They cause some sort of trouble or mischief, and one of the crew catches on and devises a way to catch it (or one of them). My Google-fu has failed me on this one.

Additional info:

* Strong feeling that this was a short story
* Likely a prolific writer from the 50s-60s that I found on Project Gutenberg
* Not Peter Watts' Blindsight, though that returns the most hits on searches
* Don't recall what the creatures did that was problematic, but one of the (two-man?) crew puzzled it out from clues and caught it maybe by anticipating its moves. It's fuzzy, so don't get hung up on this bullet point's contents.