What is a northern bottlenose whale?

Little known to the general public, the northern bottlenose whale (Hyperoodon ampullatus), also called simply the bottlenose whale, is one of the most fascinating beaked whales of the North Atlantic. Discreet, a deep diver, social, it belongs to the same family as Cuvier’s beaked whale (the Ziphiidae) and shares several diving records with it. Its history, biological as much as conservation related, is worth pausing over.

A large beaked whale

The northern bottlenose whale is one of the largest known beaked whales. Adults measure 7 to 9 metres on average, and old males can reach almost 10 metres for a weight of more than 7 tonnes. The body is massive and streamlined, adapted to prolonged diving.

Its most recognisable distinctive feature is its extremely bulbous forehead, the melon, particularly developed in old males. With age this melon becomes rounder and paler, sometimes taking on an almost white colour in old dominant males. This characteristic allows experienced observers to identify individuals and to tell age classes apart within a population.

The body shows a variable coloration, from greenish brown to dark grey, almost chocolate. The belly is generally lighter. Young individuals are darker and lighten gradually with age, the reverse of the pattern seen in Risso’s dolphins.

A diver of the deep

Like all ziphiids, the bottlenose whale is a champion of the deep dive. It can descend regularly below 1,000 metres, sometimes to 1,800 metres, and hold its breath for more than an hour. Its close relative, Cuvier’s beaked whale, holds the absolute record among marine mammals (2,992 m and 222 minutes), but the bottlenose whale is not far behind.

Its diet is made up mainly of cephalopods: squid above all, supplemented by a few deep-sea fish. This specialisation places it ecologically close to the sperm whale, with which it shares certain foraging grounds in the North Atlantic.

A social species

Unlike several other ziphiids, which lead a rather solitary life, the northern bottlenose whale is decidedly social. It lives in small stable groups of 4 to 10 individuals, sometimes more, with a social organisation comparable to that of sperm whales: matrilines, cultural transmission, perhaps even the use of acoustic dialects between groups.

This sociability has a dramatic consequence: when an individual is injured, sick or in distress, the whole group stays with it and remains nearby. During the great period of industrial hunting of ziphiids in the 20^th century (notably by Norwegian whalers), this collective loyalty was exploited by the hunters: they first killed one individual, then waited for the rest of the group to return to the spot in order to shoot them one after another. The population was decimated by this “easy hunting”.

Range and sightings

The northern bottlenose whale lives in the cold, deep waters of the North Atlantic, mainly between Canada, Greenland, Iceland, Norway and the British Isles. It rarely enters mainland French waters, but a few sightings in the Bay of Biscay are reported each year, particularly along the Capbreton Canyon and near the submarine canyons.

The species is very difficult to observe at sea. Its time at the surface is short (a few minutes between two dives of 30 to 60 minutes), its blow is barely visible, and its behaviour generally remains discreet. The researchers who study it rely on long stays on the open sea and on chance opportunities. Hyperoodon Watch, a scientific monitoring programme run in the North Atlantic, patiently accumulates data year after year.

Conservation: a vulnerable species

The northern bottlenose whale is classified as Near Threatened by the IUCN. Present populations, after the collapse caused by historical whaling (notably between 1880 and 1973), are rebuilding slowly. Like all ziphiids, the species is particularly vulnerable to mid-frequency military sonar: its extreme diving physiology makes it sensitive to acoustic disturbance, which can cause panicked ascents and fatal decompression accidents.

The other threats include bycatch in deep-water fishing gear, ingestion of plastic debris (ziphiids being particularly affected because of their squid diet and their tendency to seize anything resembling prey at depth), and chemical pollution, which accumulates in their blubber.

The northern bottlenose whale remains one of the least known cetaceans of the North Atlantic, a discreet but valuable witness to the biodiversity of the ocean depths. Every sighting, every chance encounter adds to knowledge of a species that deserves far stronger protection than it has today.

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