Santa Catalina Rattlesnake (Crotalus catalinensis). Field Museum of Natural History, Chicago. FMNH catalogue no. 1169. Conservation status: critically endangered. It is found only on Santa Catalina Island, located off the California coast at Los Angeles. The Catalina rattleless rattlesnake has evolved away from having a rattle because, according to one theory, it does not need a warning mechanism against predators. Its restricted range, the recent past presence of feral cats, the pet trade, killing by human encounters and its over-dependence on rodent food sources all contribute to its vulnerability.