Hormonal priming, induction of ovulation and in-vitro fertilization of the endangered Wyoming toad (Bufo baxteri)

Amphibian populations worldwide are experiencing unprecedented declines. In the U.S. alone, 55 of 262 amphibian species, or about 21%, are threatened with extinction [1]. One of these threatened species is the Wyoming toad (Bufo baxteri) with the last census revealing less than a hundred animals located in the wild [2]. Dr. George Baxter, from the University of Wyoming Zoology department, first discovered the Wyoming toad in 1946 [3]. Although common from the 1950's to the 1970's, a rapid population decline resulted in B. baxteri being federally listed as endangered in 1984. Several reasons have been suggested as causing the species' decline including pesticides, predation, disease, and habitat modification [4-7]. A Wyoming toad recovery group was formed in 1987 to coordinate habitat protection, environmental monitoring and research. One of the first objectives of the recovery group was to establish a captive breeding program for the long-term management of B. baxteri [8]. The Wyoming Game and Fish Department's Sybille Wildlife Research Unit first initiated the captive breeding program in 1993 followed by the U.S. Fish and Wildlife Service's Saratoga National Fish Hatchery in 1998. Over the next decade animals were loaned to several zoological institutions in order to aid the recovery and reintroduction efforts.The recovery group has led one of the most successful captive breeding and reintroduction programs for any endangered anuran, having released over fifty thousand tadpoles to the wild. Wyoming toads are now breeding in their natural habitat and new reintroduction sites have recently been established. Although these successes provide optimism for this species' recovery, captive breeding programs will continue as an important component of the recovery program. Currently, the captive breeding program is limited by low reproductive output due to poor ovulation rates, low egg numbers and low fertilization rates. Hence, the captive breeding program for B. baxteri wo