Movement Patterns and Home Range Use of the Northern Watersnake (Nerodia sipedon)

Abstract

The factors that influence spatial use and movement patterns in ectotherms may have important fitness consequences. To examine the effects of sex and condition on spatial use, we used radio telemetry to observe the movement of 18 adult Nerodia sipedon in a southwest Missouri lake. Snakes generally remained in close proximity (<5 m) to aquatic habitats throughout the summer. Home range size estimates differed according to calculation method. Monthly total home range sizes peaked in mid-summer, possibly in response to increased amounts of vegetative cover, although core area sizes were consistent across the season. Contrary to previous studies of snakes, mean movement rates and home range sizes of male and gravid female N. sipedon were statistically indistinguishable and highly variable. Body size and condition influenced spatial characteristics of females, but only appeared to influence movement frequency of males. When compared to other populations, we found that our population of N. sipedon tended to occupy similarly-sized shifting core areas associated with aquatic vegetation. Future studies should focus on the measurement of resource distribution to further understand the factors influencing variation in snake movements and spatial patterns.