Conservation Northwest

Predators and prey Prey—and their hunters—make the world go round with predators? animals will have as many babies as they can successfully rear, whether their eggs are small and many or large and few, because that's the best way of ensuring your genes survive in competition with those of your neighbors. And whether a species has many, many small eggs like a salmon, or a couple large eggs like a grizzly bear, it's all about getting more of your genes out there, which is in turn rooted in the concept of ecological niches. What is a niche? Jobs in the woods Paul Colinvaux describes a species' niche as its place in the "grand scheme of things," its "profession," that is, "everything it does to get its food and raise its babies." A plant or animal's habitat is its address. Spaces in each ecological niche, like welding jobs in a shipyard, are limited. Consequently the number of species that can fill a particular niche is more or less set by limitations on habitat imposed by climate, food, den sites, cover, etc—all the things that a species needs to survive and reproduce. The niches, or jobs, of each species are crafted over millennia by natural selection. In other words, as Colinvaux concludes, "the common stay common and the rare stay rare," unless something drastic happens to change the environment, like, for instance, clear cutting an old-growth forest or deregulating the financial industry. In each case you have a proliferation of weedy species, a reduction in diversity, and fewer real jobs. Snowshoe hares have evolved to exploit a niche that has few competitors, since the boreal forests home to hares and lynx are very tough neighborhoods, especially in winter. In other words there are lots of hare "jobs" out there as long as the boreal remains the boreal and something doesn't happen to radically alter it—like climate change. So hares have lots of babies, very often, to supply the demand for "Finely tuned interactions among species, physical environments, and ecological processes form the webs of life on our planet. Each web is not static, but continuously varies within certain bounds, and the species and systems have adapted over time to the range of variability in their particular region." —conservation biologist Reed Noss, 1999 Keeping the Northwest wild hare jobs, not because so many animals like to eat them. High hare predation rates are a consequence of hare fecundity Snowshoe hare. © Jannik Schou not a cause. Hare deaths are the grim cost of a reproductive strategy that floods the market with baby rabbits. And, lots of hares provide hare eating niches, or jobs, for many different predators. So ultimately the numbers of any wildlife species are not determined by breeding strategies. They are set by opportunities for a particular plant or animal to live according to its needs. The number of welding jobs in the shipyard, not graduates of welding schools, determines the jobs for welders. Natural selection: Nature's golden rule Cooperation and conflict drive plant and animal adaptation. Species and their habitats thrive as interactive, dynamic systems that are constantly reshaping each other. Natural selection is the ultimate arbiter—the universal law by which Mother Nature governs the biosphere. Quite simply, organisms are driven to survive, so prey animals respond over time with physical and behavioral adaptations to all the natural forces and conditions that conspire to kill them. Predators respond in kind with adaptations that allow them to exploit particular prey species. Otherwise neither would survive. Predators have helped make snowshoe hares, well, snowshoe hares. Natural selection has equipped them with outContinued next page A plant or animal's habitat is its address. © Eric Zamora Spring/Summer 2011 5

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