Mark Peter SimmondsDirector of Science
Orcas are truly remarkable and sometimes their behaviour is perplexing. Their societies and intelligence make them vulnerable to both – mental and physical suffering.
Orcas being incredible
In recent months hardly a week has gone by without a story emerging in the media about orcas. For example, the story about them ‘wearing’ salmon on their heads or the latest update on the small population that persists despite its violent interactions with boat rudders off the coast of Spain and neighbouring countries. Here Mark Simmonds, the OceanCare Director of Science, reflects on the remarkable behaviour and biology of orcas and why they need to be protected.
The Special Nature of Orcas
One of the challenging things in writing about orcas is that the species concept that governs so much of human interactions with animals, does not work very well for them. Let me get some basics about orcas out of the way and then I will come back to this. Orcas are certainly large animals, weighing up to 11 tons and measuring up to 32 feet/9.8m. Their size, distinctive black and white colouring and tall dorsal fins (especially in the males) make them readily identifiable. Most people can recognise an orca (but maybe under their alternative name of killer whale)! They are found in every ocean and are, of course, wholly aquatic mammals, feeding their young with milk, taking care of them for many years and coming regularly to the sea surface to breathe though the single blowhole (their nostril) on the top of their heads. They are included in the oceanic dolphin family (the ‘Delphinidae’) and are, in fact, the largest of the dolphins. Their scientific name is Orcinus orca. Their old and misleading name, killer whale, reflects the fact that some groups specialise in preying on other marine mammals, including large whales, and is an abbreviation of ‘killer of whales’.
They are often described as the ‘ocean’s top predator’ but they don’t prey randomly on every type of marine animal. Instead, particular orca populations, that have particular distributions in particular parts of the world and specialise in eating particular marine animals. Some eat particular fish species. New Zealand orcas, for example, prey predominantly on elasmobranchs (sharks and dog fish). Other fish-eating orca groups specialise in species such as salmon or tuna, and, as previously mentioned, other groups hunt marine mammals. Each prey-type requires a different hunting strategy, often involving teamwork and close co-operation. Film of orcas pushing a bow-wave ahead of them to wash a seal off an ice-flow has been widely seen around the world, an extraordinarily clever and well-executed manoeuvre. Other memorable footage includes images of orcas in Patagonia half stranding themselves, in an apparently life-threatening manoeuvre, in order to grab sealions at the sea’s edge. Such sophisticated hunting techniques are taught to the younger members of the group by the older animals.
This transfer of key knowledge through the generations means that the distinct groups with their hunting specialisations need to be recognised as distinct orca cultures.
Their population subunits have also been referred to as ‘eco-types’ and sometimes there are small physical variations that also help to distinguish each group. For example, slight differences in the animals’ patterning, shapes and sizes. The eco-types or cultures also tend to have differences in their calls, comparable to different dialects. Taking all these factors into account, there is a possibility that some of the distinct cultures, which do not usually interbreed, should be considered sub-species or distinct species in their own right. This is still hotly debated by experts but illustrates that thinking of orcas worldwide as a single species population is inappropriate. There is a strong case to protect each sub-population and each distinctive culture.
The first formal recognition that there were distinctly different populations of orcas occurred in the 1980s and involved several groups of orca in the adjoining North Pacific waters of the USA and Canada. In this instance, the different populations were designated Residents (found inshore and preying on fish and squid), Transients (or Bigg’s orcas, living in the same areas as the Residents but preying on other marine mammals like seals and porpoises) and Offshores (which live further out to sea and may have a wider prey choice) All three groups have differences in their calls, morphology and colour patterns. Similar situations have since been recognised all around the world, wherever small distinctive but sometimes overlapping population units live in particular habitats and exhibit particular behaviour.
Orca Fads and Fashions
Top predators do not have to spend all their time hunting and feeding, at least when prey is adequately plentiful. This gives them potential for other activities, including socialising, competing for mates and play. Biologists generally interpret animal behaviour in terms of the contribution it makes to the survival fitness of the animals concerned. The play behaviour of young mammals is typically interpreted as training for adult life. However, this is a rather reductionist approach, especially when applied to very intelligent animals.
Orcas live in tight-knit family groups or ‘pods’ that are typically led by an older female. They famously co-ordinate their activities. Recently, however, some their behaviour has been more perplexing. For example, the ramming of small boats, especially the rudders, by the small and endangered population of Iberian orcas found off the Spanish and Portuguese coasts (and occasionally also in the waters of adjacent countries). Many boats have been damaged and several have sunk. Inevitably the media has been full of theories this new behaviour, including the idea that it is some sort of revenge against humans. Fortunately, no one has drowned as a result of having their vessel sunk but for the first time ever, orca behaviour clearly poses a real threat to humans.
