Narrow-headed Vine Snake

Habitat
This versatile snake can deal with a variety of habitat situations. From solid forest to disturbed areas or secondary growth, it can survive if there are high grasses, low shrubs, or trees. Lowland dry, moist, or wet forests are helpful, but premontane moist and wet forests are acceptable as well.

Range
The vine snake also has a wide range. On the Pacific side of the continent it can be found from southern Arizona through Mexico and down to northern Peru and southern Brazil; off the other coast, it can be found in Trinidad and Tobago. Within Costa Rica, it is common throughout the lowlands up to 1,340 m in elevation except in the driest parts of the northwest.

National Parks
Corcovado National Park, Cano Negro National Wildlife Refuge, Barra del Colorado National Wildlife Refuge, Tortuguero National Park, Parque Nacional Palo Verde, Cabo Blanco National Reserve, Carara National Park, Golfito National Wildlife Refuge.

Physical Description
This distinct vine snake has a pointy, narrow head with large, round, yellow to beige eyes positioned on the front of the face. The long, skinny body is brown or grey with spots, specks, or shades of red, orange, yellow, green, or black. The snake has a cream to white upper lip, underside of the head, and throat; there is a contrasting dark streak from the nostril, across the eye, and down the side of the neck.

Two particularly striking features of this snake are its tail and mouth. The tail of this snake can be up to half of its total length. Roughly half of these snakes do not have complete tails after being attacked by predators. The inside of the snake's mouth is a dark purple to bluish black; when threatened, the snake will open its mouth widely and hold the position to intimidate predators.

Biology and Natural History
Well-disguised and cryptic in its behavior, the vine snake is common throughout the Guanacaste region in Costa Rica, where it climbs among vegetation near the forest floor during the day.

The dull coloration is well-paired with still, outstretched positions to make the snake resemble a thin vine; sometimes they rock back and forth a little to blend in with trees blown by wind. This camouflage is the snake's main defense and disguise when threatened and hunted. If hiding does not work, the snake will hiss and hold its dramatically-colored mouth open toward its attacker. This display is startling, but if it is not enough to dissuade an attacker, the vine snake may make quick strikes, not necessarily biting. If it does bite, it will do so lightly with its rear grooved fangs, but the bite only causes harm if the snake is given time to gnaw. The venom is mild and may cause some temporary blistering or swelling, but no permanent damage. This venom is more effective on prey, which the snake hunts during the day. It actively searches for prey among low vegetation or on the ground, and paralyzes the prey by injecting venom.

At night the vine snake may be found sleeping in a loosely coiled pile in a tree, as high as 5 m off the ground. It mellows during the dry season and hides in hollow trees and other moist nooks. Females wait until the peak of the wet season to lay their clutch of 3 to 5 eggs; larger females will lay more eggs.

Diet
Primarily a lizard-hunter, the vine snake will also feed on small frogs, birds, mammals, and insects.

Height/Weight
Adults can be up to 2 m in total length, but up to half of that may be tail.

Taxonomy
Order: Squamata
Family: Colubridae

Sources
Leenders, Twan. A Guide to Amphibians and Reptiles of Costa Rica. Zona Tropical, S.A, Miami, FL, 2001.
Savage, Jay M. The Amphibians and Reptiles of Costa Rica: A Herpetofauna between two Continents, between Two Seas. The University of Chicago Press, Chicago, 2002.
Savage, J. M., N. J. Scott, and D. C. Robinson in: Janzen, Daniel H. Costa Rican Natural History. Chicago: University of Chicago Press, 1983.
Scott, N. J. in: Janzen, Daniel H. Costa Rican Natural History. Chicago: University of Chicago Press, 1983.

-Amy Strieter, Wildlife Writer