Sowerbys Beaked Whale, Beaked Whale

Sowerby's beaked whales prefer the deep, cold temperate and subarctic waters of the North Atlantic Ocean, but have been reported near the ice pack as well.

Sowerby's beaked whales are distributed throughout the North Atlantic Ocean (30-71° North), which includes the Norwegian Sea, Labrador Sea, Iceland, Baltic Sea, and south to Massachusetts, Madeira, and the Canaries. Reports of this species in Canadian waters are considered rare. They are not known to occur in the Mediterranean Sea. Strandings have occurred in Florida and Italy, but these are considered outside their normal range. Their distribution may vary depending on the movements of oceanographic currents. There are no known seasonal movements or migrations for this species. Population Trends

Species Description Weight: 2,200-2,900 lbs (1,000-1,315 kg) Length: 14.5-21 ft (4.5-5.5 m) Appearance: small to medium-sized charcoal gray body with a very long, slender beak and a bulge on the forehead area Lifespan: unknown, but sexually mature at around 7 years Diet: small fish like Atlantic cod and cephalopods like squid Behavior: they have a low profile at the surface and a small, inconspicuous blow, making them difficult to observe and identify at sea Sowerby's beaked whales, sometimes known as the "North Atlantic beaked whale," are little known members of the beaked whale family (Ziphiidae). As adults, Sowerby's beaked whales can reach estimated lengths of 14.5-21 ft (4.4-5.5 m) and weigh 2,200-2,900 lbs (1,000-1,318 kg). Males, which are generally larger, can be distinguished from females and juveniles by a pair of visible teeth that erupt from the slightly arched lower jaw. Females and juveniles have teeth as well, but the teeth remain hidden beneath the gum tissue of the mouth, and their jawline is straight. This species of beaked whale is difficult to observe and identify at sea due to a low profile at the surface and a small, inconspicuous blow. Sowerby's beaked whales have a small to medium-sized body with a very long, slender beak relative to other mesoplodonts, as well as a bulge on the forehead area. The beak often emerges at a steep angle when surfacing. They have a small, wide-based, slightly "falcate" "dorsal" fin located far down (about two-thirds) the animal's back. Most of the body has a charcoal gray coloration with a pale underside. The lower jaw is usually light gray or white. Calves are generally darker than adults. This species has less visible scarring than most other beaked whale species. Many species of beaked whales (especially those in the genus Mesoplodon) are very difficult to distinguish from one another (even when dead). At sea, they are challenging to observe and identify to the species level due to their cryptic, skittish behavior, a low profile, and a small, inconspicuous blow at the waters surface; therefore, much of the available characterization for beaked whales is to genus level only. Uncertainty regarding species identification of beaked whales often exists because of a lack of easily discernable or distinct physical characteristics. Sowerby's whales are usually found individually or in small, closely associated groups averaging between 3-10 individuals. Regular dives range from 10-15 minutes, but dives of at least 28 minutes reaching depths up to 4,920 ft (1,500 m) have been recorded. While diving, they use suction to feed on small fish (e.g., Atlantic cod) and cephalopods (e.g., squid) in deep waters. Sowerby's beaked whales may reach sexual maturity at about 7 years of age. Their breeding season may be from late winter to spring. A sexually mature female will give birth to a single newborn calf that is about 8-9 ft (2.4-2.7 m) long and weighs about 375 lbs (170 kg). The estimated lifespan of this species is unknown.

• Sowerby's beaked whale was the first living species of beaked whale to be discovered. • Sowerby's beaked whale's scientific species name (bidens) is derived from the Latin word bi for "two" and dens for "teeth.

Head Shape Melon is convex, though not bulbous and is defined posteriorly by the indentation at the blowhole. The forehead merges seamlessly to the long, narrow beak. The mouthline is sinusoidal, but not strongly arched. Coloration Dorsal coloration is bluish-gray or slate. Sides are lighter, grading to a white ventral surface. Gray or white scars, visible as linear streaks or round / oval spots, may be distributed irregularly on sides. This pattern is the same for both sexes. Size Adult body length ranges between 4.5 to 5.5 m. Recorded maximum body length for adult males and females is 5.5 m and 5.2 m, respectively. Body length at birth is 2.4 m. Most Likely Confused With: Mesoplodon europaeus Mesoplodon mirus

For management purposes, Sowerby's beaked whales inhabiting U.S. waters have been placed in the Western North Atlantic stock. No current population estimates are available for this species of beaked whale. The status of the stock is unknown, but is classified as "strategic." This species may be relatively abundant in the North Sea. There are insufficient data to determine the population trends for this species, but they are probably not rare.

Diagnostic features of the skull and mandible On the vertex of the dorsal skull, the premaxillary bone extends forward of the nasal and frontal. Separates from Berardius and Ziphius. A sulcus (groove) running along the middle of the combined surfaces of the nasal bones so depresses their middle that it is the lateral portion of each nasal bone that reaches farthest forward on the vertex. Separates from Tasmacetus and Indopacetus. When the skull is upright and the long axis of the anterior half of the beak is horizontal, a horizontal plane transecting the summit of either maxillary prominence transects the mesethmoid bone. Separates from Hyperoodon. Tooth alveoli of mandible overlap or are positioned slightly anterior to the mandibular symphysis. Separates from Berardius, Ziphius, Tasmacetus, Indopacetus, Hyperoodon, M. hectori, M. mirus, M. perrini, M. densirostris, M. ginkgodens, M. peruvianus, and M. stejnegeri Basirostral groove absent or present as a shallow groove that does not extend past the prominental notch. Separates from M. grayi and M. layardii. The maxillary prominences rise less than 10 mm higher than the height of the premaxillaries where the latter passes between the former. Separates from M. bowdoini, M. carlhubbsi, and M. europaeus.

Map showing Sowerby's Beaked Whale range

Found in the temperate waters of the North Atlantic Ocean. Stranding records are more common in the eastern North Atlantic, with the bulk of stranding records from the British Isles and North Sea. The northern limit in the eastern Atlantic extends to 71o 30’ N in the Norwegian Sea; the western Atlantic range extends to Labrador. The southern limit lies between 33o and 41o N. Stranding records from Florida are probably extralimital. Water depths where sightings have occurred range from 200 to 1500 m.

By catch from fishing gear, such as driftnets and gillnets off the U.S. Atlantic coast Hunting, cetaceans are targeted in Newfoundland and by Norwegian whalers off of Iceland and in the Barents Sea Underwater sounds and anthropogenic noise - anthropogenic noise levels in the world's oceans are an increasing habitat concern, particularly for deep-diving cetaceans like Sowerby's beaked whales that use sound to feed, communicate, and navigate in the ocean

Tooth position A single pair of teeth is positioned midway between the apex of the beak and the posterior end of the mouth. Tooth exposure Erupted teeth in adult males are covered by gum tissue, with only the tip of tooth exposed. Teeth do not erupt in females or juveniles. Tooth shape In lateral profile, the anterior margin is weakly sinusoidal (convex proximally, concave distally) and is longer than the strongly convex posterior margin. A denticle is positioned at the top of the anterior edge of the tooth. When the denticle is not excessively worn, it extends well past the antero-dorsal edge of the tooth.