The Wyoming Toad: Almost extinct in America’s backyard

Wyoming toad

In 1993 what was thought to be the last 10 living toads were captured at Mortenson Lake and brought into captivity to start a breeding program. (Photo courtesy of Cheyenne Mountain Zoo)

The Wyoming toad (Bufo hemiophrys) was discovered in 1946 by Dr. George T. Baxter,  a University of Wyoming professor. This toad was originally considered a subspecies of the Canadian toad (Bufo hemiophrys). The historic range of the toad included flood plains of the Big and Little Laramie Rivers and the margins of ponds in the Laramie Basin within 30 miles of the city of Laramie, Wyo.

Wyoming toad tadpoles

More than 100,000 tadpoles and toadlets have been reintroduced since 1995. (Photo courtesy of Cheyenne Mountain Zoo)

Wyoming Toads In Decline

  • Once was one of the most plentiful vertebrate species in the Laramie River Basin Wyoming.
  • Rapid declines in the toad population seen in the 1970’s, the exact cause of these declines is unknown. Possible causes include aerial spraying of pesticides, chytrid fungus, red-leg disease and habitat alteration.
  • Federally listed as an endangered species in January of 1984.
Wyoming toads eggstrand

The Wyoming toad was declared “extinct in the wild” and still is. (Photo courtesy of Cheyenne Mountain Zoo)

US Fish and Wildlife Service Recovery Plan

  • The first Wyoming Toad Recovery Group was formed in September 1987.
  • In 1993 what was thought to be the last 10 living toads were captured at Mortenson Lake and brought into captivity to start a breeding program.
  • The Wyoming toad was declared “extinct in the wild” and still is.
  • The first successful captive reproduction of the toad occurred in 1994 at the Sybille Wildlife Research and Conservation Center in Wyoming.
  • Local land owners provide safe harbor sites for the reintroduction of Wyoming toads.
  • More than 100,000 tadpoles and toadlets have been reintroduced since 1995.
  • Sites are surveyed annually to monitor population numbers. So far we have seen mixed results.

American Zoo and Aquarium Association (AZA) Species Survival Plan (SSP)

  • The SSP was formed in 1996.
  • Only seven AZA accredited zoos and two Fish and Wildlife facilities participate in the SSP program by breeding toads.
  • Volunteers from zoos travel to Laramie to assist in surveys for toads each summer.

For more information, visit

Della Garelle, Cheyenne Mountain Zoo

Founding Frog-ers

Gray tree frog

This colorful and shimmery frog could compete with any fireworks. (Photo by Brian Gratwicke, Smithsonian Conservation Biology Institute)

Frogs found within the United States of America can be red, white, and sometimes, in rare cases, blue. As their names suggest, the California red-legged frog (Rana draytonii), Northern red-legged frog (Rana aurora) and the American white-lipped frog (Leptodactylus fragilis) embody America’s more patriotic colors. Blue frogs, however, are a rare oddity, with the color sometimes appearing in bullfrogs, green frogs and leopard frogs that are deficient in yellow skin pigments. In honor of the Fourth of July, we thought we’d take a closer look at frogs found in the States.

The United States is home to a diverse group of frog species. According to the IUCN Red List, there are 87 species of frogs living in the United States. Texas has the most with 45 species, while Alaska has only three. In general, there is more diversity in the South, with states such as Alabama, Florida, Georgia, Louisiana, Mississippi and North Carolina hosting more than 30 frog species, according to the Association of Zoos and Aquariums.

Though most American species of frogs live in freshwater environments, the Southern leopard frog (Lithobates sphenocephalus) can live in brackish or saltwater habitats. Frogs in the United States also make unique sounds. The barking tree frog (Hyla gratiosa) is named after its low-pitched calls that sound like a dog or a goose. The dusky gopher frog (Lithobates sevosus) is an endangered species with a call that AmphibiaWeb describes as a “deep snore” or “outbound motor.”

Because of the changes in seasons in many places, some frog species in the United States have incredible ways of surviving cold weather too. The wood frog (Lithobates sylvaticus) freezes in the winter, letting its breathing and heart stop. Then, during thawing season, it resumes life!

Sadly, 10 frog species found in the United States are endangered. These frogs depend on us to protect their habitats and reduce the threat of chytrid, a fatal amphibian disease. On this day of independence, we should think about the wildlife that continues to define our country in unique and diverse ways.

The list of IUCN-listed endangered, critically endangered and extinct (in the wild) frog species in the United States includes:

  1. Relict leopard frog (Lithobates onca)
  2. Dusky gopher frog (Lithobates sevosus)
  3. Ramsey canyon leopard frog (Lithobates subaquavocalis)
  4. Southern mountain yellow-legged frog (Rana muscosa)
  5. Sierra Nevada yellow-legged frog (Rana sierra)
  6. Wyoming toad (Anaxurus baxteri)
  7. Arroyo toad (Anaxyrus californicus)
  8. Yosemite toad (Anaxyrus canorus)
  9. Houston toad (Anaxyrus houstonensis)
  10. Armagosa toad (Anaxurus nelsoni)

Nadia Hlebowitsh, Smithsonian’s National Zoo

The Fascinating Wyoming Toad

Wyoming toads

At around six weeks, the toadlets look like miniature (half-inch) versions of the adults. (Courtesy of Cheyenne Mountain Zoo)

A North American toad is fighting its own battle with chytrid, a battle just as devastating as the one frogs in Panama are facing. The Wyoming toad (Anaxyrus baxteri) is one of the most endangered anurans (frog or toad) in North America. Historically, they were found in the Laramie Basin of southern Wyoming. Up until the mid 1970s, they were common throughout this region, but since then, the population drastically declined. Major threats are loss of habitat, pesticide usage and chytrid fungus. In 1994, the last wild toads were rescued from extinction when they were collected and sent to a captive breeding facility. One day, their tadpoles could be released back into the wild, thanks to Cheyenne Mountain Zoo (CMZ), and other zoos and federal facilities now breeding Wyoming toads.

