California wild cats face obstacles to survive

2013-10-11

By Sylvie Belmond

 
WHICH IS WHICH?—Bobcats are smaller than mountain lions and have a short tail. Courtesy of Mark Rachel

Despite urban sprawl, mountain lions, bobcats and coyotes remain an important part of the local ecology. But the growth in man’s footprint has made it increasingly difficult for the cats and canines to survive.

Because they are confined to small areas of natural habitat, mountain lions are vulnerable to territorial fights and inbreeding. Some are hit by cars, and others die from internal bleeding caused by exposure to rat poison.

Coyotes often suffer from the same fate.

Wildlife ecologist Seth Riley of the National Park Service spoke about the challenges facing local predators at a Sept. 7 lecture in the Santa Monica Mountains National Park Service Visitor Center near Calabasas.

Since 1996, the National Park Service has tracked 31 mountain lions (also called cougars or pumas), 170 bobcats and 110 coyotes in the region. The tracking provides data on where carnivores live, how well they reproduce and disperse and what causes are leading to their death.

“Our goal is to understand how carnivores behave and how urbanization and human activities affect these animals,” Riley said.

The NPS mountain lion study began 11 years ago with a male designated P1 (puma 1) and his family. The animals were tracked via radio collar for several years. The male eventually killed his mate and two of his offspring.

Because freeways prevent their movement, mountain lions are prone to fights and inbreeding.
“There is a reduced genetic diversity in mountain lions south of the 101. That’s the thing that we worry about. A population that is completely cut off over the long run will have less genetic diversity,” said Riley, who has researched the area’s mountain lions, bobcats and coyotes for more than a decade.

Some of the cubs found in the Santa Monica Mountains were the result of inbreeding between an adult male and his daughter. In the long term, inbreeding could make cougars vulnerable to disease and deformity.

In late 2008, researchers caught a young male, whom they named P12, in the Simi Hills. That animal is the only one out of the 31 tracked in the past 11 years that crossed the 101 Freeway in either direction, Riley said.

P12 helped to increase the genetic diversity of the cougar population in the Santa Monica Mountains. But to survive there, lions will need additional and improved wildlife corridors.

In the study, biologists monitored 15 crossing points along the 101, 118 and 23 freeways. They determined that a wildlife corridor needs natural habitat on both sides of the road for animals to cross.
The Liberty Canyon wildlife corridor in Agoura Hills is the best avenue for animals heading north. But without a proposed $10-million tunnel under the highway, researchers fear the local population might become extinct.

Segments of open space in the Santa Susana Mountains have also been identified as critical pathways.

The park service is tracking seven mountain lions in the Santa Monica Mountains and Simi Hills. One male and three females live south of the 101 Freeway in the Santa Monica Mountains, two are in the Simi Hills and one lives in Griffith Park.

“At the very most, there could be 15 adults in the Santa Monica Mountains, which is not enough for biological diversity,” said Riley, who also shared statistics on bobcat and coyote populations.
Anticoagulants used in rat poison are a concern for all large carnivores.

 
BIG CATS IN THE BIG CITY—A bobcat maneuvers on an electrical wire. Local wildlife struggles to survive in the middle of an urban environment.

Of 11 cougars tested, 10 were exposed to the poison, and some died of internal bleeding from repeated exposure.

Mountain lions rarely endanger people, livestock or pets. They stay away from homes, preying mostly on deer. Occasionally they kill and eat coyotes and raccoons.

Bobcats also prefer natural habitat and prey, and they, too, are susceptible to development, traffic, inbreeding and poisoning.

Between 2002 and 2008 an epidemic of mange—a skin disease caused by parasitic mites— killed 75 percent of the local bobcat population. Five of the six bobcats tracked in the Oak Park area during that period died from mange, Riley said.

In 2003, 17 of 19 animals that died of mange had signifi- cant exposure to anticoagulants. Blood and liver samples show that 95 percent of bobcats have anticoagulants in their system.

“Even animals mostly using natural areas are still affected by cars and anticoagulants,” Riley said.
“The poisons make bobcats less able to resist diseases,” Riley said.

However, it appears the local bobcat population is recovering from the mange outbreak.
Cars and exposure to anticoagulants were a primary cause of death for coyotes.

While coyotes have a bad reputation, none of the animals involved in the study ever posed a threat to a human. Between 1996 and 2004, researchers tracked 110 coyotes and found that the animals prefer to stay away from populated areas.

“This doesn’t mean that coyotes never bite people. But the vast majority of coyotes are just doing their thing and eating natural foods. The biggest problem is when people feed coyotes, either intentionally or unintentionally,” Riley said.

After the presentation, Riley answered questions from the audience and signed copies of his book “Urban Carnivores: Ecology, Conflict and Conservation.”

“The idea that they (mountain lions) are containing their own population through killing their offspring was a surprise,” said Irv Nilsen of Hermosa Beach.

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