Hi I'm not a biology or science student. So, please keep your replies in plain and straight language so you could be understood. Thanks. Do animals and birds also become unconscious during their deep sleep like humans? Among humans the extent to which one is absorbed in one's sleep varies, some become awake at the slightest noise, and some simply sleep like a log, or more accurately like a dead. It is my naive and general observation that animals and birds don't enter the deep sleep stage. In other words, they simply close their eyes when need to sleep, yet won't really become unaware and unconscious of their surroundings like humans.