Health assessment of the leopard seal, Hydrurga leptonyx, in Prydz Bay, Eastern Antarctica and NSW, Australia

Abstract

The leopard seal Hydrurga leptonyx is the most widely distributed of the Antarctic pinnipeds, ranging from the Antarctic coastline to the sub-Antarctic (Bonner 1994) and less frequently, temperate and sub-tropical areas, including the Australian coast. The main population of leopard seals remains within the circumpolar pack-ice (Bonner 1994) however, there is some north-south movement of individuals, the majority of which are immature, non-breeding seals (Gwynn 1953; Brown 1957; Csordas 1963; King 1983; Rounsevell and Eberhard 1980; Rounsevell 1988; Walker et al. 1998). A periodicity in peak abundance has been observed for this northward dispersal and it is suggested that this could be related to cyclic climatic variation within the region (Harris et al. 1988; Testa et al. 1991; Croxall 1992). As a large-bodied and long-lived upper trophic species, the leopard seal is considered a useful indicator of change within the Antarctic ecosystem. As such, baseline information on health status for the detection of disease, population dynamics, spatial distribution and foraging behaviour of the leopard seal can be vital to understanding the status of the ecosystem they inhabit. Developing baseline data and reference intervals for health parameters such as body condition, haematology and serum biochemistry are essential prerequisites for monitoring the impact of disease on a wild population and enables determination of the effects of natural fluctuations and anthropogenic influences on the population within the ecosystem they inhabit.