Ooh. That's a good one.
On the other hand, the bear-monster would be an apex predator on any other planet. It's hard for me to believe that anything eats them except the giant ice-monsters. And species with few predators generally don't evolve to be poisonous. That's mostly reserved for species too weak to fight back against predators and too slow to run away (like frogs and beetles), because they need a defense mechanism that works just as well even against a creature you cannot hope to defeat or escape.
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Oh, I don't care much for any of those. But I have a soft spot for Matildas specifically. Though the only one I ever got to see was in a sorry state; it took an 88 to the turret at the Halfaya Pass and hasn't been the same since.