Captive Breeding Program for America's Most Endangered Frog Leaps Ahead
October 22, 2010
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
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
"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
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."