After observing a 200 percent increase in the ground squirrel population in Palisades Park in Santa Monica between February and June of this year, Los Angeles County Department of Public Health officials notified city staff earlier this month that additional controls must be undertaken to reduce the population to acceptable levels.

Efforts begun in February to reduce and then manage the ground squirrel population in the park, including administering immunocontraceptives and educating the public on not feeding the squirrels, were not as effective as anticipated, city officials said.

To comply with the county directive, the city is contracting with Heritage Wildlife Management to do live trapping of ground squirrels in several blocks of the park later this summer.

These squirrels will be euthanized off-site using carbon dioxide and taken to a wildlife rehabilitation facility where they will be fed to hawks and other wild birds being readied for return to the wild — where squirrels are their natural prey.

The American Veterinary Association has deemed the use of carbon dioxide as an acceptable method of humane euthanasia of rodents.

While the pilot program that began in February has not produced the desired results, city officials said they have found very promising research regarding the use of a single-injection immunocontraceptive vaccine.

This research program was conducted by the USDA (U.S. Department of Agriculture) Wildlife Service and the California Department of Health Services.

The study was conducted in a park portion of the Berkeley Marina that contains a variety of terrains.

The squirrels were trapped and injected with the vaccine which inhibits their sexual development.

This research was conducted over two breeding seasons and was found to have been over 90 percent effective.

City staff, with assistance from the county Health Department, will be contacting educational institutions such as the University of California at Davis, which published the study, and Cal Poly Pomona regarding their interest in undertaking and coordinating a similar program in Palisades Park.

This type of program could become a model for reducing the use of lethal controls on ground squirrels, city officials said.

“The goal is not in any way to remove all ground squirrels from Palisades Park,” said Gail Van Gordon, county public health entomologist. “The intent is to reduce the number to a level that is acceptable for the safety of park users and pets and for the health of the squirrels. We join the city in asking well-meaning people to please refrain from feeding the squirrels.

“Allowing squirrels to naturally forage for food is a major factor in maintaining a healthy population in manageable numbers.”

Wildlife support groups and animal rights activists disagree with county health department officials who say that Palisades Park is overpopulated with ground squirrels.

Animal Advocates wants a humane ground squirrel control plan in Santa Monica.

Animal Advocates is a nonprofit organization licensed by the California Department of Fish and Game to rehabilitate wildlife and conduct wildlife education programs.

“The Los Angeles County Health Department has reverted to stating that there should only be three squirrels per acre,” said a spokeswoman for Animal Advocates. “They have never shown this to be law.

“Research has shown that 20 to 60 ground squirrels per acre is average in the wild. Earlier, the health department promised Animal Advocates that a 30 percent initial reduction would be acceptable.”

Animal Advocates stated that the original squirrel count in February indicated 236 active burrow holes and 58 squirrels visible above ground.

The group says that while squirrel numbers were up after the breeding season, the last count in July showed 171 active burrow holes and 32 squirrels visible above ground between San Vicente Boulevard and Santa Monica Boulevard.

“This is a 28 percent reduction in burrow holes,” the spokeswoman said.

Animal Advocates said the public should not feed the birds or squirrels at Palisades Park because the City of Santa Monica will kill them if there is an overpopulation.

“They will now be killed because people refuse to stop feeding them,” the spokeswoman said. “There is ample natural food in the park to sustain a normal and healthy population.”