i hate how many public resources online are just barely more informative than a 9-year-old's picture book. you try to google something like "squirrel white thrush" and get cute descriptions of their molting cycle. so you try "pnw tree squirrel diseases" and you get a colorful pamphlet describing how You Can Avoid Conflict With Your Furry Neighbors
so you say fuck it, i'm not playing around any more and search "squirrel anal bleeding" and finally find an ancient thread on an old php board where folks who rescue and rehabilitate squirrels all over the world are here and generally agree that it's a sign of severe GI distress, could be a bacterial infection, could be viral, could be worms, but yeah all the blood and lethargy is pretty serious and that poor tree rat is not long for this world if it's wild and not a creature you can get to a vet
which, okay, good, so i'm not crazy for tackling the dog before she tried to chomp and probably eat this poor sick creature, we really don't want to be patient zero for covid-24