Iberian Killer Whales

By Anna Moscrop of Marine Conservation Research

Editor’s Note: Much has been written and is talked of about damage to yachts from Orcas on the Iberian Peninsula’s Atlantic coast, and how it affects the yachting community. We asked research scientist Anna Moscrop –

• Who are these cetaceans, their habits and why they are located in this area?
• How many are there of them?
• Are we are getting in their way? It is reported in some quarters that they are angry with mankind and yachts.
• How do they socialise, what are their breeding patterns, how do they communicate?
• Are they intelligent?

It struck us that understanding them might be a good first step…

Killer whales off the Iberian Peninsula’s Atlantic coast have become rather notorious within the yachting community in recent years, with intense public interest in the interactions between some individuals in this population and passing yachts. The interactions, mostly with medium sized yachts passing through the coastal waters off Spain and Portugal (with occasional reports in the surrounding areas, France to Morocco) were first reported in summer 2020, and now number hundreds of documented interactions. At least one similar episode has been documented off Shetland, although there is little other evidence that the behaviour may be spreading beyond the Iberian Peninsula. Relatively few (20%) of these interactions have resulted in severe damage to the vessels involved, although several yachts have been lost.

However, less well publicised, are details of this population of whales themselves; with their shiny black topsides and striking white marking, killer whales (or orca) are the sleekest hunters in the oceans. The small group off Iberia number fewer than 40 individuals and is a geographically isolated, genetically distinct sub-population, which is classified as Critically Endangered by the International Union for the Conservation of Nature meaning the population has an extremely high risk of extinction in the wild (the IUCN Red list is a global list of species that are at risk of extinction). Photo-identification studies estimated just 37 individuals in 2023, and reproductive rates are low; several whales (including four juveniles, five adults and two others) have been found stranded in the region between 2011 and 2023. These individuals all died.

Although the key prey of this sub-population, bluefin tuna, have now begun to recover in the region, these whales continue to be threatened, for example, by entanglement in fishing gear. In addition, orca, as apex predators which often live in busy industrialised areas, are highly susceptible to toxic chemical pollution, which bioaccumulates in their bodies and leads to health and immune system depression, reproductive impairment and developmental problems. Persistent organic pollutants, including PCBs and similar compounds which were once used widely, including in paints, adhesives, lubricants, electrical components and motor oil, were internationally banned in 2004; however, these highly toxic compounds are particularly problematic for orca and other marine mammals, as they build up in their blubber and organs, passing to their calves through the placenta and their milk. In stranded UK orcas, levels of these banned chemicals are 30 times over the toxic threshold and no calves have been born to the west coast UK population for over 20 years. The UK sub-population is almost certainly on course to become extinct, with only two individuals seen in recent years. Iberian orca are now also perilously low in numbers, and experiencing high calf mortality; they are also sensitive to the fluctuating status of their prey, the Atlantic bluefin tuna, which have previously been considered critically endangered. In addition, there is evidence of a decrease in the survival of adult female killer whales.

Killer whales, which are found in all oceans, are the largest member of the dolphin family; they are highly intelligent, socially complex and long-lived (females can live to 80 years old or more). They are one of the few species (which also includes belugas, narwhals and pilot whales) where post-reproductive females can live for decades and play a key role in society through cultural learning and knowledge transfer. This has been termed the ‘grandmother hypothesis’ by anthropologists, a theory that grandmothers, by helping to feed and care for grandchildren, allow mothers to bear more offshoring that carry both females’ genes. Scientists have documented a similar social system in resident orcas off the Pacific northwest coast of the USA where both males and females remain with their birth pods. Post-reproductive females lead matrilineal groups, guiding younger whales in hunting techniques, and helping protect their sons from injury.

Globally, many distinct populations of killer whales (or orcas) exist and are called ecotypes; they may differ in size, appearance, behaviours as well as specialising to hunt using highly developed techniques to capture specific prey, ranging from fish to seals, sharks and rays, large whales, cephalopods and seabirds; they may also use different vocal repertoires, or dialects, to other ecotypes.

The Iberian whales migrate from the Strait of Gibraltar to the north of the Iberian Peninsula and into the Bay of Biscay during summer, following the movements of their chosen prey, the bluefin tuna. In autumn they spread out from the north into deeper waters, returning to Strait in winter, and remaining through the spring. So called cultural ‘fads’ have been reported in other, well-studied orca populations elsewhere, where a novel behaviour appears and persists in a population and then suddenly, the ephemeral fad can be over. Experts believe that the Iberian orca interacting with yachts are exhibiting such a behavioural ‘fad’ which is likely linked to play and/or social behaviour. Most of the individuals identified as participating in these interactions with yachts have been juveniles, although several are adult females.

The Iberian orca specialise in hunting tuna using active hunting, chasing tuna until the prey are exhausted. They are also known to take tuna from long-line fishing vessels which may result in injuries, including lacerations and amputations from the baited lines, as well as the risk of electrocution from a new threat, tuna stunners, with high electric currents being used to stun fish on longlines.

Although science cannot explain why some members of this small and endangered population of orcas have adopted this new behaviour, the consensus of experts is that this is playful social behaviour, not aggression. Harmful measures used by some to deter the whales appear to be ineffective; they are also illegal and may reinforce the behaviour and increase the severity of damage to vessels, as well as being potentially dangerous to mariners. When spending time at sea, humans enter the realm of marine life; thus, we should prioritise adapting our own actions and behaviour to accommodate and appreciate the presence of wild animals and their habitats, as the survival of these species, indeed our planet and ultimately humanity, depends on it.

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