Reproductive biology of the Red-necked wallaby (Macropus rufogriseus banksianus) and Bennett's wallaby (M. r. rufogriseus) in captivity



Bennett's wallaby (Macropus r. rufogriseus) of Tasmania give birth from late January to early August in marked contrast to the Red-necked wallaby (M. r. banksianus) of mainland south-eastern Australia which produced young in all months. Within the breeding season however, the lengths of the oestrous cycle and gestation period are similar in the two forms and did not differ by more than 0.5 days. The gestation period of about 30 days extended to almost the length of the oestrous cycle of approximately 33 days. Birth was closely followed by mating which normally resulted in fertilization and subsequent embryonic diapause. Renewed blastocyst development was initiated by removal or loss of a pouch young and birth followed about 27 days later.

Unlike other macropodids with a similar breeding pattern, birth, as a result of renewed blastocyst development near the end of a large young's pouch life, did not occur within a day or two of the permanent emergence of the young, but followed 16 to 29 days later. In M. r. rufogriseus, young that left the pouch permanently in the non-breeding period were not replaced by new young until the beginning of the next breeding season two to four months later, and blastocysts resulting from mating of females without pouch young at the end of the breeding season remained quiescent until the next breeding season five to eight months later.

Females of both subspecies first mated at an age of about 14 months, and males were producing mature spermatozoa by about 19 months.

Young first left the pouch for short periods at about 230 days of age and permanently at about 280 days.

Observations are also given on reproductive behaviour, interpretation of vaginal smears, sex ratio of young, selection of teat by pouch young, and development of morphological features in known-age young that may be used as an aid in age determination.