Captive Breeding Program for America's Most Endangered Frog Leaps Ahead

MEMPHIS, TENN. -- The future is looking a little bit brighter for one of America's most endangered frogs. A recent collaboration between the Memphis Zoo and Omaha's Henry Doorly Zoo has resulted in the largest number of dusky gopher frog tadpoles ever bred in captivity. Over 1,400 tadpoles hatched earlier this month after researchers carried out an in vitro fertilization (IVF) for the critically endangered species. Nearly 100 of these tadpoles were from Omaha female gopher frogs’ eggs fertilized with sperm that had been collected non-invasively from dusky gopher frogs at the Memphis Zoo and shipped to Omaha overnight to be used for the IVF. This transfer of non-invasively collected sperm for IVF was a world-first for amphibians.

Amphibian breeding and quarantine facilities, such as the Amphibian Conservation Area at Omaha's Henry Doorly Zoo, have become extremely important over the past decade as scientists try to deal with the recent global amphibian extinction crisis. Nearly two-thirds of all known amphibian species (frogs, toads and salamanders) are threatened with extinction or available data is insufficient to assess their status. Additionally, more than 500 species are already extinct in the wild or critically endangered, making amphibians the most endangered group of animals worldwide.  

The case of the dusky gopher frog is extremely grim. Though this species used to exist in many areas of the coastal regions of Mississippi, Alabama and Louisiana, the U.S. Fish and Wildlife Service estimates that there are only 100 dusky gopher frogs left in the wild with almost all of these residing in a single pond in Mississippi. Their habitat has been threatened by residential and forestry development as well as from fire suppression and the decline of gopher tortoises whose burrows the frogs used for shelter.

"Due to the species rarity, we have been working with the Memphis Zoo, Omaha's Henry Doorly Zoo and other zoos to protect assurance colonies in captivity," said Linda LaClaire of the U.S. Fish and Wildlife Service.

The first dusky gopher frogs were brought into captivity in 2001 at the Detroit Zoo. This species has been kept at the Memphis Zoo since 2003 and at Omaha's Henry Doorly Zoo since 2004. Despite numerous attempts over the past nine years to try to replicate the natural environmental cues needed to induce breeding, no natural reproduction has occurred in captivity. It has only been over the past few years, as assisted reproductive technologies such as in IVF and hormone stimulation have been adapted for Dusky gopher frogs, that the success of these captive breeding programs has begun.  

The successes earlier this month were the result of the second trip for Memphis Zoo scientists to the Amphibian Conservation Area at Omaha's Henry Doorly Zoo to perform the IVF and train staff members in assisted reproductive technologies in frogs. The Nancy and Jim Armitage Herpetological Fund helped to provide partial travel funds for this collaboration.       

"This has been a great cooperative project for all parties involved," said Jessi Krebs, Omaha's Henry Doorly Zoo Curator of Amphibians and Reptiles. "It was a great experience for the staff here and a great opportunity for them to learn new techniques."

It is hoped that the techniques developed for this dusky gopher frog project may be helpful for other endangered amphibian breeding programs as well.  Currently 57 healthy dusky gopher froglets are living at the Memphis Zoo due to a similar IVF carried out there earlier this year.  

"The number of tadpoles produced this month was amazing in itself," said Dr. Jen Germano of the Memphis Zoo Conservation and Research Department. "But the fact that we were able to successfully fertilize some of these eggs with sperm collected non-invasively and shipped between zoos was one of the most ground-breaking parts of this trip and is a great sign for future amphibian breeding projects."

The ability to transfer chilled amphibian sperm between zoos for IVF has huge implications: this technique can be used to help improve the genetic diversity of frog and toad captive assurance colonies without the extra stress of having to move individual animals among facilities. By conducting fertilizations in a petri dish, scientists were able to divide and fertilize a single female's egg mass with sperm from numerous male frogs, which helps to insure a greater level of genetic diversity.

"Although the transfer of sperm between institutions for artificial insemination is regularly practiced in mammals, the technology has never before been used to reproduce endangered amphibians through IVF and represents a conservation milestone," said Dr. Andy Kouba, Director of Conservation and Research for the Memphis Zoo. "With support from grants by the Institute of Museum and Library Services and Morris Animal Foundation, the Memphis Zoo is developing assisted breeding technologies and a genetic resource bank for many of the countries most endangered amphibian species."

Captive breeding programs have already made a huge impact on the conservation of several endangered amphibian species. If all goes well, the dusky gopher frogs bred at the Memphis and Omaha's Henry Doorly Zoo may one day be released into restored and protected habitat to help reestablish the wild populations. Additionally, this success provides zoos and government agencies a way to respond if the situation in the wild gets any worse.

"This achievement is a collaboration of varied talents in the finest sense, a perfect marriage between the art of animal husbandry and experimental science," said Dr. Steve Reichling, Curator at the Memphis Zoo. "This is where the future of zoo conservation will be found."


Connect - Chirp & Chatter

Social Butterfly: