Blainville's Beaked Whale (Mammals of Alabama)

Blainville's Beaked Whale

Mesoplodon densirostris

Summary ⁵

Blainville's beaked whale (Mesoplodon densirostris), or the dense-beaked whale, is the widest ranging mesoplodont whale and perhaps the most documented. The French zoologist Henri de Blainville first described the species in 1817 from a small piece of jaw — the heaviest bone he had ever come across — which resulted in the name densirostris (Latin for "dense beak"). Off the northeastern Bahamas, the animals are particularly well documented, and a photo identification project started sometime after...

Species description ⁶

Weight: 1,800-2,300 lbs (820-1,030 kg)
Length: 15-20 ft (4.5-6 m)
Appearance: round dark gray to brownish-bluish body with a small dorsal fin
Lifespan: unknown, but they reach sexual maturity around 9 years
Diet: small fish and cephalopods like squid
Behavior: deep divers like other beaked whales, usually found in small social groups of about 5
Blainville's beaked whales, sometimes known as the "dense-beaked whale," are little known members of the beaked whale family (Ziphiidae). As adults, Blainville's beaked whales can reach estimated lengths of approximately 15-20 ft (4.5-6 m) and weigh 1,800-2,300 lbs (820-1,030 kg). Males can be easily distinguished from females and juveniles by a pair of large visible tusk-like teeth that erupt and point forward from the heavily arched lower jaw. Females and juveniles have teeth as well, but they remain hidden beneath the gum tissue of the mouth, and their jawline is less-curved.

Blainville's beaked whales have a relatively medium-sized round body with a small, wide-based, slightly "falcate" dorsal fin located far down (about two-thirds) the animal's back. The whale's head has a low, sloping forehead and indistinct "melon". Their coloration varies from dark gray to brownish and bluish. The face and underside of the animal is pale gray or white, giving it a counter-shading appearance. The skin may appear wrinkled on the dorsal area and is covered with linear and oval-shaped scars and other markings. Individuals, especially mature males, accumulate scars and scratches with age. Also, "diatom" infestation may discolor areas of the skin.

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.

Blainville's beaked whales are usually found individually or in small social groups averaging between 3-7 individuals, but have been occasionally seen in larger groups of up to 12 animals. Groups may consist of various combinations and/or be segregated depending on age or sex. Adult populations in productive waters over the continental shelf (like the Bahamas) may be grouped in harems and consist of several adult females with a single adult mature male (Jefferson et al. 2008). Males commonly battle over access to females, which is probably the cause of the long linear scars seen on individuals.

Like other beaked whales, these whales are deep divers. Regular dives range from 20-45 minutes, and commonly reach depths of at least 1,600-3,300 ft (500-1000 m), but dives of over 54 minutes and up to 4,600 ft (1,400 m) have been recorded (Jefferson et. al., 2008). While diving, they use suction to feed on small fish and cephalopods (e.g., squid) in deep water.

Blainville's beaked whales may reach sexual maturity at about 9 years of age. A sexually mature female will give birth to a single newborn calf that is about 6-8.5 ft (1.9-2.6 m) long and weighs about 130 lbs (60 kg). The estimated lifespan of this species is unknown.