Pocket Science – back-scratching disabled chimps and free-falling aphids

Not Exactly Pocket Science is a set of shorter write-ups on new stories. It is meant to complement the usual fare of detailed pieces that are typical for this blog.Chimp see, chimp do – back-scratching technique passes among disabled chimps Tinka’s hands are paralysed. His fingers are permanently flexed, he can’t bend his wrists and to top it all off, he has a chronic skin condition. His body itches frequently and without dextrous hands, he can’t scratch himself properly. Fortunately, Tinka is an ingenious fellow. He uses his motionless hands to grab a liana (a thick, woody vine) and, stretching it taut, he rubs his itching body against it. Tinka’s a chimpanzee and he has found a way of getting to those hard-to-reach places, like a human towelling their back. Tinka’s a member of the Sonso chimp community in Uganda, which has high rates of disability, inflicted by man-made snares. The snares were intended for duiker and bush pig, but with hundreds in the area, some chimps inevitably got caught. The snares have been removed but not before they inflicted permanent handicaps on a third of the Sonso chimps. But from this tragedy came an opportunity to study the spread of cultural traditions in wild chimps – an opportunity that’s been seized by Catherine Hobaiter and Richard Byrne form the University of St Andrews. It’s clear that chimps can pick up new traditions from one another in captivity but their ability to do so in the wild is unclear. In natural conditions, it’s very hard to spot the birth of a new behaviour and to identify the individual who started it. It’s also difficult to work out if others are copying the innovator or just performing acts that were already within their repertoire. But Tinka bucks the trend. His liana-scratch technique is his invention. No other chimp in Sonso, or anywhere else in Africa, does the same thing. And Hobaiter and Byrne have found that at least 6 other chimps have taken up the technique, all of whom lived in the same area as Tinka. There’s no element of active teaching here. After merely watching Tinka perform his special move, the apeing apes could do it themselves sometime later. Chimp see, chimp do. What’s more, many of these imitators aren’t handicapped and the technique doesn’t seem to offer them any benefits – they could just scratch or groom themselves if they wanted. Hobaiter and Byrne think that this is just a “behavioural fad”, reflective of the chimpanzee’s natural predilection for copying its peers.