Three Cheers for Our Predators

For centuries, humans were more often prey than predator. However, now that we have sophisticated weaponry that relationship has changed. We are no longer easy targets for fang and claw. And as the world’s current top predator, we’ve taken it upon ourselves to control the populations of our land’s creatures, especially the most dangerous types, for seemingly good causes: to protect ourselves or other fauna and flora. But only in the past few decades have scientists begun to understand some of the negative effects that occur when predators such as alligators, panthers and wolves are systematically removed from the food web.

Alligators, for instance, don’t climb trees. Why is this important? Because they contrast dramatically with a host of other arboreal Florida natives that do climb trees. Opportunistic creatures such as raccoons, possum and snakes come to mind. This obvious difference has some serious ramifications, especially if you’re a bird lover. Here’s why.

In the mid-1970s, the St. Augustine Alligator Farm elected to remodel and expand one of its displays, and more alligators were added. Within weeks of completion, a large number of herons, egrets and wading birds began roosting in the trees at night and soon began constructing nests. At first, the farm’s staff and scientists were baffled by the birds’ seemingly strange behavior. Why would these birds choose to build their nests directly above an island crawling with hungry reptiles?

The answer makes perfect sense. Alligators can’t climb trees, but they do make quick work of tree-climbing raccoons, rats, bobcats and snakes. The birds instinctively know that anything that attempted to get to their eggs and chicks would be eaten. They were willing to sacrifice an errant hatchling or two to the reptiles for the far greater protection afforded by them.

Ironically, as the Florida Fish and Wildlife Conservation Commission struggles with an ever-growing alligator population and how to handle it, if they erroneously allow the open harvest slaughter of these reptiles they may ultimately eradicate not only our ’gators, but Florida’s famed bird populations as well. In the end: alligators = birds.

An even more bizarre ecological labyrinth connecting predator to prey was discovered in the past century in Yellowstone National Park. From the 1890s through the 1920s, in an effort to increase the elk herds and "protect the wildlife," the park service went about the business of eradicating the wolf from Yellowstone. The last wolf pack was killed off in 1926.

For half a century things were fine. The elk herds, lacking the wolf packs that historically preyed upon them, rapidly expanded. When winter arrived, knowing they had nothing to fear, the herds elected to browse the readily obtainable young cottonwoods and willows that lined the trout streams and rivers of the park. Ecologists began to note that there were always plenty of sapling cottonwoods and any number of mature, 70-year-old trees, but nothing in between.

Then the trout started disappearing. Lacking the intermediate-sized trees and heavy underbrush that had been consumed due to the elk’s overgrazing, the exposed banks of the rivers were now washing away in the spring freshets and the summer thunderstorms. Those streams, once crystal clear, were now silted over and murky. The trout, being sight feeders, either starved or swam off in search of cleaner water. The fly-fishermen of the Lamar, Yellowstone and Firehole rivers were also disappearing, much to the frustration of the local outfitters and hotels.

In an effort to reduce the overgrazing, the National Park Service, amidst a storm of local controversy, decided to capture 14 wolves from the wilds of British Columbia and reintroduce them into Yellowstone in 1995. Eventually three separate wolf packs were established within the park. With the wolves keenly aware of the elks’ tendency to browse along the riverbanks during the deep snow-packed months of winter, the wolves were inadvertently standing guard over the young cottonwoods and willows. Once the wolf packs began to thin the elk in these river valleys, the juvenile cottonwoods soon returned, the trout streams cleared, and there you have it: wolves = trout.

The Florida panther is another prime example of our species’ tendency to overkill. There are roughly 80 to 100 panthers remaining in Florida. The panther, or the puma as they are more commonly called, was once the second most widely dispersed cat in the world (living throughout North and South America). Only the leopard has a larger geographical range (Africa, Europe and most of Asia).

Across most of eastern North America, from New Jersey to New Brunswick, the puma has been bounty hunted, trapped or poisoned into localized extinction. While this has been a boon to the white-tailed deer population, it has been a curse for us. Whereas human deaths by puma are historically rare events, human deaths by deer are extremely common. In fact, more than 200 people die annually in this country due to deer/automobile collisions. In 2003 there were 1.5 million car accidents involving deer, elk and moose reported in America. In some states, automobile insurance rates have skyrocketed as a direct result of these incidents. In yet another unforeseen effect, fewer panthers = more human fatalities.

But there are other repercussions now surfacing from our nearsighted removal of these top predators. Lacking the wolf and puma populations, some of the deer herds are starting to implode. Chronic wasting disease (CWD) is ravishing deer and elk populations from Wyoming to West Virginia. In 1995, bovine tuberculosis was found to have jumped from cattle to white-tail, moose and elk herds. A third debilitating disease, cranial abscessation syndrome, is also on the rise. Florida Fish and Wildlife is keeping a watchful eye on our own white-tail deer herds, though CWD has yet to arrive in the Sunshine State.

Studies have shown that neither wolves nor pumas can transmit these diseases, but they certainly can and do slow their progress. One of the first symptoms of a deer infected with CWD is rapid weight loss, trembling, stumbling and unusual behavior. Adult pumas require 5,000 calories a day to survive. Think for a moment as a hungry puma might: Which deer do you take out? The big, healthy buck or the quivering, sickly looking doe? The puma takes out the sick animal first and the spread of the disease is kept in check. It makes sense that healthy herds require equally healthy predators.

From ’gators to wolves to panthers, we’re just now beginning to understand the ramifications of removing these vital links from the food chain. Yes, all of these creatures do, on rare occasions, kill or maim people. But to maintain a healthy top-to-bottom food chain, this just might be the price we are going to have to learn to pay.

So the next time you see a large, dangerous ’gator, remember to thank him for guarding over your great blue herons. The next time you think of shooting all the wolves, remember you’re killing off the trout as well. In the end, if you truly do love nature, love all of it.