Blainville's beaked whale
Mesoplodon densirostris
TAXONOMY
Mesoplodon densirostris (Blainville, 1817), type locality unknown.
OTHER COMMON NAMES
English: Dense beaked whale; German: Blainville-Schnabelwal.
PHYSICAL CHARACTERISTICS
Between 15 and 16 ft long (4.5–5 m), with a relatively long beak and a noticeable arch midway along the lower jaw. In
adult males, this arch becomes enlarged and two large tusks erupt from the top. Younger animals are gray or dark gray on top and pale underneath, however adult animals are often brown, gray, or dark all over. In adult males, the head and back can be covered in a very large number of white scars caused by the tusks of other males.
DISTRIBUTION
Found in all tropical to warm-temperate waters around the globe, although they are most commonly recorded around oceanic tropical islands.
HABITAT
This species is recorded in shallower waters than most other beaked whale species and can be seen in water depths of as little as 330 ft (100 m). Around oceanic islands, most sightings are in water depths of less than 3,300 ft (1,000 m).
BEHAVIOR
Relatively little is known about behavior other than the fact that they are deep-divers and often dive for up to 30 minutes or more. However, the heavy scarring found on adult males indicates that they engage in aggressive combat, presumably over access to females.
FEEDING ECOLOGY AND DIET
Deepwater squid and fish have been recorded in the stomachs of Blainville's beaked whales, and they are thought to forage at or close to the seabed.
REPRODUCTIVE BIOLOGY
Apparently polygamous, with adult males competing aggressively with each other for access to females. Groups with more than one adult male are rarely recorded. However, males do not appear to remain with a single female group and may rove between them looking for receptive females. Calves remain close to their mothers for the first year, with weaning occurring after 12 months. Both sexes mature at around 10 years of age.
CONSERVATION STATUS
Classified as Data Deficient by the IUCN. Although occasionally killed by fishermen, either purposefully or accidentally in fishing nets set for other species, this species has never been hunted commercially.
SIGNIFICANCE TO HUMANS
Generally unknown to most humans and, when encountered, few people even identify them correctly, most thinking they are large dolphins.
