The Four-Year Lemming Population Cycle

The Four-Year Lemming Population Cycle describes a sharp, recurring swing in Arctic lemming abundance: a peak every four years is followed by a decline to near-zero numbers. Its significance in the account lies not in a cycle operating alone, but in the way a shortage of small prey coincided with disrupted caribou migration in 1946, intensifying hunger across the region and contributing to an epidemic among predators.

The Recurring Cycle

Lemmings are described as a cyclic species whose numbers reach a peak every four years and then fall almost to zero. The cycle makes the supply of small prey markedly uneven over time. When rodents were abundant in early summer, they could become conspicuous across the bogs; the account describes the land becoming alive with them as June waned into July. That seasonal abundance should not be confused with a permanent food supply: the four-year pattern includes a severe low phase.

The narrative also corrects a familiar image of lemmings as suicidal animals, emphasizing instead their exceptional reproductive capacity. Their rapid increase helps explain why they can become a major food resource when abundant, while the subsequent decline gives the cycle ecological force beyond the rodents themselves.

A Food Source in the Wolf Diet

Observations at Wolf House Bay establish why changes in small-rodent availability mattered to wolves. The narrator initially struggled to explain how the wolves remained well fed when the males returned from hunting without visible prey. After watching Angeline catch and eat mice, he concluded that the wolves were living largely, perhaps almost entirely, on mice while raising families outside the summer caribou range. He later learned that hunted mice were carried back to the den in the wolves’ stomachs and regurgitated for the pups.

Other evidence broadens this account of flexible feeding without making lemmings the wolves’ sole prey. Ootek reported that wolves also ate many ground squirrels and sometimes appeared to prefer them to Caribou; he had also watched wolves catch Northern pike. In the narrator’s analysis of wolf droppings, about 48 percent contained rodent remains, alongside identifiable Caribou remains and bird feathers. These observations show that small prey formed a substantial part of the documented diet, but they do not establish that the lemming cycle alone determined wolf numbers or survival.

The 1946 Convergence

In 1946, lemmings were at the low point of their cycle. In the same year, the already depleted Caribou herds of Keewatin altered their migration and most bypassed southern central Keewatin. The account presents these conditions together: with both small rodents scarce and the expected Caribou absent from much of the region, hunger affected people, Foxes, and wolves. The lemming low was therefore one part of a wider food crisis, not a self-sufficient explanation for it.

The shortage had consequences for disease as well as feeding. The latent rabies virus flared among starving Foxes, and wolves began to contract the disease. The account places this outbreak within a broader pattern: when food scarcity weakens wolves, epidemics including rabies, distemper, and mange can sharply reduce their numbers. It does not attribute the 1946 epidemic to the lemming cycle alone; rather, it shows how a recurring prey shortage could compound other pressures, including the Caribou migration change.

Ecological and Narrative Significance

The cycle complicates any simple account of predator and prey populations. Wolves could survive and rear pups on mice when larger game was unavailable, but the existence of that adaptable diet did not remove the risk created by a widespread collapse in small-prey numbers. In 1946, the lemming low intersected with a change in Caribou migration, and the combined scarcity reached beyond one species.

The episode also gives the cycle a place in the book’s challenge to the idea that wolves alone caused wildlife decline. The evidence points instead to interacting conditions: fluctuating prey, altered Caribou movement, hunger, and disease. The recurring lemming pattern supplies a temporal rhythm to that account, while the crisis of 1946 demonstrates how a low phase could matter most when other food sources failed at the same time.