I believe this is more likely to be a play behaviour of some kind which gives the orcas some sort of satisfaction or entertainment. In other words, they are enjoying pushing the boats around and sometimes breaking bits off, occasionally carrying them away like a trophy. They may also be showing off to each other – showing how strong or creative they are in this ‘play’. One thing that we can be pretty sure about is that the orcas do not want to eat the boats or their crews. This particular population specialises in feeding on tuna and human beings are not on the menu of any orca group.
Orca experts have compared this behaviour to other temporary ‘fads’ in behaviour observed in other populations. One of the most striking of these was witnessed in the orcas of Washington State which suddenly took to wearing salmon on their heads in the 1980s, a behaviour that took hold in the population as one orca learnt it from another. This went on for some months and then stopped. Maybe it became boring. It seems that orcas, rather like people, have fashions that come and go within their groups for reasons that are difficult for us to understand. The Iberian boat ramming behaviour was also seen to spread through this small population. What is different in this latter case is that, to date, it has not stopped and has now persisted for several years.
Interestingly, there has been a recent suggestion that wearing fish has resumed in the Washington orca group based, although this is based on a single photograph in circulation showing one individual with a fish on its head. Whether this is a ‘fad’ that will catch on again remains to be seen.
Another orca group is known to have started vocally mimicking sealions for a while. Again, there was no obvious biological advantage in doing this. So, maybe it was just fun.
We know very well that orcas have large brains, but it is also reported that the paralimbic region of their brains – the part that probably deals with language, memory, and emotion – is significantly more developed than in the human brain. This cannot be simply interpreted to mean that they are actually smarter than us, but it does imply that there is a lot going on in their brains too.
Specialisation can lead to Extinction
One of the issues facing orca populations is what happens to a group if the prey that it exclusively eats becomes rare of even disappears. Do they have the capacity to switch to other prey species?
The North American orca population known as the Southern Residents, which is very well studied, faces such a dilemma. In the 1970s, the population was badly affected by removals to satisfy the dolphin captivity industry. When this stopped, the population recovered during the 1990s, but this was followed by an alarming decline eventually leading to the population being added to the USA endangered species list in 2005. Currently there are less than 80 individuals left. The primary causes of their decline include boat disturbance and pollution, however, their declining prey-base is also a fundamental problem.
These orcas are salmon specialists and the local salmon stocks that they depend on are being adversely impacted by climate change. Whilst efforts are being made to save the salmon, there is little sign that the Southern Resident orcas can adapt and find new prey. So, put simply, no salmon, no orca!
Whilst the Southern Residents are well studied and monitored, many orca populations globally could be facing similar challenges and we would simply not know because no one is monitoring them sufficiently closely. In fact, new distinctive orca populations are still being discovered in the more remote parts of the world such as the Southern Ocean.
The biggest threat to the ‘Killer of Whales’
There is another significant global threat to orcas in the form of chemical pollution, specifically certain persistent organic substances. Top aquatic predators, especially those at the very apex of aquatic food chain (in this case those preying on other marine mammals), are very susceptible to ‘bioaccumulation’ of pollution – the build up and retention in their bodies of certain persistent chemicals. These pollutants are consumed in their prey, having been concentrated prey to predator up the food chain, leaving marine mammal-eating orcas as the final destination.
A few years ago, chemical pollution impacts were modelled for orca populations globally, leading to the terrible conclusion that many could go extinct in coming decades. Their immune and reproductive systems will become so profoundly compromised that they will be unable to reproduce. No new orca calves, eventually means no population! There are signs that this is already happening. For example, one small and declining population off Scotland has not produced a calf in decades.
Saving the Orcas
It is apparent that orcas are truly remarkable and that, like other sophisticated mammals, sometimes their behaviour is perplexing. Their societies and intelligence make them vulnerable to mental as well as physical suffering (there is very good evidence that they grieve for the loss of a calf or another family member). Like other top predators they would never have been very numerous in the habitats that they live in and the small size of the family units, cultures and eco-types makes them vulnerable to being totally removed. One large net or one explosion in the wrong place at the wrong time could kill one whole discrete and unique population.
So, even though they look so big, strong and capable, we need to recognise their real vulnerability. Small numbers in a regional or local context could easily face group extinction so we should swiftly address threats where we can.
OceanCare is committed to helping orcas and other marine wildlife. Their conservation and their welfare is important to us. We work to draw attention to the challenges they face and to raise awareness of the special features of their biology, an understanding of which is essential to developing scientifically robust plans for their improved protection. We work with many others, supporting appropriate research plans and contributing to relevant international bodies including ASCOBANS, ACCOBAMS, CMS and IWC.
OceanCare’s perspective on the Iberian orcas and their interactions with boats: https://www.oceancare.org/en/stories_and_news/iberian-orcas-boats/
Sources and further Reading
The Conversation (23.05.2024): Why are killer whales attacking boats? Expert Q&A
National Geographic (09.12.2024): Why these orcas are wearing salmon as hats (again)
Smithsonian Magazine (08/2011): Understanding Orca Culture
Science (28.09.2018): Predicting global killer whale population collapse from PCB pollution