Aptitudes & Attitudes - In Brief

© Alexis Chaine
© Alexis Chaine
The female lark bunting (on the left) chooses her mate based on a number of criteria other than his physical appearance. © Alexis Chaine
The female lark bunting (above) chooses her mate based on a number of criteria other than his physical appearance. © Alexis Chaine
Female baboons delouse one another. © Shutterstock
Female baboons delouse one another. © Shutterstock

Social mothers enhance infant survival

American primatologists Jeanne and Stuart Altmann have been studying the yellow baboon (Papio cynocephalus) from Kenya's Amboseli region since 1971. The baboons have a matriarchal society; the females form long-term social bonds whereas males move from one group to another. Certain females appear to be particularly friendly, spending a lot of time delousing or intervening in cases of conflict.

Between 1984 and 1999, the researchers observed the group's demographic evolution: pregnancies, births and infant survival rates, dominance ranks and, in particular, the behaviour of 108 female baboons. The conclusion of this long-term observation in the wild was that the more social the mother is, the greater the chances of her offspring surviving their first year of life (considered to be the most crucial year). Why is this? Social contacts are known to reduce physiological stress in a number of species. The researchers also speculate that infants lucky enough to have a kind mother have easier access to food and more effective protection.

Does the theory of evolution underestimate cooperation?

A growing number of specialists believe that the theory of evolution has underestimated cooperation between organisms, which is dominated by a Darwinist survival of the fittest interpretation that focuses far too much on competition. Numerous examples of co-evolution and symbiosis attest to the spontaneous tendency of living beings to form relationships for their mutual benefit. These relationships rely on countless signals where the recipient belongs to another species or even a different kingdom. Together with British scientist James Lovelock and pioneering American microbiologist Lynn Margulis, a professor at the University of Massachusetts has developed the theory that the Earth itself can be seen as a symbiosis of all its inhabitants (1). Even without going as far as this, it is hard to deny the fundamental importance of relationships in the living world.

  1. Lynn Margulis, Symbiotic Planet: a new lookat evolution, Basic Books, 1998

Looks aren't everything...

Female passerine birds (in this case, lark buntings) look beyond physical appearances when they set their sights on a particular male. Their choice appears to depend less on his size and the colours of his plumage than on the ecological situation at the time. Researchers Alexis Chaine from the French National Centre for Scientific Research (CNRS) and Bruce Lyon from the University of California, Santa Cruz (USA), have highlighted this selection criterion designed to ensure genetic diversity. The aim of female buntings is for the largest possible number of eggs to hatch(1).

This induces them to elect a mate on the basis of his ability to feed their future offspring. If the nest is located near the ground where mice prowl they will choose a male whose wings are spotted white, which frightens the rodents. If it is a poor year for grasshoppers (the buntings' favourite food) females will take a mate with a beak large enough to catch other insects. According to the researchers, females' preferences entail a sexual selection dynamic that is almost certainly present in other species too.

  1. Alexis S. Chaine, Bruce E. Lyon, AdaptivePlasticity in Female Mate Choice Dampens SexualSelection on Male Ornaments in the Lark Bunting,Science, 25 january 2008.

Cunning ploys of prey

An insect will stand absolutely still before its predator, as when a grasshopper meets a toad. Why doesn't it jump out of the way? Because that would mean certain death. The predator will attempt to catch its prey only when it jumps. According to ethologist and philosopher, Vinciane Despret, a jackdaw does not recognise a grasshopper's shape when it is motionless and it is only when it leaps that the jackdaw can pick it out from the confusing mass of forms all around(1). The grasshopper has learned that its predator is unable to detect motionless forms.

A further finding is that small birds actually build their nests close to their predators' habitat. The reason for this appears to be that an animal's habitat is impregnated with the odour of the animal that lives there. Because the predator considers the area where its potential victim has come to live as an extension of its own body, it does not use it as a hunting ground. A creature will not eat itself. As Jacob von Uexhüll has shown (see pages 6-7), we must look to the meanings of these ploys that may seem strange to us but are in fact an important feature of the animal world.

  1. Vinciane Despret, Bêtes et Hommes,Gallimard, 2007