Rattlesnake colouration affects detection by predators

Abstract

Crypsis, or the ability of an animal to avoid detection by other animals, is strongly impacted by an animal’s colouration and pattern. Crypsis may be especially important for ambush foragers, which spend much of their time above ground and therefore benefit from being inconspicuous to predators and prey. The purpose of this study was to investigate the effect of rattlesnake skin colouration on the likelihood of it being detected and attacked by a predator, on the latency (time) to attack, and on the attack frequency on each physical body section of the models. Clay models representing four commonly observed rattlesnake colour morphs (light, dark and two intermediate colour patterns) were deployed in two different habitat types (wooded area and open field), and the marks made on the models by predators were quantified over time. We found that light snake models, which have little contrast with substrate, were less likely to be attacked and were attacked later than darker model types, which have higher contrast with substrate. Predators attacked the various body segments of the models at similar frequencies. Our data suggest dark-coloured rattlesnakes, which have the most contrast with the golden-coloured grasses and therefore have the lowest crypsis, are most at risk from predation.