This is the story of a whale that tried something new and a monkey that fell in line.
It’s about how wild animals can create cultures and traditions just as we can, through the twin forces of innovation and conformity.
In 1980, a humpback whale in the Gulf of Maine started doing something different. All its neighbours would catch small fish by swimming in circles below them, blowing curtains of bubbles, and then lunging straight up at the corralled shoal. Then one individual, out of the blue, started smacking the water surface with its tail before diving down and blowing its bubbles.
This behaviour is called lobtail feeding, and no one knows why it works. Maybe it disturbs the water above the bubble curtains and discourages fish from jumping to safety. Whatever the benefit, it went viral. Just eight years after the first innovative whale started doing it, 20 percent of the Maine humpbacks had picked up the technique. Now, it’s more like 40 percent. What began as one whale slapping the water is now a tradition.
The obvious explanation is that the whales were learning from each other. But there could be other reasons. If the technique has a strong genetic basis, it could pass down family lines without any form of social learning. Or maybe environmental changes were responsible. The whales seem to use lobtail feeding specifically to catch small fish called sand lance, and the strategy only started spreading after populations of herring, another important prey species, crashed. Perhaps hunger drove the whales to individually develop a new technique for catching a different sort of prey.
Jenny Allen worked out how to tell these possibilities apart. As a masters’ student, she had worked on whale-watching boats in Maine, and knew that the Whale Center of New England (WCNE) had collected a huge data set of the local animals’ behaviour. Over 27 years, they had recorded almost 74,000 sightings. Allen was looking for ways of using this data when she joined Luke Rendell’s lab at the University of St Andrews as a PhD student. “I realised this was the lobtail-feeding population and asked whether it was still going on,” says Rendell. “She said, ‘Yes, it seemed to still be spreading’. I knew we were in business.”
The team used the Maine data to reconstructed the whales’ social network and simulate the spread of lobtail feeding under different mathematical models—some that included social learning and others that didn’t. The results were so clear that even Rendell was surprised. “It was very, very clear that cultural transmission was important in the spread of the behaviour,” he says.
The models which assumed that the whales were learning lobtail feeding from each other were a far better fit for the actual spread of the behaviour than those which assumed no social connection. “The weight of evidence was up to 23 orders of magnitude greater for these models,” says Rendell. “It’s the difference between the weight of a single person and the weight of planet Earth.”
By contrast, genetics was unimportant. “Having a lobtail-feeding mother makes virtually no difference to whether you will become one,” says Rendell. Ecology mattered more. Whales were more likely to learn the lobtail method in the specific region where the sand lances live, and during years when sand lance numbers were high.
This doesn’t detract from the importance of social learning, which was by far the more important factor in the strategy’s spread. Instead, it shows how useful it can be to pick up skills from your neighbours. “If a species is smart enough to innovate and transfer information socially, it could adapt very quickly to new environmental pressures. This is why humans are so successful,” says Michael Kruetzen from the University of Zurich. “I find this to be a highly convincing case for a foraging tradition in a cetacean,” adds Susan Perry, an anthropologist from the University of California, Los Angeles.
Critics might point out that Allen’s study relied only on observations rather than experiments, and incomplete observations that were limited by what boat crew could see. But the team took steps to account for this, adjusting their models to account for patchy sightings, or the fact that the most commonly spotted whales would repeatedly pull off the same behaviours. None of that changed the results.
And Rendell scoffs at the notion that you can never know anything for sure from observational data alone. “It would be great to look at this experimentally, but we’re talking about a population of wild humpback whales here,” he says. “Spock and Kirk were able to beam one up in The Voyage Home, but we aren’t going to be doing that any time soon. This is really the best approach we have, and the answer it gives is unequivocal.”
Meanwhile, thousands of miles away in South Africa’s Mawana Game Reserve, there lived a vervet monkey called Groot, who was a fan of blue corn. One day, two boxes of dyed corn kernels had mysteriously appeared. The pink ones tasted disgusting but the blue ones were tasty, and Groot’s entire group quickly learned to eat the blue ones. Then, as all male vervets do when they grow up, Groot left his family behind and moved to a new group. And when he did, he saw that his new companions liked pink corn instead. He watched, he processed, and he starting eating the pink corn too.
Groot didn’t know it, but he was part of an ambitious experiment by Erica van de Waal and Andrew Whiten from the University of St Andrews to study the spread of animal traditions. Recently, Whiten’s team has studied whether captive chimps and capuchin monkeys can learn from each other. The answer is yes. Tutors, who are taught new foraging techniques in isolation, can seed their groups with these new innovations when they are reunited.
