Mexican ground pit viper, Cantil viper, Cantil, Mexican moccasin, Neotropical moccasin, Mexican yellow-lipped viper
The Mexican cantil (Agkistrodon bilineatus) is a rare highly venomous pit viper species. In Sonora, Mexico, it is feared more than any other reptile. In Nicaragua, it is considered the country's most dangerous snake. The word 'cantil' in the common name of this snake means 'yellow lips'; it is based on the Tzeltal word 'kantiil' - a Mayan language spoken in the Mexican state of Chiapas.
Mexican cantils are heavy-bodied snakes and share the same general body structure with copperheads. They have a broad, triangular-shaped head with small eyes that have vertical pupils. Coloration can vary, but most are brown or black, with darker brown or black banding, sometimes with white or cream-colored accents. There are the following distinctive yellow and/or white lines on the head: a vertical line on the rostral and mental, a fine line on the canthus continuing above and beyond the eye to the neck, a broader line on the upper lip from the anterior nasal to the last labial. Juveniles are almost always distinctly banded, with bright green or yellow tail tips, which they use to lure prey. As they age, their pattern and coloration fade and darken.
These snakes occur in Mexico and Central America. On the Pacific side, they are found from southern Sonora in Mexico south through Guatemala, El Salvador, and Honduras. Mexican cantils inhabit moist and dry forests, savannas, and cultivated areas. They can also occur in riparian vegetation.
Mexican cantils are mainly solitary and terrestrial snakes. They are most active at dusk and during the night when they hunt their prey. Mexican cantils have a reputation for being extremely dangerous, however, this reputation is probably not well deserved. They are generally shy by nature, and if threatened their first instinct is to rely on camouflage. If unable to do so they will use a threat display to ward off potential predators. The tightly coiled cantil will raise the last several inches of its tail, this portion often being bright yellow or green in juveniles and a faded yellow or green in adults, the animal will then tail vibrate, creating a loud whipping sound against its coils or surroundings. This particular behavior is very reminiscent of caudal luring, though in a more violent fashion, and is often accompanied by a strike or less commonly a gaping display. Mexican cantil usually will only display these behaviors when given no other choice.
Bite symptoms, of this species in general, may include nothing more than local pain, swelling, and discoloration, but those from adult specimens can cause massive swelling and necrosis. Some bites were fatal within only a few hours. In Honduras, Cruz (1987) describes the bite symptoms as immediate and severe pain, oozing of blood from the fang punctures, considerable edema, nosebleed, bleeding of the gums, marked hematuria, general petechiae, shock, kidney failure, and local necrosis. Polyvalent Antivenom, produced by the Instituto Clodomiro Picado in Costa Rica, is used to treat bites from this species.
Mexican cantils are carnivores. Adults of this species hunt mammals and large lizards, while young cantils mainly feed on lizards and frogs.
Mexican cantils breed in the spring. They are ovoviviparous and give birth to 5-20 live young at a time.
Mexican cantils are threatened by the loss of their native habitat as dry forests are being heavily destroyed. As these snakes are feared by people around their range they also suffer from constant persecution.
The IUCN Red List and other sources don’t provide the number of the Mexican cantil total population size. Currently, this species is classified as Near Threatened (NT) on the IUCN Red List, and its numbers today are decreasing.
