I think its something to do with lack of vitamins and nutrients and sleep. There are loads live in my town and you can spot the a mile off.
I laugh at them though...
well its a real shame but they only got themselves 2 blame for making the filthy choice in the 1st place,if i had it my way i would drive around with a shotgun hunting them down then putting them out of their misery an stop them causing more carnage.