Sell a guinea pig, go to jail.

That's the law under consideration by San Francisco's Commission of Animal Control and Welfare. If the commission approves the ordinance at its meeting tonight, San Francisco could soon have what is believed to be the country's first ban on the sale of all pets except fish.

That includes dogs, cats, hamsters, mice, rats, chinchillas, guinea pigs, birds, snakes, lizards and nearly every other critter, or, as the commission calls them, companion animals.

"People buy small animals all the time as an impulse buy, don't know what they're getting into, and the animals end up at the shelter and often are euthanized," said commission Chairwoman Sally Stephens. "That's what we'd like to stop."

San Francisco residents who want a pet would have to go to another city, adopt one from a shelter or rescue group, or find one through the classifieds.

The Board of Supervisors would have final say on the matter. But not before pet store owners unleash a cacophony of howling, squeaking and squawking.

"It's terrible. A pet store that can't sell pets? It's ridiculous," said John Chan, manager of Pet Central on Broadway, which has been in business 30 years. "We'd have to close."

'Terrible for our business'

Joe Taylor, bird manager of Animal Connection on Judah Street, called the proposal "ludicrous."

"What difference does it make if you get a parrot at the SPCA or a pet store? If it doesn't work out, in either case, you just bring it back," Taylor said. "This would be terrible for our business."

The idea originated about two years ago, when the commission began looking into a ban on dog and cat sales as a way to discourage puppy and kitten mills. But the city's animal control staff said that excess puppies and kittens are not the problem at the city shelter, thanks to the plethora of rescue groups. In any case, only one or two pet stores in San Francisco sell dogs and cats. The rest stick to small animals.

The hamster problem

The real problem, staff said, is hamsters.

People buy the high-strung, nocturnal rodents because they're under the temporary impression that hamsters are cute and cuddly. But the new owners quickly learn that hamsters are, in fact, prone to biting, gnawing through expensive wiring and maniacally racing on their exercise wheels at 2 a.m.

So the animals end up at the shelter. Just about every species has its own rescue group in San Francisco, but no one seems to want hamsters. Hamsters are the No. 1 animal euthanized at the city's shelter, said San Francisco Animal Care and Control director Rebecca Katz.

"It's definitely a concern," she said. "They're an impulse buy, and we do sometimes get tons of them, especially babies."

Committed owners

On Wednesday, the shelter, which is on 15th Street in the Mission District, had six hamsters, nine rabbits, nine mice, nine rats, two guinea pigs, a bowl of goldfish, two birds, a leopard gecko, a bearded dragon and a hermit crab named Charlie.

But those shelter hamsters almost certainly did not originate at a pet store, said Michael Maddox, general counsel for the Pet Industry Joint Advisory Council in Washington, D.C.

Studies by UC Davis and the National Council on Pet Population Study and Policy have shown that only a small fraction of shelter animals were purchased at pet stores, he said. People who buy animals at pet stores are just as committed, emotionally and financially, to caring for their pets as people who procure pets elsewhere, he said.

"This is an anti-pet proposal from people who oppose the keeping of pets," he said. "If their goal is to ban the ownership of pets entirely, then this is a good first step."

The commission plans to listen to testimony from pet store owners, among others, before voting. Among the items it will consider is the impact on small businesses, whether to allow the sale of feeder rodents for snakes and other reptiles, the sale of fish, owner education, penalties and rescue groups that host adoptions at pet stores.

"We're still in the information-gathering phase," said Commissioner Philip Gerrie, who is sponsoring the proposal. "We're trying to get at the problem of people buying these creatures with the best intentions, but then the reality turns out quite different."

Meeting tonight San Francisco's Commission of Animal Control and Welfare meets at 5:30 p.m. today at City Hall, Room 408, to consider an ordinance banning the sale of pets, except for fish, in San Francisco. -- For more information, go to sfgate.com/ZJYO.