Tracking Predators Across Vanishing Southland Turf

They are your neighbors, but you rarely see them. They have lived here longer than anyone, but odds are you’ve never met. They are killers, but they are not after you. They exist as a baleful howl from the hills, a glint of night eyes, or a flicker of fur darting through brush.

Lots of big carnivores still prowl their domain of the Santa Monica Mountains, but it is a shrinking wild kingdom. Highways and strip malls, housing tracts and golf courses replace about 1,400 acres of habitat annually across the 350-square-mile mountain range, according to scientists.

In one of the nation’s most ambitious carnivore studies, a team of state and federal researchers is documenting how urban sprawl crushes wild lands under the bulldozer’s blade and severs links among critical habitats, posing an increasing threat to the survival of Southern California’s predators.

The study, in its fifth year, focuses on 165 coyotes, bobcats and gray foxes living in the central Santa Monica Mountains, Simi Hills and to a lesser degree the Santa Susana Mountains. It is a representative sample of those species inhabiting an area from Malibu to Chatsworth, Moorpark to Calabasas.

Caught in a trap of steel and concrete, the animals are being squeezed into increasingly isolated pockets of back country, forcing them to make dangerous and often deadly treks across miles of man-made obstacles to hunt and find mates.

Unless there are greater efforts to save key migratory corridors, animal populations may soon be too separated to find each other and could eventually succumb to disease or the devastating effects of inbreeding, researchers at the Santa Monica Mountains National Recreation Area warn.

“These animals need large open spaces to survive. They need habitat to be connected, but the opportunity for large, continuous tracts of land to be intertwined are fewer and fewer,” said Raymond M. Sauvajot, senior scientist for the National Park Service.

“If we develop the only areas left that provide connectivity between open spaces, we’re going to isolate these mountains, and isolate species and they’ll die off eventually,” he said.

Many of the animals that do hang on are likely to be run over or poisoned, the research suggests. Nearly two-thirds of the 20 coyotes and 40% of the 15 bobcats that have died since the study began in 1995 were killed by vehicles or bled to death after consuming rodents contaminated with anticoagulant poisons, scientists have learned.

The substance warfarin, which prevents blood from clotting and causes rats, mice and ground squirrels to bleed to death, appears chiefly responsible for the poisonings, scientists say. Rodents are developing tolerances to the toxin, which has been used since the 1950s, requiring larger doses and stronger poisons. But higher in the food chain, the chemical concentrates to lethal levels in predators, researchers found.

“These top predators might eat four or five rodents, each one with a little bit of poison, and the chemical just accumulates in their body and then they die,” UCLA biologist Robert Wayne said.

Major highways are proving to be virtually impenetrable barriers for the carnivores, which rarely cross them, the research shows. Scientists know that because they use technology such as radio collars on the animals and still cameras hidden in the brush like booby traps to capture their movements.

The animals that do attempt passage--coyotes are willing to try their luck more than bobcats, and foxes never attempt a crossing--usually meet with disaster. Just two coyotes and two bobcats have made successful crossings over California 23 and 118 and the Ventura Freeway in five years, Sauvajot said, and one of those bobcats was later struck and killed in Malibu Canyon.

In behavior reminiscent of hyenas in Africa, some coyotes ramble vast distances, contradicting the perception that they lurk mainly in local hills by day, waiting to pounce on domestic pets by night.

For instance, three coyotes captured at Liberty Canyon Road had traveled 35 miles to Santa Clarita and Piru. Another, captured and fitted with a radio collar near the Calabasas landfill, had commuted from Moorpark.

“It was farther than we thought they would move. It’s not something we expected,” Sauvajot said. “The good news is it means they were able to successfully traverse those areas, but it clearly indicates these animals range wide distances and it demonstrates the need to retain connectivity is very important.”

Researchers use hand-held radar equipment to monitor the movement of the animals. On a recent evening, from a hilltop above Palo Comado Canyon in the Simi Hills, project volunteer Kim Asmus twisted an antenna that picks up electronic signals from collars on two coyotes, numbers 88 and 96.

“Lately, we’ve been finding a lot of dead ones,” Asmus said. “[The research shows] the actions in your neighborhood really do affect these natural areas. I think if you could hear a coyote at night, it reminds you that you are part of nature and reminds you that you are connected to the environment.”

The study focuses on animal behavior on the boundary between a wilderness and a metropolis to see how big predators cope with human encroachment. As California’s population approaches 35 million, scientists want to know if the animals will survive.

“It’s trying to sort out which animals adapt, which ones don’t and which ones won’t survive into the future,” Wayne said. “It’s a good test case to see how wild populations persist in an urban area, because these conditions are going to exist someday even in remote places in the United States.”

Top carnivores occupy an important position in the environment and in American history. Their prowess and nomadic nature gave rise to their mystique, which adds to the image of the West as an untamed wilderness.

Predators, too, play a key role in maintaining the health of Southern California’s wild lands. They act as regulators, keeping prey species in check, and they are indicators of the overall health of woodland and shrub land ecosystems, said UC Davis wildlife biologist Seth Riley.

And their presence benefits property owners because it shows that large, intact tracts of habitat are nearby, the kind of open spaces that add value to houses, make communities more scenic and enhance outdoor recreational opportunities, Riley said.

Researchers use high-technology tools to track movements of the animals around the clock. Seventy-one cameras are deployed in culverts and wooded ravines to track nocturnal movements around highways and developed areas.

DNA analysis is performed on animal waste to identify individuals. Satellite-linked global positioning systems are used to pinpoint carnivores concealed in thick brush. Four-wheel-drive vehicles, outfitted with telemetry tracking devices, are in the field almost around the clock.

Collaborators on the project include the National Park Service, the University of California, the University of Massachusetts, Cal State Northridge, the California Parks and Recreation Department and Canon U.S.A.