The harmonic mean method was used to calculate activity areas. Mean home range size was 5.4 ha, with a very concentrated core area of only 7.7% of the home range. Recause most animals tested exhibited shifting activity centers, and because home range size was positively correlated with the number of days a snake was tracked, it was concluded that N. sipedon at this site did not maintain a home range in the traditional sense. A dynamic methodology for quantifying areal utilization is proposed. N. sipedon was found to be very selective in its habitat utilization. Cattails (Typhus latifolia) and flooded meadow (primarily Phalaris and Carex spp.) were generally prefet ed in excess of availability, while open water was avoided. Dead cattail clumps were the most utilized substrate. Water (surface and submerged) and grass (dead and live) were also preferred to a lesser extent. Seasonal and daily trends are discussed in terms of responses to exogenous and endogenous cycles. Diversity of substrate use peaked during morning hours and showed an overall increase as the season progressed. Mean perch height was 10.9 cm above water, without strong differences among daylight hours. Perch heights were greatest during May; in habitats along open water; and on branches, dead cattails, and dead logs. The mean insolation level was 50.9%. On a daily cycle snakes received more sunlight during the midday hours, but it appeared snakes were not responding passively to decreased shade availability. Perch height and insolation level were positively correlated, thus high substrates were also associated with greater insolation. Three measures of snake activity were analyzed: incidence of movement (s = 27.7%), total rate of movement (? = 5.2 m/h), and conditional rate of movement (x = 18.7 m/h). Snakes were generally more active during April while they dispersed from the hibernaculum. From May-July the animals were equally active at all times of the day. Snakes exhibited greater rates of travel across open and exposed habitat types. Individual snakes differed significantly in all three measures of activity and also had variation in home range size spanning four orders of magnitude. Nevertheless, more active snakes did not utilize a larger area than their less active conspecifics.