When it comes to grabbing a snack, lizards have opted for one of two foraging styles. Some species simply sit tight until a tasty morsel wanders past, while other species carefully sniff out and stalk their prey before landing lunch. Knowing that some species are relatively sedentary, while stalkers are on the move most of the time, Eric McElroy and his colleagues from Ohio University, USA wondered whether a species' foraging style had also influenced the way they get about(p. 1029).
Collecting 18 species of lizard, the team filmed the animals as they sprinted, ran and walked along a racetrack, while recording the forces generated by the creatures. Having categorised the way each lizard moves, the team mapped their foraging styles on the family tree and found that the original lizard probably sat and waited for meals to pass their way before chasing them down with a quick dash. Moving on through evolutionary time, the team could see that foraging style had affected the way the reptiles move. Sitters have specialised in sprints and trots while stalkers evolved a new slow walk. However, when escaping predators, most stalkers could sprint, but a few evolved a peculiar slow run. Surprisingly, the team also realised that,over time, three groups of lizards that had taken up stalking had later lost the walking knack, and reverted to sitting and waiting.