Ocean life
Atomic fallout helps reveal histories of stranded whales
Scientists examining growth layers in teeth from five stranded cetaceans have discovered new clues about their lifespans, diets, and habitats.
Reported by Phys.org · · 2 min read
Traces of atomic fallout preserved deep within the dental layers of stranded whales have provided researchers with a novel method to reconstruct the animals' lifespans, diets, and oceanic travels. An investigation led by Scottish researchers applied radiocarbon techniques alongside stable isotope measurements to samples gathered from two sperm whales and three killer whales found along Scottish coastlines in past decades.
Mammalian tooth growth rings usually accumulate on a yearly schedule, functioning similarly to tree rings. By tracking the distinct spike and eventual decrease of carbon-14 introduced into the biosphere during mid-twentieth-century atmospheric weapons trials, the team tested this aging metric directly across both species.
New limits on tooth aging
The chemical signatures confirmed that dental rings form annually throughout youthful and mature stages of life. However, the study indicated that this pattern becomes compressed and less dependable in advanced age. For example, a male orca recovered on South Uist in 2015 showed approximately 50 growth rings, yet isotope data confirmed he lived prior to the testing era, putting his actual age at 65 or older and making him one of the oldest recorded males of his kind.
The researchers also explored the history of Moby, a celebrated sperm whale that perished in the Firth of Forth in 1997. Because his earliest dental layers lacked atomic fallout, scientists determined he had reached at least 43 years of age. A second sperm whale discovered in 1994 showed similar yearly ring formation, with both animals displaying rising nitrogen isotope levels over time, matching known dietary shifts toward deeper hunting grounds.
Tracking regional movements
The teeth also reflected geographic ranges and feeding choices. A female killer whale named Lulu, discovered on Tiree in 2016, carried an isotopic signal tied to discharges from the Sellafield nuclear reprocessing site into the Irish Sea. This marker indicated that she foraged largely along the western Scottish coastline and consumed prey higher on the food web, likely including other marine mammals.
Lead investigator Kieran Tierney noted that integrating radiocarbon and stable isotope analyses gives conservationists a more detailed picture of how long-lived marine species migrate, forage, and develop over time.
