GROWTH OF TIMBER RATTLESNAKES (CROTALUS HORRIDUS) IN AN AGRICULTURALLY FRAGMENTED AND A CONTIGUOUSLY FORESTED HABITAT

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Abstract

Habitat loss and fragmentation threaten Timber Rattlesnake (Crotalus horridus) populations in contiguous, mature forests of eastern North America, yet information regarding the life history of C. horridus in fragmented habitats is sparse. In this study, we used mark-recapture data on body size and rattle morphology to compare the size at birth and per ecdysis growth rates of C. horridus from a fragmented habitat in west-central Missouri (MO) with those from a closed-canopy forest in northwest Arkansas (AR). The MO population is typically exposed to a shorter frost-free period than the AR population, so individuals may have less time to acquire prey. At birth, snakes in the MO population were significantly shorter than those from AR, but MO snakes increased in length more rapidly than AR snakes through their first eight ecdyses. Sexual size dimorphism was apparent in the MO population when males and females diverged in size between the fifth and sixth ecdyses, whereas growth trajectories of AR males and females remained indistinguishable through the first eight ecdyses. Crotalus horridus in the agriculturally fragmented habitat may have grown faster than their forest-dwelling counterparts because fields and edges provide prey with stable food sources, unlike the boom and bust production typical of acorn mast crops. Although previous studies have demonstrated that C. horridus growth rates vary along latitudinal and elevational gradients due to climatic constraints on foraging, our study suggests that prey abundance may be just as important in shaping variation in life history both within and among populations.

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