Varmint undermining barn floor/foundation
Hello, I have a critter of unknown species digging the very hard-packed gravel out from under the cement floor of my barn and depositing it in a large pile outside the barn. If it continues the floor will crack and fail. I don't want to put out poison because I have dogs and cats. Can you make a guess as to species? Raccoon/possum/skunk? Any ideas on how to trap or discourage it? Thanks very much for your help!
Multnomah County Oregon vertebrate pest management
Without additional clues it would be difficult to diagnose with certainty what critter is doing this. However for now, let's think about ground squirrels - Have a look around for additional (smaller) potential entrances beneath the building through which the animals are accessing the gravel.
Managing this problem will likely require you to deploy multiple tactics. See for example, some designs http://icwdm.org/handbook/rodents/ro_b151.pdf for traps that you could use that you could modify (in placement and design) to avoid accidentally hurting your domestic animals. In the longer term, although it would potentially require a significant investment of time, money, and effort, protecting the perimeter of your barn is going to be really important to avoid losing that floor at some point. See the Foundations and floors section of this handout http://icwdm.org/handbook/rodents/ro_b137.pdf for some ideas to block the diggers' access to your building's undersides.
Finally, keep an eye out for animals near the building - If this damage is from ground squirrels, their daytime behavior should help give them away. If you're NOT seeing any daytime animals sneaking around or under the edge of the building, then we need to look for additional clues as to ID'ing the cause. Regardless, thinking of how to critter-proof the undersides of the building will be an important step moving forward.