Researchers Try to Keep Wildlife Trails Open
Some people speed through the suburbs and see only pricey stucco homes and tangled freeways wrapped around the foothills of Southern California. Biologist Kevin Crooks surveys the same landscape and envisions lifelines for wildlife.
Crooks studies an Orange County map and imagines corridors where coyotes can glide at night. He views a mundane highway bridge as the perfect conduit for wandering mule deer. And he ponders how patches of land around the periphery of the Los Angeles megalopolis could be strung together like beads, allowing tenacious mountain lions and other wildlife to forage and hunt.
Big mammals need big swaths in which to roam. Such expanses are vanishing fast as builders carve land into pieces for new homes, malls and office parks. So much so that scientists consider this region an international epicenter of wildlife extinction, in part because its remaining wilderness is being sliced into islands in an urban sea.
“Connectivity is the key,†said Crooks, 32, who has studied in Riverside, San Diego and Orange counties for five years to see how predators fare as their native lands are invaded by bulldozers and building cranes. His most recent studies focused on the Nature Reserve of Orange County, a 37,000-acre open space system created in 1996 to protect wildlife.
What he discovered is cause for both alarm and optimism.
Linking Islands of Animal Habitat
Even within the reserve, Crooks found a scarcity of land linkages that allow big mammals to roam. Some key roads, such as Crown Valley Parkway, were built without tunnels that would allow animals to cross safely without fear of traffic. Many man-made crossings are badly designed--too low and barren for deer.
A more serious flaw is that the reserve is divided in half--two major expanses of largely undeveloped land that are separated by interstate highways and miles of tract homes. Most animals can travel within those two areas, but cannot cross over barriers as formidable as Interstate 5.
One of the few feasible links between the two parcels runs along Serrano Creek under the notorious El Toro “Y,†where the Santa Ana and San Diego freeways meet in a blur of traffic. The notion of wild animals crossing under car-choked asphalt as wide as the Mississippi River seems impossible.
“It’s not necessarily the fault of the reserve design,†said Trish Smith, senior project ecologist with the Nature Conservancy, which helps manage current and future reserve land. “If we had hindsight 30 years ago, we could have prevented a lot of the fragmentation that’s occurred in that time.â€
Not all the news is bad. With better corridors and more science, Crooks believes, the big predators still may flourish. He was pleased to find mountain lions and bobcats thriving in remote reserve land close to the Santa Ana Mountains. Coyotes and bobcats can be found throughout the reserve’s central and coastal areas, signaling a well-balanced food chain.
But if the ranks of large predators dwindle, Crooks says, the natural balance of the Orange County reserve and similar wild lands will be thrown into disarray. Smaller meat-eaters such as opossums, raccoons and domestic cats can grow in numbers and travel more widely. They, in turn, will eat small native birds and other creatures already in danger of extinction.
In short: Saving the mountain lions and other large predators in the region may well ensure the health of rare songbirds.
Crooks tracked predators using dozens of remotely triggered infrared cameras, foul-smelling liquids used as lures and even gypsum powder to capture their telltale tracks. He and his researchers filled bulging scrapbooks and computer discs with thousands of photographs of startled bobcats, coyotes, deer, skunks--and, yes, mountain lions--caught wide-eyed in the dark as the cameras flashed.
Those photos are proof they do exist in the nocturnal shadows.
“People need places where they can go and say the system is operating basically the same way that it has for the past few thousand years,†said Paul Beier, associate professor of wildlife ecology at Northern Arizona University, who conducted what are considered classic studies of Southern California’s mountain lion population. “When you lose your large carnivores, you can’t say that anymore.â€
Crooks traces his fascination with predators to his youth spent near Denver, a grandson of a wildlife biologist. He received degrees in zoology and ecology before earning his doctorate at UC Santa Cruz, where he was one of Michael Soule’s last graduate students. Soule, now professor emeritus of environmental studies, is considered one of the nation’s preeminent conservation biologists.
Crooks returned to urban canyons in San Diego where Soule earlier had studied the effects of fragmented land on wildlife. In a 1999 article published in the journal Nature, Crooks and Soule described how when coyotes--the most common large predator in the region--roamed a canyon area, a richer variety of birds thrived. One factor could be that coyotes keep smaller bird-eating carnivores in check, they surmised.
Orange County has become Crooks’ latest laboratory. The Nature Reserve where he worked was established in 1996 in a landmark agreement between the Irvine Co., landowners and federal and state regulators. Developers who contributed land or money were freed from certain strict Endangered Species Act requirements on some lands outside the reserve.
A question still nagging biologists is whether the reserve will succeed in preserving wildlife.
Crooks is producing annual reports funded by the Nature Reserve that look at predators and their habits. The first, written with researcher Don Jones, found that wildlife corridors are crucial in allowing predators to roam and hunt. It also urged careful planning of future roads, homes and stores to avoid isolating large mammals on habitat islands, where they might be prone to inbreeding and disease.
Some current links are marred by poorly designed fencing that forces animals to travel long distances without the protection of trees and shrubs. Others lack fencing to guide animals into tunnels. And some stream beds have been sprayed with herbicides, destroying vegetation that could otherwise lure animals to use the stream banks as corridors.
The researchers have urged reserve overseers to study whether linkages such as Serrano Creek at the El Toro “Y†can be enhanced and restored to allow wildlife to travel south from the mountains through part of the El Toro marine base, under freeways near Irvine Spectrum and on toward the coast.
Fences would have to be relocated, culverts redesigned under some roads and a minimum 500-foot-wide swath of native vegetation created for animals to travel, said the Nature Conservancy’s Smith, who also heads the Nature Reserve’s scientific committee. County and Irvine city officials are studying the plan’s feasibility.
Crooks has conducted a second study on the number of large mammals within the Nature Reserve. Much of the field work was done by Shalene George, 30, a biology researcher who, month after month, monitored 30 cameras around the reserve. The film in some cameras had to be changed every two or three days because so many animals triggered the shutter.
In 1999 alone, the cameras shot 227 photos of deer, 124 of coyotes, 95 of cows, 90 of bobcats, 45 of striped skunks, 26 of gray foxes, 24 of opossums, 21 of dogs, 14 of raccoons and 13 of mountain lions.
“It must be pretty wild country if mountain lions are still there,†said Soule. “They’re the most sensitive indicator of the loss of wildness and nature in Southern California.â€
Many people fear that mountain lions will creep close to homes and snatch cats and other pets. In response, Smith cautioned, “living at the wildlife edge requires some responsibility for your pets, and that means keeping them inside, especially at night.â€
Crooks and his colleagues recommend continued monitoring of reserve predators with cameras and other techniques.
Even information about animals killed on roads could yield more scientific data, Crooks said.
Crooks recently departed for the University of Wisconsin at Madison and an assistant professorship in wildlife ecology. George also is moving to Madison to begin her graduate studies. Both plan to return to Orange County to continue studying predators and how to save them. And both hope that Orange County’s reserve managers can succeed in building lifelines between the reserve’s puzzle pieces.
“Hopefully,†Crooks said, “there is a plan that will give us a fighting chance.â€
