Movement Ecology of Coluber constrictor near Communal Hibernacula

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Abstract
Several aspects of the spatial biology of the racer, C. constrictor mormon, were studied in 1971 and 1972 near communal hibernacula in a desert habitat near Grantsville, Tooele County, Utah [USA]. Coluber is an abundant, winter-aggregating species at this locality. Radiotelemetry was used to track free-ranging racers during their spring migrations away from hibernacula and on their summer ranges. Males dispered a mean distance of 781 m and females 663 m. The geometric mean dispersal was 383 m, a more meaningful measure of central tendency for this parameter. Maximum dispersals recorded were 1.6 and 1.8 km from 2 separate den complexes. On days when movements occurred during spring dispersal, mean travel rate of 4 females was 99.7 m/day. Once migratory movements commenced, long unidirectional distances were traversed within several days. Directional shifts at the end of migration, and less frequent and shorter subsequent movements, made a snake''s home range distinct from its dispersal route. Mean movement on the home range was 31 m/day on days when movements occurred. Ten females had home ranges averaging 0.4 ha. After sample size bias correction, mean home range size of 7 non-gravid females was 1.4 ha. Kansas racers, C. c. flaviventris, occupy home ranges about 7 times larger than Utah C. c. mormon. This major intraspecific geographic difference in spatial biology may be related to the larger age-specific body size of Kansas racers. Total range embracing all seasonal movements of an animal lacking home range stability, was previously advanced by others for Coluber at this study locality. These findings do not support this concept. Through 1971, 93% of 283 survivors returned to hibernate in the same den used the previous winter, whereas 7% hibernated in different dens. Such high fidelity to a specific den may have an olfactory basis. Coluber homed successfully after displacements of 100-300 m N and S of the main den in autumn, but snakes displaced E, where their return brought them near other dens, used these dens for hibernation and did not home successfully. One female captured in successive springs at the same den migrated along an identical route and occupied the same home range both years.