To a prey animal, it must seem that there's a predator lurking behind every bush—that the world is filled with critters ready to make a meal out of the meek and weak. However, when we look at the relative numbers of predators and prey, we see that prey animals, unless on the brink of extinction, far outnumber predators. Why this should be so becomes apparent after a bit of thought. For one thing, eating prey animals down to the last individual is self-defeating—the byword of a predator has to be sustainability, not exploitation. Prey driven to extinction will never be available for food again. Moreover, predators have to harvest food items over their entire lifetime. This means that a one-to-one ratio won't work unless rapid reproduction by the prey immediately replaces individuals taken by predators—plus all individuals lost by other causes. Even rabbits aren't that prolific!
Perhaps predator-prey relationships are opposite to what we usually
think. Maybe fluctuations in the prey population numbers determine how many predators
survive rather than the predators governing prey numbers. Food for thought!
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.