Incidentally gathered natural history information on Bullsnakes (Pituophis catenifer sayi) in southeastern Alberta

Résumé

We present observations on Bullsnakes (Pituophis catenifer sayi) gathered during a study of Prairie Rattlesnakes (Crotalus viridis) in a multiple-use, mixed grass landscape adjacent to the South Saskatchewan River, ~30 km northeast of Medicine Hat, Alberta, in May–October 1997. Hibernacula shared with rattlesnakes were located close to the river. We captured 31 Bullsnakes, either in a drift fence array around a hibernaculum or by hand; three were recaptured once. Emergence from the hibernaculum ended in mid-May, and return to it began in early September. A gap in capture events occurred between early July and late August, possibly attributable to fossorial activity during the height of the summer. The sex ratio of captured adult snakes was 0.64 in favour of males. Males attained the greatest maximum body sizes, but there was no significant size dimorphism by sex. Bullsnakes were assignable to juvenile, subadult, and adult classes by body size. Most captures were made on slopes in the immediate vicinity of the river, in areas classed as “thin breaks”, but four captures, about 7 km east of the river, provide evidence of long-distance movements from hibernacula. Captures were seldom made in the vicinity of anthropogenic features. Gas field development has increased greatly in the years since these data were collected. Our findings provide a baseline for Bullsnake population responses to such changes.