. So that would be one bat to be tuned into. And they also will emit calls that are lower frequency calls that can be audible to the human ear. But spotted and pallid just have a much more distinct, lower frequency call.

Miller: What do you see as the most common misconceptions about bats?

Ward: Probably the one that comes to mind right away is that folks often think of the misnomer that bats are, blind as a bat, but bats are definitely not blind. They’ve got good vision, good hearing and then of course, echolocate. So they’ve got all these great, different senses to use. But they also, I guess folks also think of bats as flying into their hair or like, drinking blood. There are vampire bats that do have a blood meal, but they’re not found up here in Oregon or in the United States.

Miller: Nor do they go after humans, I imagine.

Ward: And they typically do not go after humans. No, usually they’ll actually go after livestock.

Miller: If you’re talking with somebody who, for whatever reason, maybe misconceptions, maybe some personal experience, although that maybe seems less likely. But if they have a fear of bats, where do you start to get them to love these mammals, flying mammals, even half as much as you do?

Ward: Yeah. I really think people fear most what they understand the least. So bats are, they come with all of this historical baggage or these stories, fantastical stories, of vampires. And of course, rabies too is always a concern for folks, but I think that just creating programs like this in order to educate folks on all of the interesting things about bats is a great place to start. Getting involved with something like our Audible Bats Project is another way to start learning and engaging. I think probably just reading about and learning about the diversity of bats is a great way to start. And folks could always go to the…  there’s eight different Oregon conservation strategy species, which are species that are of greatest conservation need in Oregon, and they have a website. It’s linked with ODFWs website and you can see pictures of them, look at the different habitats that they’re occurring in, look at the different threats that these bats are facing. I think just educating yourselves about the diversity of bats is a great place to start.

Miller: You mentioned rabies. How common is it for bats, various bat species, to carry rabies?

Ward:  Actually less than 1% of bats are carriers of rabies, so it’s an extremely low percentage of bats. But certainly, they do carry rabies and for… I would say if you know, or think that you have been bitten by a bat, then of course you should go and talk with a doctor about that.

Miller: It’s possible that one way people who have some kind of a fear of bats may get to appreciate them more is if they think about them as nature’s pesticides. I mean,  how many flies or bugs or mosquitoes might a bat eat over the course of a summer night?

Ward: So bats, they save the agricultural industry billions of dollars a year in pest, natural pest control.

Miller: That’s a real number, not just…  I mean, literally billions with a B?

Ward: Yes. Studies have been done, you can go online and look at this information. But yeah, billions of dollars, because an individual bat can eat up to its body weight in insects each night. So you’re looking at a whole lot of insects consumed by bats.

Miller: You said night and I said that too. Are all bats nocturnal or do some of them, are they active during the day?

Ward: Typically all bats are nocturnal and so they’re active in the evening and then sleeping during the day.

Miller: Earlier we were talking about the Citizen Science Project, so people can sit outside in evenings and listen for the few bats that make calls that are audible to humans. Is that work being done because there are concerns about bat populations in this state?

Ward: Well, certainly those two species, spotted and pallid bats, are species of concern in the state. And there are a number of threats facing Oregon’s bats from wind energy development, our changing climate and habitat loss, as well as white nose syndrome.

Miller: White nose syndrome is something, it’s been a while since we’ve talked about it on this show. Can you remind us what this is and where it started?

Ward: Yeah, of course. So white nose syndrome is a disease that has killed millions of bats in North America and it affects hibernating bats and is caused by the fungus Pseudogymnoascus destructans or PD for short. But PD can show up as a white fuzz on bat’s faces, which is how it got its name. And PD grows really well and thrives in cold, dark, damp places, like a cave. And so it grows and attacks the wing membranes and bare skin of bats while they’re hibernating, and then can cause bats to rouse from their hibernation and they can actually die because they burn up stored fat reserves that are needed to survive the winter or they will die of dehydration.

But this disease was first observed in New York State in 2006 and then pretty quickly spread south and west. The disease has been confirmed in Washington State and first showed up in Washington State in 2016. And Washington, as well as Idaho - it’s in Idaho as well, [it’s been] confirmed in Idaho -  but they have been conducting vaccine trials, because this vaccine has been shown to help curtail the fungal loads and curtail the impact of the disease. So while white nose syndrome has not been confirmed in Oregon, it certainly is in our neighboring states and we’re presuming in California, our other neighboring state. But wildlife managers here in the state continue to monitor bat populations and look for evidence of the disease in our state and treat it as a serious potential threat to the bats of Oregon.

Miller: What can Oregonians do if they want to support bat populations?

Ward: I guess one of the most important things that we can all do is to conserve their habitat, but for folks who are wanting to do something at their home or on their property, certainly building a bat box would be a good way to get engaged with bat conservation. And there are a number of different types of bat boxes that you can build and you can purchase some online, single chamber and multi-chambered bat boxes which can be installed on the side of buildings like your house, or on a pole, as long as there is proper solar exposure and it’s definitely a minimum of like 12ft. off the ground. You wanna have that elevated because bats will be dropping down from the box to then fly out. You want to give them plenty of vertical space. And typically, I’d recommend not putting them on trees, just because predators can utilize trees or branches to have access to those boxes. So usually on the side of a building is what I would recommend to folks, especially in a more urban setting. Or if you have the space to erect a pole with a box on it, that would be good too. But sighting is really important and choosing a sunny location that’s usually on an east or south facing direction, so that it can get more than six hours of sunlight a day.

