wyoming toad

Foreshadowing the Amphibian Crisis: The Wyoming Toad

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Authored by Blake Klocke, curator of amphibians for The Detroit Zoological Society

The Detroit Zoological Society (DZS) is helping a species hop back from extinction!

The Wyoming toad was once found in abundance in the Laramie River Basin. However, catastrophic population declines were observed throughout the 1970s. By 1983, the Wyoming toad was thought to be extinct. Biologists could make no clear determination for the cause of the decline.

With a bit of luck, a small population of about 20 animals was rediscovered in 1987 at Mortenson Lake, bringing hope that the species could be saved. Rescuing the species by bringing it into captivity was the only option to avoid extinction.

Amphibian Chytrid Fungus and Preventing Amphibian Extinctions

Throughout the 1980s and 1990s, amphibian declines were common around the globe – something that puzzled biologists. At the time, there was no obvious answer as to why multiple amphibian species were rapidly disappearing in Australia, Central America and the United States. In 1998, the amphibian chytrid fungus – a microscopic primitive fungi – was discovered to be the cause of disease resulting in these declines. Biologists have attributed the amphibian chytrid fungus to be the primary cause of approximately 100 amphibian extinctions and to have impacted more than 700 amphibian species. No other wildlife disease has impacted biodiversity as much as this fungus. 

The Wyoming toad is highly susceptible to the amphibian chytrid fungus. The National Amphibian Conservation Center at the Detroit Zoo was built in part as a response to the amphibian biodiversity crisis, which assisted in keeping some of the most imperiled species away from the edge of extinction. The Wyoming toads at Detroit Zoo live in a biosecure room, which keeps them safe from being potentially exposed to the disease!

Ex-situ rescue, which is when a species is brought out of the wild into captivity for conservation, is a last resort. Unfortunately, we are often left with no other options. Rescuing a species in captivity requires intensive management to maintain the population, and it’s a long-term commitment by a dedicated and passionate team.

Wyoming Toads at the DZS

The DZS was an early partner in rescuing Wyoming toads, welcoming our first toads in 1995. A Species Survival Program (SSP) was also formed in 1996 to organize efforts among zoo partners and the U.S. Fish and Wildlife Service. The amphibian team at the DZS has produced 10,730 Wyoming toad tadpoles, toadlets and adults for reintroduction since joining the program in 2001! These animals are bred at the DZS and later sent to Wyoming to be released into the wild. The Center for Zoo and Aquarium Animal Welfare and Ethics at the Detroit Zoo has also led studies that have helped improve the husbandry of Wyoming toads in captivity by comparing the preferences for substrate, which improves our care for this very important species.

Caring for Wyoming Toads at the Detroit Zoo

Mike Andrus is the primary colleague who takes care of the Wyoming toads at the DZS, and his years of experience in the amphibian department caring for these toads is one of the keys to Detroit Zoo’s success. Mike handles more than 30 toads at the Zoo

Mike Andrus is the primary colleague who takes care of the Wyoming toads at the DZS, and his years of experience in the amphibian department caring for these toads is one of the keys to Detroit Zoo’s success. Mike handles more than 30 toads at the Zoo, where he carefully cycles the temperature throughout the year, including when he places the toads in a refrigerator to hibernate. This process requires a lot of fine-tuning and experience – and prepares the toads, which are each equipped with their own individual ID to track genetics, for breeding.

Mike Andrus holds a Wyoming toad in the biosecure room.

Wyoming toad tadpole reintroductions

In June 2022, Mike traveled to Laramie, Wyoming to participate in the reintroduction of Wyoming toad tadpoles. Several thousand tadpoles were sent from SSP partners for reintroductions. It was a busy day, as tadpoles were placed in bags of about 100 animals and methodically distributed around reintroduction sites.

Tadpole reintroductions are very important to continue supporting the recruitment of new toads into the population. In the months following the tadpole reintroductions, hundreds of recently meta morphed toads are found — each one with the potential to make it to adulthood and breed in the wild.

