Those bushy tails actually serve a vital purpose, helping the squirrel balance when climbing and jumping, slowing the fall when jumping from one object to another. When the squirrel becomes distressed, they will flick their tails back and forth and chatter loudly to warn their neighbours. So they use their tails for a signalling device... (Source: Starry Skies)
Balance is something we all take for granted but it's development and degrees of finesse are beyond the most advanced programs at the moment.The inplications are interesting and there is a lot of research into it atm.
There was a tail-less squirrel in my garden yesterday. He looked really odd. Lacking a tail didn't stop him climbing the fence and running along the top of it. I'm not sure how long he will survive in the wild though, especially as we have foxes who visit every night.
I think it might have something to do with being perturbed or agitated. I've had problems with squirrels eating bird seed on our deck. So I decided to put the bird feeder where the squirrels couldn't get to it. I tied a pipe wrench to the end of a long piece of clothesline and heaved it over a high branch in ront of our second floor deck (we live on the cove of a lake). I untied the wrench from the rope and tied the bird feeder to it after filling it. I then hoisted it over a branch high enough to have a good view from our large windows. Shortly after that I noticed a squirrel climbing up the tree to the level of the feeder. He was twitching his tail vigorously when he realized that it was too far to jump to. He did this at least two or three times from two different trees. He was angry!