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“Life will find a way,” says Jeff Goldblum’s neurotic Cassandra scientist character in “Jurassic Park.” The dinosaurs were bred to be sterile, too, and we all know how well that worked out. The fact in the fiction is true. Life will find a way. It always has.

Wildlife contraception may be more humane than aerial gunning, leg-iron traps, and painful poisons, but that doesn’t mean necessarily it is benign.

Inevitably, a certain percentage of animals will be immune to immunocontraception, no matter how it’s delivered, and natural selection will select for those animals. Fitness won’t be a matter of superior strength or smarts, but based entirely on an ability to mate.

Of equal concern, what happens to a small herd like the horses on Assateague Island whose birth-rate has been PZP-engineered to near 0% should a devastating illness (West Nile?) or other catastrophe strike? Would  there be enough bounce in the population to recover, or could it be a tipping point to extinction?

And then there are the effects on social dynamics that are much harder to quantify. Animals weakened by a prolonged rutting season, or from giving birth off-season would have a much more difficult time surviving winter. What would their weakness or loss mean for the herd? Or for local predators?

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The gorillas at Lincoln Park Zoo’s Great Ape House seemed happy enough when I stopped on a frozen February afternoon. A dominant male lay on his massive silver back playing with a 2-year old who clearly knew just how to wrap his giant dad around his tiny simian finger. The intimacy and gentleness and joy were obvious. The whole troupe was besotted with its youngest member. But the little one had no one even close to his age to play with. There are too many male gorillas in American zoos and not enough places for them to live. Until the numbers even out through attrition, a gorilla-breeding ban has been put in place. Everybody’s on birth control.

Given the limits of space and budget, contraception is a critical tool for running a zoo. But zoos -- the ultimate in managed wildlife -- present  a carefully staged snapshot of  “wild.” Outside the gates, things quickly become considerably more complicated. And there are few easy answers.