The Best Way to Steal a Banana

A vervet monkey

Competition is the law of the land in the animal kingdom, but it is not the only way to end up on top. A recent study published in Nature found that among a group of vervet monkeys, those that were lower in the hierarchy were better at foraging for food, giving them a leg up among their peers. Conversely, those at the top of the hierarchy, who did not usually have to compete for a food source, struggled with foraging behavior. Interestingly, this holds true independent of the specifics of the foraging environment, with the lower hierarchy monkeys better at problem solving than their dominant relatives.

The study made use of 27 monkeys in a closed environment that included a half banana held in a plastic box, with a small hole to retrieve the food. Initially, the monkeys would pick up the box and rotate or shake it until the banana could more easily be retrieved, but they found it was quicker to not touch the box and simply stick their arms into it. All but one of the monkeys was able to accomplish this but importantly, those lower in hierarchy were able to learn the technique faster. The quickest time for retrieval clocked in at one second, with the longest being just over a minute.

One of the monkeys using the preferred "no-manipulation reach-in technique"

This division owes itself to differences in social learning, the ability of a group to impart information and survival techniques to each other. Dominants in the group are more likely to forage solitarily, as their subordinates give them a wide berth and fellow dominants also go off to explore on their own. Without valuable experience learning from each other, those at the top of the pack struggled to learn the technique best suited to retrieving the banana, in this case putting themselves at a disadvantage. 

Those lower in the hierarchy conversely had formed the habit of observing others' techniques in foraging and were more likely to closely observe others while they handled the box. They also had a greater motivation to learn the technique faster, as the hierarchy dictated how long each had to attempt to retrieve the banana. The study demonstrates that fixed hierarchy among some animals can actually have disadvantages for those on top.