COMPARATIVE ECOLOGY OF WESTERN GREY KANGAROOS (MACROPUS-FULIGINOSUS) AND EUROS (M-ROBUSTUS ERUBESCENS) IN DUROKOPPIN NATURE-RESERVE, ISOLATED IN THE CENTRAL WHEAT-BELT OF WESTERN-AUSTRALIA

The populations of western grey kangaroos (Macropus fuliginosus) and e uros (M. robustus erubescens) in a 1196-ha area of native vegetation i n the central wheatbelt of Western Australia were studied over six yea rs (1985-91). The area was isolated from other remnants of native vege tation by at least 1.4 km. Captures were made periodically throughout each year and the animals weighed and measured. In all, 152 animals we re captured (83 euros and 69 western grey kangaroos). The data for eac h sex and species were assigned to 'seasons' (February-July or August- January) and assessments made of body condition. The weights and tail circumstances, adjusted for individual size by regression on leg lengt h, were higher for western grey kangaroos but not for euros in August- January. Euro males varied significantly in weight from year to year; euro females and grey males and females did not. Too few grey females were captured to analyse seasonality of reproduction. The estimated bi rth dates of 68 euro pouch young were distributed equally throughout t he study period. There were approximately equal numbers of each specie s in an estimate made in 1988 from a helicopter survey, with a total ( +/- s.e.) of 191 +/- 29 kangaroos. The mean faecal pellet counts on 42 fixed transects of 100 m(2) did not differ significantly over the per iod 1985-88. These counts showed that the overall use of the different vegetation types varied by a factor of two. Heaths had the highest pe llet counts and open mallee or woodland the least, with Allocasuarina- dominated shrublands being intermediate. Spotlight surveys around the reserve boundary showed a highly significant difference in distributio n of the two species. This was confirmed by analysis of the home range s of 13 radio-collared individuals. Euros showed a strong preference f or areas of York gum-wandoo-jam woodland with a herbaceous ground laye r and areas with tall Allocasuarina or dense heath. In contrast, the w estern grey kangaroos preferred the heathlands and open woodlands with out a herbaceous ground cover. The sex ratios of the whole populations seen in spotlight searches was 0.72:1.00 (males:females) for western grey kangaroos and 0.81:1.00 for euros. Both differ significantly from parity. There was a higher proportion of female euros amongst the ani mals seen in the western part of the reserve than in the eastern part. These populations relied mainly on the resources of the reserve. The average number of kangaroos seen on adjacent farmland on any one night varied from 3.6 in 1986 to 13.5 in 1991. A significantly higher propo rtion of males of both species were seen on farmland.