Meeting Abstract
Sensory information drives the ecology and behaviour of animals and some animals are able to detect environmental cues unavailable to us. For example, rattlesnakes use infrared (IR) radiation to detect prey. The IR sensory system should best detect warm prey animals against cool and thermally uniform backgrounds. In addition, prey may be more easily detected at thermal transitions, i.e. areas where contrast between a moving target and background changes rapidly. We tested whether rattlesnakes select ambush positions with backgrounds that offer strong thermal contrast with endothermic prey and/or backgrounds with thermal transitions. We tracked free-ranging sidewinder rattlesnakes Crotalus cerastes to their selected ambush sites and recorded 360° near-ground thermographic panoramas from the center of the ambush site. A computer simulation then moved a simulated prey item across the panorama and computed contrasts at each azimuth. Rattlesnakes did not choose ambush directions that offered stronger contrast than average, but they did choose directions with stronger thermal transitions. Selecting such ambush directions presumably facilitates prey capture at night when visual cues are reduced. Future laboratory and field work will determine whether strike probability and success are indeed higher when facing thermal backgrounds with strong thermal transitions.
