A nocturnally-active predator is mainly a diurnal hunter

The sit-and-wait hunter, Cerastes vipera, is a presumed nocturnally-active desert snake, although it feeds mainly on the diurnally-active lizard, Acanthodactylus spp. We hypothesized that nocturnal activity of C. vipera is pri-marily to locate an ambush site, and that Acanthodactylus spp. is predated mainly diurnally. We used the pro-portion of free-ranging C. vipera that defaecated per day to estimate daily feeding rate, and prey capture per night to estimate nocturnal feeding rate. In adult snakes (n = 161), defaecation was observed in 20.5% and nocturnal feeding in 3.1% per day. The difference between the two estimates represented the diurnal feeding rate, that is, 85% of the daily feeding was diurnal. All vipers ceased movement near midnight, when approximately 50% were in ambush. They maintained their position until morning and four individuals of each sex were followed during the day. These vipers displayed caudal luring in the presence of Acanthodactylus spp., ended ambush at approximately 10:00 when air temperature reached 40 degrees C, and then moved into a nearby burrow. We concluded that nocturnally-active C. vipera adults are mainly diurnal hunters, but could be classified as cathemeral pred-ators. Diurnal caudal luring and differences in ambush strategy in C. vipera are documented for the first time.