The first writeup covered the evolution and the ecology of our March Mammal Madness Winners the Orca, and here we will look at their intelligence and behaviour, and what the future may hold for this incredible species.
Life in the pod: the behaviour and social structure of Orcas
A pod of orca (image from us.whales.org)
Aside from elephants and certain high-level primates, there are few animals that come close to the complex sociality of the orca. Pods are female led, or matrilineal, with the eldest female, or matriarch, leading the pod, surrounded by her sons, daughters and their descendants. This makes orcas quite unusual in the animal kingdom, as resident whales live with their mothers their whole lives. Orcas can reach the age of 90, and so as many as four generations may travel, forage and socialise together. These groups remain pretty stable, with individuals rarely leaving permanently, but rather for a short time to hunt.
After pods, the next social structure are clans, consisting of pods with a more distant relation and close dialects with overlapping ranges. Above this is the community, made up of several pods that commonly associate with each other. Although orcas will spend most of their time socialising, hunting and playing with their pod, males will leave to mate females from outside the pod, preventing inbreeding.
For a long time, studies of sociality in orcas could only be done from boats when they popped to the surface to breathe, making it pretty tricky to get enough data. Now, the use of drones has allowed marine biologists to study their more complex interactions from the air. New studies found that orcas spend most of their time interacting with certain individuals in their pod, generally favouring those of the same sex and similar age. It was also discovered that as the orcas age, they tend to grow apart, with friendship bonds appearing to be not so close in older age.
A shot taken from a drone. Scientists are utilising drones to better research orca sociality and behaviour (image from the New Scientist)
Culture shock: the cultural evolution of orcas
Orcas have the second biggest brains of all ocean mammals, weighing as much as 15 pounds. But does this equal high intelligence?
Often, measures of intelligence are done using the brain to body mass measurements, which puts humans at seven times the average, and orcas around chimpanzees at 2 and a half times the average. But many scientists now think this metric seriously oversimplifies measurements of intelligence, which is an incredibly difficult thing to measure, and is often seen through the eyes of human intelligence, when animal intelligence can be very different but equally as impressive. In 2001, a professor from Nova Scotia University sparked controversy when he stated in a research paper that orcas have a culture that puts them close to humans. He explained that ‘culture is about learning from others, a cultural species starts behaving differently than a species where everything is determined genetically.’ For example, the dangerous hunting technique mentioned in the part one writeup, where orcas breach themselves on the beach in pursuit of seals and sea lions. Biologists have seen mothers repeatedly pushing their calves up onto beaches, at times having to intervene to drag their beached calves back into the water. Different pods have their own unique ways of catching their prey, which is passed down from mother to child through the generations. It also appears that they are quite reluctant to change their hunting techniques, conserving strategies within the pod. In the 1800s, when unfortunately whaling was common, orcas off the coast of Australia were known to herd whales towards whaling ships and alerting the whalers to the distressed whale by breaching and tail slapping. The whalers would then kill the whale, allowing the orcas to feed for a short time before dragging the carcass away. The whales in the area were well known for doing this for hundreds of years, as local aboriginals explained. This level of cooperation with another species in this pod shows not only that they can pass their culture down, but that they have real smarts. Although orcas of different clans tend to stay pretty divided, their culture can also unite them. In 1987, a female orca off the coast of Washington started wearing a salmon on her head, like a particularly fetching fishy hat. Within weeks, others from the same pod had started doing the same, and within weeks, orcas in different pods were doing the same thing. By the following year, this behaviour had stopped. No one can explain exactly why they decided on a salmon accessory, but fascinatingly it showed how, like in humans, one trendsetter can send a fad viral. Its also true that like humans, closely sticking to culture can be damaging too. In the Salish sea, the resident orca population there developed a custom of only eating chinook salmon for no apparent reason. When chinook salmon numbers began to drop, the orcas didn’t switch to the perfectly nutritious sockeye salmon in the same waters, and began to starve.
