Dear Cathy,

My dog, a Yorkie-Pekinese mix, barks at every noise he hears. He goes into a frenzy when someone comes to the door. If I let them in, he is very aggressive and will even bite visitors. If I leash him, he gets worse. He is 4 years old. I adopted him three weeks ago from a shelter. They did not tell me that he bites. Is there something I can do to make him less frightened and less aggressive? — Myrna, CT

Dear Myrna,

You’re smart to realize that aggression can be related to fear, and your newly adopted dog might be intimidated by your visitors. Ask the animal shelter about his behavior. If he is this aggressive now, he must have shown some aggression at the shelter. Perhaps they can offer you some training support to help modify his behavior.

In the meantime, if you’re ready to roll up your sleeves, there are things you can do to reduce his aggressive behavior. Please be persistent and consistent with the training over the next several weeks. The more you practice, the quicker your dog will learn.

The first thing to do is remove him from being a door greeter. Not all dogs are built for this task. Instead, buy a wire dog kennel (large enough for him to stand, turn around and lie down in) and put it in your family room. Put him in the kennel a few times a day for about 10 minutes at a time, along with a special treat or toy, so he gets used to the space. Then, when a visitor comes over, put him in the kennel with the toy or treat. This allows your visitor to enter your home safely and keeps your dog from acting on his worst instincts.

If he barks or fusses while in the kennel, ignore him. If he settles down, let him out of his kennel on a leash (until you are sure he won’t growl or bite someone). If he gets aggressive, put him in the kennel again (no admonishments), but this time without the toy (only reward positive behavior). Over time, he should learn he won’t get to greet anyone until he behaves.

Another approach involves you modifying behaviors one trigger at a time. You can do this instead of the kennel training mentioned above or after the kennel training if you don’t want to put your dog in the kennel every time the door rings.

Have a friend come over to your home and ring the doorbell. If he gets aggressive, ask him to sit and stay. (Put a leash on him while training.) When he settles down, ask your friend to ring the bell again. If he gets up, make him sit and stay. Do this repeatedly until he sits and stays when the doorbell rings.

Next, open the door. Your dog may get up and start growling. Close the door. Ask him to sit and stay again. Repeat until you can open the door and he remains in the sit position

Next, have your friend step into the house. If he begins growling, the friend needs to go back outside, the door needs to be closed, and your dog needs to sit and stay. Do you see the pattern? He needs to be trained at every step of the greeting process.

The goal is to have him sit at the door when he hears the bell, sit when the door is opened, sit when a visitor enters, and sit until you release him. Dogs can’t do two things at once, so if he is sitting, he shouldn’t be growling.

You may have to do each step 20 times, three times a day for a few days before you can move to the next level. Be patient and make sure each behavior is solid before moving onto the next desired behavior. I know you can do this, Myrna. Keep me posted.

Dear Readers,

A few weeks ago, I shared a cat nail clipping tip from Doug in Wethersfield, Conn., in which I wrote, “Sneaking up on cats and clipping their nails while distracting them and without holding them or touching them is definitely a ninja move.” While this is actually a technique I have used many times to get a nail clipped here and there on my cats, I incorrectly reported Doug’s approach, which included picking them up gently. Doug asked me to let my readers know, that he would never sneak up on any of his cats for any reason.

Cathy M. Rosenthal is a longtime animal advocate, author, columnist and pet expert who has more than 25 years in the animal welfare field. Send your pet questions, stories and tips to cathy@petpundit.com. Please include your name, city, and state. You can follow her on Twitter @cathymrosenthal.