HOPPING TO IT

By DENNIS WEBB

Dennis.Webb@gjsentinel.com

When Josephine Hansen and fellow Girl Scouts spent a summer evening catching 14 bullfrogs at Corn Lake in 2022, it was a bad day for the bullfrogs but a good day for citizen science and efforts to protect native amphibians in the Grand Valley.

Josephine, now 13, was part of a project being led by Denita Weeks, a Colorado Mesa University assistant professor in biology. The project is assessing and addressing the threat that American bullfrogs, an invasive species in Colorado, poses to native species. The project partly consists of involving the public, through a creative campaign Weeks came up with that she calls Bullfrogs for Beers, in catching the bullfrogs to reduce their numbers and allow for the specimens to be studied.

Josephine remembers catching the slippery creatures with gloved hands or a net and delivering them to Weeks.

“Then she would weigh them and measure their height, and then put them in the bag to be collected and brought back to CMU,” she said.

The bullfrogs met their end through the use of a high dose of a fish anesthetic that Weeks said humanely euthanizes them, numbing them and essentially causing them to go to sleep before they die.

It’s not a part of the job that Weeks particularly relishes.

“Amphibians are my favorite animals and it’s difficult because it’s not the bullfrogs’ fault that they are here, but they are a problem,” she said.

Captured bullfrogs can be used in better understanding the extent of the problem. CMU students analyze their stomach contents to see the degree to which bullfrogs are preying on other amphibians or competing with them for food sources such as insects. Student also have been doing lab work to determine the degree to which bullfrogs are infected with a fungus that can spread between amphibians and cause a fatal disease in them.

Captured bullfrogs also have been used as a source for standard frog dissections by students at CMU, and Weeks said she has bullfrogs available for local schools interested in obtaining frogs for dissection without having to buy them.

“It feels good to do as much as possible with the bullfrog if we’re going to remove it,” she said in an interview.

BULLFROGS FOR BEERS

In brainstorming ways to get the public interested in helping round up bullfrogs from area waters, Weeks came up with the idea of giving people beer vouchers for captured frogs, in organized events after training of the volunteers.

“It turned out to be a really great incentive,” Weeks said during an online presentation on her project presented by the Colorado Canyons Association in December.

She said Base Camp Beer Works stepped up to donate beer for the effort, and Trail Life Brewing later did the same. With not everyone liking beer, and some volunteers such as Josephine being

See HOPPING, page 4A ➤

Royanna Crawford, now Colorado Mesa University graduate, is shown helping out with a past Bullfrogs for Beers bullfrogs capture event when she was still at CMU.

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Colorado Mesa University Assistant Professor Denita Weeks looks through a microscope inside of a research laboratory on Feb. 1. Weeks has been researching the impacts of invasive bullfrogs on local amphibians in McInnis Canyons for five years, as the bullfrogs have been to found to eat anything they see, decreasing populations of native species and limiting their food sources.

LARRY ROBINSON/ The Daily Sentinel

Locally caught invasive bullfrogs are seen inside a laboratory at Colorado Mesa University on Feb. 1.

LARRY ROBINSON/ The Daily Sentinel

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underage, Weeks found other partners who have provided other donations to reward them, including Graff Dairy and Pablo’s Pizza.

Other organizations that have been involved in things such as getting out the word about the project, recruiting volunteers or providing some funding are RiversEdge West, Eureka! McConnell Science Museum and Colorado Partners in Amphibian and Reptile Conservation (COPARC). Weeks and Colorado Canyons Association also are discussing starting to work together as well, given that entity’s involvement in citizen science and education initiatives.

“We’re really hoping to get more involved with it,” said Annie Carter, CCA’s educations programs manager, who got the chance to join Weeks last summer on a Colorado River trip through McInnis Canyons National Conservation Area with people including project funders and Bureau of Land Management personnel. McInnis Canyons is where Weeks is focusing her efforts to study and protect native amphibians.

“We did a cool night hike up Mee Canyon and it was just an awesome educational experience,” Carter said.

Nighttime is often the best time to spot frogs and toads and hear their calls in Mee and other canyons that connect with the river. Such canyons can be fairly dry but still collect enough water through rainfall or river backwash to provide often-temporary pools where amphibians can breed.

Weeks has been studying local amphibians and the threats facing them since coming to CMU after getting her doctoral degree in 2018. In her PhD work, she studied the fungal disease that is the focus of her local research today.

