Traders Risk

It is a novel book. Keeping this cargo meant death--to jettison it meant to make flotsam and jetsam of a world! More of a comic book story than a serious short story. There are two aliens, who evidently look like owls (the descriptions are not very good), transporting a ravening beast (who never gets described) to a zoo, when it escapes into their space ship. They land on a supposedly uninhabited planet to dump the animal, and find humans have colonized the planet. There is a spy among the colonists trying to discover the secret of the calming crystals.