What If Gone

Species → Snowshoe Hare

Snowshoe Hare

Lepus americanus

Density varying, depending on the cycle phase, from roughly 1 to…
Extinction risk Least Concern
Predator-prey cycleKey preyBoreal forest
Snowshoe Hare (Lepus americanus)
Photo: Fralambert, Wikimedia Commons (CC BY-SA 4.0)

What if it disappeared?

Impact High
Over 113 years

More than a century of Hudson's Bay Company fur trade records revealed a regular roughly ten-year cycle in lynx pelt harvests — a signal so clear it became one of the most widely used datasets in all of population ecology.

Documented
Detail

Elton, C. et Nicholson, M. (1942). The Ten-Year Cycle in Numbers of the Lynx in Canada. Journal of Animal Ecology, 11(2), 215–244.

The trading records, kept since 1671 to track fur exchanges rather than for scientific research, turned out to be the longest continuous series available for studying a wild population cycle — an unexpected data source that became foundational for understanding the hare-lynx cycle, decades before modern field methods existed.

Over 8 years, Yukon

By excluding predators and adding food on experimental plots, separately and then together, a field experiment showed that predator exclusion alone doubles hare density, food addition alone triples it — but combining both multiplies it by 11, an effect far greater than the simple sum of the two.

Documented
Detail

Krebs, C.J., Boutin, S., Boonstra, R., Sinclair, A.R.E., Smith, J.N.M., Dale, M.R.T., Martin, K. et Turkington, R. (1995). Impact of Food and Predation on the Snowshoe Hare Cycle. Science, 269(5227), 1112–1115.

Conducted on 1 km² plots in the Yukon using a factorial design — control, food only, predator exclusion only, and both combined — over eight years, this experiment remains one of the largest field manipulations ever conducted in population ecology. The more-than-multiplicative effect of combining both treatments demonstrates that the cycle results from a three-trophic-level interaction — plant, hare, predator — rather than a single factor acting alone.

Not measured to date

The two points above document what controls the hare's own population, not what its disappearance would change for other species: the Canada lynx depends closely on it (see its entry), but no study measures what would happen to the vegetation the hare browses — birch, willow, poplar — if the hare disappeared from the cycle rather than merely declining temporarily within it.

Insufficient

Documentation

Last verified: August 14, 2026

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