Mutualism
A partnership between two species in which both benefit, from bees and flowers to birds that lead people to honey.
Mutualism is a relationship between two species in which both gain. It is one kind of symbiosis, a close, long-term association between different organisms; in other kinds one partner benefits at the other's expense, as in parasitism.
Mutualisms are everywhere. Bees get nectar and pollen while carrying pollen between flowers. Fungi on plant roots trade minerals for sugar. Bacteria in our guts digest food we cannot, in return for a warm, well-fed home. The Hawaiian bobtail squid houses glowing bacteria in a special light organ: the bacteria get food and shelter, and their light hides the squid's shadow from predators below.
One of the most remarkable involves people. In parts of Africa a bird called the greater honeyguide leads honey-hunters to wild bees' nests. The people smoke out the bees and break open the nest to take the honey; the bird eats the wax left behind, which it could not get at alone. Among the Yao people of northern Mozambique, hunters summon the birds with a special trill and grunt, "brrr-hm". In a study published in 2016, playing recordings of that call raised the chance of being shown a bees' nest from 16 per cent, with control sounds, to 54 per cent. The birds have learned to recognise the call of a useful partner.
Mutualisms can fade if one partner disappears: where honey-hunting has died out, so has the birds' guiding.
Coming up in future stories
- The Bird That Answers When Humans Call 2016 · Niassa Reserve, Mozambique