Movies like "Beverly Hills Chihuahua" and photos of celebrities such as Paris Hilton with their "purse pups" have boosted the little dogs' popularity. But after the novelty wears off, pet owners dump them in the streets, open fields or shelters, officials said.
"As with any special breed, if Hollywood makes them famous, the shelters feel the impact," David Sidie, Humane Society of the North Bay director of animal services, wrote in an e-mail about the problem.
The numbers of unwanted Chihuahuas has risen dramatically in recent months, said the society's executive director, Peter Wilson.
Five are currently up for adoption -- about twice as many as the number of Chihuahuas usually available, Wilson said. Sidie added someone recently surrendered a pregnant one and he's caring for the mother and her puppies.
Though no one claimed the little brown Chihuahua in Vallejo, humane society staff fell in love with her, named her Athena and she's on her way to better health and a new home. A special fund has been set up to raise some $1,300 for her surgeries.
The county animal shelter has even more Chihuahuas.
Between 20 and 25 are now being cared for at the Solano County Animal Care Services in Fairfield.
County animal shelter manager Ron Whitfield said Chihuahuas are a fad and many buy them on impulse, but some pet owners don't understand or can't handle their temperament.
"They don't understand that a lot of small dogs can feel threatened very easily because of their size. If they are not handled properly, they will bite," Whitfield said.
Abandoned Chihuahuas brought to the county shelter go through a lengthy evaluation. If they bite or display other anti-social behavior, they likely will be euthanized, Whitfield said.
He's quick to point out that not all Chihuahuas bite, and many are adopted.
Perhaps the greatest threat to Chihuahuas and many other animals is the continued slump in the economy, Whitfield said.
"We see a lot of animals being dumped. With the economy the way it is, people can't keep them anymore. There's a lot of dogs left in abandoned homes and left on the streets. It's been that way for the last three years," Whitfield said.
Whitfield and Wilson advise people to consider the lifelong commitment of pet ownership before adopting a Chihuahua or any other animal.
"Pick the breed you really like and know you have to work with them and train them. Animals don't come nice and good on their own," Whitfield said.
"You can't just leave them alone and expect them to be good. You have to work with any breed of dog to be good and social around people," he added.
The Chihuahua influx isn't limited to Solano County. Of the 62 dogs up for adoption at the San Jose Animal Care and Control, at least 40 are Chihuahuas, an official there said.
Meanwhile, the Silicon Valley Animal Control Authority has so many of the dogs, they are offering a "pay what you want for a Chihuahua deal."