Fedeltà delle femmine di Leone marino alle zone di alimentazione

A.D. Lowther, R.G. Harcourt, D.J. Hamer, S.D. Goldsworthy. (2011). Creatures of habit: foraging habitat fidelity of adult female Australian sea lions. Marine Ecology Progress Series 443: 249-263
ABSTRACT: We examined the movement characteristics and seasonality of feeding behaviour for an
endemic Australian otariid, the Australian sea lion Neophoca cinerea. By combining tracking data
and stable isotope analysis of serially subsampled vibrissae from 20 adult females at 7 colonies, we
were able to characterise individual foraging specialisation across 80% of the species range. Adult
females expressed long-term temporal consistency in both foraging site (offshore vs. inshore) and
prey selection. When seasonality in foraging behaviour was detected (n = 7), there was no
consistency in variation of isotope ratios between individuals or colonies. Offshore-foraging sea lions
fed at higher trophic levels than inshore foragers. Potentially, inshore foragers could be subdivided
into those which targeted heterogeneously distributed seagrass meadows or calcarenite reef systems
for different payoffs. This data highlights the importance of understanding individual specialisation
and the dangers of generalising behaviour at the colony level. Individual specialisation in foraging
behaviour may be a mechanism that reduces intra-specific competition, but its effectiveness will be a
function of the temporal stability of individual differences. The present study is the first to identify
multi-season consistency of individual foraging behaviour for any otariid. Given the long-term
stability of adult female foraging behaviour, categorising individuals using a proxy measure such as
whisker isotopic signature appears robust, economical, and appropriate. Such data is critical to modelling
population response to anthropogenically driven fine-scale habitat modification.