The mechanics of the game won't let you tame a pet that's higher level than you are. My guess would be that, as a result of this mechanic, your pet cannot level higher than you are at any time, and therefore, will not gain exp to the next level until you are at or above it's next level.
RE: Pet experience
The mechanics of the game won't let you tame a pet that's higher level than you are. My guess would be that, as a result of this mechanic, your pet cannot level higher than you are at any time, and therefore, will not gain exp to the next level until you are at or above it's next level.