The Use of Alpha-Chloralose for the Repeated Capture of Western Gray Kangaroos, Macropus-Fuliginosus

Abstract

Alpha-chloralose was used for 9 years in a study of growth, development and population size of western grey kangaroos, Macropus fuliginosus. Grain and water at accustomed feeding and watering points were drugged at intervals, for one night at a time; dose rates varied from 1.9 to 2.7 gl-1 in the water, and from 12 to 18 g kg-1 in the food. Many individuals developed a taste aversion to the drug, so that the number captured decreased over successive drug-nights. The taste could not be masked in water, but was in food when the type of food was changed. In the year after their initial capture, 44% of females and 35% of males were recaptured. Some were repeatedly captured in subsequent years; others only at intervals of several years. Animals drugged first as young-at-foot or as juveniles were captured in subsequent years less often than those first caught as subadults or adults. The male : female ratio in the adults captured was higher than in the population. Mortality was 4.5% of 1165 animals captured; 27% of deaths being due to fox predation. Females wlth pouch young, captured several times in a year, lost 8.8% of their young.