Why Baleen Plates Are Becoming the Ultimate Time-Stamped Record for Marine Mammals

A single two-metre baleen plate can hold a continuous, ten-year record of a North Atlantic right whale's reproductive cycles, stress levels, and environmental exposure. Because these keratin sheets grow continuously, the oldest material at the bottom is filed away as new growth occurs, creating a natural, time-stamped archive of an animal's life.

Extracting Decades of Data from Keratin

Collecting blood from elusive marine mammals is often an impossible task for conservation biologists. Kathleen Hunt, a researcher at Oregon State University’s Marine Mammal Institute, has pivoted toward unconventional sample types like baleen, tusks, and whiskers to bypass this hurdle. These keratin-based structures act as biological repositories for hormones and stable isotopes.

To reconstruct a whale's history, researchers perform bulk stable-isotope analysis on nitrogen and carbon. By quantifying the ratios of $^{13}$C to $^{12}$C and $^{15}$N to $^{14}$N using a mass spectrometer, scientists can differentiate seasonal feeding cycles. This isotopic data provides a temporal framework that allows hormone levels to be overlaid onto specific foraging or migration events. In one documented case, a single whale's baleen contained 9.5 distinct isotope cycles, representing nearly its entire final decade of life.

Moving Beyond Daily Hormone Responses

Traditional wildlife endocrinology often relied on faecal analysis, but this method only captures an animal's immediate physiological state. For migratory species with slow reproductive cycles, such as the North Atlantic right whale (Eubalaena glacialis), understanding population dynamics requires a view of cumulative stress over years, not days.

This shift toward longitudinal data is critical for species in rapidly changing environments. In the Arctic, biologists studying belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) are racing to establish baseline data before climate shifts alter their habitats permanently. What were once considered inaccessible species have become the primary subjects for long-term, continuous biological monitoring.

This ability to decode the chemical signatures within keratin is transforming how we understand species resilience and population dynamics in the face of global environmental change.

Source: Meet the biologists deciphering marine-mammal histories from baleen, whiskers and tusks
Domain: nature.com