Cetaceans of Crozet and Kerguelen: the whales and dolphins of the French Southern Lands

The French Southern Lands hold the richest community of cetaceans under French sovereignty, and the least visited. Between the Crozet archipelago, the Kerguelen archipelago and the islands of Saint-Paul and Amsterdam, France administers a subantarctic maritime space that is home to a subspecies of dolphin found nowhere else in the world and to one of only two populations of killer whales known to strand deliberately in order to hunt. With 1.66 million square kilometres protected, it is also the second largest marine protected area on the planet.

A maritime territory out of the ordinary

The national nature reserve of the French Southern Lands was created by decree on 3 October 2006, extended in December 2016, then extended again by the decree of 10 February 2022. It now covers 1,662,679 km², of which about 7,700 km² of land and 1,655,000 km² of marine area. That is 15% of the French maritime space, the largest nature reserve in France and the second largest marine protected area in the world.

This figure is not an administrative abstraction. The waters of Crozet and Kerguelen lie on either side of the Antarctic Polar Front, where the upwelling of cold, nutrient-rich water sustains considerable plankton production. It is this mechanism, described on our page devoted to ocean currents and migration, that explains the density of large cetaceans in an otherwise inhospitable sector.

The Kerguelen Commerson’s dolphin, a French endemic

This is the zoological curiosity of the territory, and it is far too little known. Commerson’s dolphin lives in Patagonia and the Falkland Islands. There is also an isolated population at Kerguelen, described in 2007 as a subspecies in its own right under the name Cephalorhynchus commersonii kerguelenensis by Robineau, Goodall, Pichler and Baker.

The two populations are separated by 8,500 km of ocean and no individual, no skeleton, has ever been found on the islands in between, neither at Crozet, nor at Heard, nor at Amsterdam or Saint-Paul. The colonisation of Kerguelen therefore happened once, long ago, and contact was never re-established. The Kerguelen animals are larger and are distinguished by their coloration pattern and their mitochondrial genetics.

An important point for accuracy: no census has ever been carried out on this subspecies. It is not known how many there are. It is the only cetacean endemic to French national territory, and its numbers are unknown.

The Crozet killer whales, and what happened to them

The Crozet killer whale population has been monitored by photo-identification since the 1960s, which makes it one of the best documented in the southern hemisphere. It is famous for an extremely rare hunting technique: strand feeding. The animal propels itself onto the beach to seize a young elephant seal or a fur seal, then works itself free on the next wave. This behaviour is taught by the mothers over several years, the first successful captures coming at around five or six years of age, and it is known in only two populations in the world, that of Crozet and that of Península Valdés in Argentina.

The population trajectory, for its part, is a textbook case of collateral damage.

Period	Individuals identified
1988-1989	93
1998-2000	43
2014	33

The main cause is illegal fishing for Patagonian toothfish, which developed in the area after 1996. Killer whales and sperm whales learned to take the fish directly off the longlines, a behaviour known as depredation, which exposed them to reprisals from the clandestine vessels. The French Navy put an end to this fishing in 2002. The population has not rebuilt at the rate hoped for: in a species whose females breed every three to five years, a decade of adult mortality is not made up within one generation.

Depredation, for its part, has not stopped. It now bears on the legal, regulated fishery, and remains an open economic and scientific problem, at Crozet as at Kerguelen.

The large cetaceans passing through

The French southern waters lie on the route and on the feeding grounds of several mysticetes. The southern right whale passes through, and so does the humpback whale. The fin whale, the sei whale and the Antarctic minke whale frequent the sector in the austral summer.

The most interesting case is that of the pygmy blue whale, a subspecies of the blue whale, which exploits the productive waters of the Kerguelen Plateau and Heard Island. This sector is in fact recognised as an Important Marine Mammal Area by the IUCN working group, under the name “Heard Island, Kerguelen and Surrounding Waters”.

To these are added typically subantarctic odontocetes: the hourglass dolphin, the spectacled porpoise, and several of the most poorly known beaked whales in the world, the southern bottlenose whale, Arnoux’s beaked whale, the strap-toothed whale and Gray’s beaked whale. For the last of these, most of what is known comes from strandings.

