Abstract
Individual specialisations have been suggested to improve foraging efficiency by optimising individual capacity (physiological and behavioural) and reducing intra-specific competition in exploiting prey resources. In this study we investigated the inter- and intra-individual variation in behaviour in an opportunistic forager, the Gentoo penguin (Pygoscelis papua), at Kerguelen Island, southern Indian Ocean. We used complementary bio-logging and stable isotope analyses, coupled with morphometric measurements, to: 1) determine the inter-individual variation in morphology and foraging behaviour; 2) quantify intra-individual variation in foraging behaviour; 3) investigate the links between consistency in foraging, distances travelled and body condition; and 4) determine if dietary specialisations exist and are maintained outside the breeding season. We show that this species exhibits a large inter-individual variation in foraging behaviour with some individuals conducting very short trips close to the colony while others travelled considerably further. Heavier individuals tended to forage in more distant locations, dive deeper and perform more benthic dives. Individual specialisation in behaviour was low to moderate at the population level, yet some individuals were very consistent. The rate of travel was not influenced by consistency, and there was a lack of correlation between body condition and foraging consistency. High inter-individual variation in feeding ecology and dietary specialisations outside of a single breeding season were observed, consistent with Gentoo penguins being Type “B” generalists (i.e. generalist populations composed of individuals each consuming a different range of foods).
Highlights
According to the optimal foraging theory, individuals implement feeding strategies aimed at maximizing energetic gains while minimizing costs (Stephens & Krebs 1986)
We investigated inter- and intra-individual variation in the foraging ecology of gentoo penguins
Body condition indices were lower at Pointe Suzanne compared to Estacade but similar between sexes
Summary
According to the optimal foraging theory, individuals implement feeding strategies aimed at maximizing energetic gains while minimizing costs (Stephens & Krebs 1986). (Bolnick et al 2003, Estes et al 2003). Specialisations in foraging, involving the repetition of specific behaviours to acquire food or dietary choices over time, have until recently been poorly investigated. Individual specialists have been defined as ‘individuals whose niche is substantially narrower than their population’s niche for reasons not attributable to their sex, age or discrete morphological group’ Even populations usually thought to be generalists can be composed of individual specialists, referred to as Type ‘B’ generalists (individuals each specialising on a different but narrow range of food types) as opposed to Type ‘A’ generalists (individuals all taking a wide range of food types) (Araújo et al 2011, Loxdale et al 2011, Layman & Allgeier 2012, Fodrie et al 2015)
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