Food supplementation affects the foraging ecology of a low-energy, ambush-foraging snake

The effect of food availability on the spatial ecology of animals varies within and across study systems because a multitude of factors can affect the spatial activity of organisms. Low-energy specialists, such as ambush-foraging snakes, feed infrequently and can endure long periods without food. Because they have low-energy requirements, one possible tactic for feeding may be to simply ambush for longer periods when prey availability is low, thereby decreasing the potential costs associated with locating new ambush sites. We used radiotelemetry, supplemental feeding, and remote video cameras on free-ranging male puff adders (Bitis arietans) in South Africa to test the hypothesis that food intake affects the foraging ecology of extreme low-energy, ambush foragers and to quantify their natural feeding rates. Supplementally fed puff adders improved their body condition, spent less time foraging, and decreased distance traveled compared to control snakes. However, movement frequency and home range size did not differ between the two groups. These findings indicate that control snakes traveled farther within similar-sized home ranges compared to fed snakes and did so at no survival cost. Further, naturally foraging puff adders successfully caught a prey of small size once every 10 days on average. Hence, despite their “sit-and-wait” foraging strategy and their low-energy intake/requirements, underfed puff adders travel widely to presumably find appropriate ambush sites that maximize prey capture. Our research provides the first strong evidence that the spatial activity of a terrestrial vertebrate species with extremely low energetic demands is significantly affected by food intake. Because animals travel their home range partly to forage, their space use can be affected by the amount of food available in nature. We show that, despite a low-energy lifestyle, the movement level of an ambush-foraging snake that feed infrequently is linked to the amount of food they eat. Underfed snakes traveled greater distances in search of prey, within similar-sized home ranges, compared to well-fed snakes, and they did so at no survival cost. Hence, our research adds to our understanding of the effect of food on the spatial ecology of animals, by providing conclusive evidence that the spatial response of an organism with extremely low-energy demands can be affected by food.