What whaling left behind

Kerguelen had a shore whaling station, Port-Jeanne-d’Arc, set up by Norwegian interests in 1908 and worked intermittently until the 1920s. Its ruins survive and are listed. The industrial pelagic whaling in the Southern Ocean that followed took numbers on an altogether different scale: it is what reduced the rorqual populations of the southern hemisphere to a few per cent of their initial level, as our page on the history of whaling recounts.

The recovery observed in the sector today, in particular in the humpback whale and the southern right whale, is therefore measured from a very low floor, and not from a reference state.

How these waters are studied

There is no regular cetacean survey in this sector, for want of available naval resources. Most of what is known comes from the photo-identification carried out from the bases, from strandings, from opportunistic sightings from the Marion Dufresne, and from passive acoustics.

One indirect source deserves to be cited, provided its nature is stated precisely. Since 2004 the international MEOP consortium has fitted elephant seals with oceanographic tags and has assembled more than 870,000 vertical profiles of temperature and salinity, a considerable proportion of them in the austral winter, where no ship goes. These data concern no cetacean: the seals are the carriers, the measurement is physical. They do, however, describe the ocean in which the cetaceans of the sector live, which bears directly on thermal and bathymetric preferences.

France is the consortium’s second largest contributor, with 56 deployments and 395 tags, for 73,494 temperature profiles. The detail deserves to be known, because it says something about the real coverage of the sector: 35 deployments are at Kerguelen, from 2004 to 2024, for 58,016 profiles, and seven in Adélie Land. No deployment, by any country, has been carried out at Crozet. The archipelago that is home to the most studied killer whales of the territory is also the one for which the fewest oceanographic measurements are available.

Can you go there?

Hardly at all. There is no watching tourism in the French Southern Lands. Access is by the Marion Dufresne, the supply ship that serves the bases from Réunion four times a year and takes a very small number of passengers, by application. The rotations last about four weeks. Encounters with cetaceans are possible there but incidental, and the reserve strictly regulates any approach.

For anyone wanting to watch cetaceans under the French flag in accessible conditions, the other overseas collectivities, or mainland France, are far more realistic choices.

Frequently asked questions

Is there a cetacean that exists only in French territory?

Yes, at subspecies rank: the Kerguelen Commerson’s dolphin, Cephalorhynchus commersonii kerguelenensis, described in 2007, occurs nowhere else. Its numbers have never been estimated.

How many killer whales are left at Crozet?

Thirty-three individuals formally identified in 2014, against 93 in 1988-1989. The fall is mainly attributable to the illegal fishing for Patagonian toothfish practised after 1996, which the French Navy brought to an end in 2002.

What is strand feeding?

A hunting technique by which the killer whale throws itself onto the beach to seize a young pinniped, then regains the water. It is taught by the mothers over several years and is known in only two populations in the world, at Crozet and at Península Valdés.

Does the reserve really protect the cetaceans?

It protects the habitat over 1.66 million square kilometres, which is considerable, and fishing there is regulated and monitored. It does not resolve depredation on the longlines, nor the shortfall in survey effort: the numbers of most of the species present are not known. Our page on marine protected areas dedicated to cetaceans places this arrangement among the others.

Sources

• Décret n° 2022-157 du 10 février 2022 portant extension de la réserve naturelle nationale des Terres australes françaises, and presentation of the reserve by the TAAF.
• Robineau D., Goodall R. N. P., Pichler F., Baker C. S., 2007. Description d’une nouvelle sous-espèce du dauphin de Commerson des îles Kerguelen, Cephalorhynchus commersonii kerguelenensis.
• Society for Marine Mammalogy, list of marine mammal species and subspecies, which includes the Kerguelen subspecies.
• Important Marine Mammal Area “Heard Island, Kerguelen and Surrounding Waters”, IUCN working group.
• Roquet F., Guinet C., Charrassin J.-B. et al. “MEOP-CTD in-situ data collection: a Southern Ocean marine-mammals calibrated sea water temperatures and salinities observations”. SEANOE, March 2024 version, doi.org/10.17882/45461, under a Creative Commons Attribution 4.0 licence. French figures calculated from the inventory file list_deployments.csv of the MEOP portal.
• Marine mammal data collected and made freely available by the international MEOP consortium and the national programmes that contribute to it (meop.net).