“It’s something that’s always on my mind,” says Robin Ashlock.

Ashlock, owner of Peaceable Pets, a dog-walking and dog-sitting service, keeps an eye out for dogs that might menace or attack dogs she’s walking–even as the aggressive pet’s owner stands by. “People underestimate how badly their dog is beating up the other dog,” she says.

Though it hasn’t happened to Ashlock, dogfights can end up in a trip to the veterinarian. “Sometimes it’s just some broken teeth–they bite each other,” says James Clarkson, who owns the Westarbor Animal Hospital. But a few dogs require surgery for a punctured lung or an abdominal cavity torn open.

Though health codes prohibit all but service animals in restaurants, dogs show up almost daily at downtown’s outdoor cafes and restaurants, snoozing or waiting impatiently while their owners sip beer or share stories. But it’s “asking a lot of the dog,” says Ashlock, to sit still for an hour or more with food all around, children reaching for them, and no one paying attention to their mood or needs. So she’s not surprised that when other dogs pass, barks or even bites may ensue.

Another dog walker, Lee Taylor-Belcher, says she also sees conflicts, thought not as often as Ashlock does. But the exceptions can really create havoc. Dog trainers blame owners for much of the conflict, noting that people talking on phones or chatting with friends while sitting in outdoor restaurants often don’t watch their dogs’ behavior.

Some owners act like their pet is “just a cute little man in a furry suit,” says Ashlock. “No, he’s a dog.”

The Ann Arbor Police Department received 456 complaints about dogs in 2008. Deputy police chief John Seto notes that police are usually called only if a dog is badly injured. Most of the time, says Seto, “they get separated and move on.”