Canada lynx survival linked to life cycle of snowshoe hares

Canada lynx populations in Interior Alaska experience a “traveling population wave” that affects their reproduction, movement, and survival. 

This is the conclusion of a new study from the University of Alaska Fairbanks’s Institute of Arctic Biology.

The research sheds light on how these patterns play out and could help wildlife managers make more informed decisions about one of the boreal forest’s key predators.

Lynx survival hinges on their prey

A traveling population wave is a biological phenomenon where animal populations rise and fall across a region, like a ripple moving through water.

For Canada lynx in Alaska, this cycle is closely tied to the 10- to 12-year boom-and-bust cycle of their main prey, the snowshoe hare.

When hare populations increase, lynx numbers follow a year or two later. But when hares experience a population crash, due to limited food resources, the lynx population soon declines as well.

Following the lynx population wave

The study, led by biologist Derek Arnold, ran from 2018 to 2022 and followed the lynx population through one such cycle, beginning when hare numbers were at their peak.

The researchers tracked the reproduction, movement, and survival of lynx as the hare population collapsed.

During the study, 143 lynx were live-trapped across five national wildlife refuges in Interior Alaska-Tetlin, Yukon Flats, Kanuti, Koyukuk, and Gates of the Arctic National Park.

Each lynx was fitted with a GPS collar, allowing satellites to track their movements and providing a wealth of new data.

Three stages of the population wave

Arnold noted that the lynx population responded to the declining hare population in three stages, with these changes starting in the east and moving westward – an indication of a traveling population wave:

Reproduction decline

At the start of the study, during the peak of the cycle, researchers found dens with up to eight kittens. However, reproduction began to plummet first in the easternmost study areas and eventually ceased entirely across all sites by the end of the study.

Increased dispersal

As reproduction rates fell, the lynx started to disperse, leaving their territories in search of better conditions. They traveled in all directions, crossing mountains and swimming rivers – behavior that surprised researchers. One lynx even trekked nearly 1,000 miles to reach the Alberta border.

Survival decline

Finally, the survival rates of the lynx dropped. While some traveled eastward against the wave, those individuals had much higher mortality rates compared to those that moved westward or remained within their original territories.

How the cycle plays out

“People like trappers have observed this pattern anecdotally for a long, long time. The data just provides evidence to support it and helps us see the big picture,” Arnold said.

The study also clarifies how this cycle plays out across the landscape. “We’ve long known that hares and lynx operate on a 10- to 12-year cycle, but we didn’t fully understand how it played out across the landscape,” Arnold added. 

“It wasn’t clear if the cycle occurred simultaneously across the state or if it happened in isolated areas at different times. Knowing that the wave usually sweeps from east to west makes lynx population trends more predictable.”

This newfound predictability will help wildlife managers make better decisions by allowing them to anticipate population behavior on a more localized level.

Canada lynx survival: The bigger picture

Another significant finding is the importance of maintaining refuge populations. “The lynx that disperse during population declines don’t usually survive. Most of them don’t make it when they leave their home areas,” Arnold said.

He emphasized the crucial role that refuge areas play in preserving lynx populations during tough times.

“The combination of these factors supports the idea of a hierarchical response to snowshoe hare population declines with a drop in lynx reproduction followed by increased dispersal, and finally reduced survival,” wrote the researchers.

“All of this evidence is consistent with the expected characteristics of a population undergoing a traveling wave and supports the hypothesis that lynx presence may facilitate and mirror the underlying wave patterns in snowshoe hare.”

The study is published in the journal Proceedings of the National Academy of Sciences,

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