It’s Kind Of a Bat Time

A misty evening

“By the time they notice a net, they’re sailing into it,” said Dan Neubaum, Colorado Parks and Wildlife’s (CPW) Species Conservation Coordinator, while carefully pulling apart the loops of a mist net, a common tool for capturing bats. 

The setups that Dan and the others in our group were putting together looked like super-fine, out-of-place volleyball nets. Stretching the nets between two poles across a small, marshy pool, the team was hopeful that this July bat survey would show what species of bats roost, forage and breed on Heartland Ranch, a preserve near Lamar, Colo., owned by the Southern Plains Land Trust (SPLT). 

The prairie became thick with the liminal dimness of twilight as Dan ensured the poles were well set and the nets were taut. If any bats came through that night, they would land in the paper-thin nets like a fly in a web: The material is so thin that echolocation, the sonar-like system that bats use to navigate, doesn’t pick up the net until the bat is too close to change course. They’re not harmed when captured, which is good for bats — and good for science. Mist nets give researchers the opportunity to study an animal that’s often seen, but rarely up close. Scientists can use successful captures to take measurements, record reproductive activity and sometimes fit bats with small tracking devices. On bat surveys, flying shadows become sources of valuable data.

Let the Blitz begin

“You know you’ve only seen the tip of the iceberg with bats,” said Jay Tutchton, who manages the bison herd on Heartland Ranch, reflecting on what it’s like to sit by a campfire and watch bats zip into and out of the meager light, never getting a good look — but wanting to know more. 

If you’re into bats, this was the place to be. The Bat Blitz brought together bat specialists from around Colorado. The data collected at these surveys would be submitted to the North American Bat Monitoring Program (NABat), a repository for bat-related data records. There isn’t much existing data on bats in Colorado’s southeastern plains; it’s an understudied part of the state, but with plenty of habitat to be found. These two nights in July were meant to fill in some of the gaps, starting with a basic question: What kind of bats are here?

“Right now, we’re at the level of just basically finding out what’s here, what issues might be here,” said Jay, a former environmental lawyer and current Colorado Parks and Wildlife commissioner. For Jay, the Bat Blitz was not only a “knowledge-building exercise,” but “a great opportunity to hang out with experts and learn.”

The ranch is a stronghold for shortgrass prairie habitat. It’s a site for ecological restoration projects and rare-species protection. The property contains populations of some species listed on Colorado’s State Wildlife Action Plan (SWAP). The SWAP is compiled by teams of wildlife experts, and identifies the Species of Greatest Conservation Need (SGCN) in Colorado. Species that face threats to their population health are ranked in one of three tiers — Tier 1, Tier 2 or Species of Greatest Information Need (SGIN) — according to how urgently they require conservation interventions, such as habitat restoration, captive-breeding programs and others. All 50 states publish a revised SWAP every 10 years, with new information on species, their habitats, the threats they face and what conservation strategies they may benefit from. SWAP animal species that live on the ranch include black-footed ferrets, black-tailed prairie dogs, burrowing owls — and an indeterminate number of bat species.

Of the 20 species of bats found in Colorado, 18 are SGCNs.  While populations are relatively healthy at the moment, bats face new and looming threats that could cause declines in the future. Though understudied, the Lamar area is key to understanding the newest threat to western bats: white-nose syndrome (WNS).

White-nose syndrome

WNS is an infection caused by the fungus Pseudogymnoascus destructans (Pd). The nose is where clusters of the white fungus grow most visibly on an infected bat, but any hairless part of the animal can be affected. Severe infections can turn the elastic stretches of skin that make up a healthy bat’s wings into brittle parchment, making flight impossible.

Pd is an invasive species. Genetic research has found that the strain that infects North American bats originated in the region of Podillia, Ukraine. The first bats known to be infected in North America were documented in caves near Albany, N.Y., in 2006. Since then, bats in Europe and Asia have been found to carry the fungus, but don’t suffer symptoms like North American bats. The fungus thrives in cool, humid environments, making caves the perfect spot for spores to hide. Experts believe that most bats are exposed to Pd in the fall or early winter, just before they go into hibernation. During the deep, sleep-like state of hibernation (when their heart rate and metabolism slow down, and their body temperature drops almost to the ambient temperature of their roost), their immune systems are less active, allowing the disease to take hold. The Pd spores grow into ugly, dense clumps of white speckles. WNS can cause tissue damage, but it’s not the most destructive effect. The advancing infection causes bats to wake up in the middle of winter. Bats hibernate to save the fat reserves they build up by gorging on insects during the fall. In winter, hardly any insects can be found on the landscapes (just try to find a junebug in January). If a bat wakes up too early, it can burn through its fat reserves before insects return in spring — and can starve to death.

