Smart, loyal and affectionate, shelties make great family pets. They are easy to train and handle in part because they are eager to please. Unfortunately, shelties have an inherited tendency that's not so pleasing: nipping humans in an effort to round them up, thanks to their long sheep-herding heritage.
In most cases a sheltie nipping at someone's heels is not a sign of aggression but an expression of generations of herding instinct. Shelties were bred and trained to herd sheep by nipping at their ankles. This trait manifests today in attempts to herd humans, especially children, by nipping at heels, ankles and hem lines. Knowing that the behavior comes from herding instinct, not from aggression or intentional misbehavior, is important in stopping it. Your sheltie needs to learn that herding humans is unacceptable behavior; however, he should not be treated too harshly since he is responding to a situation out of instinct, not to intentionally hurt someone.
Puppies often nip each other during play; it's this roughhousing that helps them learn boundaries. If one puppy bites too hard, the bitten one cries out and the biter ceases. In the same way, a human can stop a sheltie from nipping by blurting "ouch!" or "no!" when he nips. Sheties are sensitive to displeasure, and a scowl or deep-voiced "stop" should discourage a Sheltie from nipping. The idea is to get the dog's attention immediately when the bad behavior occurs and help him understand that the behavior is unacceptable.
It's not quite the time-out you'd give to an unruly child, but has much the same effect. As highly social creatures, shelties crave attention. Simply ignoring a sheltie for a minute or two will often result in him trying to find a way back into your good graces. Once he realizes that nipping results in social isolation, he is likely to stop. For an especially exuberant dog or puppy, a few minutes in a crate or kennel may have the same effect.
The best way to keep a sheltie from nipping is to train him to obey specific commands, such as "sit" or "stay." Basic obedience training takes time and consistent practice, but is an effective way to take control any time your sheltie nips or displays any unwanted behavior. Any time he acts as though he is about to nip or actually starts to do so, use a command to direct his attention to obeying you, causing him stop. also provides an extra safety measure for a sheltie that decides to try to herd cars or animals that could harm them.