SPATIAL ECOLOGY OF BLACK RAT SNAKES ON REMINGTON FARMS, MARYLAND

Black rat snakes (Elaphe o. obsoleta) are important predators of nesti ng birds and small mammals in fragmented landscapes. Thus, we used rad iotelemetry to study movements of 32 black rat snakes at Remington Far ms, Maryland, during 1988-89 to determine potential ways to minimize t heir depredations. Yearly home ranges were similar (P > 0.05) for male s and females (xBAR +/- SE) (convex polygon, 9.49 +/- 1.01 ha; 95% har monic contour, 10.52 +/- 1.24 ha), but males covered more (P < 0.05) o f the home range earlier in the spring. Snakes were familiar with habi tat features within their home range, returning to the same areas afte r prolonged absences. Snakes used forest edge, residential, hedgerow, and herbaceous/brush habitats more (P < 0.05-0.001) than expected by c hance. Use of hayfields increased, and use of forest decreased from ea rly (mid-May-30 Jun) to late (I Jul-28 Aug) season. Snakes rarely used crop fields. Low frequency of movement within forest interior and res idential areas indicated their importance as refuges. Activity was hig h in non-forest habitat and forest edge, suggesting their importance f or foraging. Males traveled more often (P < 0.01-0.001) than females d uring late spring and early summer. Movements were infrequent (<5%) be tween dusk and dawn. Use of major structural features in the home rang e differed (P < 0.05-0.001) between sexes and among seasons. Females u sed shelter (trees and buildings) more often (P < 0.001) than males, e specially during early season. Snakes used elevated sites on >50% of a ll observations. Females used higher (P < 0.001) perches (xBAR +/- SE) (6.3 +/- 0.2 m) than males (3.4 +/- 0.1 m). Suitable habitat for blac k rat snakes in agricultural landscapes contained small forest blocks with a high edge-to-area ratio. Fallow fields, fields planted to orcha rd grass and clover, and a network of strip vegetation, especially bru shy hedgerows, provided important foraging habitat. To minimize predat ion on nesting birds and small mammals, we suggest decreasing habitat suitability by creating broad expanses of unsuitable habitat bordering forests, or maintaining large forest blocks with a low edge-to-area r atio.