Re-introduction of the northern corroboree frog in the Northern Brindabella Mountains, New South Wales, Australia

Summary

The northern corroboree frog (Pseudophryne pengilleyi), Endangered and reduced by chytrid fungus to fewer than 200 mature individuals across its Brindabella genetic populations, saw its Northern Brindabella population crash from 66 calling males in 2010 to just three by 2012, prompting an ex-situ insurance and supplementation program led by Taronga Zoo and the NSW Office of Environment and Heritage. Eggs collected from wild nests between 2003 and 2005 founded a captive colony at Tidbinbilla Nature Reserve, mostly transferred to Taronga Zoo by 2011; because decline continued gradually even under sustained fungal pressure, researchers judged supplementing wild populations alongside the pathogen feasible and possibly a route to selecting for disease resistance. Between 2010 and 2014, eggs and tadpoles (785 total) were released at two historically significant sites, followed in December 2014 by 160 one-year-old and 49 five-year-old captive-reared frogs, each photographed for pattern-recognition identification, to compare the effectiveness of different life stages at release. Annual surveys found seven calling males at each site in 2014, likely survivors of the first 2010 tadpole cohort reaching maturity, and up to 13 males with confirmed eggs at one site by 2015, though cryptic juveniles and non-calling females remain very difficult to track. Difficulties included the inability to monitor young life stages for years, no reliable method for tracking females, and a small captive population limiting available offspring. The project rates itself too early to judge, noting confirmed captive breeding and survival to maturity of some released cohorts, but stating a further five years of monitoring are needed before a verdict.