How animals choose a new leader

Last week, the UK voted in a general election, but group decision-making isn’t limited to humans.

In some species, there’s a simple way of deciding on a new leader – the oldest female elephant, the wolf most successful at fighting, the last contending female fire-ant left alive – but in others it’s a more complicated progress.

 

Our close relatives, chimpanzees, have a different system to us. Male chimps fight between themselves to gain control of a group, but the winner has to earn the approval of the group’s females or his victory is useless. If they don’t accept him as their new leader, they’ll refuse to mate with him and it’s not long before another male challenges him.

 

The fastest pigeon in a group tends to become the leader, but this doesn’t mean they’re always obeyed. If a leader is misinformed or attempts to steer the flock off their course for home, they are overruled by the others and lose their place at the front. The other pigeons then use their combined knowledge to put themselves back on track.

 

Stickleback are attracted to large, fat and healthy potential leaders. If there’s a choice between two fish, some group members will head towards the one they prefer and the rest will go with the largest group. Although usually accurate, this consensus decision-making can sometimes result in the shoal following the less attractive candidate.

 

Honeybees choose a new nest site democratically, with scouts dancing to campaign for the locations they’ve found, but when they swarm and move into their new home some stay behind. The mother queen takes most of the hive with her, but some young female bees remain along with some of the workers. These larval females have been fed the royal jelly that gives them the potential to become queens, and the race for the throne can go one of two ways.

In a small hive, the first contender to emerge destroys the others and assumes control. If more bees remain, however, a second swarm can set off for a new site. In this case, the workers stop any would-be queens from killing the others, instead waiting until the next female emerges. These two bees duel until one is left, and she then faces the next contender to emerge in a winner-stays-on contest. The last (wo)man standing wins the title of queen, with the bodies of the unfortunate losers thrown out of the hive.

Scientists have found that, when emerging females duel in isolation, it’s almost always the bigger one who wins even if she’s less likely to benefit the group. But when the workers are around this isn’t the case; size no longer matters. The workers appear to influence the result so that it’s not just the strongest who survives.

 

(psst – if you’re interested in learning more about bees, keep your eyes peeled for World of Animals magazines over the next couple of months)

 

(Photo: Rob Bertholf/flickr)