uOttawa and UBC researchers use math to show how climate change could change predator-prey relationships

Posted on Tuesday, November 29, 2016

Great horned owl / Grand-duc d'Amérique

Researchers at the University of Ottawa and the University of British Columbia have developed a mathematical model showing how climate change could change predator-prey relationships, leading to the extinction of some species.   

Frithjof Lutscher, a professor in the University of Ottawa’s Department of Mathematics and Statistics, and Rebecca Tyson, associate professor in mathematical biology at the University of British Columbia, looked at data on the snowshoe hare and one of its main predators, the great horned owl. The data was extracted from the Kluane long-term monitoring project, a wildlife monitoring initiative in the Yukon.

“What really caught our eye in the dataset from the Kluane long-term monitoring project was that the relationship between the great horned owl (the predator) and the snowshoe hare (the prey) differs so radically between winter and summer. We wanted to find out how this difference changes ecosystem dynamics when climate change continues.”

The researchers used a mathematical model to predict how the numbers of hares and owls would change as summers get longer due to climate change. They looked at the types of feeding behaviours displayed by predators, which are key to maintaining cyclicity (the rise and fall of populations) and balance in predator-prey relationships.

“Generalist” predators rely on a variety of sources of food, while “specialists” depend on the availability of one specific food source to survive.  The latter often cause populations to cycle, whereas the former tend to dampen cyclic dynamics. The great horned owl can switch from generalist to specialist behaviour as seasons and available foods change, feeding on a wide number of prey in the summer, but relying exclusively on snowshoe hares throughout the winter. 

Using mathematical modelling, Lutscher and Tyson found that longer summers resulting from climate change could lead to extinction of snowshoe hare populations by lengthening the great horned owl’s hunting season on its alternative prey and causing owl populations to grow faster. With more owls hunting hares to extinction, the survival of several other specialist predators, such as the lynx, which rely on snowshoe hares to survive winter months, would also be jeopardized.   

“Two findings really surprised us. First, the dynamic between a prey and a predator that switches behaviour was so different from the dynamic of either a generalist or a specialist (and its prey). Secondly, the model predicts that even very small increases in summer season length could bring about very large changes in dynamics, for example, the extinction of the prey.”

The study shines new light on the potential vulnerability of predator-prey relationships to climate change. Lutscher and Tyson hope their research findings can help drive conservation strategies in sensitive ecosystems. 

“Ecosystems that exhibit large changes when environmental conditions change only by a little are really difficult to manage. Our next research question is to include the lynx in the model and see how the dynamics play out between the three species.”

Read the full study in the American Naturalist

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