Mesoplodon grayi von Haast, 1876

English: Gray's beaked whale
German: Gray-Zweizahnwal
Spanish: Zifio de Gray, ballena picuda de Gray
French: Mésoplodon de Gray

Mesoplodon Grayi © Wurtz-Artescienza (see links).

1. Description

Adults are dark grey, with pale patches on the under-sides. The small head leads to a narrow beak which becomes white in adulthood. The tips of two relatively small, triangular teeth erupt from the lower jaw in males, about one half from the tip of the beak. There are 17-22 pairs of small teeth in the posterior half of the upper jaw. Maximum body size was 5.6m in males and 5.3 m in females (Jefferson et al. 2008). Body mass in adults reaches 1,100 kg; size of newborn calves ranges between 2.1 and 2.4 m (Reidenberg and Laitman, 2009).

2. Distribution

Gray's beaked whale is circumglobal in cool-temperate waters of the Southern Hemisphere, with specimen records from Argentina (Tierra del Fuego, Chubut, and Buenos Aires), Brazil, Falkland Islands/lslas Malvinas, the Estrecho de Magallanes in Chile, Peru (Paracas), Cape Province in South Africa, 31°S, 47°E, in the Indian Ocean, Western Australia, South Australia, Victoria, New South Wales, Tasmania, New Zealand, Chatham Islands, (Rice, 1998).

Distribution of Mesoplodon grayi (Taylor et al. 2008; © IUCN; enlarge map). The species is found in
cold temperate waters of the Southern Hemisphere and ranges South into Antarctic waters
(Pitman, 2002, Jefferson et al. 2008).

There are many sighting records from Antarctic and sub-Antarctic waters, and in the summer months they appear near the Antarctic Peninsula and along the shores of the continent (sometimes in the sea ice; Van Waerebeek et al., 2004; Taylor et al. 2008). Gray's beaked whale is the most common beaked whale species to strand in New Zealand and a cluster of sightings in the area between the South Island of New Zealand and the Chatham Islands may indicate a distributional "hot spot" (Dalebout et al. 2004). There is a record from Brazil (Soto and Vega, 1997), which extends the northern limit of the distribution (Pinedo et al. 2001).

3. Population size

Unknown, although this is one of the more common and widespread mesoplodont whales in the Southern Ocean (Pitman, 2002, 2009). In New Zealand, it is known from both North and South Islands, where it is the second commonest single stranding species after Kogia breviceps, with 180 recorded specimens (Van Waerebeek et al. 2004).

4. Biology and Behaviour

The species is rarely seen at sea due to their oceanic distribution, deep diving ability, elusive behaviour, and possible low abundance (Dalebout et al. 2004). There are an increasing number of confirmed sightings reported from the Southern Ocean in a circumpolar distribution (Van Waerebeek et al. 2004), although most available information is still from stranded animals.

M. grayi appears to be social, which is unusual for beaked whales (but see other species accounts). The limited number of sightings suggests that M. grayi may be more conspicuous at the surface than other beaked whales: it seems to be more active and may live in larger groups. Most animals were observed singly, in pairs, and in small groups, but a mass stranding of 28 animals in the Chatham Islands, east of New Zealand, in 1874 suggests that fairly large numbers may be encountered together (Carwardine, 1995).

The occurrence of early foetuses in May, near-term foetuses in September, and mother with calves in January-February indicates summer breeding in the New Zealand region (Van Waerebeek et al., 2004).

5. Migration

Unknown, however strandings between 30°S and 50°S occur most frequently from December through March, suggesting an inshore movement in summer (Van Waerebeek et al., 2004).

6. Threats

Ship strike: An adult female observed in Mahurangi Harbour, near Warkworth, on the North Island of New Zealand had a series of deep corrugated scars behind her dorsal fin, likely the result of a ship strike (Dalebout et al. 2004).

7. Remarks

Range states: Argentina; Australia ; Brazil; Chile; Falkland Islands (Malvinas); Heard Island and McDonald Islands; Maldives; New Zealand; Peru; South Africa; South Georgia and the South Sandwich Islands ; Uruguay (Taylor et al. 2008).

The species is categorised as "Data Deficient" by the IUCN. Gray's beaked whale is not listed by CMS, but because it also occurs in southern South America, the recommendations listed in Hucke-Gaete (2000) also apply (see Appendix 1). The species is listed in Appendix II of CITES.

8. Sources and further information

see "Genus Mesoplodon - Beaked whales: Introduction and Sources"

© Boris Culik (2010) Odontocetes. The toothed whales: "Mesoplodon grayi". UNEP/CMS Secretariat, Bonn, Germany. http://www.cms.int/reports/small_cetaceans/index.htm
© Illustrations by Maurizio Würtz, Artescienza.
© Maps by IUCN.