EFFECT OF AGE AT RELEASE ON THE SUSCEPTIBILITY OF CAPTIVE-REARED MALLEEFOWL LEIPOA OCELLATA TO PREDATION BY THE INTRODUCED FOX VULPES-VULPES

Captive-reared juvenile Malleefowl Leipoa ocellata (3-5 months old) ex perimentally released into Yathong Nature Reserve did not survive. Fro m the first day after release Malleefowl were found dead, and mortalit y continued at a rapid rate until none remained alive: 50-58% were dea d within 7 days; 83-96% were dead within 36 days; and none survived lo nger than 104 days. Predation by the introduced Red Fox Vulpes vulpes was the principal cause of mortality, accounting for at least 50% and perhaps as many as 92% of young Malleefowl. Twelve older captive-reare d sub-adults (14-28 months of age) experimentally released into Yathon g Nature Reserve fared somewhat better; three survived longer than 428 days. Again, predation by foxes was the chief cause of mortality. Mor tality was particularly high during the first week following liberatio n, but the two age classes differed in their long-term survival. One t hird of sub-adults survived to breeding age (2.5 years), while no juve nile survived its first year. This implies a decrease in the vulnerabi lity of Malleefowl to foxes between the first and subsequent years of life. Predation by foxes remained the major cause of mortality among s ub-adults. Fox predation may well threaten the continued survival of M alleefowl in New South Wales because they killed sub-adult Malleefowl of a weight comparable to that of many adults, which suggests that the duration of vulnerability to foxes is protracted. Furthermore, this t hreat is not confined to the fragmented remnants of mallee vegetation within the wheat-belt but extends to Malleefowl populations in the rem aining large expanses of mallee, remote from agriculture.