Types of vipers

Metlapilcoatlus is a genus of pit vipers in the family Viperidae, the group that includes rattlesnakes, lanceheads, and other true vipers. The genus was named in 2019 to hold a set of species that had long been placed in the genus Atropoides. The name comes from the Nahuatl word for a grinding-stone, a nod to the heavy, blunt build of these snakes. Roughly half a dozen species are currently recognized, all of them found in Mexico and Central America.

These are heavy-bodied, relatively short snakes with broad triangular heads, keeled scales that give the body a rough texture, and notably short tails. Their muted brown, tan, and gray patterning, often arranged in dark blotches or chevrons, blends into leaf litter on the forest floor. Like all pit vipers they have a heat-sensing pit between the eye and nostril on each side of the head, which they use to detect warm-blooded prey. The common name jumping pit viper refers to the way these snakes can throw the front of the body forward when striking, sometimes lifting clear of the ground.

Members of this genus live mainly in wet and humid forests, including lowland rainforest and cooler mid-elevation cloud forest, across southern Mexico, Guatemala, Honduras, and neighboring countries. They are largely terrestrial and tend to stay among leaf litter, logs, and undergrowth rather than climbing. Because they rely on camouflage and hold still rather than fleeing, they can be easy to step near without noticing, which is the main way people encounter them.

These are venomous snakes and should be treated as dangerous. Their venom can cause significant local tissue damage, pain, and swelling, and bites are a genuine medical emergency. Never attempt to handle, catch, or move a wild jumping pit viper, and do not rely on the assumption that a strike cannot reach you. If a bite occurs, keep the person calm and still, do not cut, suck, or apply a tourniquet, and seek professional medical care immediately. In the United States contact Poison Control at 1-800-222-1222 or call local emergency services; in other regions contact local emergency services right away.

Ecologically, jumping pit vipers are ambush predators that wait motionless for prey to pass, feeding mainly on small mammals such as rodents along with frogs and lizards. Like many New World pit vipers they give live birth rather than laying eggs. Despite their reputation, they are not aggressive toward people and bite defensively when threatened or accidentally disturbed, so the practical safety rule is simple: give them distance and leave them alone.