Boxer Bark/Howl

Question
I have a male boxer, almost 2 years old. Just recently we got a female boxer, 5 months old.   They get along very well and play all of the time.  My male has always had a calm demeanor, but recently has been barking/howling/growling at everything that goes bump.  He would bark at people who come to the door, or if he hears a doorbell, etc.  But over the last week has been dramatically different with his barking and such.  Before when the fedex guy would come he would bark.  Now he puffs up, the hair on his back stands up, and he low growls or howls at him or anyone else he sees.  Is this a cause for concern or a normal behavior for the boxer?  

Answer
He is exhibiting the typical alpha protector behavior. He has a female in the house now, and will play the part of the big, bad protector.

In order to teach him it is unacceptable behavior you will need to be consistent in training.

Get a whistle and each time he barks, growls, or acts aggressive, blow it to stop his behavior- it will startle him and he will stop. Then you can verbally reprimand him and if necessary, leash him and remove him from the area he displayed the aggression.

After awhile, you can leash him and make him stand at your side at a heel position while talking to the person at the door-- soon, he will be able to ignore it.

The whistle will become an alarm to him to stop what he is doing. It will be an instinctive sound.

You should see an improvement within a month if you are consistent.

If necessary, give him a treat when he does not bark at the front door. Soon, knocking at the door will become a delight for him. Maybe keep a cookie jar of treats on a foyer table near the front door for these occasions.

(BTW, most Boxer howls are what we call a "woo-woo" which is playful-- if it is a real howl, then it is an alarm signal for you to beware of impending people.)