Updated. I threw a little flavor text in there, based on the Wikipedia entry.
Caves might not be available, so I suggest "preferred" instead of "usual". Oh, and mention where they live if caverns aren't available.
I'm thinking "inbex" should be "ibex". Also, I don't believe they habitually prey on wooly rhinos, they're more an occasional victim. Also, the Fiend Folio uses rhinoceroses for multiple examples of the dire rhinoceros, so I think we should use that spelling instead of rhinoceri.
How's this:
Cave hyenas get their name from their preferred choice of lairs. If caves aren't available, they dig out deep dens.
Cave hyenas are opportunistic predators and scavengers. They mainly prey on herd animals such as horses, ibex, and deer, but occasionally eat creatures as big as wooly rhinoceroses. They are willing to steal kills from neanderthals and other predators, and in lean times may turn to cannibalism. Cave hyenas often drag prey back to their caves, accumulating bones and horns for later consumption or for their young to play with.
A cave hyena is about 4 to 5 feet long, stands up to 3 feet tall, and weighs around 225 pounds.
Oh, and the trip should have a +8 modifier (+4 for Str 18, +4 for Large), not +6.
That just leaves tactics, something like this...
COMBAT
Cave hyenas favor flank attacks. A couple of hyenas distract the foe from the front, while the rest of the pack attack from the sides and back. They focus their attacks on a chosen victim, trying to bring them to the ground with trip attacks.
A cave hyena are as courageous as most other carnivores. They will withdraw from a losing fight to save themselves injury or wasted effort, but are certainly not cowards.