Wildlife Losing Area Habitat to Development

They are your neighbors, but you rarely see them. They have lived here longer than anyone, but odds are you have 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 and adjoining hill country of east Ventura County, 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 between critical habitats, posing an increasing threat to the survival of Southern California’s predators.

The study, now 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 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, often deadly, treks across miles of man-made obstacles to hunt and find mates. Absent 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 in-breeding, 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 opportunities 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 Animals Killed by Vehicles, Poisoning

Many of the animals that do hang on will likely get 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 rodenticide warfarin, which prevents blood 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 up 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, who rarely cross them, the research shows. Scientists know 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 disastrous results. 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 on Las Virgenes Road in Malibu Canyon.

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

For instance, three coyotes captured at Liberty Canyon Road traveled 35 miles to Santa Clarita and Piru. Another, captured and fitted with a radio collar near the Calabasas landfill, 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 Finding More Dead Animals

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 animals, coyote 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 of a wilderness and a metropolis to determine how big predators cope with human encroachment. As California’s population approaches 35 million people, scientists want to know whether the animals will persist.

“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 ephemeral nature gave rise to their mystique, which adds to the image of the West as an untamed wilderness.

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

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

Researchers use an array of high-tech tools to track movements of the animals around-the-clock. Seventy-one cameras are deployed like booby traps in culverts and wooded ravines to track nocturnal movements around highways and developed areas. DNA analysis is performed on animal wastes to identify individuals. Satellite-linked global positioning system techniques 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 throughout the week.

Talc Powder Used to Track Animals

Any animals that escape the dragnet sometimes give away their whereabouts by leaving tracks in swaths of talc powder sprinkled liberally at 16 culverts and drainpipes that run beneath highways in the Conejo Valley and Simi Valley.

That low-tech strategy identified a bobcat that slipped through a pipe under California 23 near Tierra Rejada Road, as well as a cougar, a species not monitored in the study, that crossed a tunnel near Corriganville Regional Park in the northern Simi Hills last month. By studying those underpasses, Sauvajot said, he hopes to identify which types are used by animals, and which are not, perhaps so highways can be designed to become less obstructive for wildlife.

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

Some animals are surviving the urban onslaught better than others.

To no one’s surprise, coyotes appear most adaptable to human encroachment, the researchers found. A far cry from their hapless cartoon cousin, the species is wily--coyotes seldom fall for the photo booby traps because they have learned to avoid stepping on the trigger that activates the camera--and adept at navigating city streets to forage for domestic cats and dogs.

“Coyotes are amazingly effective at surviving every effort to get rid of them, and all of those efforts have failed,” Sauvajot said. “They are amazingly adaptable and more careful than they seem to be. They are not careless and they know what’s dangerous and what’s unusual and what is safe.”

Gray foxes, on the other hand, could be in serious trouble. Coyote attacks are the leading cause of death for foxes, the study found. For the fox, losing habitat while facing continued--and perhaps increased--predation from coyotes could imperil its chances for survival in Southern California, Sauvajot said.

Bobcats also fare poorly in the face of habitat fragmentation. The wild cats are highly territorial and rarely venture far from their den, the researchers found.

“They stay in isolated areas and don’t cross home ranges very much,” Sauvajot said. “Once they get into a really small patch, when habitat gets too fragmented and too small, they won’t venture out to find other bobcats to mate or set up dens.”

4 Critical Wildlife Corridors Identified

Highways emerge from the study as a major impediment to the movement of the carnivores. Crossings are usually attempted in places where large expanses of habitat abut both sides of the freeway. But those sites are shrinking as development chips away at the wild lands.

Researchers have identified four critical wildlife corridors: The Conejo Grade between Newbury Park and Camarillo; Tierra Rejada between Moorpark and Simi Valley; the Santa Susana Pass, where the Santa Susana Mountains meet the Simi Hills, and Las Virgenes Canyon, which connects the Simi Hills to the Santa Monica Mountains.

But those spots face intense development pressure. For instance, not far from where scientists spotted the cougar tracks in the tunnel under California 118, heavy equipment is grading terraced building sites near Kuehner Drive.

“We still have enough wilderness space to preserve fairly impressive populations of large mammals, even mountain lions, but we’re on the brink of losing these links and connections between habitat parcels these animals need to survive in the long term,” Wayne said.