Fido’s getting more aggressive. Insurance claims for dog bites jumped 18 percent to 18,123 last year in the U.S., according to an industry group. The average attack cost $33,230, a decline from 2015, but up more than 70 percent from 2003 because of increased medical costs and larger settlements, the Insurance Information Institute said in a statement.

Attacks from pets are an increasing expense for insurers. State Farm Mutual Automobile Insurance Co., the largest provider of property-casualty coverage in the U.S., said its costs from dog bites climbed 15 percent in 2016 to more than $121 million. Children account for more than half of the injuries, according to State Farm, which is highlighting safety efforts as part of National Dog Bite Prevention Week, which runs through April 15.

“If they haven’t been properly trained by their parents on how to approach a dog, that’s a big issue,” Loretta Worters, a vice president with the Insurance Information Institute, said in an interview Friday. “Children just go up, they see a cute dog, and they just start trying to pet it.”

Kids should be taught to ask permission before petting a dog, and not to run away, because such behavior can encourage pets to chase, she said. The animals can be most aggressive if they are frightened or defending their puppies. Owners should make sure they socialize puppies, helping them learn appropriate behaviors when they’re young, and have the dogs spayed or neutered, according to the institute.

Letter carriers haven’t escaped unscathed either. Attacks from canines increased by more than 200 last year to 6,755, according to a press release from the U.S. Postal Service. Workers in Los Angeles and Houston were victims of the most confrontations.