Transformers.
One died in my tree. I actually took a photo. I’ll find the photo and post it. It looked like it was sleeping.
The poor thing looked like he curled up for a nap and never woke up.
My thought was, “the gullets of terriers.”
My parents had one die in their driveway. Looked like it had a heart attack. It was laying there, on it’s back with it’s feet all up in the air.
I was once involved in a test series at a site that had previously been used to study the effect of explosive blast waves on the human body. In order to be as realistic as possible, cadavers were placed in various positions at incremental distances, with different amounts and types of shielding from ground zero. The testing was classified, of course, and so instead of talking about cadavers, those directly involved with the test setup nicknamed them squirrels. Until the test series was over and they were allowed to talk about it, those of us not involved in the testing were very confused as to why they were taking all those squirrels up the mountain, and why we weren’t allowed to see said squirrels.
To answer the OP, the squirrels were already dead. They just weren’t as messy.
Sometimes the squirrels in my back yard will fall from the top branches of mature pine trees and scurry away, seemingly unharmed. Before I saw it I was sure such a drop would kill anything larger than an insect.
I came to post “transformers,” but was beat to the punch.
When I was in high school, I saw a bog standard grey squirrel leap off the back porch of a 3 story Chicago apartment building and glide to the alley below, land, and scamper off. It was definitely NOT a flying squirrel.
Unless they land badly, or on cement, they’ll probably survive most falls. In addition to their being a small animal which presents a lot of surface area in proportion to their weight, the huge bushy tail introduces a lot of drag. I wouldn’t be surprised if they pretty quickly adopt an optimal posture while falling, too. I don’t know what the terminal velocity of a squirrel is, but I’ll bet it’s very low.
This faq (appears to be a kid’s page), agrees:
http://www.squirrels.org/faq.html
Don’t know about that “cushion” bit, though. Have you watched how they land after exiting your pine trees?
Yep, when we were kids we forced a squirrel out of a tree with a football. It leaped out of the top of the 20 foot tree and sailed to the grass below and scampered away.
“Hey Chirpy, go long!”
Umm, yeah, cough cough…
It’s not like we chased the poor thing up the stairs with brooms or anything…
::backs out of thread::
They quickly run to cover, which would be expected, as long as the injury is not incapacitating.
After that, I can’t observe them well enough. But they seem to have a stable population.
After all, the squirrel falls are too infrequent for me to really notice.
Mental image of Optimus prime & others in redneck-esque hunting outfits
When I bought my house, I soon found out that the garage was hosting a large family of squirrels. Once I cleared them all out, I was removing the damaged soffits so they wouldn’t move back in. I found three skeletons, several partial skeletons, and one mummified squirrel. So I suspect a lot die over the winter. They just stay stuck in the nests, and get hauled away slowly by insects under the cover of spring’s lush green canopy.
Well, *I * thought it was funny. 
Before I learned this was not the way to do it, I would set spring mouse traps all over the basement. Of course I forgot where I put some in obscure places and once I uncovered the results of a years-old mouse. Only fur and bones were left; no skin, flesh, body or other parts whatsoever. It was just a flat, fuzzy, bony blob. I imagine bacteria and insects worked on it for a very long time.
That’s when I decided to use only one or two traps in more accessible places and check them often. Make the trap attractive enough and the mice come to me; it’s a lot easier and less morbid.