Captive management and experimental re-introduction of the Booroolong Frog on the South Western Slopes region, New South Wales, Australia

Summary

The Booroolong frog (Litoria booroolongensis), Critically Endangered and confined to western-flowing streams of New South Wales' Great Dividing Range, faced local extinction in the Maragle Creek catchment during the 2006-2007 drought, prompting NSW's Department of Environment and Taronga Zoo to collect a 32-frog founder population from three sites to establish an insurance captive breeding colony, the species' first ever kept and bred in captivity. Held under strict quarantine at Taronga Zoo, most founders produced fertile spawn by late 2007; eight spawn from 16 founders, released in two cohorts two months apart to maximize genetic diversity, were reared to four and two months of age, individually toe-clipped for identification, and screened for pathogens, including one previously unknown but naturally occurring brain parasite that nearly derailed the release before it was confirmed present in the wild population too. In February 2008, 610 captive-bred frogs were released along a 1.5 km transect of Maragle Creek, accompanied by an educational campaign for local schools culminating in a community expo in nearby Tumbarumba. Post-release surveys captured 105 individual frogs, with 29 surviving to sexual maturity and engaging in confirmed breeding activity by the first season, comparable in size and condition to wild frogs; however, only four released frogs were detected in the 2009-2010 season, reflecting high mortality likely compounded by renewed stream drying and chytrid fungus infection. The project rates itself Successful, citing successful captive breeding and confirmed wild breeding by released frogs despite the species' short lifespan and ongoing environmental threats.