The biology, origin and adaptation of the Miniopterus australis (Chiroptera) in New South Wales

Abstract

The biology of Miniopterus australis was investigated in north-eastern New South Wales (latitude c. 30ºS) between 1960 and 1966. In this area the species reaches the southern limit of its distribution and is largely confined to the subtropical coastal belt. Mating occurs in the winter months June and July, and is followed by a period of retarded embryonic development to mid-September. Births occur in December. The only nursery colony of M. australis located was that of the southernmost population of the species. It included about 4000 individuals (approximately 1800 young) in December and was intimately associated with a much larger nursery colony of M. schreibersii. A comparison of the winter behaviour of M. australis with that of M. schreibersii at the same latitude revealed that pre-winter increase in weight is less marked, that feeding behaviour persists longer, and that there are fewer, and less rigid, periods of torpidity in the former species. In its reproductive and wintering characteristics M. australis, at 30°S., has diverged less from the tropical, and presumably ancestral, pattern for the genus than has M. schreibersii at the same latitude. It is argued that M. australis has colonized New South Wales from low latitudes later than M. schreibersii and that colonization southwards may have been dependent upon, or promoted by, the prior existence of M. schreibersii nursery colonies. An analysis of retrapping data for the southernmost population of M. australis suggests that this is represented as two subpopulations (highland and lowland) between which adult individuals seldom exchange. Spermatogenesis, and hence mating, occurs slightly earlier in the highland subpopulation. It is suggested that earlier mating in this subpopulation may be selectively advantageous, and that the long-term effect of selection here could be to shift the timing of reproductive events in the entire population back towards that observed in M. schreibersii. Earlier mating should be correlated with a stronger manifestation of pre-winter increase in weight and of winter torpidity. The combination of all these changes in M. australis would permit further range expansion to the south and west, provided that suitable nursery sites are available and can be found.