The CMZ Amphibian Propagation and Research Center is a bio-secure area and closed to zoo guests to help keep chytrid fungus and other diseases out of the breeding population. CMZ’s Wyoming toad population for 2011 consists of 17 males and 17 females. However, due to limited space for tadpoles, not all of the toads are bred each year. The Wyoming toad studbook keeper and population manager determine what the best matches are to maximize and maintain genetic diversity. CMZ also monitors the overall health of each toad and decides whether they are fit for reproduction.

During most of the year, CMZ’s goal is to keep the toads healthy and growing with exceptional water quality, properly supplemented feeder insects and regularly changed UV bulbs. As spring approaches, we confirm our recommended pairings and prepare for something somewhat disconcerting for an animal keeper–we have to chill our toads in the refrigerator! In order for them to breed successfully, the toads require a period of cool hibernation as would be experienced in the wild. This is a very delicate time for them because their immune systems are suppressed.

Amphibian Propagation Center

Cheyenne Mountain Zoo's Wyoming toad room in the Amphibian Propagation Center. (Courtesy of Cheyenne Mountain Zoo)

A few days prior to hibernating, the toads are not given food. As their metabolism slows, so does their digestive tract, and undigested food could make them sick. Their room is slightly cooled from 75 degrees to 65 degrees and the lights are turned off the day before entering the hibernaculum, which is basically a fancy refrigerator. Each tank of toads has its own tub filled with wet gravel, carbon, sand and moss. The toads are weighed, placed in the tubs and the temperature is set to 52 degrees. The next day, it’s turned down to 45 degrees, the following day to 41 degrees and finally, down t

o a chilly 38 degrees. The toads will remain at this temperature for 35 days, misted with chilled water to maintain humidity and checked on about twice a week. We have to limit the number of checks to reduce the amount of environmental disturbance.

After 35 days, the toads are slowly warmed up in reverse order of the cool down. It’s believed the hibernation helps produce the natural hormones that would trigger reproductive behavior in the wild. The toads are placed back in their normal husbandry tanks and offered a few insects. They should be ready for breeding the next day.

Many species of amphibians are not able to be bred in a captive environment. For the Wyoming toad, it was discovered they require supplemental hormones in addition to hibernation in order to reproduce. The females are given their first hormone injection in the morning and placed in a breeding tank. Six hours later, the males are given a hormone injection and the females their second. The breeding tank has about one-and-a-half inches of water and some plastic floating plants. A recording of Wyoming toad breeding calls is played for 24 hours while the pairs are together. (Hear a sample of the Wyoming toad call) By the next morning, the female should have hopefully produced eggs fertilized by the male.

On June 1, 2011, six pairs of Wyoming toads were placed together at CMZ, and all of them produced eggs! Unfortunately, two of the egg masses were infertile, but in total, CMZ had about 2,000 tadpoles. 1,792 of them were released back into the wild in Wyoming. Based on valuable genetics, CMZ held back 60 tadpoles for future breeding.

Wyoming toad

A Wyoming toad in the wild. (Courtesy of Cheyenne Mountain Zoo)

Each year, staff from CMZ, other zoos and U.S. Fish and Wildlife Service survey Mortenson National Wildlife Refuge for offspring from previous released Wyoming toads. This is a non-public access refuge, and reintroductions were stopped at this site in 2005 due to chytrid. The site allows us to see if the population could continue even though chytrid was present. Tadpoles are now released at a different location, which prevents us from confusing recently released animals with those naturally produced in the wild.

Length, relative size, weight, habitat conditions, temperature and wind speed are just some of the data recorded during the survey. Most importantly, though, is collecting a swabbed sample from each found toad to see if chytrid is present. The toads are also given a microchip under their skin for permanent identification, enabling us to know how many different toads are found. If a microchipped toad is caught again, a scanner will tell us.

Cheyenne Mountain Zoo is very proud to be an important participant in the Wyoming toad recovery program!

Jeff Baughman, Conservation Center keeper, Cheyenne Mountain Zoo

Wart’s Up?

Wyoming toad (Anaxyrus baxteri)

Wyoming toad (Anaxyrus baxteri)

Cute Frog of the Week: February 21, 2011

This lumpy looking, wart-covered Wyoming toad (Anaxyrus baxteri) may not be easy on the eyes, but it probably doesn’t even know it–Wyoming toads can’t see very well. At about two inches in length, its spots and brown color help it blend in. So does the cover of night, when the toads are most active.

Up until the early 1970s, the Wyoming toad was abundant in the Laramie Plains of none other than Wyoming. Within a few years, the species had a major population crash most likely due to pesticides, fertilizers, habitat loss, climate change, and the chytrid fungus. In 1994, the remaining six toads were removed from Mortenson Lake National Wildlife Refuge and placed in a captive breeding program. There are now several Association of Zoos and Aquariums (AZA) participants, including Cheyenne Mountain Zoo, and two U.S. Fish and Wildlife Service facilities housing breeding populations. Through extensive captive breeding efforts, Cheyenne Mountain Zoo has produced more than 5,000 tadpoles for release. Unfortunately the reintroduction of this species has been slow to take hold due to chyrtid present in the reintroduction sites, predation and other diseases. To learn more, visit Cheyenne Mountain Zoo’s Wyoming toad page.

Photo credit: Jeff Baughman, Cheyenne Mountain Zoo

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