PROJECT: Changing climate and the winter foraging behaviour of Antarctic fur seal populations
RESEARCHER: LEA, Mary-Anne, Ben Arthur (PhD student)
LOCATION: Three circumpolar breeding sites
Until recently little was known about the habitat use and foraging (feeding) ecology of the female Antarctic fur seal (Arctocephalus gazella) during the extreme climate experienced in the Southern Ocean winter.
To fill these gaps researchers tracked the winter movements of 186 fur seals between 2008 and 2013, with a further 20 tracked in 2014 at sub-Antarctic Marion Island. Such a large coordinated study greatly increased their ability to tackle larger questions surrounding climatic change and associated influences on higher trophic levels in the Southern Ocean ecosystem.
The majority of Antarctic fur seal studied show strong loyalty to open-ocean feeding sites, consistently returning to certain parts of the Southern Ocean to search for food over multiple years. These areas of consistent use are characterized by high levels of variability in physical parameters such as ocean temperature.
Such high levels of site fidelity raise questions about the ability of long-lived individuals to respond to future environmental change.
Seals exhibited two main foraging strategies:
- Local foraging and remaining North of the Polar Front typically with deeper and longer dives and an increased foraging effort.
- Foraging further afield, South of the Polar Front, with short, shallow dives and a reduced foraging effort. This reduced foraging effort potentially offsets the energetic costs for those animals investing in a long-distance trip South.
This is the first investigation into the winter diving behavior of Antarctic fur seals. Further analysis of dive and track data will enable the development of a spatial foraging index for Antarctic fur seals in winter that will be used to model changes to foraging habitat under various climate scenarios.
Forage: Search for food
Site fidelity: loyalty to a particular location
Trophic level: the position an animal holds in the food chain