Description & Behavior

Arnoux’s beaked whales, Berardius arnuxii (Duvernoy, 1851), aka Arnux’s beaked whales, southern four-toothed whales, southern beaked whales, New Zealand beaked whales, southern giant bottlenose whales and southern porpoise whales, are a rare cetacean species. These whales reach up to 9.75 m in length, and their females are thought to be slightly larger than the males. Arnoux’s beaked whales resemble Baird’s beaked whales, but Arnoux’s is slightly smaller. They are predominantly dark brown in color with paler coloring on their head and ventral sides (undersides), which also have white patches. Like other whale species, males show extensive scarring, particularly around their dorsal fins. They are often called southern four-toothed whales because of their 4 teeth found in their lower jaws that are visible even when their mouth is closed. Their head is relatively small and their beak is slender.

Arnoux’s beaked whales are a gregarious species generally found in groups of 6-10, but larger groups of 80 individuals have been recorded. Groups of these whales have been observed swimming under sea ice up to 7 km deep between breaths, a remarkable distance for any cetacean. During breathing intervals near the surface, these whales have been observed changing direction before diving between 249-366 m for long periods of time, up to an hour, in extremely cold water. The surface temperature of the water in the area studied in this case was -0.8°C. In spite of these amazing swimming skills, Arnoux’s beaked whales have been known to become trapped under ice.

World Range & Habitat

Arnoux’s beaked whales, Berardius arnuxii, are found throughout the southern hemisphere from the Antarctic continent and ice edge north, to about 34°S. They are found in the southern Pacific including southeastern Australia 29°S and northern New Zealand 37°S, and in the southern Atlantic to Sao Paolo 24°S, and the Indian Ocean. They are widely distributed; however they are not common within their range. Most reported sightings have been in the Tasman Sea and around the Albatross Cordillera in the South Pacific. Strandings have predominantly been found around New Zealand.

Arnoux’s beaked whales are known to enter pack-ice and are thought to live close to the ice edge in summer and farther out in open water during winter.

There have been many sightings of Arnoux’s beaked whales in the Cook Strait during summer, and sightings of large pods were reported along the western Antarctic coast during spring.

The Arnoux’s beaked whale has been found in both shallow, coastal waters, as well as near continental slopes and seamounts.

Feeding Behavior (Ecology)

Arnoux’s beaked whales, Berardius arnuxii, likely feed on benthic (bottom-dwelling) and pelagic (open water) fishes and cephalopods.

Life History

Arnoux’s beaked whales, Berardius arnuxii, are thought to share similar reproductive habits with Baird’s beaked whales.

Conservation Status & Comments

Arnoux’s beaked whales, Berardius arnuxii, are too widely dispersed in remote areas for commercial hunting. Several individual whales have apparently been taken for scientific study.

References & Further Research

Approximately 60 Arnoux’s beaked whales were seen and photographed frolicking on the surface in the Gerlache Strait, Antarctica (November 4th, 2009).
Whale strife: Elation turns to sorrow
Department of the Environment (2019). Berardius arnuxii in Species Profile and Threats Database, Department of the Environment, Canberra
Center for Cetacean Research and Conservation (CCRC) – Beaked whales (+ videos)
Jefferson, T.A., S. Leatherwood, and M.A. Webber, FAO species identification guide, Marine mammals of the world, Rome, FAO. 1993. 320 p. 587 figs.

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