Full Breakdown
Scottish Scientists Use Tooth Rings to Date Historic Orca and Whale Remains
By Drooid · · How we work
New Findings on a Historic Orca
Researchers from the SUERC – Centre for the Isotope Sciences and partner universities examined a tooth from a male killer whale that washed ashore on South Uist in the Western Isles. By counting the annual growth rings and analysing the radiocarbon content of each layer, the team concluded the animal was at least 65 years old, making it one of the oldest male orcas recorded. The absence of radioactive fallout from mid-20th-century atmospheric nuclear weapons tests in the oldest tooth layers indicated the whale was born before those tests began.
Radiocarbon Fingerprints as Birth-Year Indicators
Atmospheric nuclear tests conducted by the United States, Russia and the United Kingdom before the 1963 test-ban released radiocarbon that entered marine ecosystems and was incorporated into marine animal tissues. The researchers used the presence—or lack—of this “nuclear fallout” signal to bracket the whale’s birth period. In contrast, a tooth from an orca named Lulu, found on the Isle of Tiree in 2016, displayed a distinct “Sellafield signal” derived from radiocarbon discharges at the Sellafield reprocessing plant, confirming that different nuclear sources leave identifiable marks in marine tooth enamel.
Age Estimates and Lifespan Context
The study noted that male orcas typically live about 30 years, a figure derived mainly from Pacific populations. Two Scottish males, Aquarius and John Coe, are already thought to be over 50 years old, while females can reach their 80s or beyond. The sperm whale known as Moby, whose skull is displayed at the National Museum of Scotland, was estimated to have been at least 43 years old at death after a 1997 stranding.
Institutional Collaboration and Publication
The investigation was a joint effort involving the universities of Glasgow, Edinburgh and St Andrews, National Museums Scotland, and the Scottish Marine Animal Stranding Scheme, which supplied the teeth. Findings were published in *Frontiers in Marine Science*. Dr Kieran Tierney of SUERC explained that his childhood curiosity about Moby’s sudden death motivated his career at the intersection of marine science and isotope research, underscoring the personal drive behind the project.
Why the Research Matters
By linking tooth-ring counts with radiocarbon signatures, the work provides a robust method for ageing large marine mammals, improving understanding of their longevity, population dynamics, and the long-term environmental impacts of historic nuclear activities.