Mammals are the only animals with external ears or pinnae. To call them ears is a little misleading as the main part of the ear is internal and the pinnae are merely a receptor to pick up the sounds that are then sent to the inner ear for processing.
By Leigh Kemp
Botswana Wildlife Guide to Animal Hearing
The pinnae are able to swivel
enabling the animal to listen in more than one direction. When watching animals it is noticeable that, even though they are looking in a particular direction, their pinnae are listening all around them by swivelling.
The pinnae are not used solely to pick up sounds as with many mammals, including Elephant and Steenbok, they have intricate networks of veins
in them that cools the blood flowing through the pinnae and this in turn keeps the animal cool.
All the Better to Hear With
Kudu live in woodlands where often their vision is obscured by trees and bushes - making it necessary to have good hearing. With large pinnae the 'reception' are is greater allowing for excellent hearing.
Bat-eared Foxes also have large pinnae allowing them to pick up the sounds of insects up to 30 cm under the ground. They hunt with their ears close to the ground. Hippos on the other hand have very small pinnae as they spend a great deal of time under water and due to their size they do not have many predators.
As part of the conservation plan for the larger national parks in Africa such as Kruger National Park in South Africa and Hwange National Park in Zimbabwe, animals were culled to prevent the park from been overgrazed. In the beginning only selected individuals in a herd were taken out but it became obvious that the whole herd suffered trauma and the social behaviour of the herd changed after each cull.
It was then decided that whole herds would be culled. What was then found was that herds in the vicinity would react to a cull. Questions were asked as to whether the sound of the helicopters and rifles were heard by the other herds that had experienced culling in the past. It has been found that Elephants communicate ultra-sonically over great distances and this is why the other herds in the area reacted to the trauma.
Despite the fact that most animal behaviour studies have discarded the idea of animal intuition, or ESP, it needs to be discussed as it may well it play a major part in species behaviour and survival.
When the great tsunami struck in 2005 most animals in the affected areas survived and there were reported sightings of them heading for higher ground before the wave struck land in most places. How can this be explained by using the five senses? It is argued that the animals felt or heard the vibrations of the initial earthquake or the rolling of the massive waves.
There was a concern for the tribes living on the remote islands
but most of them survived the wave. How? By moving to higher ground! How could they know what was about to happen? These were 'uncivilized' people and yet they survived the most tragic natural occurrence to hit the earth in recent history. With all our advanced technology we were unable to forewarn those affected.
The animals and remote tribes had a forewarning! Did the people take their cue from the reaction of the animals or did they have their own inner warning? How can we as a developed species understand this? With our advancement we have lost much of our natural instinct as we do not need it anymore.
We were once as the remote tribes are now but have advanced and become arrogant believing that our technology and development is our salvation.