B07
B07
Niche conformance as a mediator of niche choice in Galápagos sea lions
Oliver Krüger
The early environment is known to commonly shape the entire life history of individuals. Whether it is the amount of resources provided by parents or the amount and complexity of social interactions, the effects are often lasting over a lifetime. Pups of Galápagos sea lions (Zalophus wollebaeki) born on the small island of Caamaño in the centre of the archipelago are no exception. Some parts of the island have a very low local population density and other parts have a very high one, thereby providing pups with either no, a few, or a lot of social interactions. Due to island tameness, all this behavioural variation can be observed and documented at close quarters. In addition, this sea lion colony has been under study for 20 years with almost every animal born on the island being individually marked. This allows for unusually detailed research on how individuals conform to the early social niche they are born into, detailed analyses of how their personalities unfold and what the long-term consequences of both their early social niche and personalities for their foraging strategies and fitness are.
Over the last couple of years, we have established personality tests that reveal personality dimensions in pups. We documented that hormones as important infochemicals correlate with personality and island exploration. We used time-depth recorders (TDRs) to unravel a foraging polymorphism in adults where some are choosing to forage on the sea floor (benthic foragers), some are pelagic foragers and some are almost exclusively foraging at night. These foraging niches are related to hormonal differences and in turn are related to fitness: when the ocean is warm, the benthic foragers enjoy a fitness benefit and when the ocean is cold, both the pelagic and night-time foragers enjoy a fitness benefit.
We propose to link the early environment to later foraging tactics and the individual life histories. Pups will be behaviourally phenotyped with personality tests and an ethogram, we will collect saliva and hair samples to document their hormonal profiles and we will use both stable isotope analyses as well as faecal analyses to study the ontogeny of the foraging niche polymorphism in conjunction with further deployment of time-depth recorders in sub-adults and adults. This combination of analytical techniques combined with the long-term individual-based data set will unravel how the pups’ niche conformance during their first year of life predisposes them to choose a foraging niche in later life and what the ensuing fitness consequences are.
