A drive by nutting from a rival squirrel gang.
He's finally had enough of his wife bugging him about acorn hulls all over the nest.
Are you sure its a squirrel as I have not seen chipmunk ernie lately
He could have eaten the poison put out for rats and mice.
Squirrel turf wars? I saw a squirrel using a little red hankerchief this morning. *he was actually licking something off a square piece of plastic
Snake spider bite
Generic heart disease ? Lol
Scared off before he could snack perhaps
Leave it out there
Maybe a mocking bird dive bombed him and hit him just right...or wasps, a scorpion, a spider, poisoned nuts. It is curious. Too bad he disappeared before you could look more closely.
Well, if my dog is in your neighborhood ......
Oh! Everything dies at some point. Could be just an old rodent.
Yeah, old domestic animals look ragged but animals in the wild die a lot younger than our pets.