Sperm whale society is structured into distinct clans, groups of which appear to make decisions together, but with some apparent disagreement beforehand
A recent paper published in the Royal Society Open Science journal, documenting the behaviour of sperm whale populations and their relation to human societies has revealed that groups of sperm whales make decisions by reaching a consensus – but after up to an hour or more of discussion.
Sperm whales (Physeter macrocephalus) are the largest toothed predators alive today – they also have the largest noses in the animal kingdom and the biggest brains in the world, even bigger than blue whales, the largest animal of them all.
They were a primary target of whalers for their spermaceti, an oily substance contained in their heads which was once thought to be sperm – hence the name – but which is actually part of the whale’s melon, the group of organs responsible for generating the clicks the animals use for directional echolocation.
It may also be used for buoyancy control (still up for debate) and possibly for fighting and/or defence. Even, in some cases, as 50-tonne battering rams: Moby Dick was inspired by real-life cases of sperm whales ramming – and sinking – whaling ships with their giant melons. Good for them!
Despite the devastation of their populations by whalers, sperm whale numbers appear to be on the increase since the worldwide ban on commercial whaling in 1987. Although they are listed as Vulnerable by the IUCN Red List of Threatened Species, the Royal Society paper estimates their Pacific population numbers around 300,000 individuals, divided into at least seven distinct clans with an average of 20,000 females in each.
The clans are further sub-divided into pods which are almost exclusively comprised of females and their calves. The much larger bulls tend to appear for a short time – probably to mate – before disappearing off again, leaving the female whales in charge.
Scientists believe the clans function in a similar way to the ‘ethno-linguistic’ groupings found in human societies, wherein groups of otherwise genetically similar people are divided by the languages they speak. The inability of citizens of one nation to communicate with citizens of another means that even neighbouring countries evolve historically different cultures, and individuals travelling outside of their home nations will tend to seek out and group together with members of their own nationality – or at least, speakers of their own language – rather than mingle with people with whom they cannot talk.
It seems that sperm whales share a similar ethnic-linguistic arrangement. Individual pods are comprised of around 10 whales, but researchers have found that the whales are encountered in groups of 30 or more. They further determined that these social groupings were quite specific, in that some pods would mingle and others – even though they occupied the same stretch of water – would not.
Analysis of vocalisations within the groups determined that those pods that mingled voiced a similar pattern of clicks, and they did not socialise with pods that voiced a different pattern. You can sort of imagine a situation where lots of Europeans are on holiday in the same resort: Germans are hanging out with other Germans – whom they may never have met before – the French with the French and the British with the British, even though an outside observer would see very little difference in physical appearance between the different groups.
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The report’s author – Canadian researcher, Hal Whitehead – cautions against over-anthropomorphising the whales’ behaviour. There are thousands of different ways that humans express their cultural differences, whereas the whales – even though there’s a great deal we most assuredly don’t know – have so far been determined to exhibit just 12.
However, Whitehead also says we should not engage in ‘unthinking anthropodenial’, in which we refuse to recognise that humans and other animals do share certain characteristics. In fact, research into the division of social groups within other species may provide insight into how humans navigated the development of our own cultural landscapes.
One particularly outstanding behaviour with anthropomorphic relevance is the apparent democratic nature of group decision-making in sperm whales. In a 2016 paper, Whitehead observed that groups of sperm whales – which can travel more than 50km per day – would make gradual, but ‘messy’, changes in direction, taking an average of 1.3 hours to complete the turn.
The inference from the collection of subtle changes in heading that eventually result in one coherent change in direction is that the group has no leader; that each animal is effectively contributing to a (very lengthy) discussion on which way they all should travel, and the final decision is, essentially, arrived at by consensus.
One might argue that there is no more anthropomorphic representation of mammalian decision-making than having to sit through interminably long committee meetings in order to do so.
On the other hand, at least the sperm whales actually make a definitive decision to change the status quo once the meeting ends.
‘Sperm whale clans and human societies’ by Hal Whitehead is published in the Royal Society of Open Science
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