Birds of a feather may flock together, but do birds that flock together develop distinct cultures? Two studies published today in Science find strong evidence that, at the very least, monkeys that troop together and whales that pod together do just that. And they manage it in the same way that humans do: by copying and learning from each other.
A team led by Erica van de Waal, a primate psychologist at the University of St Andrews, UK, created two distinct cultures — 'blue' and 'pink' — among groups of wild vervet monkeys (Chlorocebus aethiops) in South Africa. The researchers trained two sets of monkeys to eat maize (corn) dyed one of those two colors but eschew maize dyed the other color. The scientists then waited to see how the groups behaved when newcomers — babies and migrating males — arrived.
Both sets of newcomers seemed to follow social cues when selecting their snacks. Baby monkeys ate the same color maize as their mothers. Seven of the ten males that migrated from one color culture to another adopted the local color preference the first time that they ate any maize. The trend was even stronger when they first fed with no higher-ranking monkey around, with nine of the ten males choosing the locally preferred variety. The only immigrant to buck this trend was a monkey who assumed the top rank in his new group as soon as he got there — and he may not have given a fig what anyone else ate.
“The take-home message is that social learning — learning from others rather than through individual trial and error — is a more potent force in shaping wild animals’ behavior than has been recognized so far,” says Andrew Whiten, an evolutionary and developmental psychologist at St Andrews and co-author of the paper.
The study is striking because it is one of very few successful controlled experiments in the wild, says Frans de Waal, director of the Living Links Center at the Yerkes National Primate Research Center at Emory University in Atlanta, Georgia. “It hints at a level of conformism most of us until now held not possible,” he says.
Whale see, whale do
In the second study, a team led by St Andrews marine mammal science student Jenny Allen examined 27 years of whale-watching data from the Gulf of Maine, off the eastern coast of the United States, to determine whether social cues helped an innovative feeding method to proliferate among humpback whales (Megaptera novaeangliae).
Humpbacks everywhere feed by blowing bubbles under schools of fish, which then bunch together closely to avoid swimming through the bubbles. When the whales lunge upward, they can gulp down a super-sized serving of fish. But in 1980, observers in the gulf saw something new: a humpback slapping the surface of the water with its tail fluke before proceeding with a standard bubble feed. That year it happened just once in a sample of 150 feeding events, but by 2007, 37% of the humpbacks in the Gulf of Maine were observed using the technique, since dubbed lobtail feeding.
To determine how lobtail feeding became so popular so quickly, Allen and her colleagues applied a method called network-based diffusion analysis to observations of humpback behavior collected by the Whale Center of New England in Gloucester, Massachusetts, between 1980 and 2007. The technique assumes that individuals who spend more time together are more likely to transmit behaviors to each other. Allen's analysis found that up to 87% of whales that adopted the lobtail-feeding technique learned it from other humpbacks.
“We know that humpback songs are also culturally transmitted,” says Luke Rendell, a biologist at St Andrews and co-author of the whale study, “so here we have a population with two independently evolving cultural traditions — a culture.”
David Wiley, research coordinator at the US National Oceanic and Atmospheric Administration's Stellwagen Bank National Marine Sanctuary in Scituate, Massachusetts, says that the work is important and innovative. “It adds to a growing body of information demonstrating the complexity of humpback-whale behavior and its apparent roots in social learning,” he says.