Generally specialized or especially general? Habitat selection by Snapping Turtles (Chelydra serpentina) in central Ontario

Abstract

Habitat selection is the disproportionate use of habitat compared with availability. Many studies have focused on specialists, but few have considered habitat selection in populations that are generalists, which can be composed of generalist individuals or individuals that specialize on different habitats. We tested habitat selection and individual specialization in a northern population of a supposed generalist, the Snapping Turtle (Chelydra serpentina (L., 1758)), during the active season and winter using telemetry. Habitat selection was tested at two spatial scales by comparing random points to home ranges and turtle locations using Euclidean distances. Turtles selected home ranges from the habitats available in the population range. However, at the population level, all aquatic habitats were equally preferred, and the population behaved as a generalist owing to individuals specialized on different habitats. Over half of the individuals showed evidence of individual specialization on different habitat types. Turtles did not select habitat within home ranges during the active season, but overwintering turtles chose locations that were colder than haphazard stations in the same habitats, likely to reduce metabolic costs and the risk of acidosis. These findings have implications for the management of this species at risk and for understanding the evolution of resource generalization.Résumé : La sélection d'habitat est une utilisation disproportionnée d'un habitat par rapport à sa disponibilité. Plusieurs études se sont intéressées aux spécialistes, mais peu ont considéré la sélection d'habitat dans des populations généralistes, qui peuvent être composées d'individus généralistes ou alors d'individus qui se spécialisent pour des habitats différents. Nous avons évalué la sélection d'habitat et la spécialisation individuelle dans une population nordique d'un généraliste pré-sumé, la tortue serpentine (Chelydra serpentina (L., 1758)), durant la saison active et durant l'hiver à l'aide de la télémétrie. Nous avons évalué la sélection d'habitat à deux échelles spatiales en comparant des sites aléatoires aux domaines vitaux et aux positions individuelles des tortues par des distances euclidiennes. Les tortues choisissent leurs domaine vital parmi les habitats disponibles dans l'aire de répartition de la population. Cependant, au niveau de la population, les habitats aquatiques sont sélectionnés sans discrimination et la population se comporte en généraliste parce que les individus se spécialisent pour des habitats différents. Plus de la moitié des individus présentent des signes de spécialisation individuelle sur des types différents d'habitat. Les tortues ne choisissent pas d'habitat dans leur aire vitale durant la saison d'activité, mais les tortues qui hibernent choisissent des sites qui sont plus froids que les stations aléatoires dans ces mêmes habitats, qui sont susceptibles de réduire les coûts métaboliques et le risque d'acidose. Ces résultats ont des conséquences sur la gestion de cette espèce menacée et sur la...

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