Animals' ears are very sensitive and can hear sounds that humans can't hear. In nature, all kinds of sound waves and signals can be heard all over the world, most of which are inaudible to human beings. Scientists estimate that humans can hear less than 10% of animal sounds. People's ears can only hear vibration waves with frequencies between 20 Hz and 20000Hz. People on other frequencies are deaf. However, the frequency range of sounds heard by different animals is also different. For example, cats can distinguish between 30-4500 Hz, chimpanzees can hear up to 30000 Hz, dogs can hear up to 60000 Hz, foxes can hear up to 65000 Hz, bears and rhesus monkeys can hear up to 80000 Hz, cats and guinea pigs can hear up to 1000000 Hz, and mice and mules can hear up to 65438.

Mammalian external ear includes auricle and external auditory canal. Auricle is unique to mammals, supported by elastic cartilage, and has become a highly precise and sensitive sound acquisition device. However, the auricle structures of various mammals living in different environments are quite different, thus forming various "ears".

Undoubtedly, the most striking thing is the huge "wind ear". Big ears can increase the sound collection area and make you hear more clearly. Humans often put their hands behind their ears in open places to improve their hearing. Generally speaking, nocturnal mammals or mammals living in open areas have relatively developed ears, such as bats, rabbits, dogs and ungulates.

As hearing organs, animals' ears can work even when they sleep, but they are not as sensitive to sound as when they are awake. However, because animals have an "early warning center" in their brains, their hearing becomes a reliable guardian, which can report the danger to them in time and force animals to wake up and take action.