Bags of tadpoles produced by zoos around the country and U.S. Fish and Wildlife Service acclimate before reintroduction.

Wyoming toad surveys

In August 2022, I participated in the Wyoming toad field surveys and an annual SSP meeting. The team was successful in finding many young toads, likely from tadpole reintroductions and some wild breeding. The most exciting part was finding more than 15 breeding-sized adults! Some of the toads had a small identification tag, demonstrating that reintroduced juveniles and adults from captivity are surviving in the wild.

Wyoming toads were found at all four field sites the team visited, a very good sign for a species that was once thought to be on the verge of extinction. Currently, there is no method to mitigate the amphibian chytrid fungus in the wild, but in recent years there are an increasing number of rediscoveries of species once thought to be extinct and vulnerable species persisting in the presence of chytrid.

We’re optimistic that the Wyoming toad will soon hop back from extinction!

A toad reintroduced months beforehand was found during our surveys and appeared in good health. Adult toads receive a tiny tag, much like a micro-chip for a cat or dog, that let us know who they are when they are found in the wild! 

Thank you to our SSP partners, who make saving this species possible:

• U.S. Fish and Wildlife Service

• Kansas City Zoo

• Cheyenne Mountain Zoo

• Omaha’s Henry Doorly Zoo and Aquarium 

• Como Zoo

• Mississippi River Museum

Animal Welfare: A Compassionate Approach to Toad Conservation

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Staff members from the Detroit Zoological Society’s (DZS) National Amphibian Conservation Center and Center for Zoo and Aquarium Animal Welfare and Ethics are collaborating to find out what toads like. By doing so, we can ensure we are providing for their welfare while they’re in our care and also contributing to the conservation of this species in the wild.

Wyoming toads (Anaxyrus baxteri), also known as Baxter’s toads, are considered extinct in the wild, and their numbers must be bolstered each year by reintroductions of individuals born and reared in the care of humans. They can be found in two locations within the Laramie Basin in Wyoming, thanks to efforts by the U.S. Fish and Wildlife Service and other dedicated organizations including the Detroit Zoological Society.

Wyoming toads were abundant until the 1970s when their numbers began to plummet due to the spraying of aerial pesticides, habitat alteration and the fungal infection caused by chytridiomycosis, which is decimating amphibian populations worldwide. By 1984, the species was listed as endangered and in 1993, that listing changed to extinct in the wild. That year, what were believed to be the last 10 remaining Wyoming toads were brought into a facility to safeguard them and begin a breeding program in the hopes of one day reestablishing the species in the wild.

The Association of Zoos & Aquariums started an official Species Survival Plan for the Wyoming toad in 1996, a program in which the DZS has been very active, including releasing thousands of toads hatched at the Detroit Zoo since 2001. Through the efforts of this collaborative breeding program, more than 1,500 Wyoming toads are currently believed to live in the wild.

Because breeding success continues to be a great concern for this species, the Wyoming Toad Species Survival Plan established strict guidelines for habitat setup at the participating institutions. The habitats are rather sterile to reduce the potential development of any disease processes and consist of a dry area typically made of PVC, a water feature, a basking lamp and a shelter. This type of setup was necessary to properly monitor conditions to promote higher survival rate and breeding success. Due to the success of the reintroduction program, new habitat parameters can be explored, providing the toads with a more stimulating environment.

It is important that we assess how this affects the toads and what preferences they might have. To that end, habitats are being created that provide the toads with a choice between the standard habitat and one that has more naturalistic elements, such as soft substrates, multiple shelters and water features of varying shapes and sizes. With the assistance of our current resident, Emilie Gupta, we will be studying the toads to determine if this choice is important to them. Providing animals with choices and agency – or control – over certain aspects of their lives has been proven to positively affect welfare in some animals. This research will augment what we know about amphibian well-being and will add a compassionate dimension to this conservation success story, in which ensuring the welfare of individuals is a critical part of protecting the species.

– Dr. Stephanie Allard is the director of animal welfare for the Detroit Zoological Society and oversees the Center for Zoo and Aquarium Animal Welfare and Ethics.

