Foraging Fidelity as a Recipe for a Long Life: Foraging Strategy and Longevity in Male Southern Elephant Seals

Abstract

Identifying individual factors affecting life-span has long been of interest for biologists and demographers: how do some individuals manage to dodge the forces of mortality when the vast majority does not? Answering this question is not straightforward, partly because of the arduous task of accurately estimating longevity in wild animals, and of the statistical difficulties in correlating time-varying ecological covariables with a single number (time-to-event). Here we investigated the relationship between foraging strategy and life-span in an elusive and large marine predator: the Southern Elephant Seal (Mirounga leonina). Using teeth recovered from dead males on îles Kerguelen, Southern Ocean, we first aged specimens. Then we used stable isotopic measurements of carbon () in dentin to study the effect of foraging location on individual life-span. Using a joint change-point/survival modelling approach which enabled us to describe the ontogenetic trajectory of foraging, we unveiled how a stable foraging strategy developed early in life positively covaried with longevity in male Southern Elephant Seals. Coupled with an appropriate statistical analysis, stable isotopes have the potential to tackle ecological questions of long standing interest but whose answer has been hampered by logistic constraints.

Decadal changes in habitat characteristics influence population trajectories of southern elephant seals

“…Earlier studies have suggested that individual loyalty to regions is stable over a number of years (Authier, Bentaleb, Ponchon, Martin, & Guinet, 2012;Bradshaw et al, 2004), but some realms are also better quality habitat for elephant seals than others (Biuw et al, 2007;Thums et al, 2011); high-Antarctic habitats appear better than sub-Antarctic habitats (Authier, Bentaleb, et al, 2012;Hindell et al, 2016). Earlier studies have suggested that individual loyalty to regions is stable over a number of years (Authier, Bentaleb, Ponchon, Martin, & Guinet, 2012;Bradshaw et al, 2004), but some realms are also better quality habitat for elephant seals than others (Biuw et al, 2007;Thums et al, 2011); high-Antarctic habitats appear better than sub-Antarctic habitats (Authier, Bentaleb, et al, 2012;Hindell et al, 2016).…”

General conclusion to the special issue Moving forward on individual heterogeneity

“…The enthusiasm for such models is growing in ecology. For instance, mixture models are increasingly used to uncover life-history tactics that may occur within a population (Authier et al 2012, Chevallier et al 2013, Fay et al 2016, Hamel et al 2017, 2018 and to partition the variance in lifetime demographic traits into components due to heterogeneity fixed at birth and heterogeneity generated by stochasticity during a life course (Hartemink et al 2017, Jenouvrier et al 2017, Hartemink and Caswell 2018. Joint models are used to assess the full co-variation among traits, thereby improving our understanding of positive and negative relationships among numerous traits (Cam et al 2002, Pavitt et al 2016, Careau and Wilson 2017, Hamel et al 2017.…”

Southern elephant seal foraging success in relation to temperature and light conditions: insight into prey distribution

“…the main foraging habitat of Kerguelen Island sub-adult and adult males; Bailleul et al 2010, Dragon et al 2010, Authier et al 2012. As part of this work we focused on the pelagic portion of the tracks by excluding data from areas where water depths were <1000 m ( Fig.…”