Common Gartersnakes show density dependence in habitat selection despite no density dependence in growth

William David Halliday, Gabriel Blouin-Demers


Density-dependent habitat selection is widespread and is caused by a decrease in mean fitness in a habitat as density in that habitat increases. Yet density dependence may not be at work in all organisms. Snakes, for example, eat infrequently and have thus been inferred to have weak responses to density, although no empirical evidence has demonstrated this yet. In this study, we used an enclosure experiment with different densities of Common Gartersnakes (Thamnophis sirtalis Linnaeus 1758) to examine whether density dependence affects growth and habitat selection. We found no evidence of density dependence in growth. Surprisingly given the absence of density dependence in growth, we did find evidence of density-dependent habitat selection, although gartersnakes did not select habitat based on the location of food supplementation within our enclosures. Our study is the first to demonstrate density-dependent habitat selection by snakes. 

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