By Adam Cogan • MSc Human Evolution and Behaviour (2017-18)
Imagine you are a young orca, less than ten years old. The Argentinian sun is scorching your dorsal fin as you follow mum closely, keeping safe. You are hungry and there is no prey in sight. Then you see it. A white stretch of shoreline, a glorious sickle-shaped beach flecked with blubbery seals. You want them, badly. But there is one major problem – you can’t leave the water. Or can you? You watch as mum picks up speed, charging towards the beach. She slides in with a wave, catching a dormant, sun-soaked seal by surprise. The seal barks furiously, twisting and thrashing in desperation and – with the retreating surf – mum rolls back into the water, the seal firmly clenched in her jaws.
This highly specialised and dangerous technique is unique to a population of orcas at La Crozet archipelago near Argentina. It is an example of marine mammal culture (or socially learned behaviour) because it is a tradition which is passed down from parent to offspring, which takes up to six years to learn and perfect for juvenile orcas under close parental supervision. This scenario is one among many examples of whale and dolphin cultures. Cultures that have recently come under increasing pressure from human-induced environmental change.
In the past few years, there have been a number of large-scale reports published in the world’s leading scientific journals. The picture painted by these reports is by no means a pretty one. In 2017, a study published in Proceedings of the National Academy of Sciences suggested the earth was entering a sixth age of mass extinction. In the following year, another study in the same journal bolstered these claims, finding that humans are responsible for the elimination of 83% of wild mammals. The 2018 WWF Living Planet report – a comprehensive examination of the current state of global biodiversity – was equally damning, finding a 60% reduction in overall wildlife population sizes since 1970.
Among the animals highly affected are marine mammals, including whales and dolphins, who have suffered a fivefold decrease in their biomass due to intensive whaling and over-exploitation. On top of that, a recent survey of marine mammals around the UK found that every single individual had microplastics in its digestive system. Seaborne pollutants are an increasing scourge to marine life and no case better demonstrates this than the plight of the orca.
A recent research article examining global orca populations found that over 50% of them were at risk of being wiped out due to PCB (polychlorinated biphenyl) contamination – a highly toxic chemical which has been linked to reduced fertility in humans. Some of the most at-risk populations (such as the resident salmon-eating orcas of the Pacific Northwest) have recently featured heavily in the media, with reports of dying calves and grieving mothers carrying the corpses around for days. This is the unfortunate result of drinking the mother’s PCB-contaminated milk. These heartbreaking incidents have sparked a response from local government in the state of Washington, USA – with pledges to limit orca watching, reduce pollution, knock down dams and, crucially, restore the Chinook salmon stocks on which the orcas rely. Yet with a rapidly dwindling population these resident orcas risk imminent collapse. And with them would disappear a suite of unique behaviours that have been passed down from generation to generation – their culture.
The notion of learned cultures in whales and dolphins has been rising steadily to prominence since the 1970s, when scientists discovered incredible complexity in humpback whale songs. These songs were later found to be periodically supplanted in “cultural revolutions” by new song styles that spread successively to each neighbouring population from west to east. Recently, a landmark book by famed cetologists Hal Whitehead and Luke Rendell titled The Cultural Lives of Whales and Dolphins tied together all the disparate strands of research into whale and dolphin culture. What became apparent was an astonishing range of unique learned behaviours across (and within) species. While many of these learned behaviours are useful for survival, such as common call systems for better group communication or learning a special technique to hunt better, other behaviours are seemingly random fashions or fads.
But what makes these behaviours culture and not just random curiosities? Well, in the species that have strong culture, individuals – much like humans – associate predominantly with those others who behave in the same way and, in some cases, actively avoid groups with different cultural “markers”. This could be compared to the fans of two sports teams who avoid (or are belligerent towards) those wearing shirts and colours of the opposing team. Not only this, but within each group, the cultural traditions are learned and passed on (again similar to human societies) and help a population learn skills and behaviours that increase their chances of survival in their local environment.
Orcas, the most widely distributed animal on earth after humans, have multiple populations scattered across the globe with many such cultural traditions. The Pacific resident orcas themselves have some astonishing examples. One group of southern residents one year began carrying dead salmon around on their heads. One individual started it, then it rapidly caught on before eventually dying out – like a seasonal fashion trend. These orcas also have unique dialects within pods, which they use to recognise and communicate with each other. Further out at sea, groups of the offshore shark-eating orcas have a habit of performing unique greeting ceremonies when they bump into each other.
Yet unique learned behaviours are not just found in orcas. A group of Irrawaddy dolphins in the Ayeyarwady River population (Myanmar) has long maintained a tradition of fishing co-operatively with local fisherman – herding fish towards them for easy netting and then dividing the spoils. The bowhead whales of Spitsbergen in the Arctic – able to live to 200 years of age (there are likely some individuals older than the unification of Italy!) – sing through the night with hauntingly beautiful learned songs. The beluga whale (of recent River Thames fame) has been known in captivity to invent games and to imitate human observers. Examples include a marine version of “king of the hill”, in which individual belugas fight to gain and maintain a perch on a platform, and one beluga calf blowing her mother’s milk at an observer who was smoking a cigarette, mimicking the effect of smoke. Belugas also have special name-like signature whistles and population-specific call types.
No discussion of dolphin culture, however, would be complete without mentioning bottlenose dolphins. A striking example is a population in Moreton Bay, Australia who, for a time, was rigidly separated into two groups: those who would beg for fish from passing trawlers and those who (to anthropomorphise) you can imagine refused to stoop so low. The groups barely associated with each other, passing down their respective traditions until trawling in the area ceased, after which they promptly re-joined into one group!
Apart from culture, what do all these species have in common? They all have populations which are vulnerable or endangered. And some, like the Ayeyarwady River dolphin, the Spitsbergen bowhead whale, the Cook Inlet beluga whale, and the Puget Sound resident orca populations are critically endangered. If they were to go extinct, we risk losing not only the animals themselves, but the behaviours which make them so unique and irreplaceable. Behaviours which have been innovated, developed, learned and upheld for generations. Behaviours which made these groups ideally suited to their local environment – before we began to destroy it. On the other hand, many dolphin cultural traditions are closely intertwined with human ones, such as the dolphin-human fishing co-operatives found not just in the Ayeyarwady River, but also elsewhere around the world (for example between bottlenose dolphins and artisanal fisherman off the coast of South Brazil). Human contact is therefore not entirely destructive. These interactions have proven mutually beneficial – but the key is respect for other animals and their environment.
The loss of cultural diversity is not often mentioned in most mainstream media discussions of conservation, where a round number for a species’ remaining size is usually cited. This reduces a species to a uniform block and does not consider the value of each and every behaviourally unique population, some of which are at more risk than others. Yet it’s these behaviours – the orca fashions, the chimpanzee handshakes, the orangutan umbrellas, the capuchin eye-poking, the whale songs, the bird songs – which make the animal world all the more fascinating and diverse. To lose this diversity (and losing it would be irreversible) would truly be a tragedy.