Dolphins show right-flipper bias, scientists have said. Studies on one group in the Bahamas found they also preferentially use their right eye and echolocating “lips” on their right side while hunting for prey.
A study published in the Royal Society Open Science journal suggests this indicates a specialisation in the left-hemisphere of their brain, the side that processes information from the right visual field.
Similar to other aquatic mammals, bottlenose dolphins show a right-side bias in foraging behaviour, according to Dr Jennifer Kaplan, from the Dolphin Communication Project in Florida, and colleagues.
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In Bimini, they display a unique behaviour, making sudden sharp turns while echolocating on the bottom for prey.
Researchers found the animals frequently execute a sharp turn before burying their snouts in the sand.
Based on data collected from 2012 to 2018, they found a “significant” right-side (left turn) bias in these dolphins.
Out of 709 turns recorded from at least 27 different individuals, 705 were to the left – right side and right eye down.
Only one individual turned right – left side and left eye down – in four out of four turns.
The authors say: “The dolphin brain is capable of integrating visual and echoic information, enabling it to ‘visualise’ an object’s shape through sound alone.
“Thus, these crater feeding dolphins may be processing and integrating visual and echoic information in their left hemisphere.
“Whether driven by anatomical structure or hemispheric specialisation in sensory processing, a left turn/right-side bias in crater feeding common bottlenose dolphins provides a strong demonstration of laterality in behaviour.”
Reader Q&A: Why are some people left-handed?
Asked by: Oliver Stewart, Cobham
Being left-handed is the result of genes and environment. About 50 per cent more males than females are left-handed and 17 per cent of twins are, compared with about 10 per cent in general. The ‘vanishing twin’ hypothesis suggests that left-handers were originally a twin, but the right-handed foetus failed to develop.
Brain dominance also appears to play a part. Most people are right-handed and have language controlled by the left hemisphere, and most left-handers are the opposite. However, some left-handers have language processing in the left hemisphere, or in both.
The genetic basis for left-handedness is complicated. Even if both parents are left-handed there is only a 26 per cent chance of their child being left-handed. Possessing the ‘LRRTM1’ gene increases the chances, but only if it is inherited from the father.
But whether you become left-handed or not is also dependent on development. It may be influenced by levels of testosterone or oestrogen during pregnancy, and early experience with holding and throwing things can also affect later hand use. Finally, damage to the right hand can make people left-handed.