Overbrowsing, and Decline of a Population of the Koala, Phascolarctos cinereus, in Victoria 11. Population Condition
Roger W. Martin
Department of Zoology, Monash University, Clayton, Vic. 3168.
The physiological condition of a population of koalas at Walkerville, Vic., which was severely defoliating its preferred food trees, was monitored by means of haematological studies and measures of growth rate and age-specific body size. Juvenile and subadult animals from Walkerville had significantly lower growth rates than animals from a population on French I. On an age-specific basis the Walkerville males were significantly smaller than the French I, males in most age classes.The body weights of females were lower but the difference was not significant. Males, because of their larger body size, have greater food requirements and may have been affected by the shortage of preferred food more acutely than females. The haematology of the females indicated that nutritionally induced anaemia was significant by January 1981. The heavy tick loads on the animals probably exacerbated the effects of the food shortage on their condition, but were not the cause of the anaemia. The low fertility rate of the females appears to be due to their poor nutritional state and to reproductive tract disease.