Cheryl brings the nail clippers out and moves cautiously toward Cooper, her Lhasa apso. She has learned that Cooper puts up a fight each time she tries to clip his nails. Cooper even bit her once during a previous attempt.

Cooper sees her approach and retreats to a corner of the room, ears down and tail tucked. When Cheryl reaches for a paw, he growls at her. When she brings the clippers to the nail, he snaps at her. Cheryl fears a bite will come next, so she steps away, putting off nail clipping for another day.

This scenario is a common one and can represent a serious issue in the dog-owner relationship. Many dogs like Cooper also show aggression toward their owners in other situations, such as when they are being moved from a couch or bed, when they are stepped over or awoken while sleeping, or when they are approached while eating or chewing on a toy.

These behaviors (traditionally called

dominance aggression) are characterized by animal

behaviorists today as avoidance, or escape-maintained aggression. What this means is that dogs learn to use aggression as a way to avoid, or escape from, annoying or aversive situations.

For example, when an owner approaches a dog in possession of a valued resource (such as food or a comfortable resting place), the dog may perceive this approach as a threat. Fearing loss of that resource, he may use aggression. If the owner retreats, the dog learns that aggression was effective in protecting the resource and is more likely to use the same aggressive response in similar situations in the future.

Similarly, many dogs find nail clipping mildly uncomfortable.

They may choose aggression as a strategy to escape from or avoid these grooming situations. When they are successful in getting the owner to back away and cease grooming, their aggressive behavior is reinforced and more likely to occur again the next time they are in that situation. Once the aggression is fully developed, however, most owners cannot simply force their dog through a nail clipping routine because they will be bitten. (This also can be quite stressful for the dog.)

Instead, owners must change the motivation for their dog’s aggression in the first place. Owners can accomplish this using a strategy called shaping, in a program of rewarding calm, tolerant behavior during grooming. Shaping involves reinforcing, or rewarding, baby steps along the way toward a goal behavior.

In the case presented above, Cheryl’s goal behavior is to have Cooper calmly tolerate nail-clipping without growling, snapping, biting or pulling away. She first breaks down into steps the behaviors she will reward along the way to reaching that goal. She brings a bowl of highly valued treats (e.g., chicken or hot dog pieces) to Cooper. She first pets Cooper’s leg, immediately praising and providing a treat as she does so.

When she has done this several times and sees that Cooper is relaxed and focused on the treats, she then touches his paw, praising and treating the

moment her hand caresses his nails.

When he is relaxed at this stage, she lifts Cooper’s paw in her hand just briefly before she praises and treats. From there, Cheryl would move on to tapping his nail with the nail clippers, placing the clipper around the nail itself with gentle pressure, and finally clipping the nail, providing praise and treat each time.

At every stage of this process, Cooper should remain calm and treat-focused. If he is becoming tense or aggressive, this tells Cheryl she is moving too quickly and she should drop her criterion to something easier until Cooper is again relaxed and tolerant.

By moving gradually and systematically through a series of shaping steps, Cheryl can teach Cooper that nail clipping is something to enjoy and look forward to, thereby eliminating his motivation for being aggressive toward her in this situation.

Cheryl hopes that one day soon she will have Cooper bouncing merrily toward her for his regular nail clipping, having learned that nail clipping means yummy morsels for him.

Megan E. Maxwell is a certified applied animal behaviorist. She owns Pet Behavior Change LLC ( www.petbehaviorchange.com) in State College.