Generalist Habitat Selection By Cottonmouths (Agkistrodon piscivorus) in a Hydrologically-Dynamic Wetland
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Abstract
Wetlands are typically transitional habitats that represent a dynamic hydrologic gradient between terrestrial and aquatic systems. As hydrologic fluctuations within a wetland can cause the environment to become periodically unsuitable and resource-limited, species with traits that can adapt to these environmental changes will be favored. Populations inhabiting highly dynamic environments with high frequencies of disturbance may have extensive niche overlap and less habitat specialization among residents. This study examined the habitat selection of North Cottonmouths (Agkistrodon piscivorus) inhabiting an isolated riverine slough along the Cumberland River (Middle Tennessee). I hypothesize that cottonmouths use generalist habitat selection as an adaptation to hydrologically-dynamic ecosystems they are inhabiting and have extensive habitat niche overlap among the population as a result of temporal instability of habitat resources.
Field collection was by visual-encounter surveys, and environmental variables (abiotic and biotic) were recorded for each snake location (N = 149), and paired with a random location to assess available macro- and microhabitats within the study area.
Multivariate analysis found that cottonmouths have a broad affinity for a variety of microhabitats within the riverine slough. In addition, I found no intra-specific differences in habitat use between adult males, adult females, and juveniles. However, there was an ontogenetic shift with younger individuals selecting more terrestrial habitats with a higher availability of cover objects.
Random Forest modeling determined that cottonmouths tended to select sites associated near or within water, even though fully terrestrial habitats were available, emphasizing cottonmouths affinity for wetland ecosystems within the gradient between terrestrial and aquatic systems
My findings suggest that a fluctuating hydrologic regime may promote cottonmouths to exhibit a strategy of generalist habitat use, potentially to increase opportunities to obtain resources in a dynamic wetland environment.