Chihuahuas crave attention, affection, exercise and being petted. They can be hyper, but eager to please. They have a reputation as a 'yippy' dog, which can be resolved with proper training. Chihuahuas with proper breeding are not 'yippy'; the AKC standard calls for 'a terrier-like attitude.' Long haired chihuahuas tend to have a more mellow temperament.
Chihuahuas are not well-suited as small children's pets because of their size, temperament, and tendency to bite when frightened. It is recommended that children be school age or older before adding a Chihuahua to one's home. Also, many Chihuahuas focus their devotion on one person, becoming overly jealous of that person's human relationships. This can be mitigated through socialization. Chihuahuas also tend to have a 'clannish' nature, often preferring the companionship of other Chihuahuas over other dogs.[10]
In southern California in 2009, three Chihuahuas protected their mistress, a three-year-old girl, from a 100 pound mountain lion.[11]"