Looking for the author and name of a short story that is about a Roman caravan that is traveling to the Colosseum to sell animals for combat with gladiators.
They have all kinds of animals, including a tiger. Somewhere along the way, they've picked up an alien who has claws and seems wicked-smart - though doesn't talk.
Eventually, the alien escapes. The only thing that saves the protagonist is that the tiger HATES the alien and escapes himself and they fight it out to the death of both of them.