Lance head rattlesnake

Class: Reptilia
Order: Squamata
Family: Viperidae
Genus and Species: Crotalus polystictus
  • A lance head rattlesnake curled up in the sand
  • A lance head rattlesnake in the sand
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Lance head rattlesnake

The lance head rattlesnake is native to Mexico. This snake's colors range from tan or brown to gray and sometimes white, with an orange-brown stripe down its back. The dark spots along its body are unique to this species of rattlesnake.
Physical Description

The lance head rattlesnake's scientific name, Crotalus polystictus, translates from the Greek "poly" meaning many and "sticto" meaning spotted, describing the snake's general appearance. The characteristic dark spots that mark lance heads are unique to this species of rattlesnake. They are often oval or elongated toward the front of the body and more circular toward the middle of the animal. The snake's coloration ranges from tan or brown to gray and sometimes white. An orange-brown stripe also runs along this species back, most noticeably between spots. 

Lance head rattlesnakes yield a fairly large amount of venom per bite—80 to 100 milligrams—and are also equipped with long fangs, earning them a dangerous reputation. A sexually dimorphic species, males tend to have a larger head, which correlates to their preference for preying upon larger mammals. Smaller-headed females tend to seek out smaller prey. 

This species will vibrate its tail when alarmed, creating a rattling sound in an attempt to ward off potential predators. The rattling sound is created through the rapid vibration of a series of loose-fitting, interlocking scales at the base of the tail. When vibration occurs, the edges of the scales rub against one another to create the rattlesnake's characteristic sound.

Size
Small-to-medium sized rattlesnakes, most lance heads grow between 27.5 and 31.5 inches (70 to 80 centimeters), occasionally reaching lengths of 39 inches (100 centimeters). 
Native Habitat
Lance head rattlesnakes are native to Mexico, inhabiting the central portion of the Mexican plateau at elevations ranging from 4,750 to 8,500 feet (1,450 to 2,600 meters). This species is terrestrial, preferring a habitat of various types of grasslands, scrublands, pine and oak forests with rocky outcrops and even areas of old lava flows.
Food/Eating Habits
These rattlesnakes primarily prey upon amphibians and other reptiles, as well as the occasional insects or mammals. A venomous snake, they use a quick strike, penetration and injectoin of venom to subdue prey.
Reproduction and Development
Lance head rattlesnakes are viviparous. At birth, young lance head rattlesnakes range from 9 to 39 inches (230 to 985 millimeters) in length.

Lance head rattlesnakes are considered to be a species of least concern by the International Union for Conservation of Nature's Red List, as of a 2007 analysis. Habitat loss is considered their greatest threat, as their natural habitat is converted to agricultural space. Lance head rattlesnakes are also often killed when encountered by people, as they are considered dangerous animals. 

This species has a wide distribution and can live in a range of habitats. It is present in the national park of Hidalgo, but further protected areas are needed to ensure its survival. Lance head rattlesnakes are currently managed under a Species Survival Plan through the Association of Zoos and Aquariums. Further research is required to better understand the species and its ecological needs.