It isn’t just their behaviour that is cultural, but also their language. Like all cetaceans, orcas rely heavily on underwater sound to orient themselves, communicate and find prey. They use three categories of sounds; clicks, likely used primarily for navigation and discriminating objects, although they are heard in social interactions, and whistles and pulsed calls. Different pods use different dialects, composed of distinctive repetitive calls that rarely change over time. Orcas can even hear their mother in the womb, so are learning their pods language before they are even born! Scientists can actually distinguish different orca ecotypes just by listening to recording of their clicks. Orcas hear these sounds through their lower jaw, where a body of fat picks up the vibrations in the hollow jawbone and are carried to the middle and inner ears. In their foreheads, orcas have large sinuses which they use to produce sounds.
The physiological structures that allow orcas to hear and communicate (image from www.seattletimes.com)
Captivity and conservation: the future of the Orca
Currently, the orca is listed as data deficient by the IUCN. This came about in 2008 when there was recognition that the different orca ecotypes could be suffering differing levels of threats to their population numbers. Although orcas are abundant and widely distributed, some small regional populations are known to have declined significantly and if they were assessed separately by the IUCN would most likely be assigned threatened status. There is still a lot of research to be done to fully understand the taxonomy of the orca, and until this is done an IUCN category can’t be assigned. Given how complex orca societies and interactions are, this data deficient category may be hard to shake.
On the topic of their complexity, there is a difficult conversation ongoing about Orcas in captivity. Given our better understanding of their intelligence and social complexity today, many scientists and conservationists, along with the public, are considering the ethics of keeping such animals in captivity. Although there are some discussions about releasing captive individuals, it seems unlikely that all orcas in aquariums and sea parks will be released, but it does seem likely that we will not see any more of orcas in captivity in the future,
Although orca populations are considered relatively stable in most cases, they are not escaping the pressures of the human world. In particular, certain orca ecotypes are especially vulnerable to prey depletion, thanks to their dinner preferences. Off the coast of British Columbia and Washington state, the salmon loving orcas living there have been facing year on year salmon depletions due to overfishing and habitat disruption. In the Strait of Gibraltar, the loss of Bluefin Tuna stocks has definitely affected the continued survival of orcas in the region. Globally, there have been large scale reductions in fish populations as a result of overfishing and disruptions to the marine food webs. This not only affects the fish-eating orca ecotypes, but also affects those that prefer a mammal for dinner. Collapse of prey species has led to decreases in mammal populations, like seals, limiting the food available for orcas. Fish eating orca ecotypes are also in direct competition with many fishermen, and there have been issues with orcas being shot.
A graphic depicting how so called ‘forever chemicals’ end up bioaccumulating in top ocean predators like the orca (image from Alava et al, 2012)
As the highest trophic level of the food webs, orcas are especially susceptible to poisoning from the bioaccumulation of toxins that are building up in the food web level upon level, from krill all the way up to seals and sharks. A lot of focus has been applied to PCBs (polychlorinated biphenyls), highly carcinogenic chemicals that were once widely used in consumer products but have since been banned due to their links with cancer. The Southern Resident and Transient orcas of British Columbia and Washington are considered some of the most contaminated cetaceans in the world, and some of the rarer ecotypes are in serious danger of poisoning from these chemicals, as well as risks to their reproduction.
Although ecotourism can be an excellent way to generate income for locals that doesn’t include the hunting of animals, there are some concerns expressed by marine biologists over the effects of whale watching boats. For example, boats approaching too close to orca pods can cause avoidant behaviour, which although not yet tested presumably carries some energetic costs. There are also some risks from fast moving boats, which can strike and seriously injure or even kill any unfortunate orcas that didn’t hear it coming. Like most cetaceans, the increasing clamour underwater from shipping lanes and undersea drilling is a serious concern. Echolocation can be seriously disrupted, affecting hunting and communication, distracting the orcas from catching their dinner and leaving them hungry.
Fortunately, with their incredible intelligence, orca can be incredibly adaptable, and in many places their numbers are holding strong despite the changes going on around them. However, the oceans are being placed under intense pressure across much of the big blue, and who can say exactly how orca will cope, especially given how varied the different ecotypes are and how little we truly understand them.
