It could be a herd. [ That's actually an interesting theory, eyes still on the two beasts ahead of them as he muses out loud. ]

Judging from their trails, they could also be searching for something specific on the ship. Or it might be their instinct to find and kill specific traits.

But that also might mean there's someone who set them loose here on purpose, unless there's a reason for a bunch of them to climb on to a space ship somehow.