Prairie Rattlesnake

Crotalus viridis

Species at Risk: Sensitive

The prairie rattlesnake is Alberta’s only member of the Viperidae family, the vipers. More specifically it belongs to the subfamily Crotalinae, the pit vipers. Members of this family have verticle pupils and a heat sensitive pit organ inbetween the eye and the nostril. This is used to detect it’s warm blooded prey. This snake is dangerously venomous, but not considered lethal. Nevertheless, it should be admired from a distance when found in the wild. It is a moderately large snake by Alberta standards, and adults sizes range from 40cm to 1.4 metres. Interestingly enough populations near urban areas seem to be selected towards smaller adult sizes, with larger animals being killed off by human activity.* The males are the larger of the two genders, and both may show variants of colouration from grey, to tan, to an olive green. All have the typical pattern of well defined, darker blotches on a lighter background. Of course their namesake rattle is at the end of their tail. They are born with a single “button”, and each time they shed a new rattle is added to the length of the rattle. Rattles regularly break off as they get worn or damaged.

The prairie rattler is in the most northern part of it’s range here in Alberta. It can also be found all along the great plains down into northern Mexico. Among rattlesnakes, this species is most known for it’s communal denning habits. Some of the largest rattlesnake dens in the world are right here in Alberta. These snakes live in the short grass prairie in the southeastern corner of our province, utilizing mammal burrows, crevices and caves as daily refuges, or to hibernate during the winter. It is mainly crepuscular, active during sunrise and sunset, but may be found active at any time.

Habitat destruction is a large problem for most reptiles. Conversion of rangeland to cultivation is the problem associated with the prairie rattlesnake. Unfortunately the number one threat towards rattlesnakes seems to be human hatred. While this species is very economically significant as a rodent controlling predator, it is targeted on roads by vehicles and killed on site by many fearful landowners. Accounts suggest that Albertan populations have been reduced in past decades but it appears the rattlesnake is still present in healthy numbers.

The Amphibians and Reptiles of Alberta by A.P.Russell and A.M.Bauer
A guide to the Rattlesnakes of the United States by Brian Hubbs and Brendan O’Connor
Snake by Chris Mattison
*Personal communications – CARCNET Saskatoon 2009

Photo by Alyssa Metro

Defensive rattle