Zikes!  That is a nasty infestation on that squirrel though, I sometimes wonder how long an animal will last with such an overload as the ticks are parasitic, deprive the host of nutrients and cause disease within the host. The picture below is the unique reaction from a tick bite, it is commonly known as a "Bulls eye rash" the medical term is Erythema  Migrans sign ,  the rash size usually ranges from approx 2-18 inches but can be up to a metre and occurs in around 65-80% tick borne in