The fungus, Batrachochytrium dendrobatidis, or Bd, is found in water and causes a disease called chytridiomycosis in amphibians. The fungus embeds in amphibians’ skin, which the animals rely on to take in water rather than drinking it, and the fungus impacts things such as water balance and electrolyte levels in affected animals. The animals can become lethargic, stop eating and eventually suffer from cardiac arrest, Weeks said.

Weeks has a cooperative agreement with the BLM for her project and also is partnering with Colorado Parks and Wildlife and the U.S. Geological Survey. Her research has been focused in part on learning what amphibians are living in McInnis Canyons, a first step in being able to work to protect them from threats such as drought and invasive species, through means such as management decisions by agencies. Native amphibians being found it the McInnis Canyons region are the Woodhouse’s toad, red spotted toad, Great Basin spadefoot, canyon tree frog, tiger salamander and northern leopard frog. The latter frog is listed in Colorado as a state species of concern.

EATING ‘ANYTHING THAT MOVES’

In terms of bullfrogs, their presence locally as an invasive species “is an issue because bullfrogs will eat anything that moves, so you can roll a ping pong ball in front of them and they will try to eat it. But that also means that they will try to eat our native species and they do,” Weeks said.

According to Colorado Parks and Wildlife, American bullfrogs grow up to eight inches long and weigh up to one pound. They’ll eat whatever moves and fits into their mouths, including fish, frogs, birds, bats, snakes, tarantulas, small mammals and a variety of invertebrates, the agency’s website says. They are on Colorado’s aquatic nuisance species watch list.

Native to the eastern United States, they were reintroduced to Colorado both intentionally, as game animals and to control mosquitoes and other pests, and unintentionally, such as when tadpoles were introduced along with introduced sports fish, Parks and Wildlife says. It says they also have been released when no longer wanted as pets or as laboratory or classroom animals. They are widely distributed in eastern Colorado and increasing their range in western Colorado river valleys.

Weeks conducts her bullfrog capture events under a Parks and Wildlife permit.

Weeks said there is evidence indicating the arrival of bullfrogs has led to declines of northern leopard frogs in other parts of the state. One question is whether bullfrogs are eating things like northern leopard frogs locally. Fish, a Woodhouse’s toad, a pelvis from some kind of frog and even a juvenile garter snake have been found in the stomachs of some of the locally collected bullfrogs.

Local amphibian survey efforts can include trying to spot/capture them or hear and identify their calls. Cotton swab can be used take samples from captured animals before their release to test them for Bd. Water samples also can be collected to see if it has DNA from bullfrogs, even if they can’t be seen or heard in an area.

Through such methods, evidence of bullfrogs has been found in Salt and McDonald creek and Rattlesnake, Mee and Moore canyons in the McInnis Canyons regions. Upstream, the bullfrog capture events have been conducted in places known to have healthy bullfrog populations such as Corn Lake, Connected Lakes, Audubon Nature Preserve and Snooks Bottom Open Space. Weeks thinks such sites along the Colorado River could be source locations for bullfrogs downstream in McInnis Canyons.

Within McInnis Canyons, evidence of bullfrogs has been found usually close to the Colorado River rather than far up side canyons, except in Mee Canyon, where — despite barriers to travel such as dropoffs and waterfalls — they have been found up to two miles into the canyon.

The fungus Bd has been found in locations such as Snooks Bottom and the Audubon Nature Preserve, but in McInnis Canyons has been found only once, in 2019 in Mee Canyon. Weeks said bullfrogs are among frogs that will carry the fungal infection and show no sign of the disease, whereas some native species in Colorado are extremely susceptible to the disease. She said the 2019 detection, while isolated, is still concerning, and efforts continue to monitor McInnis Canyons for the fungus.

Weeks hopes to expand the citizen science effort to include river boaters who can easily access river side canyons and do bullfrog collections in places such as Mee Canyon. She also has purchased remote acoustic and water-detection devices that she is using in Mee Canyon to know when water is present, what the temperature is and when various species of frogs are calling. When combined, that data will help determine things such as if bullfrogs are showing up only at certain times of years. Weeks said it would be great to have help from hikers and boaters visiting the canyon to download data from these devices using Bluetooth.

