SPATIAL ECOLOGY OF THE CONCHO WATER SNAKE (NERODIA-HARTERI-PAUCIMACULATA) IN A LARGE LAKE SYSTEM

The distribution, movements, activity range, and habitat use of the Co ncho water snake, Nerodia harteri paucimaculata, were studied by mark- recapture and radio telemetry in a large lake system, in central Texas , USA. Concho water snake emigration and distribution were largely dri ven by alteration of habitat availability caused by fluctuating water levels. Habitat characteristics associated with the presence of snakes at the study area were turbid water, minimal wave action, a gentle sh oreline gradient, a silt substrate, and a rocky shoreline. Males and g ravid females were equally vagile, and the likelihood of a snake under taking an emigrational movement was independent of age and/or reproduc tive condition. However, males had significantly more movement days th an gravid females. Radio-tagged males had detectable movements on 64% of monitored days, compared to 43% of monitored days for gravid female s. Mean activity range length was 278 m for males, 219 m for gravid fe males, and 210 m for juveniles. Concho water snakes generally selected retreat sites within 3 m of water, although gravid females selected s ites as far as 15 m from water. As a management procedure for lake pop ulations, we advocate increasing the vertical distribution of rocky sh oreline.