I’ve encountered coyotes in odd places—the men’s room of a park in Tucson, for one—but never, unlike a friend who knows his wildlife, in downtown Berkeley. He says it was crossing Shattuck Avenue, early in the morning before significant traffic. This shouldn’t have surprised me: I knew they were in the East Bay Hills (Tilden Park and Briones), and it was only a matter of time until they came to town.
The coyote is one of the few medium-to-large predatory mammals that have prospered since the European settlement of North America.
We think of them as Southwestern: the iconic baying-at-the-moon-beneath-a-saguaro pose, Chuck Jones’s maladroit schemer pursuing the Roadrunner through canyons and mesas. But they were also native to the Plains, and they’ve now wandered far beyond their original range, filling the niche of the timber wolf in the Northeast.
We’ve shot, trapped, and poisoned them, but they keep coming back.
They’ve inhabited the cultures and belief systems of North Americans for a long time, from Mexico (“coyote” comes from the Nahuatl coyotl) to the Arctic. Coyote—trickster, worldmaker, shapeshifter—features in thousands of creation myths and bawdy stories: see Malcolm Margolin’s “The Way We Lived” for a California sample.
The coyote’s image is everywhere--Harry Fonseca’s paintings, Santa Fe kitsch—and its song, thanks to all those Westerns, is part of our collective soundtrack.
What concerns me here, though, is their role as predators. Wile E. Coyote is atypical; most coyotes are very good at what they do. They’re opportunistic, scavenging carrion, eating fruit, taking insects, frogs, snakes, rodents, pronghorn, deer. Mostly solitary, they’ll join forces to run down an antelope, or follow a badger around to see what it flushes.
As predators, coyotes are major architects of natural communities. There’s a sizable body of research showing how predators regulate ecosystems. Everyone knows that hunters keep the numbers of the hunted in check: The canonical story is of the deer on Arizona’s Kaibab Plateau, whose population exploded past sustainable levels when wolves and mountain lions were killed off.
But it’s more complicated than that.
Predation is also a force for biodiversity. Without predators, some species in a natural community would outcompete others and come to dominate. This seems to work the same way for starfish in a tidepool (keeping the mussels from taking over) as for tigers in a jungle.
In a Texas study, coyotes were removed from test plots of grassland with multiple species of rodents. Nine months later, rodent diversity had declined; after a year, only one species of kangaroo rat was left.
It also appears that predators don’t just regulate prey: they regulate other predators.
Predators come in all sizes. Most terrestrial ecosystems have “mesopredators,” in the weasel-to-fox range. Larger predators like coyotes may either compete with mesopredators or prey on them directly. When top predators are eliminated, the smaller guys experience what conservation biologist Michael Soule dubbed “mesopredator release.”
Their populations increase, and so does their impact on their prey base.
Soule described the process in 1988, in a study of chaparral “islands” in the canyons around San Diego. He found that fragments without coyotes had fewer ground-nesting birds: quail, roadrunners, thrashers, towhees. The variable seemed to be the abundance of foxes, domestic cats, and other bird predators in the coyoteless areas.
Indirectly, it seems, the coyote is a benefactor of the roadrunner.
Since then, other researchers have supported this notion. Recent surveys of riparian corridors among Sonoma County vineyards found more large predators (coyotes, bobcats) and fewer small predators in the wider, better-vegetated patches.
In the prairie pothole country, North America's duck factory, the presence of coyotes seems to reduce red fox predation on duck nests. A similar dynamic involving lynxes, mongooses, and rabbits was described in a Spanish national park.
Soule and Kevin Crooks revisited coastal southern California a few years ago for a closer look at competition among predators and how prey species were affected. They found a strong positive correlation between coyote presence and chaparral-nesting bird diversity, and strong negative correlations between both of these and the abundance of gray foxes, opossums, raccoons, and domestic cats.
Crooks and Soule wrote in the journal Nature: “The interactions between coyotes, cats and birds probably have the strongest impact on the decline and extinction of scrub-breeding birds.”
Basically, coyotes kill cats. About a quarter of the coyote scat specimens collected in their study area contained cat remains.
I can hear the Cat Lobby already: cats, house or feral, get a bad rap, they’re not really destructive predators, they didn’t wipe out the quail in Golden Gate Park.
Let me cite the classic paper by P. B. Churcher and J. H. Lawton. Churcher and Lawton persuaded the cat owners of the English village of Felmersham to keep track of what their pets brought home in a year’s time. The village’s 70-odd cats accounted for a total of 1090 prey items, mostly mice, voles, and shrews, but about 300 birds. (And this doesn’t include whatever the cats ate on the spot).
Interestingly, individual success varied: six feline slackers brought in nothing at all, while one overachiever accounted for 95 kills.
So it seems straightforward: more coyotes, fewer cats, more birds.
But roles can change; sometimes a top predator gets demoted. The coyotes of Yellowstone had a good thing going, with pronghorn antelope fawns a prominent item on their menu. Then the wolves returned, and wolves have zero tolerance for coyotes. Last year, according to pronghorn authority John Byers, antelope numbers increased for the first time in years. Byers credits the exclusion of coyotes by wolves: “It’s likely the wolves are going to be the single-most-important force to save the pronghorn of Yellowstone.”