Site-specific differences in the spatial ecology of northern cottonmouths

Abstract

We conducted a yearlong telemetric study on 44 northern cottonmouths (Agkistrodon piscivorus) and recorded their weekly spatial position and use at two different and unconnected wetlands: Cooper Wildlife Management Area (Cooper WMA) and Texas A&M Commerce Wetland Area (Commerce WA). These wetland sites differed in size, but were nearly identical in general locality, structure, hydrology, vegetative composition, available resources, and biodiversity. Home ranges for male cottonmouths at the larger Cooper WMA (n = 16; 95% kernel density estimate (KDE) (Formula presented.) = 54.69 ha ± 9.36; 100% minimum convex polygon (MCP) (Formula presented.) = 22.9 ha ± 4.19) were significantly larger than those at the smaller Commerce WA (n = 10; 95% KDE (Formula presented.) = 19.88 ha ± 4.71; 100% MCP (Formula presented.) = 8.98 ha ± 2.27). The home ranges of males (n = 26; 95% KDE (Formula presented.) = 41.3 ha ± 6.84; 100% MCP (Formula presented.) = 17.55 ha ± 3.00) were also significantly larger than those of females (n = 7; 95% KDE (Formula presented.) = 7.04 ha ± 1.81; 100% MCP (Formula presented.) = 3.08 ha ± 0.82) at both sites. We found no relationship between body size and home range size at either study site. Average weekly distance traveled by males ((Formula presented.) = 110.07 m ± 10.80) was significantly greater than that of females ((Formula presented.) = 45.04 m ± 4.34), and male movement rates were bimodal in distribution with peaks of movement in the spring and fall. These peaks in movement rates coincided with the spring and fall migrations for mating, thermoregulation, parturition, and access to hibernacula and food resources. We found home ranges within these two-dimensional wetlands to be larger than those reported for linear or one-dimensional riparian sites. We discuss how wetland size and the size-dependent dispersion of potential resources within similar wetlands may influence movement patterns and home range sizes. Such information may serve to evaluate effective wetland size for the conservation and management of wetland species.