The Snowshoe Hare and Canada Lynx are 2 mammals seen on some of EALT’s conservation lands. They share the land year round, but this is not the only thread that links them. If you have been in an ecology classroom recently you may recall learning about the cycle between these 2 species. But new research is shedding light on the hidden processes that contribute to their fluctuating populations.
The 10-Year Cycle
The Lynx is a specialist predator on the Canadian landscape. This wild cat species prefers to hunt Snowshoe Hares when it can, so much so that it is mainly nocturnal, like the hares. The Snowshoe Hare on the ofter hand is a herbivore and a prey species for many carnivorous birds and mammals. Both of these species have been traditionally trapped, dating back to the fur trade and even further back by our Indigenous ancestors. Over 100 years ago, data from the fur trade was being analyzed and a 8-11 year oscillating cycle for both of these species was found to closely follow one another.
Source: University of Alberta LynxProject
So what is the cause of the this trend? Well most textbooks will tell you it is a perfect example of a predator-predator oscillation. The Snowshoe Hares can reproduce quite quickly, being able to have multiple litters per summer. But as their numbers increase, predation from Lynx will also increase. Having plentiful prey species means that Lynx populations can also rise. Soon the higher numbers of predators will cause the hare populations to decrease. With less ideal food sources the Lynx populations will also slowly decline. This cycle repeats about once every 10 years.
New Research
The focus in the past was mostly on the direct mortality of Snowshoe Hares by Lynx. New research is now also showing the indirect impacts of this predator prey relationship. As the Lynx predation levels become higher, the increased amount of chasing may stress the female hares, which then reduces their reproductive output. This predation stress can be inherited and can contribute to low hare populations for 2-4 years.
Other research is also showing how hares may be naturally contributing to their own population fluctuations by their herbivorous feeding. At their peak, when hare numbers are high, their habitat cannot support their large population. This means that they over graze on the plants in their environments. When the plants they feed on decline, so too does the hare numbers as they face starvation. The Lynx populations also fluctuate with the Hare population declines, as they are forced to hunt less nutritious species such as mice and carrion. This means that may face starvation or reduced reproduction. This research shows how Lynx populations are dependent on the hares naturally oscillating cycle, but Lynx predation is likely not the primary cause of Hare population fluctuations.
Conservation Lands Connection
Both the Snowshoe Hare and Lynx have been found on some EALT’s conservation lands. They have been spotted using some of wildlife trap cameras. In the winter, we may spot Snowshoe Hares during one of our Winter Wildlife Walks. Tracks of Lynx may also be found on these walks, which you can register to join by going to our Volunteer Events page.
These conservation lands provide great opportunities for people to connect to the landscape, but they are also key areas of habitat protection for lynx, hares, and many other species. This type of cycle is part of the natural changes found in our ecosystems. Having both plentiful native plant species for Snowshoe Hares to graze on as well as a large expanse of natural habitat for Lynx to hunt in, can help ensure this natural process continues on.
Sources:
Charles J. Krebs, R. B. (2001, January 1). What Drives the 10-year Cycle of Snowshoe Hares? The ten-year cycle of snowshoe hares—one of the most striking features of the boreal forest— is a product of the interaction between predation and food supplies, as large-scale experiments in the yukon have. Retrieved from BioScience: https://academic.oup.com/bioscience/article/51/1/25/251849
Charles J. Krebs, R. B. (2017, June 1). Using experimentation to understand the 10-year snowshoe hare cycle in the boreal forest of North America. Retrieved from https://www.zoology.ubc.ca/~krebs/papers/314.pdf
Government of Northwest Territories. (2019). Lynx-Snowshow Hare Cycle. Retrieved from Environment and Natural Resources: https://www.enr.gov.nt.ca/en/services/lynx/lynx-snowshoe-hare-cycle
Zhibin Zhang, Z. L. (2007, June). Factors affecting harelynx dynamics in the classic time series of the Hudson Bay Company, Canada. Retrieved from Research Gate: https://www.researchgate.net/publication/242783962_Factors_affecting_harelynx_dynamics_in_the_classic_time_series_of_the_Hudson_Bay_Company_Canada