They dominate the oceans, chase in groups, are transmitted know-how and weave family ties of remarkable complexity. For decades, orcas have embodied social intelligence in the wild. But sometimes, only one individual is enough to shake all certainties. The history of this lonely orca, observed for twenty years in the cold waters of the Northwest Atlantic, forces scientists to review their most established benchmarks.
His annual return fascinates tourists as much as he intrigues marine biologists. Unlike its Pacific fellows, familiar with the temperate waters of British Columbia or Alaska, this orca frequents a territory where its presence should fall under the exception. Scientists from the region, accustomed to track the formidable large white shark, had never considered that such a cetacean could settle, even temporarily, in this unmanned corner of the North Atlantic.
And for good reason, a study conducted by the Canadian Department of Fisheries and Oceans, published in the Journal of the Marine Biological Association of the UK, lists barely 67 distinct individuals throughout North West Atlantic, an estimate still deemed far below reality. Less than 10% of the 836 historical reports could be confirmed by photo-identification, and the majority concern water-Neuve and Labrador waters. In the Gulf of Maine or off the coast of Massachusetts, observations remain extremely rare.
What the solitary orca reveals about social ties among cetaceans
It is not so much the geographic scarcity of Old Thom that disturbs experts, but its way of life. Orcas are renowned for their strong social cohesion. Individuals generally evolve in family groups, often matrilinear, with lasting ties between mothers and their adult sons. The idea that an adult male, probably eater of fish, could live isolated for years goes against all established models.
Usually, the Piscivorous Orcs never leave their original group. However, Old Thom has always been seen alone, without any other orca. Its frequent proximity with dolphins on white Atlantic sides, sometimes described as a camaraderie, is not enough to compensate for the absence of contacts with its fellows. This behavior raises deep questions about its adaptability, and on the social plasticity of orcas.
Deborah Giles, researcher at the University of Washington, underlines the anomaly that this individual represents. In resident orcas of the North Pacific, the disappearance of a mother often leads to a rapid decline in the health of the adult son. However, Old Thom returns every year, apparently in good shape. This resilience suggests that are still poorly understood compensatory mechanisms, or an extraordinary form of social learning. Perhaps he developed a mimetic communication mode with the dolphins that accompany it, such as some documented cases in isolated orcas having imitated seal sounds or boat engines, according to Smithsonian Magazine.
When the exception calls into question a whole science
Old Thom is not only a photogenic animal that has become a local star of observation cruises. It is also the symptom of a structural bias in research on the Orcs of the North Atlantic. Unlike their Pacific counterparts, widely studied since the 1970s, cetaceans in this region have long escaped monitoring efforts. Even the New England Aquarium airline campaigns, however intensive, report few observations of orcas, for lack of means or targeted strategies.
The case of Old Thom highlights the limits of current knowledge on the real distribution of orcas off the American and Canadian coast. The study of Lawson and Stevens also indicates that the majority of historical reports focus on some specific areas, such as Newfoundland or the Strait of Belle-Isle, which suggests that other individuals may go unnoticed elsewhere. Researchers now call for strengthening biopsy, acoustic monitoring and sampling campaigns, even faeces, to better understand the genetic origin of this individual and its possible belonging to a little -known population.
The story of Old Thom forcefully illustrates the immense part of the unknown that remains in the study of the great cetaceans. Through a black silhouette arising between two waves, a whole section of marine science flickering, revealing the need to rethink what we believed acquired about the distribution, the behavior and the social dynamics of one of the most fascinating species of our oceans.
