Wax inside a whale’s ear stores all sorts of useful information on the animal’s exposure to pollutants and stress levels throughout life, researchers have found.
Decimated by historic whaling practices, blue whales number just 5,000–12,000 individuals worldwide, and they are threatened by entanglement in fishing nets, environmental noise and pollution. Scientists have long used whale blubber as a record of the chemicals that these enormous creatures absorb as they traverse the ocean. But analysis of blubber does not indicate when chemical contamination occurred, or how long it lasted.
Whale earwax is a fat-rich deposit that stores the same chemical data as blubber. But it also records time — similarly to the rings of a tree, the wax is laid down in light and dark bands, with each band correlating roughly to a six-month period. In baleen, or filter-feeding, whales, earwax forms a solid plug that may be tens of centimetres long and remains intact even after its death. Learn more here or here.