From the LA Times:

Animal shelters seeing glut of Chihuahuas The once-fashionable little canines are replacing pit bulls as the breed most often left at shelters.

... And at the Peninsula Humane Society in San Mateo, "the number of Chihuahuas has eclipsed pit bulls as the most common breed" ...

Chihuahuas, pit bulls. Pit bulls, Chihuahuas ... It seems like there ought to be a solution to the dog pound overcrowding problem in there somewhere.