Do big animals have big ears and small animals have small ears? No, animal ears are many sizes and shapes.
Most ears have an outer ear (a pinna, a canal, and an eardrum), a middle ear, and an inner ear.
The pinna is the fleshy part that is visible. It is made of cartilage, not bone, so it is soft. It usually also has an ear lobe. The pinna directs sound through the canal to the eardrum.
The pinna has a muscle that moves the ear. For example, elephants and dogs can move their ears. Animals move their ears in the direction of a sound so that they can hear better.
Not all animals can move their ears because they have weak and non-functioning ear muscles. Animals that cannot move their ears include gorillas and monkeys. Humans cannot move their ears (without touching them).
The pinna (also called the auricle) can be large, small, rounded, pointed, hairy, hairless, moveable, and not moveable.
Only vertebrate animals have outer ears – the pinna. Vertebrate animals are animals with a backbone or spine.
Reptiles do not have an outer ear – they have an opening (often with an ear flap) and an eardrum. Snakes do not have outer ears, but they have internal ears, and respond to vibrations and movement, rather than sound. Birds do not have outer ears, and their ear opening is usually covered by feathers.
Invertebrate animals, such as insects, often do not have ears. Insects may have a tympanal organ (eardrum) on its head or elsewhere – crickets have an eardrum on each side of their abdomen. Spiders and cockroaches do not have eardrums – they have hairs on their legs, which help them to hear sounds and detect vibrations.
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM