Whale earwax reveals the detrimental impact human activity has on marine mammals

A new study co-authored by the Museum, and published in Nature Communications, shows that whales experienced a physical stress response when they were hunted on an industrial scale in the 1920s, 1930s and during the Second World War.

Researchers led by Baylor University in Texas, USA wanted to examine earplugs; a waxy material continually formed within the ear canal throughout a whale’s lifespan. Earplugs contain fats and proteins which reveal the type and quantities of hormones inside a whale's body at various points of its life, offering insights into its experiences. The team, which included the Museum’s principal curator of marine mammals Richard Sabin, were particularly interested in cortisol, a hormone that mammals produce at times of stress.

Using whale earplugs from the Museum's Collection, the collection of the Smithsonian National Museum of Natural History and samples taken at recent strandings, the group were able to create lifetime 'stress profiles' of 20 whales from three species: humpback, fin and blue whales - some of the most hunted species of the twentieth century when the global whaling industry boomed.

The profiles resulted in a 146-year dataset, measuring the stress responses of animals from 1870 to 2016. It discovered that the whales were particularly stressed during the 1920s and 1930s; a time of extremely high whale harvests in the northern hemisphere. Approximately 50,000 fin, humpback and blue whales were killed in the 1930s.

‘Earplugs have been of interest to scientists since the start of the century,’ says Richard Sabin, curator of marine mammals at the Museum. 'This research really shows the power and significance of archived natural history collections. Each year, new analytical techniques allow more information to be extracted from the often centuries-old preserved remains of museum specimens.

The study also showed that the Second World War (1939-1945) provoked a stress response from the animals. Commercial hunting had slowed dramatically at the time, but researchers found that the cortisol levels in whales kept increasing. The data suggests that naval battles and underwater bombs, for example, may have simply replaced the whaling industry as a source of stress. It is thought that Baleen whales may be particularly affected during a period of global conflict because they migrate so far around the world during their lifetimes, increasing the chances of them coming into contact with battles at sea.

The Museum contributed eight earplugs from its research collection for this study, covering the period from 1870 to 1956.

Richard adds, 'How incredible it is to be part of a study which shows not only the stressful effects of commercial whaling, but also the ongoing stress caused by other anthropogenic activities. It really demonstrates the importance of combining long-term datasets to help us understand the causes and effects our actions have on the natural world.'

Ends

Notes for editors

Images: Please download and credit: © The Trustees of the Natural History Museum, London (Link not for publication)

Media contact: Tel: +44 (0) 20 7942 5654/+44 (0)7799 690151 Email: press@nhm.ac.uk

·         The Natural History Museum exists to inspire a love of the natural world and unlock answers to the big issues facing humanity and the planet. It is a world-leading science research centre, and through its unique collection and unrivalled expertise it is tackling issues such as food security, eradicating diseases and managing resource scarcity. The Natural History Museum is the most visited natural history museum in Europe and the top science attraction in the UK; we welcome more than 4.5 million visitors each year and our website receives over 500,000 unique visitors a month. People come from around the world to enjoy our galleries and events and engage both in-person and online with our science and learning activities through innovative programmes such as citizen science and family festivals. www.nhm.ac.uk