This approach is impractical in the wild, because it’s very hard to isolate a tutor individual. Instead, scientists have studied differences in behaviour between groups of wild chimps, orang-utans and other species. These studies have been pivotal for our understanding of animal culture, but they’ve run against the same refrain that Rendell dislikes: they’re just observational, not experimental.
So, van de Waal tried something new—she seeded new traditions in entire groups rather than individuals. She gave four groups of wild vervets, which included 109 individuals between them, a choice between blue corn and pink corn. In each case, the group would only ever eat one colour because the other was coated with a repulsive extract from local aloe plants. (They tried vinegar and chilli powder, but the vervets happily ate those. Only aloe worked. “The experimenters tested the corn themselves and had the bitter taste for a whole day in their mouths,” said Whiten.)
Van de Waal took the corn away for 4 to 6 months and during that time, new babies were born into the vervet communities. The corn eventually returned and this time, both colours were tasty and palatable. Even so, it seems you can’t teach an old vervet new tricks, and the monkeys stuck with their existing colour preference.
More importantly, their infants, who had never seen dyed corn before, just ate whatever they saw their mothers eating. Those born into pink cultures ate pink corn. Those born into blue cultures ate blue corn.
It’s not surprising that infants follow their mothers, but the strength of their preferences caught the team off-guard. “Infants chose only what their mother ate despite there being right in front of them a box of perfectly edible corn of a different colour,” says Whiten. “Some even sat on that, to eat the ‘right’ colour of corn!”
Emigrating males also took up the traditions of their new groups. By sheer luck, during the experiment, ten males moved into a group that preferred a different coloured corn than their original group did. Seven of these newcomers seven immediately started eating whatever colour their new comrades preferred, and two more soon followed suit. The only exception was a male called Lekker who immediately took up a dominant rank in his new group, which may explain why he stuck to his old ways.
Perry praises the elegant experiments but notes that the numbers are quite small. “Seven out of ten is only 2 data points greater than chance preference for a particular colour,” she says. “I appreciate the difficulty in obtaining a larger sample—you have to wait for males to migrate—but I hope the authors will persevere in increasing that sample size.”
This degree of conformity is surprising especially for vervets, which “are often thought to be opportunistic”, according to Whiten. This “when-in-Rome” mentality makes sense. In the wild, foraging animals have to make decisions about the nutritional quality of potential foods and the presence of poisons. When moving into a new environment, it pays to copy what local experts are doing, even when it means overriding the knowledge you’ve gained in a different context.
The tendency to conform could also explain other social learning experiments have failed. Scientists have tried to teach new behaviours to wild tutor individuals, including vervets and meerkats, but found that these nascent traditions are difficult to spread. That may be because these traditions face an uphill struggle, says Whiten, “whereas, in our study, the naïve infants and immigrant males were already surrounded by a majority doing the same thing.”
The team now wants to see if the wild vervets will also learn more complicated behaviours from each other, such as techniques for dealing with their food. Based on work with captive monkeys, they think the answer is yes. It’s now time to take these experiments into the field.
Thanks to decades of research, it is now clear that animals can learn from each other in ways that create different cultures in the wild.
As Frans de Waal writes in a commentary accompanying these new studies, “The early debate about animal culture focused on the mechanism of behavioural transmission.” Are apes apeing each other in the way that humans can? When whales and dolphins imitate each others’ songs and actions, do they understand each others’ goals and methods? When blue tits peck open the tops of milk bottles, is it because they’ve picked up the technique from other tits, or because those birds just drew their attention to the bottles?
Now, studies of animal culture are moving beyond just asking whether it happens to probing why it happens and how strongly it does. The humpbacks show that new traditions can easily spread within a group, but the vervets show that the conformity can also suppress new behaviours in favour of old rituals. We see the same tension between innovation and conformity in our own societies, and it’s fascinating to see the same patterns in animal groups.
All of this requires intensive field work and long-term studies. To watch the vervets from the comfort of nearby chairs, de Waal and Whiten had to spend over a year with the monkeys, getting them used to their presence and learning how to recognise over 100 individuals by eye. To understand what the whales were doing, Allen and Rendell had to use a 27-year set of data. “That shows how important it is to have long-term research so you can create these data sets,” says Kruetzen “If people had just gone there for a year or two, it would have been very hard to document these changes.”
Reference: Allen, Weinrich, Hoppitt & Rendell. 2013. Network-Based Diffusion Analysis Reveals Cultural Transmission of Lobtail Feeding in Humpback Whales. Science http://dx.doi.org/10.1126/science.1231976
Van de Waal, Borgeaud & Whiten. 2013. Potent Social Learning and Conformity Shape a Wild Primate’s Foraging Decisions. Science http://dx.doi.org/10.1126/science.1232769