Stranger things: young mongooses learn from unrelated adults
Cultural inheritance edges out genetics for African mammal. Andrew Masterson reports.
When it comes to mongooses, nurture is definitely more important than nature. A newly published study reveals that young mongooses learn food choices and behaviour patterns from unrelated adults rather than from parents.
A team led by Michael Cant from the University of Exeter in the UK set out to examine the effects of an unusual infant-care strategy used by the banded mongoose (Mungos mungo), a grassland species found in central and eastern Africa.
The animals live in social groups of about 20 adults. Care of the young, however, is not carried out by either parent. Instead, after the first few weeks, each pup teams up with an unrelated adult, called an escort, for three months.
Observing a colony in southern Uganda, Cant and colleagues tested the ongoing influence of unrelated escorts on pups that had grown to independence, by analysing the isotopes present in the whiskers of both. They discovered that the grown-up pups continued to eat the same niche diets as their former mentors. These were often different to the niches exploited by biological parents.
“It was a big surprise to discover that foraging behaviour learned in the first three months of life lasts a lifetime,” says Cant.
“This is pretty remarkable, since we have no evidence that pups and escorts preferentially hang out together after pups become independent.”
The researchers say that their discovery is strong evidence of what is known as “cultural inheritance” – behaviour and strategy passed from one generation to another by learning, rather than by genes.
“We behave the way we do not just because of our genes but also because of what we learn from parents, teachers and cultural role models,” explains Cant.
“It is less well appreciated that cultural inheritance is a major force shaping behaviour in a wide range of non-human animals, from insects to apes – and mongooses.”
The findings go some way towards resolving one of the trickier problems arising from evolutionary theory.
Variation is critical to evolution, in the cultural as well as the genetic realm. Genetic changes come about not only through sexual reproduction, but also through random mutation and genetic drift (which ensure evolutionary pressures are present even in asexual organisms).
Cultural variation has been seen by some critics as harder to maintain. If the young of any species all learn behaviour from a single source (a dominant individual, for instance) or from multiple sources (with contributions from all members of a group) then variation should reduce.
Cant and his colleague have found evidence that other models exist, and produce different results.
“Cultural inheritance is usually expected to lead to uniformity within groups,” explains co-author Harry Marshall.
“But our work confirms a classic theoretical prediction that where individuals learn from their own personal teacher, cultural inheritance can work to maintain diversity.”
The research is published in the journal Current Biology.