Reproductive characteristics of wild native Australian Rattus (Rodentia : Muridae)

Abstract

Reproduction in field populations of the five species and 13 of 14 subspecies of native Australian Rattus is compared, using both materials personally collected and museum specimens. We have separated each subspecies into juvenile and adult categories, the dividing point reflecting the approximate size at which sexual maturity is reached. Occurrence of pregnancies and juveniles, treated monthly, permit estimates of time and length of seasonal breeding for each subspecies. Information on gonads and accessory sex glands is given for both breeding and non-breeding adults and for juveniles. All Australian subspecies of Rattus have a fundamentally similar mechanism of reproduction. Those attaining high densities have the highest ovulation rates, the largest litter sizes, and the greatest number of teats. Furthermore, in the two subspecies of high reproductive potential for which we have evidence, females can be precocious in attaining sexual maturity under field conditions.

Seasonally and experimentally induced changes in testicular function of the Australian bush rat (Rattus fuscipes)

“…The observations in this study on the wild-trapped rats confirm and extend previous studies that male bush rats are seasonal breeders (Warneke, 1971 ;Taylor & Homer, 1973;Kerr et al, 1980 (Lincoln & Peet, 1977) in which serum testosterone levels rose in parallel with an increase in testicular growth, as in this study, but were out of phase with LH levels which were declining at the same time. Lincoln & Peet (1977) Dalterio, 1978).…”

“…Previous studies of wild populations of the Australian bush rat, Rattus fuscipes, have shown that the males of this species have a seasonal reproductive cycle (Warneke, 1971 ;Taylor & Homer, 1973). During the summer breeding season they exhibit complete spermatogenesis, while in the winter months the spermatogenic cycle is arrested at the primary spermatocyte step.…”

Reproduction and ontogeny of Mastacomys fuscus (Rodentia: Muridae) in the Australian Alps and comparisons with other small mammals living in alpine communities

“…In both locations, the proportion of pregnant females is greatest from spring to autumn (October-May). In the laboratory, R. fuscipes breeds throughout the year (Taylor 1961;Taylor and Horner 1973).…”

Adapting to the unpredictable: reproductive biology of vertebrates in the Australian wet–dry tropics

“…That variation was generated by annual variation in rainfall late in the wet season; the rats depend upon moist soil for burrowing to obtain corms and other food, and thus cease reproducing when the flood plain begins to dry out. Under favourable conditions in captivity, this species breeds year-round ( Taylor & Horner 1973). A causal link between annual climatic (rainfall) variation and the duration of rodent breeding is supported by the observation of synchronized across-year variation in the duration of rat breeding across widely separated flood plains (Williams & Newsome 1991).…”