Captive breeding programme launched for unique Darwin’s frogs in Chile

Male Darwin's frogs develop their young in their vocal sacs. Credit Dante Fenolio

Darwin's frog breeding centre success 
Courtesy of Danté Fenolio, Ph.D., Atlanta Botanical Garden
October 2010. Darwin's frogs (Rhinoderma darwinii and Rhinoderma rufum) are native to Chile and Argentina and have a unique way they care for their young. Males take up eggs or newly-hatched tadpoles into their mouths. The developing larvae are maintained within the male's vocal sac until he "coughs" up either tadpoles or fully formed juveniles. Both species of Darwin's frogs are high on the list for conservation action.

Unique reproduction system
The developing larvae are maintained within the male's vocal sac throughout development in R. darwinii. The male "coughs" up fully formed juveniles when their development is complete 50 to 70 days later. In R. rufum, the male "coughs" up tadpoles, which he releases into water. This reproductive mode is unknown in any other species of amphibian

The special breeding centre at the National Zoo in Santiago. Credit Dante Fenolio.

The National Zoo in Santiago has built a special captive breeding centre, in partnership with the Atlanta Botanical Garden, dedicated to conserving Darwin's frogs. The overall aim of this project is to facilitate an integrated program including captive breeding efforts in Chile and in situ conservation work to preserve Darwin's frogs through updates of population status, searches for R. rufum, and monitoring of amphibian chytrid fungus.

The IUCN/CBSG's Amphibian Ark and Conservation International support the captive breeding of critically endangered amphibian species as a preservation tool. Because of their uniqueness, both species of Darwin's frogs are high on the list for conservation action.

Two threats to survival - Disease and habitat destruction
Two key problems are believed to be driving the decline of Darwin's frogs. First, habitat loss plagues these species, steadily reducing both the range and numbers of Rhinoderma in the wild. Destruction of native forests and replacement with non-native pine plantations, plus forestry operations, have probably had a profound negative effect on these species.

Second, the presence of an emergent infectious disease, chytridiomycosis, is suspected to have significantly contributed to the decline of these frogs as well. Swabs taken from wild Rhinoderma in Chile have tested positive for the chytrid fungal infection. This fungus is responsible for the decline of many species of amphibians worldwide, has wiped out many populations, and is even responsible for the extinction of at least one species.

Female Darwin's frog. Once a female breeds with a male, she deposits eggs and the male frogs take over from there. Males attend the developing eggs before taking their young into their mouths and on into their vocal sac. Credit Dante Fenolio.

Darwinii population crash
Rhinoderma darwinii currently inhabits only a portion of its original known range. Some formerly dense populations have disappeared; others are much smaller (Crump, pers. comm.; Crump and Veloso, 2005; Stuart et al. 2008).

Rufum not seen since 1978
There have been no confirmed reports for Rhinoderma rufum since 1978 despite attempts to find it. Rhinoderma darwinii is listed on the 2008 International Union for the Conservation of Nature (IUCN) Red List as Vulnerable. Rhinoderma rufum is listed as Critically Endangered on the 2008 IUCN Red List.

Frogs settled in very quickly
Once all of the environmental systems in our captive breeding facility checked out, the first group of frogs was added very quickly. Somewhat surprisingly, the frogs immediately began enacting reproductive behaviour. There was calling and dancing around between males and females.  The center is seeing a lot of reproductive behavior now.

The National Zoo in Santiago has built a special captive breeding centre with support from many institutions such as The Shared Earth Foundation, The American Zoological Association's Conservation Endowment Fund, Chicago Zoological Society - Chicago Board of Trade Endangered Species Fund, The George and Mary Rabb Foundation, Sysco Systems, The Sophie Danforth Conservation Biology Fund, Fauna Australis and ZooMed Inc.