Register      Login
Australian Journal of Zoology Australian Journal of Zoology Society
Evolutionary, molecular and comparative zoology
Shopping Cart: ( empty )
You are here: Home > Journals > ZO > ZO06015
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.


References

Baharav, D. (1983). Reproductive strategies in female mountain and dorcas gazelles (Gazella gazella gazella and Gazella dorcas). Journal of Zoology 200, 445–453.
Caughley G. (1977). ‘Analysis of Vertebrate Populations.’ (John Wiley & Sons: Brisbane.)

Clark, M. M. , Moghaddas, M. , and Galef, B. G. (2002). Age at first mating affects parental effort and fecundity of female Mongolian gerbils. Animal Behaviour 63, 1129–1134.
| Crossref | GoogleScholarGoogle Scholar | Clutton-Brock T. H., and Albon S. D. (1982). Parental investment in male and female offspring in mammals. In ‘Current Problems in Sociobiology’. (Ed. King’s College Sociobiology Group.) pp. 223–247. (Cambridge University Press: Cambridge.)

Cole, L. C. (1954). The population consequences of life history phenomena. Quarterly Review of Biology 29, 103–137.
| Crossref | GoogleScholarGoogle Scholar | PubMed | Eberhard I. H. (1972). Ecology of the koala Phascolarctos cinereus (Goldfuss), on Flinders Chase, Kangaroo Island. Ph.D. Thesis, The University of Adelaide, Adelaide.

Eberhard I. H. (1978). Ecology of the koala, Phascolarctos cinereus (Goldfuss) Marsupialia: Phascolarctidae, in Australia. In ‘The Ecology of Arboreal Folivores’. (Ed. G. G. Montgomery.) pp. 315–328. (Smithsonian Institute Press: Washington, DC.)

Festa-Bianchet, M. , Jorgenson, J. T. , Lucherini, M. , and Wishart, W. D. (1995). Life-history consequences of variation in age of primiparity in bighorn ewes. Ecology 76, 871–881.
| Crossref | GoogleScholarGoogle Scholar | Handasyde K. A. (1986). Factors affecting reproduction in the female koala (Phascolarctos cinereus). Ph.D. Thesis, Monash University, Melbourne.

How, R. A. (1976). Reproduction, growth and survival of young in the mountain possum, Trichosurus caninus (Marsupialia). Australian Wildlife Research 24, 189–199.
Lack D. (1954). ‘The Natural Regulation of Animal Numbers.’ (Oxford University Press: Oxford.)

Lunn, N. J. , and Boyd, I. L. (1993). Effects of maternal age and condition on parturition and the perinatal period of antarctic fur seals. Journal of Zoology 229, 55–67.
Martin R., and Handasyde K. (1990). Population dynamics of the koala (Phascolarctos cinereus) in southeastern Australia. In ‘Biology of the Koala’. (Eds A. K. Lee, K. A. Handasyde and G. D. Sanson.) pp. 75–84. (Surrey Beatty: Sydney.)

Martin R. W., and Handasyde K. A. (1995). Koala, Phascolarctos cinereus. In ‘The Mammals of Australia’. (Ed. R. Strahan.) pp. 195–198. (New Holland Publishers: Melbourne.)

McColl, K. A. , Martin, R. W. , Gleeson, L. J. , Handasyde, K. A. , and Lee, A. K. (1984). Chlamydia infection and infertility in the female koala (Phascolarctos cinereus). The Veterinary Record 115, 665.
McLean N. (2003). Ecology and management of overabundant koala (Phascolarctos cinereus) populations. Ph.D. Thesis, The University of Melbourne, Melbourne.

McNally, J. (1957). A field survey of a koala population. Proceedings of the Royal Zoological Society of New South Wales 56, 18–27.
Obendorf D. L., and Handasyde K. A. (1990). Pathology of chlamydial infection in the reproductive tract of the female koala (Phascolarctos cinereus). In ‘Biology of the Koala’. (Eds A. K. Lee, K. A. Handasyde and G. D. Sanson.) pp. 255–259. (Surrey Beatty: Sydney.)

Pearse, R. J. (1981). Notes on breeding, growth and longevity of the forester or eastern grey kangaroo, Macropus giganteus Shaw, in Tasmania. Australian Wildlife Research 8, 229–235.
| Crossref | GoogleScholarGoogle Scholar | Roff D. A. (1992). ‘The Evolution of Life Histories: Theory and Analysis.’ (Chapman & Hall: New York.)

Saether, B. E. , and Heim, M. (1993). Ecological correlates of individual variation in age at maturity in female moose (Alces alces) – the effects of environmental variability. Journal of Animal Ecology 62, 482–489.
| Crossref | GoogleScholarGoogle Scholar | Seddon G. (1975). Phillip Island: capability, conflict and compromise. A report to the Western Port Regional Planning Authority. Centre for Environmental Studies, University of Melbourne, Victoria.

Setchell, J. M. , Lee, P. C. , Wickings, E. J. , and Dixson, A. F. (2002). Reproductive parameters and maternal investment in mandrills (Mandrillus sphinx). International Journal of Primatology 23, 51–68.
| Crossref | GoogleScholarGoogle Scholar | Spiegelhalter D. J., Thomas A., and Best N. G. (1996). Computation on bayesian graphical models. In ‘Bayesian Statistics 5: Proceedings of the Fifth Valencia International Meeting, June 5–9, 1994’. (Eds J. M. Bernardo, J. O. Berger, A. P. Dawid and A. F. M. Smith.) pp. 407–425. (Clarendon Press: Oxford.)

Stearns, S. C. (1976). Life-history tactics: a review of the ideas. Quarterly Review of Biology 51, 3–47.
| Crossref | GoogleScholarGoogle Scholar | PubMed | Stearns S. C. (1992). ‘The Evolution of Life Histories.’ (Oxford University Press: Oxford.)

Stefan, C. I. , and Krebs, C. J. (2001). Reproductive changes in a cyclic population of snowshoe hares. Canadian Journal of Zoology 79, 2101–2108.
| Crossref | GoogleScholarGoogle Scholar | Tyndale-Biscoe C. H. (1979). Ecology of small mammals. In ‘Ecology of Small Mammals’. (Ed. D. M. Stoddart.) pp. 343–379. (Chapman and Hall: London.)

Tyndale-Biscoe H., and Renfree M. B. (1987). ‘Reproductive Physiology of Marsupials.’ (Cambridge University Press: Cambridge.)

Velando, A. (2002). Experimental manipulation of maternal effort produces differential effects in sons and daughters: implications for adaptive sex ratios in the blue-footed booby. Behavioral Ecology 13, 443–449.
| Crossref | GoogleScholarGoogle Scholar | White N. A., and Kunst N. D. (1990). Aspects of the ecology of the koala in southeastern Queensland. In ‘Biology of the Koala’. (Eds A. K. Lee, K. A. Handasyde and G. D. Sanson.) pp. 109–116. (Surrey Beatty: Sydney.)

Williams G. C. (1966). ‘Adaptation and Natural Selection: a Critique of Some Current Evolutionary Thought.’ (Princeton University Press: Princeton.)

Withers P. C. (1992). ‘Comparative Animal Physiology.’ (Saunders College Pub: Fort Worth, TX.)

Young, B. E. (1994). Geographic and seasonal patterns of clutch size variation in house wrens. Auk 111, 545–555.