And the design is important too. There’s a lot of different designs out there and you could just go buy whatever off the internet but, the best types of boxes are larger box designs that are tall and have, they’re four sided boxes that allow bats to have enough space to move up and down within the box so that if that box is getting blasted by the sun, they can move around to the back side of the box and have the ability to move around which can prevent overheating in the bat box. That has been, with our warming climate, this could potentially happen more often where those boxes get really hot. And if the bats don’t have room to move around, then there can be mortality from actually being in those bat boxes. So bat boxes are an excellent way to provide some habitat, but all I can say is, do a little bit of research and be smart about the placement of where you put them. And within a couple of years, usually bats will find those boxes. Keep that in mind too, it might take a couple of years for those bats to actually move into the box, so don’t get discouraged if they don’t occupy the house immediately.

Miller: So, you talked about the bat boxes. I’m wondering if folks may have pollinator gardens, or be aware of these. Sometimes people will plant things that will actually attract, or give food to butterflies. Is that another way to help bats? And how would that work to actually create habitat that could somehow help bats?

Ward: Bat gardens are a good way to attract insects that bats will eat for food. I guess I would start by saying plant, do your best to plant native plants and trees. And you want to use native plants that match your region and site conditions because yeah, native plants will attract native insects, which in turn provide bat food. Bats eat night flying insects, so you’ll want to plant flowers that either stay open through the night or bloom through the evening. You can also plant flowers that are really fragrant, like herbs such as rosemary or lemon balm or chives and light colored flowers that will attract moths and other nighttime pollinators. And then another thing I would recommend that you could do for a bat friendly garden or on your property -if you have some property - is to leave your dead trees, if they aren’t threatening your home or your neighbor or someone, leaving those dead trees standing, because bats will use exfoliating barks, cracks and crevices of those dead trees as roosting structures. So you’re really leaving a good habitat for bats and birds and other creatures.

Miller: In other words, it’s not just bats that might benefit from that. What other kind of habitat are you either inadvertently or on purpose creating when you let a dead tree stay where it fell?

Ward: Yeah, I mean, dead trees are excellent for bats, but also, I know woodpeckers love to use dead trees and also a large variety of insects and other plants and certainly our forests on the western side of the Cascades will… those dead trees become nursery logs for mosses and all sorts of other plants. It’s like a whole little ecosystem or universe of other things going on those dead trees.

Miller: We’ve talked a lot about what bats eat. But do they have natural predators themselves in Oregon?

Ward: They do have a couple of predators. Certainly owls or other raptors, like hawks, and snakes are typically the predators of bats. They otherwise don’t have a whole lot of major predators.

Miller: The Oregon Zoo just announced this week the birth of some rare flying fox bats there.

Ward: Ah!

Miller: That was an awe of excitement?

Ward: Yeah. Yeah. That’s great.

Miller: What should we know about this species, which I understand is not native to Oregon?

Ward: Correct. Yeah. We don’t have any flying foxes in North America.

Miller: You say flying foxes, but these are bats that just have the nickname, flying foxes, right?

Ward: Correct. So bats are part of the order Chiroptera and those, there’s this order [that]  is split up between Megachiroptera and Micro. And so Megachiroptera are the large flying foxes which you find in, like Indonesia and Australia. And they can actually have up to a 6ft. wingspan, and they’re certainly the largest of all of the bats throughout the world.

Miller: What’s the life cycle of bats? I noted that some that hibernate in, say in caves, are waking up right around now in the springtime and others are migratory. But what’s the average regular life of a bat?

Ward: It’s variable, depending on what type of bat we’re talking about. But because we’re talking about the bats in Oregon, I’ll just say the average life cycle of, let’s say, a little brown bat, they can live, on average, six to seven years, but could be up to 20 years. They’re actually, they have the ability to be quite long lived for the size of this mammal. But they’ll mate in the fall and then hibernate in the winter in caves or other structures. And interestingly enough, they’ll actually delay fertilization and then give birth to their pups in the summer.

Miller: Wait, so they mated, but the egg and the sperm don’t actually meet each other until after the female wakes up?

Ward: That’s right. Yeah. Pretty, pretty amazing, delayed fertilization. And, then they’ll have their pups in the summer or early summer, And many species of bats will form maternity colonies where the females all roost together and they have their pups and they tend to their pups in these maternity colonies. Most bat species only have, on average, one pup per year, so pretty low reproductive rate when you compare that with other mammals.

Miller: That also seems very different from rodents. And one thing that I think I learned or maybe was reminded of is that despite, I don’t know, their nicknames sometimes, bats are not rodents.

Ward: That’s correct. Yeah, bats are not flying rats. They are in their own order, Chiroptera, which means handwing, kind of an interesting group of animals. But their bat wings are actually basically modified hands, so that you can imagine a human skeleton hand, but with elongated fingers. And then in between those fingers, this membrane is stretched between each finger and they’ve got a little thumb with a claw on the end of it. But yeah, their wings are really flexible, because of this membrane and it just makes them really maneuverable, much more maneuverable than birds, because of that adaptation.

Miller: And maybe explains the sort of “herky jerky” flying style where they can seemingly stop on a dime and do some other weird flying angle that you only barely see at dusk. Beth Ward, it was a pleasure talking to you. Thanks very much.

Ward: It was great talking to you. Thanks so much for having me.

Miller: Beth Ward is the Northwest Bat Hub coordinator with the HERS Lab at OSU Cascades Campus in Bend, the Human and Ecosystem Resilience and Sustainability Lab.

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