New State of Cetaceans report reveals changing picture for whales and dolphins

As the UK and much of Europe experiences another period of extreme heat, the signs of a changing climate are hard to ignore. But the impacts are not confined to land. Our seas are changing too - with warming waters, shifting food webs and more frequent marine heatwaves adding to the growing pressures already facing whales, dolphins and porpoises.

Recent climate reporting from Copernicus has highlighted an exceptionally early and intense heatwave across western Europe, alongside unusually warm sea surface temperatures in parts of the Atlantic and Mediterranean, with some areas more than 5°C above normal for the time of year. These rapid changes make long-term, real-world monitoring of marine wildlife more important than ever.

ORCA’s latest State of Cetaceans report brings together two decades of sightings and environmental data collected by trained citizen scientists from ferries, cruise ships and expedition vessels around the world.

Since effort-based monitoring began in 2006, ORCA has completed 4,731 dedicated surveys, covering 1,848,758 kilometres - the equivalent of travelling more than 46 times around the Earth’s equator. Across that period, surveyors have spent 60,059 hours and 30 minutes actively searching for whales, dolphins and porpoises, almost seven years of watch-keeping effort.

The dataset now includes 54 species of whales, dolphins and porpoises. Common dolphins remain the most frequently recorded species, with 180,818 individuals logged since 2006, followed by harbour porpoises and striped dolphins. Among the larger whales, humpback whales are the most commonly recorded, followed by fin whales and minke whales.

This year’s report also includes a major new analysis of ORCA’s 20-year ferry-based dataset in UK and adjacent waters. Using density surface modelling, ORCA has produced abundance estimates and distribution insights for six commonly recorded species: harbour porpoise, bottlenose dolphin, common dolphin, Risso’s dolphin, white-beaked dolphin and minke whale.

The findings underline the value of long-term citizen science. Harbour porpoises were most frequently recorded in the North Sea, with the analysis reinforcing the growing importance of the southern North Sea for this species. Several Marine Protected Areas in the region, including the Southern North Sea Special Area of Conservation, were designated because of their importance for harbour porpoises.

The report also suggests that common dolphins may be changing how they use the English Channel. ORCA’s analysis estimated around 11,923 common dolphins in the Channel, with high densities in the western Channel and around the Isles of Scilly, but with records also pointing to continued use further east. Understanding whether these changes are linked to prey movement, warming seas or wider ecosystem shifts will be critical for future protection.

In the Southern Ocean, ORCA’s work is also expanding. In partnership with IAATO, expedition teams used the OceanWatchers app to record marine mammal sightings across the Antarctic season. In total, 25 vessels submitted data, recording 12,940 marine mammals, including more than 4,000 humpback whales, 33 blue whales, 166 beaked whales and multiple orca ecotypes.

These records are helping identify where whales and vessels overlap, strengthening work to reduce the risk of ship strikes in some of the world’s most remote and important whale habitats.

As the ocean changes, monitoring must keep pace. ORCA’s long-term citizen-science dataset is helping reveal where whales and dolphins are, how their distribution is changing, and where action is needed to create safer ocean spaces.