Rats - dealing with what appears to be a colony of them
If you're not squeamish, a trash can with a diving board and a pool of water in the bottom will kill hundreds of rats with low effort.

Actual trap: https://www.ebay.com/itm/Original-Dunk-The-Rat-Trap-Rat-Squirrel-Trap-Auto-Reset-USA-MADE/132422341963?ssPageName=STRK%3AMEBIDX%3AIT&amp;_trksid=p2055119.m1438.l2649

Review/setup: https://www.youtube.com/watch?v=YfaDQJVplYI