The damage caused by WNS in New York was immense. Entire colonies, particularly of little brown bats (Myotis lucifugus), disappeared. In just a few years, bat scientists all over the eastern United States were reporting outbreaks.

“I worked for the state of Kentucky, and we saw white-nose come into the state, and it was pretty devastating,” said Brooke Hines, a bat biologist and the manager of the environmental section of Burns & McDonell, an engineering company. Brooke moved to Colorado in 2018. Accompanied by her daughter, this was her first night mistnetting in her family’s relatively new home.

“Watching the bat populations just drop was heartwrenching,” she said of her experiences in Kentucky. “I was keeping my fingers crossed that it hasn’t moved west. … I’m curious to see how the hibernation counts out here go.”In March of 2023, staff with the National Park Service discovered the first bat with WNS in the same area as Bat Blitz. The species was a Yuma myotis (Myotis yumanensis).

The Yuma myotis

Myotis is the most geographically widespread genus of bats (and possibly of any terrestrial mammal, besides humans). A combination of the Greek words for mouse and ear, it describes the roughly 100 “mouse-eared,” mostly insect-eating species found on every continent except Antarctica. The Yuma myotis is one of eight myotis species in Colorado. As bats go, it’s one of the cuter species — with puffy, tan fur; a short, terrier-like muzzle; button eyes; and long, elfin ears. Though puppet designer Chris Walas based the creatures in “Gremlins” on the tarsier (a small nocturnal primate), the Yuma myotis would have been an equally charismatic model for the iconic imps of Kingston Falls.

As a colony-roosting, hibernating bat with a history with WNS, it’s listed as a Tier 1 species on the SWAP. Since the first case near La Junta, a little brown bat (also a Tier 1 species) found near Longmont tested positive for the disease in 2024. WNS is emphasized as a major new conservation concern in the SWAP, and species that are known to hibernate in Colorado could see rapid declines — if the fungus spreads in the same way it has in the eastern United States. The effects of WNS in Kentucky were “heartwrenching,” as Brooke put it, but how much of an impact the disease will have on Colorado bats is uncertain.The upcoming SWAP is entirely online, and includes the new Data Hub, where the existing and prospective research and conservation projects are listed for each Tier 1 and Tier 2 species.  For the Yuma myotis, information on survey efforts and WNS research and management is included.

A slow night

“I call it the confluence. We’re standing in the main mud creek,” said Jay. The nets were set. Crickets were steadily chirping. The cliff swallows that had been flying overhead ceded their aerial hunting grounds to the creatures of the night. Now was the time to sit, wait for the fall of darkness — and hope for some action.

“We have done a lot of conservation work trying to improve the streams,” said Jay, describing the work he and the others at Heartland Ranch have done to enhance riparian areas. “So I was kind of excited to see if bats were utilizing the improved stream habitat.”

The Yuma myotis isn’t a picky eater, happily taking beetles as well as moths, mosquitoes and other soft-bodied insects. It is particular about where it hunts, though, which is almost always over water. Once darkness hits, it leaves its day roost, often a narrow rock crevice on a cliffside or an abandoned cliff swallow nest, and begins foraging in wetland areas of deserts and dry forests, darting this way and that to catch insects flying over the water. It can even slow down its flight enough to pick off insects sitting on the water’s surface, a technique called gleaning. Yumas are particularly tied to water, but setting up near a pond, marsh or slow-moving stream at sunset, between May and September, is a good way to spot any kind of bat in Colorado.

Sounds of thunder occasionally rolled over the prairie when darkness was complete. The flashes of electrical storms light up the clouds in the distance. No bats so far.

I learned quickly to keep my headlamp off. Seconds after turning it on, hoards of moths would rush towards the light, making a human lamppost out of me and leaving moth dust on my face. So, I was more than certain that moths were here — but where were the bats?

Eventually, the threatening sky gave way to rain. If we waited too long, the rain would have turned the ranch’s sandy dirt roads into untraversable trails of mud. Preferring not to be stranded, we packed out early. No bats, but we still had night two.

Survey speculations

So, where were the bats? 

