Inside Seven
Current Issue: September 2014
A family photo near Liberty Canyon and  the Ventura Freeway (U.S. 101).

The Call of the Wild: Caltrans Studies Help to Preserve Animal Habitat
by  Judy Gish
Issue Date: 10/2010

How much space does a bobcat need? For some wild animals, a mountain can seem like a tenement.

[Click on photos to read captions.]

Before Caltrans builds a freeway project, it studies the surrounding environment to ensure that impacts are either avoided, minimized or mitigated. One of the elements studied is wildlife, which depend on freedom of movement to survive.

A new wildlife corridor study is soon to begin on the Simi Valley Freeway (SR-118) between SR-23 and SR-126 in Ventura County. Funding for the $226,000 study has been provided by a grant through the Federal Highway Administration and 20 percent matching funds by the National Park Service.

Senior Environmental Planner Barbara Marquez suggested that a better term for wildlife corridors is linkages. A linkage connects two main areas of habitat, allowing wildlife to travel between them. “Without linkages, wildlife populations are in danger of inbreeding, starving, becoming aggressive toward humans and, ultimately, extinction,” she said.

The wildlife in question in this region is primarily larger mammals such as bobcats, coyotes, mountain lions, badgers and mule deer, whose main impediments are freeways and urban development, Marquez added.

Environmental impacts were not a consideration in the less-enlightened time when the bulk of southern California’s freeways were constructed. “Unfortunately, we can’t mitigate for existing freeways,” said Reza Fateh, project manager for the new study. “But when a new project comes up we try to minimize such impacts, although mitigation has to be proportionate to the size of the project.”

Funding (or lack thereof) is always a factor in the measures Caltrans can take to preserve animal habitat and mobility. For example, a proposed wildlife corridor off the Ventura Freeway (U.S. 101) at Liberty Canyon is fully supported by a host of environmental and conservation organizations and government agencies as well as local communities and elected officials. Only one obstacle stands in its way: there is no money to build the corridor, estimated at somewhere in the neighborhood of $10 million.

Despite financial setbacks, however, Caltrans Environmental Division will continue to pursue funding possibilities, Marquez said, and is currently exploring a TIGER (Transportation Investment Generating Economic Recovery) grant, part of the American Recovery and Reinvestment Act (ARRA) of 2009, through the Santa Monica Conservancy.

Last year, District 7 received an Excellence in Transportation Award for a wildlife corridor study and mitigation on SR-23 in Ventura County. The project set up 12 one-way wildlife gates and cleaned out three culverts to make them wide enough for animals to use as crossings. It also increased the height of right-of-way fences to deter animals from jumping over them and buried the fences two feet deep so wildlife could not burrow underneath. Signs also were placed to alert motorists to watch out for wildlife.

This certainly has to be a welcome development for the wildlife, 222 of which became road kill during the three years prior to the project’s installation (data on animals were provided by cameras the National Park Service had set up in the culverts as part of the study, as well as regular field surveys).

Mitigation measures also have been undertaken on the San Diego Freeway (I-405) at Sepulveda Boulevard and Skirball Overcrossing because of the widening of the freeway as part of the northbound HOV project from the Santa Monica Freeway (I-10) to U.S. 101. Those measures include installation of a wildlife culvert, directional fencing bridge widening, landscaping and some existing fence removal to facilitate movement.

Often, the data necessary to determine the best mitigation measure is not available during the narrow window of project development. The new study on SR-118 is being undertaken independent of a particular project, which means that when it’s needed, the information will be ready.

“The important word is ‘connectivity’,” Fateh said. Larger animals need a very large habitat. It isn’t enough to have the Santa Monica Mountains, for example, unless those animals can connect with other habitats throughout the entire region. U.S. 101 is a major limitation for them.

It’s a concept that is getting more attention among transportation planning agencies. This year Caltrans, along with numerous other state agencies, concluded a two-year study called the California Essential Habitat Connectivity project, whose purpose was to develop a statewide wildlife habitat connectivity map using GIS analysis, provide a framework for detailed regional studies and help to sustain California’s unique natural heritage.

“All transportation agencies that play a major role in development need to be more conscious of this issue,” Fateh said, citing as progress the fact that the Southern California Council of Governments (SCAG) recently developed an open space plan that identifies wildlife corridors.

“We have an opportunity to make positive improvements because here in southern California we still have wildlife,” Marquez said. “But because of the number of freeways and amount of urban development, we have to make those improvements just to keep the current population levels.”


A wildlife crossing example, courtesy of the Federal Highway Administration. Two mule deer graze in the Sepulveda Pass near I-405. This puma was photographed near Skirball as part of a study for mitigation of the northbound I-405 HOV lane project. A map showing the SR-118 wildlife study location.