The population pattern of Miniopterus schrebersii (Chiroptera) in north-eastern New South Wales

Abstract

In north-eastern New South Wales Miniopterus schreibersii is found at a wide range of cave and mine roosts as colonies that may include up to several thousands of individuals. Between April 1960 and September 1963 a field study of the biology and population characteristics of this species was carried out. Field criteria permitting aging of individuals were developed. Age classes considered were juveniles (< 9 months), yearlings (9-21 months), and adults (> 21 months). Seasonal changes in numbers, and in the sex and age composition of colonies were followed in detail at several roosts and comparative information was obtained at others. Movement patterns were assessed by a marking and recapture programme in which 1365 recoveries were obtained from a marked (toe clips and bands) population of 8775. Conspicuous sex or age biases or both were shown to exist in clusters of M. schreibersii at specific roosts and it was suggested that clustering in this species functions, in part, as a social spacing mechanism. Segregation of different sex or age classes at specific colonies permitted classification of colonies as (1) maternity colonies in which adult females and their young predominate, (2) "adult" colonies which are predominantly adult, or adult and yearling, in composition, and (3) "juvenile" colonies in which juveniles, or juveniles and yearlings, are almost prevalent. The observed social biases of colonies appeared to be related to particular phases of the reproductive cycle. Certain adult colonies were interpreted as important sites of copulatory behaviour. Recovery data for two of these mating colonies showed that adult females were more transient members of the colony than adult males. Juveniles are often well represented at adult colonies in the autumn, and during this season their presence may be correlated with a drop in the abundance of older males.