It could be that shortgrass prairies in Colorado just naturally don’t have many bats. “Maybe they are just very few and far between,” said Kieran Andreoni, Conservation Director at SPLT, the morning after night one. “And that could be just because that’s the carrying capacity [the number of individuals a habitat can provide food, water and shelter to] of the area.”

With a decade’s worth of study and experience, grasslands are Kieran’s specialty. “If you were to say, ‘I’m going to go out in nature for a few days,’ the first thing that comes to your head probably is a nice subalpine forest in the mountains or something like that,” he said. “But grasslands really are so important economically, ecologically and all that. My specialty has always been in plants. I really love prairie wildflowers.”

While scoping out survey sites for that evening, Kieran gave us a brief botanical tour of the ranch. He proudly showed us the Colorado green gentian (Frasera coloradensis), a small, green plant with white-edged leaves. An endemic plant, southeast Colorado is the only place in the world it exists. It’s listed as a Tier 1 species on the SWAP.

Despite my group’s lack of bats, night one wasn’t a total Bat Bust. Kieran’s group, which set up nets over a stock dam at the southern end of the ranch, captured three male hoary bats (Lasiurus cinereus).

Hoary bats have white-tipped fur on their backs and bellies, tall foreheads, and bear-like faces surrounded by short, tan fur. In some ways, they’re the opposite of the Yuma myotis: They roost alone rather than communally, and migrate rather than hibernate in winter. Because they don’t roost communally or hibernate, WNS is not a major concern for hoary bats, but as another Tier 1 species, they face threats of their own.

Hoary bats are known to travel long distances on winter migration, following currents that lead them into the territories of wind farms. Throughout its range, the hoary bat has declined from collisions with turbines. The site Kieran’s group surveyed was near a wind farm. 

To mitigate the effects of wind farms, specialists have developed schedules that reduce turbine activity during peak migration periods. As with the Yuma myotis, the SWAP makes recommendations and describes the threats the hoary bat faces, which can be found in the Data Hub.

Kieran’s team captured three male hoary bats (Lasiurus cinereus) on night one. Photos by Kieran Andreoni. 

“Maybe it could be disease dynamics, something like white-nose syndrome,” said Kieran, continuing to guess why my group didn’t find any bats. Bad weather could also have been a factor. “Here on the south end, we were actually just beyond the edge of the storm, and so maybe that allowed us calm enough weather for the bats to feel comfortable coming out to forage.”

Surveys can be messy and weather dependent, but they’re a necessary tool for establishing where species occur and in what abundance. 

“There hasn’t been enough monitoring and testing in this part of the state to really know,” said Kieran. “So I think that’s why this is really important, to be out here doing this.”

Two buttes are better than one

The bat that Dan held in his hand chattered in protest. 

Most of our group from the previous night — Dan, Jay, Jonathan Reitz (an Area 12 Terrestrial Biologist for CPW) and I — along with Tina Carpenter, a seasonal employee with CPW, had driven to Two Buttes State Wildlife Area, night two’s survey site. Our first stop wasn’t a natural marsh or a cliffside day roost — but a barn. It was late afternoon, a few hours before sundown. Dan, equipped with thick work gloves under a layer of blue nitriles, walked into the barn to investigate. Moments later, he walked out with a small bat in his hand. The bat struggled to get free, but to no avail, all the while squeaking indignantly. While echolocation clicks are, in most species, higher than our range of hearing, other bat vocalizations — including apparently those that roughly translate as “unhand me, vile ruffian!” — are audible to the human ear.

Swollen mammary glands on the bat told Dan that she had reproduced this year. But this barn was sparsely populated and definitely not a maternity roost, which would be teaming with mother bats and pups at this time of year. This bat had either lost a pup or the pup weaned early. 

Though confident he had a Yuma myotis in hand, Dan took a DNA sample to send off to the lab, just to be sure. Yuma myotis can be very similar to little brown bats in size, color and roosting behavior, making genetic verification of a species often necessary. To get genetic data, Dan took a wing biopsy punch, cutting a tiny circle of tissue from the bat’s wing, avoiding critical veins. Biopsies are the best samples for extracting DNA, and bat wing tissue is some of the fastest-healing tissue among mammals. 

“We’re doin’ a hundred percent better than last night,” said Jay.

“We’re up by one!” said Dan, laughing.

