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Toads on the Range
Fisheries biologists fight fierce fungus to reach breeding record
By Leith Edgar
Photo Credit: David Paddock, USFWS
Fisheries biologist Dave Paddock arrived in 1997 for his first day of work at the U.S. Fish and Wildlife Service’s Saratoga National Fish Hatchery in Wyoming ready to spawn trout. Soon after, Paddock found himself a biologist working on recovery of the Cowboy State’s most imperiled amphibian: the Wyoming toad.
Although Paddock had no formal training in amphibian husbandry, he went straight to work caring for the first few dozen toads brought to Saratoga for breeding.
“This was pretty much trial by fire; I had no formula,” said Paddock who has worked on recovery of the endangered species for more than a decade. “I relied on my fisheries background, which I applied to the amphibians. For me it was a chance to learn amphibian husbandry on the fly.”
Paddock soon noticed the toads were prolific egg producers. In order to keep from breeding too many toads, he implemented controlled breeding techniques similar to those used when spawning fish. These basic fisheries principles served as a foundation for the record propagation of Wyoming toads in 2009 at Saratoga NFH, releasing 9,520 tadpoles and toadlets. The total accounted for about 40 percent of all toadlets released last year.
“Not only was 2009 the best year for Saratoga, but it was the best year for the program,” Paddock said of the Wyoming toad Species Survival Plan, which guided the release of a record 20,138 tadpoles and toadlets. In the past, toads produced by Saratoga were released into Mortenson Lake National Wildlife Refuge in Laramie, Wyoming. To date, more than 37,000 have been released into the refuge.
The Wyoming toad is a species out of place. Scientists believe the species is a glacial relict, isolated from its sister species, the Manitoba or Canadian toad, 10,000 years ago at the end of the Pleistocene epoch. Now, the Wyoming toad population is separated from its ancestors by more than 500 miles.
Over time, the Wyoming species became distinct within its limited range. During the 1950s, surveys indicated the toads were doing well. But in the following decade something changed. The decline in population numbers proved precipitous in the 1960s and 1970s. By 1980, the species was thought by many to be extinct in the wild. The species was listed in 1984 as federally endangered.
The year 1987 brought new hope for the species when a wild population was discovered at Mortenson Lake. The following year the U.S. Fish and Wildlife Service and its partners raced to start a captive-breeding program and learn more about the toad before it went extinct.
Despite the best efforts of many concerned conservationists, the Wyoming toad still faces an uphill battle to a successful recovery. “Population declines are thought to be a consequence of a number of factors adversely affecting the toads,” said Jan McKee, a U.S. Fish and Wildlife Service biologist who has worked on Wyoming toad recovery for more than three years.
“We don’t know exactly why the Wyoming toad was fine until the 1960s and then started dying off,” she said. “Our unproven hypothesis is that a number of factors converged to create a perfect storm, which has really tested the species’ resiliency and challenged every biologist’s resolve.” Although pesticides, herbicides, irrigation, grazing, drought, predation and climate change have all been attributed as causes of toad population declines, it’s the chytrid fungus, first discovered in Queensland, Australia in 1993, that is most often charged as the culprit.
Photo Credit: Lee Bender, USFWS
Moreover, chytrid fungus (Batrachochytrium dendrobatidis), also referred to as Bd, is the culprit responsible for a worldwide decline in amphibians across six continents (see Eddies, Fall 2008). The zoosporic fungus causes a disease of the skin in amphibians. Exposed frogs die from the fungus in 10 to 18 days. Since 1993, chytrid has been found to be ubiquitous and is found on all continents except Antarctica. The fungus is likely spread through many avenues, including invasive bull frogs, the global pet trade and salamanders used as fish bait, McKee said.
At Saratoga, Paddock is constantly on the lookout for the less-than-friendly fungus. Paddock said keeping a close eye on the toads can be the difference between life and death.
“One of the hardest things is that the toads don’t exhibit many symptoms when they’re sick,” he said. “We monitor them constantly, looking for any signs they may need treatment.”
Before treating any potentially infected toads, biologists verify there is a chytrid fungal infection by swabbing the specimen and sending the swab to Dr. Allen Pessier, a pathologist at the San Diego Zoo, for analysis. When the test comes back positive for the fungus, the infected toad is bathed in an anti-fungal solution. The solution includes an active-ingredient called Itraconazole, an anti-fungal drug also used to treat humans.
To ensure the toads remain on an upward trajectory, three annual surveys assess how the Wyoming toad is doing in the wild. Participants comb the riparian ecosystem searching for the diminutive toads to photograph, record weights and test for chytrid. Participants also do the same at two nearby sites on private lands enrolled in the Safe Harbor program. A Safe Harbor Agreement is a voluntary agreement involving private or other non-federal property owners whose actions contribute to the recovery of species listed as threatened or endangered under the Endangered Species Act.
Prior to release at Mortenson Lake or one of the two safe harbor sites, Saratoga’s toads reside in aquaria. Each aquarium is one-third water and two-thirds dry with a basking light for heat. Typically, eight toads share an aquarium and are fed crickets or worms.
Meeting the toads’ needs is all in a day’s work for Paddock, who continually refines his amphibian husbandry skills. His ever-improving skill set is, in large part, responsible for much of Saratoga’s record setting toad propagation—not bad for a fisheries biologist who learned Wyoming toad recovery “on the fly.”
Leith Edgar is a Public Affairs Specialist at the U.S. Fish and Wildlife Service’s Mountain-Prairie Regional Office in Lakewood, Colorado.
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