Cross fostering and pouch isolation studies in kangaroos wallabies and rat kangaroos: Implications for conservation and species management

Cross fostering refers to the rearing of young by foster mothers of a different species. In marsupials this technique has been used as a method for studying lactation and pouch young growth and development. Recently, this procedure and that of pouch isolation have been adopted by some wildlife agencies as tools for Macropodoid conservation and species management, in an effort to enhance female reproductive rate and manipulate genetics of captive and wild-based animals. Data on cross fostering is now available for 5 potoroid and 13 macropodid species. Success of cross fostering studies varies widely between donor and surrogate species from complete failure to an 8 fold increase in the production of pouch young (PY) 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. Studies have shown that females regulate milk composition and production irrespective of PY age and that transfer to species with teats of more immature or advanced staged mammary glands, will result in either a slowing or acceleration of pouch young growth / development. Success of this technique in the Macropodoidae relies on post-partum oestrus, mating after the removal of pouch young and embryonic diapause. This paper reviews the available data in this field and examines its potential application to conservation and species management in this group