Ecosystem Functioning

Effects of variation in marine productivity on reproduction in Weddell seals and Adelie Penguins

Principle Investigator: Dr Lloyd Davis
Organisation: University of Otago

What we do: 1) We assess the relationship between foraging performance of Weddell seals breeding in McMurdo Sound and a range of oceanographic parameters encountered during their winter foraging in the Ross Sea. Oceanographic variables recorded include sea surface temperature, productivity and bathymetry. We plan to link their over-winter performance to their breeding performance in the subsequent breeding season. We determine how the winter diet, mother's body condition, and rate of energy transfer during lactation relate to pup body condition and the ontogeny of disease resistance. Ultimately, we assess how these factors interact and if they are determinants of pup survival within the first year.

2) We observe a behaviour in Adelie penguins known as the feeding chase, whereby a parent is chased by its crèche-aged chicks before feeding them. Typically, these chases take the chicks outside the boundaries of their sub-colony, making them vulnerable to predation by skuas.

Why we do it: 1) These data will help us understand how Antarctic predators will respond to changes in the distribution of marine resources as a result of global climate change or commercial fisheries activity.

2) The brood-reduction hypothesis proposes that feeding chases lead to preferential feeding of one chick when food resources are scarce; whereas, the contradictory brood maximization hypothesis suggests they serve to distribute food evenly among chicks, thereby thwarting the effects of sibling competition. The grounding of two immense icebergs near Ross Island has created a natural experiment, making it difficult for penguins breeding there to get enough food for their chicks. By comparing feeding chases of penguins at Cape Bird, Ross Island, with those under normal feeding conditions, we can (i) determine the function of feeding chases in Antarctic Pygoscelid penguins (ii) help assess the consequences of the grounded bergs for the Ross island penguins, and (iii) potentially provide management options to help mitigate the effects of such events in the Antarctic marine ecosystem.