Transmitters Track Wildlife Living at Civilization’s Doorstep

Standing on the ridge of Castro Crest, with the flanks of the Santa Monica Mountains sweeping down and away, Mike Williams swings the antenna in a wide arc, panning the ravine below. Midway through the sweep, the beeps start again.

“This isn’t where we’d expect to find him,” said Williams, making notes in a logbook. “This could be his home range, but it’s a little more likely he hasn’t established a home range yet. That could be what we are seeing.”

“He” is a gray fox, a young male and one of four gray foxes equipped with radio transmitters scurrying through the underbrush of the Santa Monica Mountains National Recreation Area near Agoura Hills.

The beeps pulse steadily, indicating an animal at rest, not unusual for a gray fox in the middle of the day. Williams, a National Park Service resource management specialist, uses a compass to draw a bearing on the animal.

Williams radios down to volunteer Gail Bramhall, out of sight on a knoll a mile away. Bramhall also has a fix on the young fox. Using the two bearings, the youngster’s position is noted. That he is outside his normal range is unusual but not surprising.

“Once you make a rule, it’s bound to be broken real fast,” said Williams, smiling. “Although our job is prediction, sometimes it’s hard to predict anything out here.”

For the past two years, the National Park Service has been monitoring the movements of a small group of bobcats, coyotes and gray foxes in a sliver of the Santa Monica Mountains. After capturing the animals with padded leg traps and affixing radio transmitters, researchers track them to see what they do, where they go and how they interact with each other.

Dubbed the Critical Habitat Study, Park Service personnel hope such observations will help them better understand the habitat needs of three of the area’s most important predators, which, in turn, will help them manage the land the animals call home.

There are no conclusions yet and there might not be for some time, but researchers believe the study is needed to determine the impact of encroaching development on 150,000 acres of wilderness bordered by one of the country’s largest urban centers.

“A lot of people don’t realize it, but the Santa Monica Mountains are an excellent wildlife habitat,” said Robert Plantrich, a Park Service forester and the project leader. “Unfortunately, thousands of acres are being developed every year. We’re losing important habitat for many species without really knowing what it is they need.”

For the past two years, Plantrich, Williams and a small cadre of volunteers have logged the food, water and spatial needs of about 30 animals in 10 square miles of Malibu Creek State Park, a rugged expanse of deep canyons, wind-swept crests and rolling savannas. The emerging picture has been informative, interesting and, at times, surprising.

It has also been frustrating. Canyon walls block transmissions. Interference can smother telltale beeps. Even clear transmissions are no guarantee. On one occasion, puzzled researchers followed a signal into the Simi Hills far outside the study range, only to find they were tracking an Andean condor tagged by Fish and Wildlife for another project.

Williams and Bramhall have spent the past six hours bumping along rutted fire roads, stopping at ridge tops to pan the sky with antennae, electronically groping for signals emanating from the three bobcats, four gray foxes and seven coyotes they are monitoring. In the course of a six-hour day they can usually locate all the animals. Today they have found one, the young gray fox that has apparently wandered outside his normal range.

Standing on the ridgeline of Castro Crest, notching the day’s sole find in his logbook, Williams shrugs.

“Those are just some of the things that go with the territory,” he said. “There are days when everything goes right, and there are days when nothing is easy. Like the animals you’re tracking, constant change is the name of the game.”

Nowhere is this change more evident than at civilization’s edge, a portion of the predator-study area bordering the Malibu Lake community. There sits a group of residences around a man-made lake, providing an opportune look at development’s effect on the three predators, especially the coyote, which seems to be thriving right on man’s doorstep.

The behavior patterns of tagged coyotes living on the edge of Malibu Lake appear markedly different from their counterparts in more secluded areas. In remote areas, researchers found coyotes spreading over a wide range of habitats, foraging day and night for the small mammals, fruits and nuts that comprise their natural food supply.

The coyotes living near the lake, however, seldom stray far and rarely forage during day. Instead, the animals rest in the brush just outside the development during the day, then pad down into the neighborhoods at night. There they find a ready supply of food in the form of garbage and occasionally pets, upsetting the natural predator-prey balance.

“We now see and hear many more coyotes adjacent to residential areas than in areas that are less populated,” said Plantrich, who sees increasing potential for problems as development continues to displace and then provide for the opportunistic coyote.

“In urban areas,” he said, there eventually will be a larger population of coyotes exhibiting less fear of humans. “That’s where problems may arise.”

Development’s effect on bobcat and gray fox is less obvious. Far more reclusive than the coyote, these animals usually keep to thick brush and avoid contact with man.

But researchers have observed a surprising habitat separation between coyote and gray fox. Natural enemies--the larger coyote sometimes feed on the gray fox--as coyotes become more numerous, they may drive the gray foxes farther afield. Bobcats, equally intolerant of humans, also disappear in areas next to development.

According to Plantrich, portions of the Santa Monica Mountains Recreation Area, notably eastern areas in and around Los Angeles, already provide an example of just such displacement.

“When you isolate an area, make it a park and then build boundaries around it, ultimately all you have left is coyotes,” Plantrich said. “Any biologist will tell you that as you fragment your habitat into smaller and smaller pieces, a species diversity will decline.”