Farmers Insurance Group has joined several insurance companies in discontinuing coverage for bites from certain dogs.
The company will no longer cover bites from American Staffordshire terriers (pit bulls), rottweilers and wolf hybrids under homeowner's insurance for California policyholders.
"We reviewed our liability claim history and determined that these three breeds accounted for more than 25 percent of our dog bite claims," Farmers spokeswoman Erin Freeman said.
The company also determined that the breeds cause more harm than others when they attack, she said.
Farmers' policy change applies only to customers in California, where the majority of its dog bite claims have generated. Freeman declined to speculate why the state has a higher number of claims than others.
Farmers notified policyholders of the change on Jan. 15, she said.
The company asked customers who had previously reported owning dogs to sign an exclusion waiver acknowledging that the breeds will no longer be covered.
Freeman said the company will not immediately cancel policies but will not renew them if waivers are not returned.
The limit applies to both pure and mixed breeds, according to Freeman.
"The breed is determined by what customers self-report," she said. "We trust our customers to tell us what kind of dog they own."
Nationwide, dog bite claims cost home insurers a total of $479 million in 2011 - an average cost of $29,400 per bite, according to Insurance Information Institute President Bob Hartwig.
Insurance companies as a whole receive more than 16,000 dog bite claims annually and the amount has increased over the years, he said.
The number of claims in 2011 showed a 15 percent increase from 2010 and a 48 percent increase from 2003, he said.
"Many insurers have excluded some of the more-vicious breeds," he said.
Mother Lode area humane societies said it has been difficult to find homes for pit bulls and other dogs that are perceived as aggressive.
"It's just a total misconception," Tuolumne County Humane Society Board President Doryene Rapini said of pit bulls. "People need to give them a chance."
Rapini, who owns a pit bull, said the dogs become violent when they are trained to be tough rather than gentle and obedient.
She also said people who want to adopt pit bulls are often unable to because of limits in insurance policies.
"It's just very discriminatory," she said.