Right-flippered humpbacks and left-pawed tomcats
http://www.irishtimes.com/newspaper/wee ... 08512.html
MICHAEL VINEY
Sat, Jun 18, 2011
ANOTHER LIFE: IN THE 13TH YEAR after her rescue from a dog orphanage, Meg, a cuddly cross of Labrador and spaniel, is living on borrowed time. A swim through the river to the big strand below us no longer prompts those wide and ecstatic circlings over the sand; instead, more and more often, there are hopeful pauses to suggest we might go home again.
When she did run, which way was it: clockwise or anticlockwise? My mind’s eye says the former. A reader, John Elwes of Kilballyquilty, in Co Waterford, reports that his “very intelligent border collie” runs anticlockwise, prior to rounding up bullocks. He suggests an exploration of the handedness of animals in general: how unique are people in using left or right?
Debate on the significance of handedness in nature goes back centuries to philosophers like Leibniz and Kant. Even in this column, over the years, the handedness of snails and climbing beans has seemed fit for disquisition. Down in the dunes, the prettily banded Cepea nemoralis follows most snails in coiling to the right (except occasionally it doesn’t). And, down in the polytunnel, all the climbing beans are coiling up their strings anticlockwise (unless you’re looking up from the bottom, like a bean).
Back to the circling dogs, engaged in what science now calls “behavioural lateralisation”. One might conjecture about inheritance from wolves, reported as patrolling their hunting routes “always counterclockwise”. But the abundant research into lateralisation now spans almost the whole of the natural world, whether as preference for a single paw or foot, or for going around in circles.
Earlier this year a report from an Australian university made newspaper headlines around the world. Dr Culum Brown and a student, Maria Magat, of Macquarie University, in Sydney, studied 322 parrots of 16 Australian species to see which eye and claw they preferred in looking at and picking up food.
For every species except one, and in almost every bird within a species, eye and claw were matched. And in four of the species almost every bird had the same preference, with matching eye and foot.
“Ocular dominance” seems to be the key, and preference for one eye or the other is linked to which side of the brain deals with certain functions. Parrots are among the few families in nature that show as marked a handedness as humans, about 89 per cent of whom (let’s be accurate here) are right-handed. But while sulphur-crested cockatoos all end up left-footed, they start off in life experimenting with both claws, much like human babies. And as the left hemisphere of the brain controls the body’s right side and vice versa, handedness may depend on how analysing information and control of tasks are shared and co-ordinated between the two sides of the brain.
Humans have eyes at the front and don’t have to choose which one to use. But most fishes make the same choice as most birds (though diving gannets have exceptional binocular vision), and tormenting fish in tanks with scary stimuli can suggest a preference for keeping the left eye on danger. That fascinated some researchers, as the brain’s right side is often involved in emotional response.
Among dogs and cats, however, paw preference seems strongly linked to gender. Research at the canine-behaviour centre in the school of psychology at Queen’s University Belfast by Dr Deborah Wells found the paw-use preference in 53 dogs was strongly linked to their sex: males preferred the left paw, females the right. Her team then turned to family cats, 42 of them, studied in their familiar domestic settings. Invited to reach for a chunk of tuna in a jar, or a toy mouse suspended on a string, tomcats, again, preferred the left paw and females the right. (Do try this at home.)
Whales are mammals, too, and Atlantic humpbacks are under increasing study as identifiable individuals. A Woods Hole scientist, Dr Philip Clapham, has judged from scars on their jaws that 80 per cent turn on their right side when brushing along the bottom to scare up sand eels. They also use their right flippers much more in water-slapping displays. All this, he suggests, shows a measure of “population-level asymmetry” matching well with right-handedness in humans.
Most of the 11 per cent of human lefties are men. What, if anything at all, that signifies for behaviour could rashly be inferred from the work of Prof Lesley Rogers with a long-established colony of marmosets in New South Wales. The right-handed marmosets, she finds, are more adventurous, tending to rush into new surroundings and not always able to find their way out. The lefties hang back and think twice. Where that puts President Obama, who signed the visitors’ book at Áras an Uachtaráin with his left hand, may properly be left to history.
Humans have eyes at the front and don’t have to choose which one to use. But tormenting fish with scary stimuli can suggest a preference for keeping the left eye on danger
