Description: The Neotropical rattlesnake is the second longest venomous snake in Mexico. The head of this species is stout and broad. The brown-black diamonds on the back of these rattlesnakes, contrast to the lighter colored sides. The back quarter of the snake turns to a solid black or brown. The underside is a solid cream to brown color. Stripes on the head and neck distinguish Neotropical rattlesnakes from other rattlesnakes. Their venom affects not only the circulatory system, but also the nerves, causing paralysis. The venom contains both hemotoxic (destructive to red blood corpuscles ) and neurotoxic (toxic to the nerves or nervous tissue ) components, making it the most potent in this genus and highly dangerous. It damages the kidneys and death can occur after only a few days by kidney failure. Nearly 75 percent of humans die, if they do not receive large quantities of serum soon after a bite.
Size: Neotropical rattle snakes can reach lengths up to 72 inches (80 cm). Females are slightly smaller.
Behavior: They are crepuscular (feed only in the twilight) and feed on rodents, lizards and small birds. They are able to climb trees and swim to catch prey. They are not particularly aggressive if unprovoked.
Diet: Feed mainly on small mammals and birds, but will also eat amphibians and lizards.
Senses: Two small pits located between their eyes sense the heat of their prey.
Communication: Their rattle is shaken to warn intruders that are too close.
Reproduction: Crotalus simus are live-bearing. The young are developed in an egg capsule but break free of it at birth. Twenty to fifty babies are born (usually in August) and leave their mother in less than a day. Within seven to ten days, they shed skin for the first time, displaying the first ring of the rattle.
Habitat/range: They are found from central Mexico to Costa Rica in open, grass-rich areas and areas with low thorn bushes.
Status: Listed as Least Concern on the IUCN Red List.