Similar in appearance to Baird’s beaked whale, this species has a small head, with a long tube-like beak, moderately steep bulbous forehead, small rounded flippers, short slightly falcate dorsal fin, and (usually) un-notched flukes. A pair of V-shaped throat grooves is present.
Arnoux’s beaked whales are slate gray to light brown; the head region is generally lighter than the rest of the body. The body is often heavily scarred and scratched, and the underside tends to be lighter, and covered with white blotches.
Two pairs of triangular teeth are present at the tip of the lower jaw; they erupt in both sexes and are visible outside the closed mouth. The pair nearest the tip of the jaw is larger.
Arnoux’s beaked whales reach a known maximum size of 9.75 m; females are probably larger than males, as is generally true in beaked whales. Length at birth is unknown, but is probably around 4 m.
Can be Confused With
Arnoux’s beaked whales can be easily confused with southern bottlenose whales, which share much of their range. Differences in head shape, dorsal fin shape, and tooth size and position should be sufficient to distinguish them, if clearly seen. Individuals of some species of Mesoplodon and Indopacetus could also be confused with this species, but they are generally much smaller.
Although this species probably has a circumpolar distribution in deep cold temperate and subpolar waters of the Southern Hemisphere, most records are from the southeast coast of South America, near the Antarctic Peninsula, South Africa, and the Tasman Sea.
Ecology and Behavior
Not much is known of the biology of this species. Most groups number between 6 and 10 individuals, but some as large as 80 whales have been seen. Arnoux’s beaked whales are reportedly shy of boats and can dive for over an hour, making observation difficult.
This species’ reproductive biology is poorly known.
Feeding and Prey
The feeding habits of Arnoux’s beaked whales are assumed to be similar to those of their Northern Hemisphere relatives, Baird’s beaked whales, thus consisting of benthic and pelagic fishes and cephalopods.
Threats and Status
This species has never been hunted to any significant level, and other threats are not known at this point.
Currently, Arnoux’s beaked whales are listed as ‘Lower Risk/Conservation Dependent’ (IUCN) and ‘Not Listed (ESA)’.