Battle defense put the paralyze and disarm on the pet.
Battle Defense: Trains the creature in the disarm and paralyze special moves. Also trains the creature in the Heightened Senses, Shield Bash and Bodyguard mastery abilities.
The only thing that I can verify that it does is the Bodyguard Mastery from Parry. That is why it does not show up as a training choice on pets that can get it, until they have 100 wresting skill, which then activates Parry.
This is the
player mastery abilities:
Parry
Title: The Deflector

Shield Bash
When activated the shield user will execute a shield bash on successfully hitting or parrying their opponent causing physical damage and paralyzing their opponent, interrupts spells if players are not immune to paralyze, based on parry skill, best weapon skill, and mastery level. Damage is capped in pvp at 35.

Body Guard
The shield user chooses a protectee to absorb a percentage of damage done to the protectee based on parry skill, best weapon skill, and mastery level.

Heightened Senses
Toggle ability that provides the Parrying Master with increased chance to parry based on parry skill, best weapon skill and mastery level that consumes mana while active.
On Pets:
Body Guard on pets does not work like it does on Players. When you tell the pet to Guard you, it will activate Body Guard when it chooses to. You will see the buff in your buff bar.
Then it reduces damage to both the player and the pet by by 50%. I have never seen the pet lose HP when only I lose HP.
It lasts 60 seconds.
Heightened Senses Sounds like confidence and provides the Pet with increased chance to parry based on Parry skill and Wrestling. It consumes mana while active.
Shield Bash on Pets: To be determined
But, Disarm is useless in PvM and Paralyze was nerfed to a point of lameness, that those 2 are wasted moves that the pet will use.
I do not know what shield bash does or sounds like.
Maybe you are hearing one of those.
But Body Guard on the pet makes it take half damage when active, It Allows the pet to tank very well, But usually you can not put it on a pet with enough other things to make it a useful pet. But I will check out this on a Beetle.