Snakes give many of us an “icky” feeling. But they are quite fascinating after you spend some time looking at how they live, survive, and play a role in our environment.
At this time of year, they will start to come out of their hibernacula – places below the frost line where they can overwinter. The most well-known hibernaculum in Saskatchewan is by Fort Livingstone, where garter snakes overwinter in the many limestone crevices. They usually emerge in the two weeks around Mother’s Day and immediately start to mate, forming large ‘mating balls’ of many intertwined snakes. The tail is considered important in successful mating and in movement on the ground(1). Shortened tails may hinder these activities.
Snakes can lose their tails deliberately by making forceful twisting and whirling motions if a predator grabs them by the end, but the tail never grows back. External injury could cause loss, and it has been wondered if thermal injury (cold, heat) and toxins may sometimes be involved. Healthy terrestrial snake tails taper to a point, with the tail becoming gradually thinner, and tail length is measured from the vent (where waste is eliminated) on the underside, to the tip of the tail.
We know little about snakes on the prairies. This article will focus on the plains garter snake, one of three species of garter snakes in Saskatchewan; the other two are the red-sided and the wandering garter snake. Saskatchewan is also home to the bullsnake, prairie rattlesnake, hog-nosed snake, smooth greensnake, red-bellied snake, and the yellow-bellied racer. The bullsnake, rattlesnake, hog-nosed snake, and the yellow-bellied racer are all now listed as species at risk of extinction in the province(2).
History
A plains garter snake was submitted to the Western/Northern regional office in Saskatoon by the organization Snakes on a Plain. While doing work on behalf of Environment and
Climate Change Canada (Canadian Wildlife Service), they noticed that many snakes coming out of one hibernaculum in southwestern Saskatchewan had shortened, blunted tails, with some tails almost completely missing (Figure 1). They also noticed a few individuals with roughened head scales and were concerned about snake fungal disease (SFD). Caused by the fungus Ophidiomyces ophiodiicola, SFD has been spreading in wild snake populations in North America. Its presence has not yet been confirmed in Saskatchewan.
This garter snake was found in the fall along the side of a road, having died from being crushed, likely by a vehicle. Road injury is a common hazard for snakes as the site may be warmer and prey more abundant. Garter snakes are carnivorous and prey includes insects, earthworms, frogs, and small rodents.
Diagnostic work-up
The submitted snake was a female with good fat stores. It had several crushing injuries consistent with being run over by a vehicle (Figure 2).
Besides the crushing injuries, the tail had a roughened, reddened, blunt end, and the underside of the tail was roughened and reddened as well (Figure 3).
No fungi were seen in the snake skin or elsewhere in the body and a sensitive test for SFD by PCR was negative. Serial sections of the tail were taken starting from the vent area.
Many immature stages of a parasite belonging to the fluke family were found in the loose tissue underneath the vertebrae of the tail (Figure 4).
The parasites were more abundant near the blunted end and became fewer closer to the vent; none were seen in the vent area. The parasites were accompanied by significant inflammation and death of the tissue where they were most numerous. A similar injury was found in an earlier study of red-sided garter snakes in Manitoba, where the authors proposed it caused tail loss (3).
The parasite
Although no additional testing has been done to identify the fluke, it likely belongs to the genus Alaria based on its morphology. Adult Alaria are found in the small intestine of
carnivores including dogs, cats, foxes, and mink. Alaria species parasites have a complex life cycle, as seen in Figure 5.
The immature stages of Alaria can infect a wide range of animals, including rarely people. People become infected through ingestion of the infective larval stage (metacercariae/mesocercariae) in inadequately cooked frogs or transport (paratenic) hosts, including snakes. The Western College of Veterinary Medicine, University of Saskatchewan website about Alaria species parasites describes some cases in humans: “One case of Alaria in northern Ontario – associated with a large number of immature flukes in most organs – was fatal. Occasionally what appear to be Alaria mesocercariae have been recovered from the eyes of people, including one probable case in Saskatchewan in 2005”(4).
What role the accumulation of the immature stage of the parasite plays in tail blunting or loss in snakes is unknown. Could the weakened tissue separate on its own? Could it help the snake separate their tail when they twist and twirl after being caught by a predator? How common is this condition in Saskatchewan snakes? Are only garter snakes affected?
Nature is such a wonder, including its snakes. We have much to learn about them and hope you keep this in mind if you stumble upon a snake while enjoying nature’s diversity.
If you find a dead snake, please contact the regional CWHC office in your area. In Saskatchewan, you can contact the Western/Northern node by phone at 306.966.5815 or by email at **@cw*******.ca.
Risks associated with the collection of specimens are low if reasonable sanitary precautions are taken, but some animals present more serious concerns than others, including venomous snakes, bats with potential rabies, and waterfowl at risk for avian influenza. Your regional office can provide advice or guidance if needed. The Canadian Wildlife Health Cooperative website has specimen handling instructions on their website.
Written by: Shelagh Copeland & Sabine Kirsch, CWHC Western/Northern
References
- Shine, R., Olsson, M. M., Moore, I. T., LeMaster, M. P., & Mason, R. T. (1999). Why do male snakes have longer tails than females? Proceedings of the Royal Society of London. Series B: Biological Sciences, 266(1434), 2147–2151. https://doi.org/10.1098/rspb.1999.0901
- Saskatchewan’s Snakes: Slithering to Risk? (2024, August 30). Nature Saskatchewan. https://www.naturesask.ca/resources/news/2024/498
- Uhrig, E. J., Spagnoli, S. T., Tkach, V. V., Kent, M. L., & Mason, R. T. (2015). Alaria mesocercariae in the tails of red-sided garter snakes: evidence for parasite-mediated caudectomy. Parasitology Research, 114(12), 4451–4461. https://doi.org/10.1007/s00436-015-4686-6
- Alaria species – Learn About Parasites. (n.d.). Western College of Veterinary Medicine, University of Saskatchewan. https://wcvm.usask.ca/learnaboutparasites/parasites/alaria-species.php