Berkeley to kill squirrels, gophers at Cesar Chavez Park

Ground squirrels favor the rocks along the shoreline at Cesar Chavez Park, a former landfill, near the Berkeley Marina. Ground squirrels favor the rocks along the shoreline at Cesar Chavez Park, a former landfill, near the Berkeley Marina. Photo: Paul Chinn, The Chronicle Buy photo Photo: Paul Chinn, The Chronicle Image 1 of / 12 Caption Close Berkeley to kill squirrels, gophers at Cesar Chavez Park 1 / 12 Back to Gallery

The chubby, whiskery ground squirrels that scurry over the Berkeley waterfront might be cute to some, but to Berkeley city officials, they're a burrowing menace that must be stopped.

The city has hired a pest control company to trap and kill the ground squirrels and western pocket gophers that live at Cesar Chavez Park, a former landfill near the Berkeley Marina. The process will begin with a 1-acre pilot project, then, if successful, expand to the rest of the 90-acre park.

The reason for the death sentence, according to city staff: The squirrels and gophers burrow into the landfill, which holds an estimated 1.9 million tons of residential, industrial and commercial waste. The burrowing erodes the landfill cover and causes toxins to leach into San Francisco Bay. Also, in 2009, the San Francisco Bay Regional Water Quality Control Board ordered the city to reduce the squirrel population.

"The squirrels dig holes, then dogs chase the squirrels and make the holes bigger," said Berkeley city spokesman Matthai Chakko. "The problem is they might be threatening the water quality."

The city has made previous attempts to eradicate the squirrels, including an effort to lure squirrel-eating predators by building owl boxes and raptor perches. That didn't work, Chakko said.

No one knows how many squirrels live at Cesar Chavez, but it's likely to be thousands. Gophers appear less populous but more difficult to survey because they spend most of their time underground.

Squirrel-feeding park visitors are to blame, staff said. The city has posted stern warning signs throughout the park that read: "Please do not feed the squirrels. Feeding the squirrels at the marina is causing overpopulation. When this happens, the squirrels become sick and die. You will be helping the squirrels by NOT feeding them."

The whole imbroglio struck at least one park visitor as morbidly ironic.

"First they tell us not to feed the squirrels because it'll kill them, and now they want to kill them," said Bill Lee, 72, who was tossing peanuts to the Cesar Chavez squirrels on a recent afternoon. He said he visits the squirrels several times a week, loves observing their antics and was deeply saddened at the city's plan to kill them.

'Why not move them'

"The squirrels aren't hurting anyone," he said. "If it's such a big problem, why not move them somewhere else, like Alameda?"

Sadly for the squirrels, the options appear limited. State law prohibits relocating wildlife, and poison would hurt other species. Filling the squirrel holes is ineffective over the long term because the squirrels will just dig new holes. That leaves trapping and "abating," as the city put it - a costly and labor-intensive practice that's moderately effective, according to the University of California Division of Agriculture and Natural Resources.

Neither city staff nor the pest control company, Animal Damage Control, would reveal the exact method of killing the squirrels, but according to the UC Davis Department of Wildlife, Fisheries and Conservation Biology, the standard method is to kill them off site with carbon dioxide gas.

Berkeley's problem appears to be unusual. San Francisco Bay is lined with many former landfills that have been cleaned up, covered and transformed into parks or developments. Ground squirrels - which are native - abound at all of them. They favor the rocks along the shoreline, and forage amid the grass and snacks left by humans.

Unique problem

A brief survey of other Bay Area cities revealed that none have taken steps to eradicate squirrels, because they're apparently not causing problems. The East Bay Regional Park District will get rid of squirrels that burrow around valuable infrastructure, such as the historic farm buildings at Ardenwood in Fremont, but leaves them be if they're just scampering around parks - including those that are former landfills along the shoreline.

"It's their habitat," district spokeswoman Emily Hopkins said.

The water quality board is adamant, though. Berkeley's squirrels must go. Their tunnels stretch several feet into the dirt and the clay cap that seals the former dump, causing something the water board described as "garbage juice" to leak into the bay. Garbage juice is a murky stew of metals, petroleum and other toxins.

"For some reason, the ground squirrels in Berkeley are invasive," said Lindsay Whalin, an engineering geologist with the water board. "We don't think it's a flaw in the design of the landfill. But we're trying to minimize the damage."