We all know marine mammals are intelligent . Dolphins in particular can remember events and learn concepts , adapting their behaviour as a result of previous experiences . They communicate with each other to create complex hunting and feeding strategies , manage relationships in their pods and have intimate bonds with their young . They understand not only words , but can interpret the order of words . The signature whistles produced by dolphins even show some evidence that dolphins have a self-awareness , or the capacity to have a concept of ‘ self ’ and to know that one exists as an individual being .
Much of this comes about through the remarkable nature of marine mammal brains . The sperm whale has the world ’ s largest brain , weighing in at up to 8kg compared to human ’ s 1.3kg brain . However , the current
PHOTO : SIMON ROGERSON record holder for total number of brain neurons – those wonderful nerves that process and deliver information - is the killer whale , with over 40 billion cortical neurons .
Pilot whales come a close second , with 32 billion , twice the number of an average human . Dolphins also have the most folded brain surface of any creature on the planet . The more folded the brain ’ s cortex area , the more room within the brain to house additional neurons with which to perform processing of information .
Further , marine mammal brains contain a special kind of brain cell called a spindle neuron , associated with advanced abilities such as recognising , remembering , reasoning , communicating , perceiving , adapting to change , problem-solving and understanding . What marine mammals ’ brains do seem to have lost , however , is a pretty standard layer of mammalian cells that help information process from one side of the brain to the other . Why would this have happened ? It seems it ’ s likely to be related to cetaceans ’ ability to sleep with one hemisphere of the brain remaining awake while the other half sleeps . A very useful thing indeed .
All these innovations in the brain feed through to the senses . Apart from river dolphins that live in murky , sediment laden waters , dolphins have good eyesight , albeit mostly in shades of black and white . But where they excel is hearing . Their upper limit of hearing is over three octaves higher than that of humans ; they have an ability to map sounds 30 faster than humans .
They can also echolocate , producing short broad-spectrum burst-pulses that sound to us like clicks . These clicks are reflected from objects of interest to the whale and provide information on food sources . But how ? It all comes down to two areas of fat deposits in the head . When the animal creates the echolocation sounds , they are focused into a directional beam by the bigger of the fat deposits , known as the ‘ melon ’, that sits in the brain case . In turn , the echoes reflected from food sources are received at the ‘ acoustic window ’ fatty area in the lower jaw , where the bone is very thin and from there transmitted to the middle ear and onwards to the brain for interpretation , where there is an entire region of the brain dedicated to understanding the results of echolocation .
Whales and dolphins really are incredible creatures . Their intelligence is of an unearthly kind , almost literally , evolved and adapted to survive and thrive in their lives in the ocean . How incredibly lucky are we when we dive to be able to enter their worldview for a short while , to even hear – or feel – their communications , see their curiosity and inquisitiveness at the presence of what must be strange and awkward divers in their waters . �
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