A Rocky Future for the Northern Pacific Rattlesnake

Photo: Emily Lomas

The northern pacific rattlesnake (Crotalus oreganus oreganus), also referred to as the western rattlesnake, is the only species of rattlesnake in British Columbia. It’s also the only venomous species in the province. But it looks like we’re doing more damage to the snake than the snake is likely to ever do to us – it’s listed as Threatened due to habitat loss. The Canadian Wildlife Federation is giving researchers Karl Larsen and Emily Lomas of Thompson Rivers University $17,900 through its Endangered Species Fund to discover how human disturbance has affected the snake’s behaviour and population and what we can do to save the species.

This species is At Risk due to urban development and the alteration of their critical habitat from human activity. Since, aside from the few months it hibernates, the snake is constantly on the move to and from its summer foraging grounds, a change in their route can devastate the species. And boy do they move.

As the female northern pacific rattlesnake moves around her habitat, she leaves a trail of odour the male simply can’t resist. The odour’s origins? Her fat. Once pregnant, it’s that fat the female relies on for survival – females don’t eat a morsel while pregnant. And since she births her young from September to October, birthing between two and eight snakes, she might simply emerge from hibernation, birth and head back to her den without eating anything. That means females can go over a year without eating. Now that’s extreme dieting. But females need to spend  time to recuperate from the ordeal. They usually only reproduce every two to three years so they can take that time to regain the weight they lost during the pregnancy.

In the spring, the snakes emerge from their den. Most of them mosey on to their summer hunting grounds, and it’s only pregnant females that opt to stick around close to the den (which the snakes call their winter abode year after year making these dens crucial to their survival) where they’ll bask on cliffs and slopes – perfect to provide some heat and shelter for their young.

Conservationists are scrambling to find ways to reduce the risk of human activity impacting the northern pacific rattlesnake. Thus far they’ve tried relocating, fencing them out (or in), and creating safe pathways for the snakes. But all these options come with their own share of problems including altering the snake’s movement patterns, basking regimes and the time they spend foraging.

How Larsen and Lomas’s Research Fits In

In the town of Osoyoos, B.C., researchers Karl Larsen and Emily Lomas of Thompson Rivers University are studying how development in the town is affecting the species. In particular, the researchers are studying a new condominium project that is currently being constructed in identified habitat for the snake. The snake uses this area as a migratory corridor and it’s not far from its dens and shedding sites. Larsen and Lomas are interested in how the fencing impacts the movements of the northern pacific rattlesnake and what they can do to minimize any negative impacts on the snake. A permanent wall was erected to stop rattlesnakes from entering territory where they might come across humans and human altered habitat.