NATIVE SPECIES ‘IN TROUBLE’

Emily McCall, a wildlife biologist for the BLM now working for its Colorado River Valley Field Office, used to work at the Grand Junction Field Office and said she helped out a little with Weeks’ efforts at that time. She’s excited about the work Weeks is leading.

“All of the data she is collecting is highly relevant to land management, as trends are showing that our native amphibians are in trouble and under some significant environmental pressures,” she said, pointing to disease, bullfrogs and other threats such as lengthy droughts and warming temperatures.

She thinks the community involvement aspect of the project is important in spreading awareness about largely nocturnal native species that don’t get much attention and about the fact that the American bullfrog isn’t native to the West.

One concern both she and Weeks have is that bullfrogs can be purchased at pet and bait shops, potentially leading to situations where bullfrogs end up in local waters in cases such as bait slipping off hooks or out of buckets, or people releasing pet bullfrogs once they get big.

“I think many of these animals are likely getting released into local waters every year,” McCall said.

On its website, Colorado Parks and Wildlife includes messaging urging people not to release things such as aquarium fish and pets into the wild, and to instead opt for alternatives such as returning them to a pet shop or giving them to a shelter.

An employee with J&M Aquatics and Pet Center in Grand Junction who asked not to be identified said that store sometimes carries bullfrog tadpoles. She said the store displays a poster from www.dontletitloose.com explaining why people shouldn’t release pets into the wild and listing options other than releasing them. That website and initiative are sponsored by the U.S. Fish and Wildlife Service and managed by the Invasive Species Action Network.

The employee said her store always lets people know when they buy things such as goldfish and reptiles how big the animals will get, how long they live, and the fact that the store will take the animals back if they can’t keep them anymore. She also said she hadn’t been aware that bullfrogs were a problem locally, and expressed an interest in sharing information about bullfrogs with other store employees.

EDUCATION VALUE

Weeks said she thinks that when people who don’t want bullfrogs as pets anymore realize they can be dangerous animals to release into the environment, that shift in

See HOPPING, page 11A ➤

Picture above are one of the locally caught invasive bullfrogs and a garter snake that was found in its stomach contents, as seen inside a laboratory at Colorado Mesa University on Feb. 1.

LARRY ROBINSON/ The Daily Sentinel

The northern leopard frog is a local amphibian facing threats including the presence of the invasive American bullfrog.

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perspective can have a big impact.

She doesn’t think fullscale eradication of local bullfrog populations is possible.

“But I do think that the benefit of this project is getting the community involved in conservation and educating the community about an invasive species because many people don’t realize bullfrogs are invasive,” she said.

Weeks sees value in removing even a single bullfrog because of how many eggs they lay, and hopes that reducing bullfrog numbers will help bring back species such as northern leopard frogs. That is something she will be monitoring to see if it happens, and already she is hearing anecdotally that northern leopard frogs may be doing better in some places locally due to fewer bullfrogs being present.

Josephine Hansen said of the project, “I’m pretty hopeful about it. I think the stuff they’re doing is really cool and good for the environment and in the long term will have quite a positive benefit.”

She said it was fun on the night she and fellow Girl Scouts captured bullfrogs to see some other frogs, including northern leopard frogs.

Josephine’s father, Eriek, is a biology professor at CMU and colleague of Weeks’. He said that as a parent, he enjoyed seeing the Girl Scouts being so engaged in the capture effort, and he’s impressed with Weeks’ efforts getting the community involved in citizen science.

“Denita’s going great work. It’s an awesome project. Getting the Girl Scouts involved and different members of the community is fun to see,” he said.

Weeks said involving the community has expanded the opportunity for data collection related to her research.

“We’ve started to develop a really great database because of these citizen science activities,” she said.

Brett Walker is a Parks and Wildlife researcher who isn’t involved with Weeks’ project but has been involved with his kids in the bullfrog collection effort. He said in an email that her work “is so great. It’s at the intersection of aquatic invasive species, conservation of native amphibians, emerging diseases, and education. And she’s brought expertise at CMU together with CPW, conservation organizations, local businesses, and the community that care about the Colorado Canyons and Colorado River to make it all happen.

“The research she’s doing is helping native species that don’t otherwise get much attention and are in decline. And many people don’t realize that bullfrogs are invasive here, so the project is helping people understand the issues. Plus, catching bullfrogs for beers (or root beers or ice cream) is so ridiculously fun!”

Local research into native amphibians in the McInnis Canyons area and the threats they face includes field work in their habitat.

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