Terrier is a type of dog rather than a single breed. The name comes from the Latin terra, meaning earth, because these dogs were developed to hunt rats, foxes and other vermin, often by following them into burrows. Dozens of breeds share the label, and a terrier listing often means a mix of Jack Russell, Rat, Cairn, Schnauzer or Chihuahua lines.
Most adoptable terriers are small to medium, weighing roughly 10 to 35 pounds, with wiry or smooth coats and a confident, lively outlook. They tend to be loyal and affectionate, but barking, digging, chasing small animals and an independent streak are common. In San Juan, where small dogs share condo towers and busy sidewalks, that alertness works well with consistent training. A dog's size, coat and energy depend on its ancestry, so the dog you meet says more than the label.