The effect of coachwhip presence on body size ofNorthAmerican racers suggests competition between these sympatric snakes

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AbstractWhen sympatric species compete, character divergence may help maintain coexistence. Snakes are often found in species‐rich assemblages while exploiting similar resources; because snake body size is a relatively plastic trait that determines the range of prey sizes an individual may consume, divergence in body size between sympatric species may arise as a result of interspecific interactions. TheNorthAmerican racer,Coluber constrictor, and the larger coachwhip,Coluber flagellum, have a close taxonomic relationship and similar foraging strategies. Therefore, we hypothesized thatC. constrictorwould be smaller where they co‐occur withC. flagellum, as compared to whereC. flagellumis absent, throughout the southeastern extent of their range. To evaluate this hypothesis, we obtained data on body size for 2321 adultC. constrictorand 526 adultC. flagellum, along with habitat data and other potentially important factors influencing body size.Coluber constrictorwas smaller than elsewhere when in peninsularFlorida, in pine forests, on hydric soils and in the presence of the larger and potentially competingC. flagellum. Body size ofC. flagellumdid not vary by any measured habitat variables. The trends we documented are consistent with the hypothesis thatC. constrictorbody size is influenced by several variables, including co‐occurrence withC. flagellum.