Reproduction in the parma wallaby, Macropus parma, Waterhouse

Abstract

Female M. parma in captivity reach sexual maturity at 11 1/2-16 months of age. Scrota1 size indicates that sexual maturity is attained in males at about 22 months. One male had spermatozoa at 19-20 months and another had a first fertile mating at 24-25 months. Mating behaviour is described and resembles that of other small macropodids. M. parma is monovular and polyoestrous. The oestrous cycle has a mean length of 4197810.72 days (n = 58; range 36-59 days) while the gestation period is 34.54*0.13 days (n = 28; range 33-36 days). Post-partum oestrus and mating occurred from 4 to 13 days after birth in a small proportion (16.7%) of those animals examined. However, most animals had an oestrus, while carrying a pouch young, between 45 and 105 days after birth. A few animals did not come into oestrus at all while carrying a pouch young. Removal of pouch young typically resulted in return to oestrus between 6 and 15 days later, in females that had not had a post-partum oestrus or an oestrus while carrying a pouch young. Females which mated at some stage during lactation prior to removal of pouch young gave birth 31.16 days later (n = 3; range 30.5-32.0 days). Three females at the Melbourne Zoo had estimated delayed gestation periods of 31, 31, and 32 days. The earliest observation of a young with its head out of the pouch was at 146 days of pouch life. Most young had left the pouch for short intervals by 175 days with the youngest observed out at 160 days. Young permanently leave the pouch at 211.9+-1.0 days (n = 10; range 207-218 days). Permanent exchange of pouch young has been observed in two cases, both at approximately the time young were first leaving the pouch for short intervals. Some females that mated while carrying a young in the pouch gave birth 6-11 days after permanent pouch exit of the primary young. Unmated females returned to oestrus 12-24 days after permanent pouch exit of their young. Young were weaned at 2 5 3 ) months after pouch exit. Most females entered anoestrus in 1968 following transfer of the animals into small holding pens. In 1969 only 5 of 24 matings resulted in young in the pouch, while in 1970 the corresponding figure was 21 of 44 matings. In both years there was evidence of young being born but apparently being lost during the climb from the urogenital opening to the pouch, probably because of overcrowding of the mothers. Evolution of embryonic diapause is discussed in relation to the reproductive pattern established for M. pavma. It is postulated that embryonic diapause first arose at the end of pouch life and has come to occupy the entire length of pouch life in most macropodids.