Page 89 - University of Pretoria RESEARCH REVIEW 2016

MARINE MAMMALS
AND ENVIRONMENTAL CHANGE
Marion Island, far removed from any human encroachment and teeming with
animal life, forms part of the Prince Edward Islands archipelago, situated about halfway between South Africa and Antarctica. Under South African legislation, the archipelago is a ‘Special Nature Reserve’, holding the highest level of protective status and set aside solely for the purposes of biodiversity conservation and research.
For more than three decades, Marion Island has been the base of the Marion Island Marine Mammal Programme (MIMMP), a research programme of
the Mammal Research Institute at UP. The island is home to unique flora and fauna and is the terrestrial base of three species of seals: the southern elephant seals Mirounga leonina (SES), the Subantarctic fur seals Arctocephalus tropicalis (SAFS), and Antarctic fur seals Arctocephalus gazella (AFS), as well as of the resident killer whales Orcinus orca (KW).
Professor Nico de Bruyn leads a small and highly dedicated team that studies these marine mammals. An important current research activity is to measure the response of these mammals to environmental change. Over the past 34 years, originally led by Professor Marthán Bester and now by Professor
de Bruyn, these teams have undertaken a long-term census of population numbers, and developed an understanding of the complex interactions between predator, prey and the marine environment.
The long-term nature of the studies has also opened up many research avenues. For example, researchers have been studying the tendency of individual
southern elephant seals to repeatedly use the
same foraging areas, particularly in unpredictable environments, by using satellite tracking and diving data from multiple winter migrations. These data provide clues to the adaptability of elephant seals to rapid environmental change.
Subantarctic islands are sensitive to environmental change because of their comparatively simple ecosystems. Through the uninterrupted southern elephant seal mark-recapture experiment, and the continued use of satellite-linked tracking devices on elephant seals, fur seals and killer whales, the research team has uncovered factors that drive large mammal population dynamics and how these link to a changing environment. Populations of most of Marion Island’s precious marine mammals are steadily rising, despite a steadily warming subantarctic climate. However, recent evidence of pup production trend change in one species, the abundant SAFS, is again testing our understanding of the ecology of these top predators and their ecosystem and underscores the importance of continued investigation.
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Elephant seal – Nico de Bruyn