Notes from the Field: Saving the Wyoming Toad

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For the past few summers, I have traveled to Laramie, Wyoming for the Wyoming Toad Species Survival Plan (SSP) meeting, which is an effort by the Association of Zoos & Aquariums (AZA) to cooperatively manage species populations within accredited zoos and aquariums.

First, I fly into the Denver International Airport, which is followed by a 140-mile road trip to Laramie. The trip is full of spectacular views of mountains, canyons, vast plains, huge clouds and pronghorn antelopes. Sometimes I drive the distance alone but this year I made the trip with three colleagues from different zoos. Each of us is a representative for our respective institution, all sharing the same goal of saving one of North Americas most endangered amphibians, the Wyoming toad.

After a stop for groceries and gas, we arrived at our destination for the next five days – a cabin in this remote area of Wyoming. We’re joined there by most of the other members of the SSP – this year, 10 people stayed at the cabin. Most of us have known each other for some time, so sleeping together in a room full of triple-layered bunk beds seems like a week at camp with old pals. But it’s far more than summer camp – we take part in discussions and updates on a number of important topics such as husbandry, health, management, fieldwork and research on this toad.

The next morning, representatives from the U.S. Fish and Wildlife Service (USFWS) arrived along with the AZA SSP coordinator to begin the meetings. Besides the zoos and aquariums involved, there are two USFWS facilities in Wyoming that hold, breed and release the toads. Many important topics are discussed with the last being choosing captive breeding pairs for 2016.

The Detroit Zoological Society (DZS) breeds these critically endangered Wyoming toads at the National Amphibian Conservation Center (NACC). Since 2001, the DZS has released more than 6,500 Wyoming toads into the wild as tadpoles, toadlets and adults. In 2007, the Detroit Zoo earned the highest honor on the AZA’s list of the Top 10 wildlife conservation success stories for that year.

The population of toads is maintained in special bio-secure off-exhibit rooms of the NACC. We have enough room to breed four pairings each year, and any tadpoles produced by the pairings are shipped out to Wyoming for release into protected wetlands in efforts to create self-sustaining populations.

Like each of the organizations present, I brought detailed notes on every adult toad in our resident population so that the best pairs could be chosen. Captive Wyoming toads need to be of ideal weight and health to take part in a month-long hibernation, followed by a June breeding event. Through the AZA, there is an identified “studbook keeper” who matches toads pairs that are least related and most likely to produce offspring that will be the most genetically fit.

On the second day in Laramie, we received training for the USFWS field surveys. Field surveys are done three times during the warmer months of the year around Mortenson Lake. This lake is the last known area the Wyoming toad lived before it was removed from the wild to protect the species from extinction. It is also the site of past and present releases of captive-produced tadpoles and toadlets. Present-day releases are more protected and provide several topics for research. Members of the SSP have been assisting with the mid-summer field surveys for more than five years and the training is just the beginning of a two- to three-day process to see how many Wyoming toads can be found around the lake.

The third and fourth day of my stay is spent almost entirely out in the field surveying for toads around the lake. Teams of two or three people carry backpacks full of equipment for data collection. Each plot must be surveyed in a specific allotted amount of time and by walking in an S-shaped pattern. Toads can be found hiding under grass, sitting on hard-packed sandy areas or swimming near the shore of the lake. If a toad is located, the timer is stopped, and data collection starts. Toads are photographed for identification, weighed, swabbed for disease testing and, if large enough, “microchipped”. It is particularly exciting when an older toad or a toad with an existing microchip is found. This usually means the toad has survived one or more very cold winters and may potentially breed in the lake.

Weeks later, back at the Detroit Zoo, I receive the compiled results of the survey. This year, we located and collected data on 224 toads – 129 toadlets that were captive-born and released into the lake this spring; 29 toads that were captive-born, released last year and survived the winter; 33 adult females and 33 adult males. Until next July, go toads!

– Rebecca Johnson is the associate curator of amphibians for the Detroit Zoological Society.