Prey Drive

Dogs who were bred to hunt, such as Terriers, have an inborn desire to chase--and sometimes kill--other animals. Anything whizzing by, such as cats, squirrels, and perhaps even cars, can trigger that instinct. Dogs who like to chase need to be leashed or kept in a fenced area when outdoors, and you'll need a high, secure fence in your yard. These breeds generally aren't a good fit for homes with smaller pets that can look like prey, such as cats, hamsters, or small dogs. Breeds that were originally used for bird hunting, on the other hand, generally won't chase, but you'll probably have a hard time getting their attention when there are birds flying by.

• See Dogs Who Have Low Prey Drive