Abstract:
Understanding predator responses to extrinsic drivers requires knowledge of their life history parameters and the nature of interactions amongst them. Linking variation in vital rates to particular environmental factors requires a thorough understanding of the mechanisms, adaptive responses, and possible population change associated with such linkage. In particular, how environmental variation may interact with individual heterogeneity. Assessing cause and consequence of individual variation and its impact on population processes is the focus; as a population’s stability can be strongly affected by between-individual variation in frequency-dependent interactions. Annual climatic variation likely causes changes in resource accessibility and availability, influencing top predator vital rates. Current long term studies of top predator southern elephant seal Mirounga leonina (SES., Subantarctic fur seal Arctocephalus tropicalis (SAFS., Antarctic fur seal A. gazella (AFS. and killer whales Orcinus orca (KW., that variously breed, moult and feed at Marion Island (MI., facilitate observation of climate impacts. Mark-recapture in capital breeding SES investigates individual life-history. Body composition changes of SES individuals, a proxy for foraging success, are measured through photogrammetry, whilst satellite tracking of individuals identifies foraging variability. Dietary, hormonal and genetic profiles inform differential individual breeding and foraging identified in SES females. These investigations collectively aid in disentangling intrinsic and extrinsic drivers of individual heterogeneity. Income breeding sympatric populations of SAFS and AFS are assessed for a different scale of responses to environmental change through long-term dietary composition, individual foraging behaviour and breeding success. Potential top-down pressure on seal prey is investigated by intensive photographic mark-resight observation and foraging assessment of the local KW population. Here I report on the current status of populations and latest research findings within the context of the 35-year old Marion Island Marine Mammal Programme dataset, specifically related to our current objectives. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.
