Cross-fostering, growth and reproductive studies in the brush-tailed rock-wallaby, Petrogale penicillata (Marsupialia : Macropodidae): efforts to accelerate breeding in a threatened marsupial species

Pouch-young removal and cross-fostering trials were undertaken in the brush-tailed rock-wallaby, Petrogale penicillata, to assess whether this procedure could be used to accelerate breeding and recruitment in this threatened marsupial species. Basic reproductive data, lacking at the time of the study, were also collected. Eighteen pouch young, weighing 1–106 g, were fostered to either tammar wallaby, Macropus eugenii, or yellow-footed rock-wallaby, Petrogale xanthopus, surrogate mothers. Sixteen P. penicillata pouch young were transferred to surrogate mothers whose own young were greater or equal in size to the P. penicillata young being transferred. Fourteen of these young survived (88%). Two of the P. penicillata pouch young were transferred to surrogate mothers whose own young was smaller in size than the P. penicillata young being transferred. Neither survived. Growth curves for pouch young on mothers and surrogate mothers were estimated. P. penicillata young reared by surrogate mothers grew at a similar rate, and were weaned at a similar age, to the pouch young of the foster species. Like other rock-wallaby species, P. penicillata underwent embryonic diapause and had a gestation period of ~30 days. Permanent pouch exit occurred at ~200 days and young became sexually mature at ~23 months for males and no later than 21 months for females. This study clearly demonstrates that pouch young of P. penicillata, as small as 1 g (~8 days old), can be removed and cross-fostered successfully. These procedures can be used to accelerate breeding and recruitment by up to six times in this threatened species provided an adequate source of surrogate mothers is available. David A. Taggart, David Schultz, Craig White, Peter Whitehead, Geoff Underwood and Kevin Phillip