The prairie rattlesnake, Crotalus viridis. Photo courtesy of J.N. Stuart.

URBAN VIPERS 1: The prairie rattlesnakes of Lethbridge

Posted onJune 8, 2021byOjibway Massasauga|Massasauga Rattlesnake, News and Events, Ojibway Prairie Reptile Recovery, Urban Vipers

“Rattlesnakes” and “cities” are two words that aren’t often thought of as complementary. However, around the world there are major urban areas where people live alongside venomous snakes. Previously, WPC’s Ojibway Prairie Reptile Recovery team wrote two blogs about urban populations of venomous snakes – the prairie rattlesnakes of Lethbridge, and the timber rattlesnakes of Boston, Massachusetts. We like this topic so much that we’ve decided to kick off a dedicated series on urban vipers, and what better way to start than to revisit the topic of our first urban rattler post – the prairie rattlesnakes of Lethbridge, Alberta.

We hope for these posts to provide insight into how urban residents around the world successfully coexist with venomous snakes, and how their experiences can inform our own efforts in Southwestern Ontario, Canada. We will be profiling the urban areas, their local venomous snakes, and the various conservation or translocation efforts targeting urban vipers.

The Species

The prairie rattlesnake (Crotalus viridis) is a wide-ranging rattlesnake found from southwestern Canada to northern Mexico. Within Canada, this species’ range is restricted to southeastern Alberta and southwestern Saskatchewan, and they are found largely within proximity of the major river valleys in these provinces. As of 2014, there were an estimated 20,400 – 28,300 prairie rattlesnakes living in Canada. These rattlesnakes are shy reptiles who depend on their camouflage to avoid detection, and use their rattle to warn people and other animals of their presence; they have no interest in confrontation, and would much rather retreat from a perceived threat than to strike at it. Unfortunately, road mortality and habitat destruction pose a threat to prairie rattlesnakes, which are considered a Species of Special Concern both federally and provincially in Alberta. Female prairie rattlesnakes give birth to live young once every 2+ years, and it takes up to 7 years for a female to reach maturity. These snakes can live up to 30 years!

The City

With a population of over 101,000 people, Lethbridge is one of the largest cities in Alberta. The city’s economy grew from mining and agriculture, but today it is known as one of Alberta’s major commercial, transportation, and technological centres. In 2006, Economic Development Lethbridge helped form the Southern Alberta Alternative Energy Partnership, an initiative to promote the development of wind, solar, and biofuel energies. Lethbridge also hosts a population of rattlesnakes within its city limits. The coulees – steep-sided river valleys within the 16km2 park system that divides the city – are home to prairie pattlesnakes. The snakes spend most of their time in these dry, desert-like slopes, amongst the short grasses and prickly-pear cactus, but will wander into nearby cottonwood forests and wetlands in search of food. This is a spectacular landscape, indeed, the steep coulee banks of Lethbridge descend sharply from the growing city above.

Aerial,View,Of,Lethbridge,,Alberta,,Canada

Photo: Kent Raney, Shutterstock

The Methods

Although prairie rattlesnakes face various threats, Lethbridge is home to a fairly healthy population of these snakes. A 2010 study estimated the population within city limits was between 204-374 individuals of all ages, which made use of 3 known overwintering locations. So, you may wonder – how do the residents of this city handle living alongside a venomous animal? Firstly, the City of Lethbridge operates a rattlesnake mitigation program; if a rattlesnake wanders onto a residential property, or if a snake is in an area where it poses a risk to public safety, a hotline number can be called and a rattlesnake expert will come to the rescue! The snake will be collected and translocated a short distance to a known den or birthing site. The City also provides extensive information on how to avoid an encounter, what to do if you’re bitten, and how to snake-proof your yard with snake barrier fencing (just like the fencing we have installed in Southwestern Ontario to mitigate road mortality!). The Helen Schuler Nature Centre, the hub of Lethbridge’s natural parks, delivers public presentations throughout the year on snake safety, living alongside snakes, and the unique ecology of Lethbridge’s wildlife. Part of this public education also includes spreading positive information about the benefits of living alongside rattlesnakes! Rattlesnakes consume mice, voles, and other rodents, keeping their populations under control and preventing the risk of disease transmission to humans; rodents carry hantavirus, are vectors for the spread of lyme disease to ticks, and are partially accountable for the spread of black-legged ticks to new areas. If all of this isn’t reason enough for Lethbridgians to be proud of their reptilian neighbours, Alberta’s Wildlife Act provides Prairie Rattlesnakes with legal protection from harm, harassment, or collection, and provides protection to their hibernacula.

Final Thoughts

Five key points stood out during our review of the Lethbridge case of urban vipers: the threat of encroaching residential development, the key role of the local nature centre in spreading factual and positive information about rattlesnakes, the importance of having someone to address human-snake conflict by translocating ‘problem’ snakes, the strategic use of barrier fencing to prevent snake access to residential areas, and the sheer beauty of the park system.
Protecting urban species-at-risk can be a challenge, but we can see from this example that it is possible for urban populations of rattlesnake to thrive. If you are interested in reading more about the prairie rattlesnake, urban vipers, or some of the past research on Lethbridge’s rattlesnakes, you can start with the links below:

Urban Vipers 2: Western Rattlesnakes of Osoyos, BC

Urban Vipers 3: The black mambas of Durban, South Africa

Urban Vipers 4: The jararacas of São Paulo, Brazil

Kelly Antaya

Field Technician – Ojibway Prairie Reptile Recovery

Kelly started working with Wildlife Preservation Canada as an intern, and is now a field technician. She has worked in reptile conservation throughout Ontario, and has also assisted on population studies of skinks and snakes on islands in northern Madagascar. Kelly is a graduate of Fleming College, where she received her diploma in ecosystem management.

Jonathan Choquette

Lead Biologist – Ojibway Prairie Reptile Recovery Program

Jonathan manages the recovery program for the Ojibway population of the massasauga rattlesnake in Southern Ontario. Jonathan’s research interests lie in the field of urban herpetology, having studied both biology and landscape architecture at the University of Guelph. Jonathan has authored or co-authored numerous reports and publications about the conservation of Canadian reptiles and amphibians in urban environments.