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Evolutionary, molecular and comparative zoology
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RESEARCH ARTICLE
Contents Vol 54(6)

Sexual maturity, factors affecting the breeding season and breeding in consecutive seasons in populations of overabundant Victorian koalas (Phascolarctos cinereus)

Natasha McLean A B C and Kathrine A. Handasyde A
+ Author Affiliations
- Author Affiliations

A Department of Zoology, The University of Melbourne, Vic. 3010, Australia.

B Present address: The Department of Sustainability and Environment, 8 Nicholson Street, East Melbourne, Vic. 3002, Australia.

C Corresponding author. Email: natasha.mclean@dse.vic.gov.au

Australian Journal of Zoology 54(6) 385-392 https://doi.org/10.1071/ZO06015
Submitted: 22 January 2006  Accepted: 20 October 2006   Published: 9 January 2007

Abstract

It is important to have knowledge of basic population parameters to understand how these vary geographically and temporally and how they contribute to population dynamics. This paper investigates three of these parameters in Victorian koala populations: sexual maturity, aspects of the breeding season, and the continuity of individuals’ breeding. The investigation was carried out in koalas of known-age in two free-living (Redbill Creek on French Island and Brisbane Ranges) and one semi-captive (the Koala Conservation Centre on Phillip Island) population as well as koalas of unknown age in four Victorian populations of overabundant koalas: Mt Eccles and Framlingham in south-west Victoria, French Island in Western Port and Snake Island in south Gippsland. At sexual maturity, female koalas had a mean age (±95% confidence interval) of 24.4 months (23.5–25.3 months), a mean head length of 125 mm (124–127 mm) and a mean body mass of 6.6 kg (6.3–6.8 kg). Only 7.4% of independent females (of unknown age) were carrying young when they weighed less than 6 kg. The breeding season was more restricted in the south-west populations. At Framlingham and Mt Eccles 85% and 91% of births, respectively, occurred between December and March. At Snake and French Islands only 46% and 53% of births, respectively, were recorded in the same period. In the Chlamydia-free population (Red Bill Creek) none of the koalas that were monitored stopped breeding and then resumed breeding in a subsequent season whereas many females from Chlamydia-infected populations (Brisbane Ranges and the Koala Conservation Centre) did so. This variation in reproductive patterns is likely to make an important contribution to the variation in the demography observed in different koala populations.


Acknowledgments

We thank Roger Martin for permission to use unpublished data collected with KAH at Redbill Creek, French Island (1980–1985) and the Brisbane Ranges. We thank Ash Reed and the Phillip Island Nature Park; Parks Victoria and the Department of Sustainability and Environment. Much of this work was carried out during State Government koala-management programs.


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