Food acquisition is vital for the maintenance, growth and survival of an animal. Predators employ two hunting strategies to capture their prey, sit-and-wait ambushing and active hunting. Active hunters generally come in contact with more prey items, but expend more energy in capturing prey and are more likely to be spotted by a predator, and thus have a higher risk of being captured than do sit-and-wait ambushers. Cerastes vipera is a small, nocturnal predator that captures its prey mainly by sit-and-wait ambush and occasionally by active hunting. This viper consumes predominantly lizards and, of the prey available, the diurnal Acanthodactylus spp. was most abundant. We tested the hypothesis that the time of activity coincides with hunting and, consequently, we predicted that C. vipera would prey on diurnal species. To test this prediction, we determined dietary intake of male and female free-living adult and neonate C. vipera by fecal analysis. We also estimated the time of prey capture by these vipers.
Results/Conclusions
C. vipera started its active movement after sunset and terminated movement prior to midnight when it presumably selected a suitable site for sit and wait ambush. The ambush position lasted until mid-morning (10:00 am±0:30 min) and averaged 10.0±2.02 hours. It emerged that Cerastes vipera fed mainly on diurnal Acanthodactylus spp. and occasionally on nocturnal lizards and, thus, our prediction was rejected. Acanthodactylus spp. were captured by 25 neonate and 43 adult C. vipera; neonate C. vipera consumed only neonate Acanthodactylus spp. but only 2 adult C. vipera consumed neonate Acanthodactylus spp. Based on feeding rates in free-ranging adult C. vipera, we estimated that more than 78% of their prey was captured diurnally. An interesting occurrence emerged in the study - most nocturnally-active lizards were captured by adult female vipers, suggesting a sex-biased hunting success at night. Sexual dimorphism is evident in C. vipera; besides being slightly larger than males, females have pronounced black markings at the tip of their tails whereas males do not. We suggest that females use caudal luring at night to a greater extent than do males, enabling them to have better hunting success.