Marsupial Cross Fostering & Pouch Isolation Techniques: Tools for Threatened Species Management
Cross fostering (CF) in marsupials refers to the rearing of young by foster mothers of a different species. In threatened marsupials CF has been developed and applied as a tool to enhance female reproductive rate, the production of pouch young and to manipulate the genetics of captive and wild-based animals. Data on cross fostering in threatened marsupials is now available for northern bettongs, gilberts potoroos, brush-tailed and black-footed rock wallabies and the mainland tammar wallaby. In all cases pouch young of the donor species have been readily accepted by the chosen surrogate species. Following transfer, growth of the young on their surrogate mother, pouch emergence and weaning has reflected that of the surrogate species with survival rates of transferred young to weaning between 60-85%. Within these species cross fostering and pouch isolation has resulted in a 100-800% increase in the production of young annually. Factors implicated in successful cross fostering include; size of donor and host females, size of PY at weaning, length of pouch life between species and size difference between donor and surrogate young at transfer. Pouch isolation studies have shown that even very small young can survive relatively long periods isolated from a teat at controlled temperature and humidity. Pouch young as small as 3gm from some of these species have been successfully isolated (<10hrs) from their wild-based mothers and foster reared by surrogate mothers in captivity. Success of this technique relies on post-partum oestrus and mating after the removal of pouch young. This paper examines CF and pouch-isolation techniques, as tools to assist in threatened marsupial recovery programs and their boarder application to the genetic management of fragmented marsupial populations.