Predators and Prey

By Sarah Cubells

I am fascinated by predator-prey relationships. I relish the opportunity to catch a glimpse of charismatic apex predators especially, like a large cat or bear, in their natural habitat. Apex predators are species that are at the top of the food chain—and have few, if any, predators themselves. These predators can be used as indicators of an overall health of an ecosystem. Without them, everything gets out of balance, potentially leading to ecosystem collapse.

Apex predators are essential to the health of the other species within an ecosystem. And in turn, these predators rely on other species for food. For example, predators kill the sick, weak, and dying prey animals, which helps keep the prey populations healthier overall. Diseases are less likely to spread around the herd if the sick animals are culled by predators.Both predator and prey populations fluctuate; When one goes down, the other will eventually follow. I recall first learning about this pattern with a popular example—the lynx and the snowshoe hare. Snowshoe hares are a staple in a lynx’s diet. If the population of snowshoe hares is high, lynx will have better chances of survival and reproductive success, leading to an increase in lynx numbers. But, if lynx numbers grow over the following few years, snowshoe hare populations will begin to decline because of increased predation. When hare populations decline, lynx numbers will begin to decline too because their food source is diminishing. And the cycle repeats. Overtime and on average, in a balanced ecosystem, the populations of both the lynx and the snowshoe hare will hold relatively stable. If the lynx is removed from the ecosystem entirely, the snowshoe hare population can become out of control and they can overgraze, preventing the regrowth of vegetation. This can ultimately lead to the decline of their food source, causing starvation. This type of scenario can unfortunately lead to collapse of a balanced ecosystem.When I first learned about predator-prey relationships, I was completely intrigued. “Nature has it figured out,” I thought. Of course, the example of the lynx and snowshoe hare is oversimplified and there are many other factors that play into ecosystem health. But, it is an excellent example of the importance of balance in nature. It is why nature is so harsh—it keeps its players in check. I feel so grateful to live among the species of this ecosystem. Not just the large mammals, but the birds, fish, plants, and small critters too. They all make up important pieces of a complex web of species that allow each other to continue to coexist.

Sarah is the Program Coordinator for Henrys Fork Wildlife Alliance.