Rarely seen at sea
The chance of seeing any of the 11 species of beaked whales known to inhabit New Zealand waters is slight. In some cases the only proof of their existence is their bodies washed up along the coastline.
These enigmatic creatures are the least known marine mammals. Their ancestors first appeared about 25 million years ago, making beaked whales one of the earliest whale groups to evolve. Worldwide there are 21 species, and fresh discoveries continue to be made. For example, a pygmy beaked whale, believed to exist only off South America, was found stranded near Kaikōura in 1991.
Beaked whales live in the open ocean, diving at least 300 metres for squid. Varying in length from about 3 metres to 13 metres, they have a small head, a beak and bulging forehead, and pockets for their flippers. The males of some species have teeth that emerge from the bottom jaw like tusks, which they may use to fight other males for females – they have ample scratches to support the theory. However, no one has ever witnessed such battles.
New Zealand’s national museum, Te Papa Tongarewa, has the world’s largest collection of beaked whale skeletons. In the absence of any work on the behaviour of live animals, research in New Zealand concentrates on stranded whales.
The stranding of a Shepherd’s beaked whale (Tasmacetus shepherdi), also known as the Tasman beaked whale, allowed researchers to see exactly what the whale looked like. Up until then, the colour pattern had been determined largely by guesswork. This beaked whale was first discovered and named in 1933 by George Shepherd, curator of the Wanganui Museum, who collected a specimen along the Whanganui coast that year. The skeleton is held at the museum.
Little is known about beaked whales’ vocal signals. In 1995 researchers, including Otago University’s Steve Dawson, first recorded signals from a species known as Baird’s beaked whale off the North American west coast. Instead of clicks made in sequences, with the click rate changing gradually (as for sperm whales and dolphins), Baird’s whales produce an irregular series of few clicks. Some beaked whales also whistle, while others, such as Cuvier’s, appear to make no signal at all.
More common beaked whales
The beaked whale that becomes stranded most often in New Zealand waters is the Gray’s beaked whale (Mesoplodon grayi), also known as the scamperdown whale. It is therefore assumed to be the most common beaked whale in the region. These whales form small herds, and in the 19th century there was a mass stranding of 25 in the Chatham Islands. This implies a similarity with social species such as pilot whales, which sometimes become stranded in large groups.
The male strap-toothed beaked whale has teeth that wrap around its jaw so that it can barely open its mouth. So how does it feed? And how do females, which have no teeth, grasp their prey? Scientists believe the whale sucks up its prey – squid from deep offshore canyons. That belief is backed up by observations of a captive Hubb’s beaked whale, which, when offered some squid, instantly slurped it up.
Three other beaked whales found occasionally in New Zealand are Arnoux’s, Cuvier’s, and the strap-toothed beaked whale. Each has different tooth formations. Arnoux’s beaked whale, or the Southern four-tooth whale (Berardius arnouxi), has two pairs of teeth, one at the front of the jaw and one further back. Cuvier’s beaked whale, or the goose-beaked whale (Ziphius cavirostris), has a single pair of teeth at the very tip of the jaw. The strap-toothed beaked whale (Mesoplodon layardii) has a pair of tusks.
Rare beaked whales
Other beaked whales which have been found rarely in New Zealand waters are the southern bottlenose whale (Hyperoodon planifrons), Andrew's beaked whale or splay-toothed whale (Mesoplodon bowdoini), the dense-beaked whale (Mesoplodon densirostris), the gingko-toothed whale (Mesoplodon gingkodens), Hector’s beaked whale (Mesoplodon hectori), and the Peruvian beaked whale (Mesoplodon peruvianus).