Conservation optimism
To truly understand how to safeguard the future of the orca, far more research is needed into the different ecotypes and their population structures, abundance and life history. It is likely that there are unknown populations across the oceans that are currently struggling, but we just don’t know about it.
But this is where organisations like the Centre for Whale Research step in. Since 1976, the organisation has been conducting annual surveys of various orca populations, monitoring population numbers, orca health and number of calves year on year. The detailed information the Centre collects has been used to inform management decisions in both Canada and the United States. Currently, the Southern Resident Orcas, one the main focuses of the Centres’ research, has been listed as one of the most critically endangered populations of marine mammals in the USA, and are registered on the Endangered Species Act. Their research into Chinook salmon has shown how closely linked orca and salmon populations are, with higher orca mortality linked to lower salmon abundance. The Centre is the leading organisation studying the Southern Resident Killer Whales in their most critical habitat: the Salish Sea. Visit them at Orcas // Killer Whales | United States | Center For Whale Research to learn more about their amazing research and how you can help save these champions of the podcast.
If you are interested in adopting an orca for a friend, loved one or even yourself, Whale and Dolphin Conservation are a UK charity that offer adoption of orcas, humpbacks and dolphins at Adopt a whale or dolphin – Whale and Dolphin Conservation (whales.org). WDC don’t focus solely on orcas but on another cetaceans, and aim to safeguard healthy seas for all whales and dolphins.
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References
Alava, J.J. Ross, P.S. Lachmuth, C. Ford, J.K.B. Hickie, B.E. and Gobas, F. A.P.C. (2012) ‘Habitat based PCB environmental quality criteria for the protection of endangered killer whales.’ Environmental Science and Technology
Filatova, O.A. Samarra, F.I.P. Deecke, V.B. Ford, J.K.B. Miller, P.J.O. and Yurk, H. (2015) ‘Cultural evolution of killer whale calls: background, mechanisms and consequences.’ Behaviour
Fisheries and Oceans Cananda (2017) ‘Action Plan for the Northern and Southern Resident Killer Whale in Canada.’
Foote, A.D. Vijay, N. Avila-Arcos, M.C Baird, R.W. Durban, J.W. Fumagalli, M. Gibbs, R.A. Hanson, M.B. Korneliussen, T.S. Martin, M.D. Robertson, K.M. Sousa, V.C. Vieira, F.G. Vinar, T. Wade, P. Worley, K.C. Excoffier, L. Morin, P.A. Gilbert, M.T.P. and Wolf J.B.W. (2016) ‘Genome culture coevolution promotes rapid divergence of killer whale ecotypes.’ Nature Communications
Muka, S. and Zarpentine, C. (2023) ‘Southern resident orca conservation: practical, ethical and political issues.’ Ethics, Policy and Environment
Ross, P.S. (2006) ‘Fireproof Killer Whales: flame retardant chemicals and the conservation imperative in the charismatic icon of British Columbia, Canada.’ Canadian Journal of Fisheries and Aquatic Sciences
Weiss, M.N. Franks, D.W. Giles, D.A. Youngstrom, S. Wasser, S.K. Balcomb, K.C. Ellifrit, D.K. Domenici, P. Cant, M.A. Ellis, S. Nielsen, M.L.K. Grimes, C. and Croft, D.P. (2021) ‘Age and sex influence social interactions, but not associations within a killer whale pod.’ Proceedings of the Royal Society B
Whitehead, H. (2020) ‘Cultural specialisation and genetic diversity: killer whales and beyond.’ Journal of Theoretical Biology
Williams, R. Lusseau, D. and Hammond, P.S. (2006) ‘Estimating relative energetic costs of human disturbance to killer whales.’ Biological Conservation
MASSIVE THANK YOU TO RACHAEL DA SILVA FROM THE UK FOR THIS WRITE UP! PLEASE FOLLOW HER ON INSTAGRAM AND HER WILDLIFE ARTWORK AT TILLY_MINT08
