April 27, 2013 | 3
This article is the second part of a two-part series on animal culture. The first part discusses some new findings of adopting local food preferences in vervet monkeys.
In a double-whammy of animal culture in the most recent issue of Science, Jenny Allen, Mason Weinrich, Will Hoppitt & Luke Rendell report a study based on twenty-seven years worth of data showing that humpback whales culturally transmit a particular way of catching fish.
In 1980 a single whale was first seen engaging in a novel feeding behaviour called ‘lobtail feeding’. This was a new twist on a more common way of feeding that had been seen previously, so-called ‘bubble feeding’. In bubble feeding, the whale dives down below a shoal of fish, blows bubbles up at them, creating a net around its prey, and then lunges up through the discombobulated group of fish with its mouth open. What this whale was doing hadn’t been seen before: it lobbed its tail down, hard on the water surface before blowing bubbles.
The following year, Mason Weinrich observed five whales doing this, and year by year after this more and more individuals seemed to be adopting this feeding strategy. Could it be that they were learning from each other? As the data collected were observational, rather experimental data like those collected in the vervet monkey study, initially it might seen problematic to tell whether the whales really were learning from each other or not. Perhaps there had just been more whales doing it each year because people had noticed more each year (like when you first become aware of something new, and then seem to see it everywhere). Perhaps the whales weren’t learning from each other at all, but were learning how to lobtail feed by themselves. Another potential problem with observational data like this is trying to separate environmental and genetic effects. In other words, what if individuals were just inheriting it from their parents, and it appeared as if they were learning it from each other as they just spent more time with their parents? This is often a problem in wild studies, as groups with different cultures are also often more likely to be more closely related. In a useful allegory made by Rendell, ‘Inuit greet by rubbing noses to cheeks (called a ‘kunik’), people in Italy by kissing cheek to cheek. There are undoubtedly detectable genetic differences between these populations, and they live in very different ecological settings, but few would argue that the different greeting are not a cultural thing.’
So how did the scientists manage to disentangle all these possible explanations for this novel feeding behaviour? With the use of a neat analysis, the ‘network-based diffusion analysis’, they could reveal what the most likely explanation was for the spread of this behaviour. Just as with human culture where we expect that individuals that interact more with each other are more likely to share the same culture, so the model the scientists used assumed that if the lobtail behaviour was learned, so individuals that lobtailed would be spending more time with other individuals that also lobtailed. To make sure that individuals weren’t just spending more time with family members that might all have the same ‘genes for’ lobtail behaviour, they included information in their model about whether an individual’s mother had been a lob-tail feeder. By plugging in all the information they knew about who was hanging out with who, who was related to who, and other factors to do with the animal’s environment that might affect lob-tail feeding, the scientists could say what the most likely situation was that was actually going on.
What the ‘best’ model told the scientists was really quite interesting. It showed that it was extremely likely that whales were learning the lobtail behaviour from each other. Indeed, the models that ‘said’ that the whales learned from each other were 54,000 times ‘better’ (i.e. more likely to be the case) than the models that had the whales learning by themselves. They also found that even though individuals were learning from each other, they were also performing the behaviour more when a particular fish, the sand lance, were abundant. This would seem to imply that there is something special about this fish that makes the behaviour particularly useful when trying to eat it.
Whether lob-tail fishing is only used for sand lance isn’t yet clear. It’s also not clear what exactly lobtail feeding achieves. Rendell says it’s likely that it disturbs the prey and causes them to bunch together more. But, it might also be totally functionless, maybe it just makes the whales feel good. However, even if the behaviour didn’t serve a function, it would still be interesting (and possibly even more interesting). Like many memes that spread through human culture, animals may too have pointless traditions.
One particularly unique feature of this study is the length of time over which it was conducted: Mason Weinrich, and his colleagues at the Whale Center of New England collected 70,000 sighting records of over 600 whales over decades. With most grants for early career scientists being for only a year or two, and even more senior scientists only tending to have grants for just a few years, it makes collecting this kind of data extremely difficult, and makes this study all the more impressive. This study has allowed us to see these creatures in a new light, as well as providing new tools for looking at other animals in a similar way. However, this would have not been possible without the broad perspective afforded by years of observation. Even though cultural evolution is generally faster than biological evolution, being able to take a longer view and see how behaviours can change over a few decades offers insight that cannot be gained from the brief glimpse work from a year or two gives.
What can animal studies tell us about our own culture?
How exactly the whales are learning from each other is not yet clear, but this study is another step towards a greater understanding of animal culture. As culture is something we consider such a key part of being human, it’s hard not to look at animal culture and compare it to our own. I asked Rendell about how comparable non-human animal culture was to our own, and what studies like his might be able to tell us about our own culture. He pointed out that there is a vast chasm between our own culture and what we see in non-human animals: ‘These differences [between humans and other animals] are so huge that it makes no sense to many perfectly reasonable anthropologists to even call anything non-humans do culture. To them, with their focus on symbols and meanings, they are just not the same. However, evolutionary biologists tend to focus on culture as an alternative information stream from genes – a second inheritance system – and from this perspective the differences are more of degree than kind. There is no universally accepted right answer to this disagreement right now, but everyone accepts that human culture is unique (but then, so is whale culture, chimp culture, bird culture, just like flying, walking, slithering and swimming are all unique ways of locomoting)… understanding what nonhumans are and are not capable of with respect to culture helps us focus on what it is really that makes human culture unique.’ To take this a step further, by understanding what conditions lead to the culture we see in animals, we can better understand what conditions may have lead to the more primitive culture in our evolutionary past, and how our culture evolved to the point it is at today.
Lobtail photo: Jennifer Allen, Ocean Alliance
All other whale photos: Jennifer Allen, Whale Centre of New England
Allen, J., Weinrich, M., Hoppitt, W., and Rendell, L. (2013). Network-Based Diffusion Analysis Reveals Cultural Transmission of Lobtail Feeding in Humpback Whales. Science 340, 485-488.