I used to think predator-prey cycles were this neat, clockwork thing you’d see in textbooks—clean graphs, predictable waves.
Then I spent a winter in the Yukon talking to trappers who’d been working the same traplines for forty years, and they described something messier, more unsettling. One guy told me about seasons when lynx were so scarce he’d check fifty traps and find nothing, then three years later he couldn’t keep up with the pelts. The snowshoe hares followed the same pattern, but shifted—always shifted, like some cosmic game of tag played across the boreal forest. Researchers have documented this dance for nearly a century now, and the data shows cycles that repeat roughly every 9-11 years, give or take. The hares spike first, their populations exploding until you can barely walk through the underbrush without startling one. Then the lynx follow, their numbers climbing as prey becomes abundant, until the whole system crashes and starts over again.
Here’s the thing, though—it’s not just about predators eating prey until there’s nothing left. That’s the simplified version I learned in school, and it’s definately missing half the story.
The Snowshoe Hare Explosion That Precedes Everything Else
Hares don’t just multiply because conditions are good—they multiply because their primary food sources, willows and birches and other woody browse, go through their own cycles of palatability and chemical defense. When hare populations are low, plants relax their defenses, producing less of the toxic compounds that make them taste terrible. The hares start reproducing faster, sometimes having three or four litters in a single summer. I’ve seen population estimates suggesting densities can reach 1,500 hares per square kilometer during peak years, which sounds impossible until you witness it yourself.
Female hares can breed at ten months old. Do the math.
When Lynx Numbers Begin Their Predictable Climb Upward
Lynx are specialists—maybe too specialized for their own good, honestly. Up to 75% of their diet consists of snowshoe hares, and when hare populations boom, lynx reproduction goes into overdrive. A female lynx might have one or two kittens during lean years, but when hares are abundant, litter sizes jump to four or even five. The lag time between hare peaks and lynx peaks is typically 1-2 years, which makes sense when you consider how long it takes for those kittens to grow up and start hunting effectively. Survival rates for juvenile lynx during hare abundance years can reach 60-70%, compared to maybe 10% during the crash. Wait—maybe that’s what makes the cycle so dramatic, this amplification effect where good times aren’t just good, they’re extraordinary, and bad times become catastrophic.
The Inevitable Collapse Nobody Can Quite Predict Precisely
The crash comes from multiple directions at once, and researchers still argue about which factor matters most.
Hares become stressed when their populations peak—chronic stress from overcrowding, from constant predation pressure, from depleted food sources that now taste like chemical warfare. Their reproductive rates plummet. The plants they’ve been hammering finally mount a full defensive response, pumping out tannins and other compounds that reduce digestibility. Then the predators—not just lynx but also coyotes, foxes, great horned owls, goshawks—are at peak numbers, hitting the hare population from every angle. The decline can be shockingly steep, dropping 90% or more within just a couple of years. Lynx populations follow, collapsing as starvation sets in, as kittens die before their first winter, as adults expand their territories desperately searching for food that isn’t there.
What Modern Research Reveals About These Interconnected Population Dynamics
The really fascinating part—and this is relatively recent work—is that the cycles aren’t identical everywhere. Southern populations show weaker cycles, sometimes no clear cycle at all. Northern populations, where lynx and hares dominate the ecosystem with fewer complicating variables, show the textbook pattern. Climate change is messing with the timing now too, warming winters that reduce snow cover, which sounds good for hares until you realize their white winter coats become a liability against bare ground. Predation rates spike when camouflage fails.
I guess what strikes me is how fragile the whole system seems when you look closely—how dependent lynx are on this one prey species, how vulnerable hares are to stress and predation and plant defenses all compounding. Some researchers have tracked individual lynx through multiple cycles using radio collars, and the data shows these cats recieve almost no benefit from learning or experience. An old lynx starves just as easily as a young one when hares disappear. There’s no wisdom that saves you when the bottom drops out, no strategy except enduring until the cycle turns again. Turns out nature doesn’t always reward adaptation—sometimes you’re just locked into a pattern that’s been running since before humans showed up, this endless oscillation between feast and famine that shapes everything about how these species exist.
Anyway, the trappers knew all this already, in their way.