Dan returned the bat — who, despite not being a terribly good sport, provided us with some valuable data — to the barn, placing her back where she was to finish off a day’s rest. Before we left, he collected guano (bat droppings) samples. Guano was all over the floor of the barn, but it wasn’t as gross as you might imagine: In species that eat beetles, the hard exoskeletons are crushed up in the gut, but come out with their metallic shine intact, making the ground below a bat roost into a sparkling glitterscape. A guano sample, which also contains DNA, would confirm that the Yuma myotis Dan had caught was representative, not just a one-off in a roost that’s typically used by a different species. Guano can also contain evidence of WNS. Bats groom by licking their fur, like cats; if Pd is present on a bat’s fur, the bat will swallow the spores and pass them in its guano. 

After seeing our first bat of the Blitz, the five of us drove to the survey site. The area was a small valley bordered by tall, red cliffs. At the bottom of the cliffs was a concrete drainage tunnel holding shallow, standing water. Dan and Jonathan set up nets just outside the tunnel, finding spots to plant the poles among the thick wetland foliage. As we learned earlier in the evening, bats can take advantage of human structures for roosting. This site had adequate shelter for bats and water that nighttime insects would be flying over — it was a promising spot.

The rattling sounds of insects ushered in the evening. The nets were set by sundown — and it didn’t take long for the Blitz to truly begin.

About a half hour after sundown, our first bat hit the net — then another, and another, each flapping in vain to get free before Dan took her out of the net, tucked her into a small sack and brought her back to his data-collection setup. Bat in hand, Dan talked us through his process, giving us some lessons about bats along the way.

“With bats, you tell the age by looking at their finger knuckles,” he said, pointing to the bat’s wing. “And when they’re really knobby, that’s an adult. If I shine my light through it, it’ll look solid. But if it was a juvenile bat, which we’ll start catching here in a few weeks, that’ll look more like a puffy sausage rather than a knot, and the light will actually pass through it because the bone hasn’t fully ossified yet. And so that’s a really good way to tell age because the juvies will be almost as big as the adults by the time they start flying.”

The bats we were catching were likely more Yuma myotis, and Dan repeated the wing biopsy process for each one. In between measurements, he stretched out the wing of one bat to highlight a familiar structure.

“It’s just finger bones with a forearm and an elbow, just like you have,” he said. “All the same bones, except they have skin grown between them, and they’re stretched way out to make a wing.” According to Dan, we may think of bats as bizarre and divergent, but bats’ body structures and behaviors are just slight tweaks of all the mammalian basics.

A light rain began, pushing the process to the shelter of a vehicle’s trunk door to protect the captured bats and the data sheets. Along with age, Dan took down weight, sex and reproductive status. All 12 bats were lactating females, evidenced by bare skin around the nipples. We had found a bustling maternity colony, all mothers raising up — if you will — children of the night.

With the bat from the barn earlier, we were at 13 bats for the entire evening. As the weather started to look more and more like the previous night, we decided to pack it out a few hours early. Though perhaps cut short, the night’s results were instructive.

Bats of Colorado

Each of Colorado’s bats has a unique set of habits and adaptations. From the spotted bat (with its massive, pink ears and a trio of white spots on its back) to the silver-haired bat (which sings, communicating with vocalizations that are complex in pitch and rhythm, like bird songs), bats in Colorado vary widely in their ways of life. You can learn more about each of our state’s bats in CPW’s new pocket guide, “Bats of Colorado: Shadows in the Night.”

You can find free copies of the booklet at CPW’s educational and wildlife viewing programs related to bats — call your local state park or regional office to ask about upcoming events and booklet availability. During Bat Week, the week leading up to Halloween, many state parks will be running bat programs and events and will be handing out booklets. 

The future for bats

The appearance of white-nose syndrome in Colorado was inevitable, but its consequences are not. 

During an interview in November 2023, Dan told me that some differences between western and eastern hibernation roosts could affect how WNS plays out in Colorado. In eastern states like New York, bats roost in caves that stay cool and humid year round, exactly the conditions that the fungus thrives in. Most of Colorado’s bats, however, don’t roost in caves. Little brown bats, for example, hibernate in deep rock crevices and in talus, the spaces between broken rocks on mountain slopes. Some talus in Colorado have been found to vary in temperature and humidity between seasons, which could make them less hospitable to the fungus.As we said goodbye at the end of the Blitz, Dan left me with an optimistic message. We not only found a thriving maternity colony, but a thriving maternity colony of the same species in the same area where WNS was first found in Colorado. That could be good news for the Yuma myotis — and for bats in the West more broadly.

By: John Anglin, CPW Communications Specialist