bestiary question!

[Neronoxx]

Small snag in a campaign i am in. many monsters in their entry, such as wolves have an attack that reads as follows; bite +3 (1D6+3 plus trip)
Does this mean the wolf performs a trip CMB after hitting? Or does he auto trip? Can someone direct me to the appropriate rules section please?

[Suthainn]

It means he gets a chance for a free trip attempt at his usual CMB after a successful bite attack.

http://www.d20pfsrd.com/bestiary/rules-for-monsters/universal-monster-rules #TOC-Trip-Ex-

[MurphysParadox]

When you hit with an attack that says "plus trip", you may choose to take a free trip attempt which does not provoke an AoO. It occurs after damage is dealt and may only be taken if the attack hit.

[Neronoxx]

Cool, thanks guys!