ONCE BITTEN, TWICE SHY Rattlesnake bite only as a last resort. Their venom is made to secure prey, not hurt people, and some producers say they’d prefer to have snakes on their land than gophers
Feared by many and misunderstood by most, the rattlesnake has long been persecuted in every nook and cranny of its range from South to North America. In Canada, there are three species. The prairie rattlesnake (Crotalus viridis viridis), one of the most successful of the 32 species in the Americas, finds the most northern point of its range in Alberta and southwest Saskatchewan.
All species tend to struggle near the limits of their range, because they encounter conditions they aren’t adapted to deal with, and despite the overall success of the prairie rattlesnake, the population is in decline in Alberta. A second species, the northern Pacific rattlesnake, (Crotalus oreganus oreganus) lives in B.C., and there is a third dwarf species in southern Ontario.
Alberta’s rattlesnake population is found near the river hills and valleys south of the Red Deer River and east of Lethbridge, in the short grass and mixed grass prairie. They share their habitat with cacti, black widow spiders, and in some places, Canada’s only species of scorpion. The ecosystem often features Ord’s kangaroo rats, pronghorn and sage grouse.
Their range is likely limited by habitat containing suitable over-wintering sites, called hibernacula. These den sites provide shelter during winter, and rattlesnakes usually return to their hibernaculum by late September and emerge to bask on warm days in the late fall and early spring. By late April, or early May, the snakes will disperse from their hibernaculum and spread out to their feeding ground in the neighbouring prairie.
Rattlesnakes cannot be killed or collected, and their hibernacula are protected year-round. Other Alberta snakes such as the western hognose and bull snake are afforded the same protection. The status of the rattlesnake is currently under review, and may be listed as endangered in the near future.
“We’ve managed the prairie rattlesnake in the species at risk program for over a decade,” said Joel Nicholson, senior species at risk biologist for Alberta Fish and Wildlife.
“The same old issues are there with habitat loss, development in habitat that causes road mortality, and increased urban expansion in certain places,” said Nicholson. “We don’t have any indications that the population is stable or increasing.”
The rattlers thrive in native prairie, so sometimes there are encounters between ranchers and snakes. However, most producers are content to share the land with the reptiles. “They say they’d rather have the snakes than the gophers,” Nicholson said.
Rattlesnakes like to stay close to to their hibernacula, so won’t just use any spot to overwinter. If their den site is tampered with or destroyed, it can wipe out an entire local population. But this tendency also means the population can be high in some areas and for producers, that means excellent rodent control. Different sizes of snakes can get into holes of various sizes, so rats, mice and gophers are all fair game for a rattlesnake.
The prairie rattlesnake can reach five feet in length. They take a number of years to mature sexually, and take a long time to reach their full size. Nicholson said although they aren’t entirely sure, the largest individuals may be 20 years old. “They are a natural part of our landscape here, and they’re part of the little bit of wild that’s still in the West,” said Nicholson.
Rattlesnakes give live birth (they don’t hatch out of eggs) to baby snakes in the early fall at special sites called rookeries near the main dens. Females may only give birth once every two or three years, and the survival rate of the young can be very low. One bad year of many road-killed rattlers can take years to recover from. Fall is a bad time of year, as many rattlers are killed on the roads trying to migrate back to their den sites. Alberta posts signs to alert motorists to avoid the snakes on roads with a high kill rate.
Most ranchers in rattlesnake country wear boots out in the field, and den sites are given a wide berth. Livestock bites are relatively rare. Rattlesnakes aren’t keen on being stepped on, so they’ll almost always escape to safety down a hole in the ground rather than try and face off against an animal many times their size.
There is an average of between nine and 13 reported bites every year in Alberta, but they are rarely life threatening with prompt medical attention. The venom attacks local tissue rather than breathing and circulation. Antivenom is kept at hospitals in rattlesnake country, and in most cases can prevent severe tissue damage.
Rattlesnakes prefer to be left alone, and if confronted, will only stand their ground if they have no easy exit. They are reluctant to waste their venom, since its main purpose is to capture prey, so even when provoked often inflict a “dry” bite. Most bites are accidental from catching a rattler unawares and stepping on it, or from handling the snake to remove or kill it. If you meet a rattler, it’s best to back away and let it retreat without causing anyone undue stress.