Reproduction of a threatened semi-arboreal Australian rodent, the brush-tailed rabbit-rat (Conilurus penicillatus) in captivity

Extant ‘tree-rats’ in the genera Mesembriomys and Conilurus are declining in the Australian wet–dry tropics. Paucity of information on their life histories makes it challenging to assess some population parameters and long-term threats. This study of a laboratory colony of up to 117 brush-tailed rabbit-rats (Conilurus penicillatus) was conducted during 1982–1986. Data were obtained using vaginal smears, changes in external vaginal appearance, matings and birth of young. Males matured at about 18–20 weeks. Vaginal opening occurred at 11 weeks (6–19 weeks) with oestrus up to 2 days later. Mean oestrous cycle length was 10.7 days (range 7–21), with oestrus lasting 1–2 days. Non-lactational gestation length was 35–38 days (x̄ = 35.8, n = 11) and that associated with lactation was longer (x̄ = 43.0 days, 39–48). Postpartum oestrus occurred within 1 day of parturition and if this did not result in conception, oestrus resumed about 50 days later. Mean litter size was 2.5 (range 1–4). Births in the laboratory occurred throughout the year, with a reduction in pregnancies during January/February. The reproductive characteristics of C. penicillatus are similar to those of other species in the phylogenetic ‘Conilurus division’ (Conilurus, Leporillus, Mesembriomys).