Thermal and bathymetric preferences of cetaceans

An ecological map of cetaceans

Each cetacean species occupies a precise ecological niche defined by its preferred temperature and its depth. Cuvier’s beaked whale lives between 200 and 3000 m, the bowhead whale at the edge of the sea ice (-1 to 4°C), the tropical dolphin in warm surface water (24-30°C).

Ecological niche: why each cetacean has its own temperature

The thermal preference of a species follows from a trade-off between its thermoregulation (blubber thickness, rete mirabile, body surface) and the availability of its prey. The large blue and bowhead whales tolerate polar waters because their mass and their fat limit heat loss, whereas small tropical delphinids stay in warm waters for lack of sufficient insulation.

One also speaks of a bathymetric niche: Cuvier’s beaked whale dives to more than 2,000 m to hunt mesopelagic cephalopods, while the harbour porpoise stays on the continental shelf (less than 200 m). Ocean warming is shifting these niches, pushing temperate species such as the common bottlenose dolphin northwards and thinning out the bowhead whale at the edge of the retreating Arctic sea ice.

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Habitat governs distribution: annual migrations, ocean currents, sighting hotspots and climate change.