Blainville’s Beaked Whale, Mesoplodon densirostris

Blainville’s Beaked Whale, Mesoplodon densirostris. Photographs taken in coastal waters off Kona, Hawaii, September 2015. Photography and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny:  Blainville’s Beaked Whale, Mesoplodon densirostris (Blainville, 1817), is a member of the Ziphiidae Family of Beaked Whales. The Ziphiidae Family contains one subfamily and six genera. This species is one of sixteen species of the Mesoplodon Genus, and is the most prevalent. They are also known as the Dense-beaked Whale.

Morphology:  Blainville’s Beaked Whales have robust bodies and a head with a moderately long beak. The mouth line makes a sharp curve up at its midpoint. In mature males, large teeth extend from the lower jaw, above the upper jaw, which may have barnacles attached. The dorsal fin is small and triangular or falcate and lies about two-thirds of the way back on the body. The flippers are small. Dorsally these whales are dark gray transitioning to lighter gray ventrally. They have brownish heads and some have tan or lighter gray blotches. Many are marked with round, white, scars that originate from Cookie Cutter Shark bites. They have lower jaws that are unusually dense, denser than elephant ivory. It is thought that this may be necessary for strength in violent conflicts between males of the species, or that it may improve acoustic accuracy for echo location. The species is known for making a very little splash when they surface, though it lifts much of its head out of the water. Females may reach a maximum 4.6 m (15 feet) in length and 1,000 kg (2,200 lbs) in weight; the males are smaller with a maximum of 4.4 m (14 feet 6 inches) in length and 800 kg (1,800 lbs) in weight.

Habitat and Distribution:  Blainville’s Beaked Whales are an open ocean species. They live from the surface to depths of 1,520 m (4,986 feet). They are usually found in small groups of two to seven individuals. Blainville’s Beaked Whales have a wide distribution in temperate to tropical seas and are found in all Mexican waters of the Atlantic and Pacific Oceans.

Reproduction: As mammals, Blainville’s Beaked Whales are gonochoric and reproduce sexually, with internal fertilization. The males often fight to compete for females, using their tusk-like teeth within their dense jaws. The species is thought to form harems, with a dominant male and several females. Sexual maturity occurs at approximately nine years old. Females give birth to a single calf that can be 2.6 m (8 feet 6 inches) in length and 60 kg (132 lbs) in weight.

Diet:  Blainville’s Beaked Whales are carnivores with their diet typically including, but not limited to, fish, shrimp, and cephalopods such as armhook squid and cock-eyed squid. They feed in deep water and can dive from 500 to 1,000 meters and can remain submerged for up to 45 minutes while feeding.

Predators: Blainville’s Beaked Whales are eaten by Killer Whales, large sharks including the Cookie Cutter  Shark.

Ecosystem Interactions: Blainville’s Beaked Whales host internal parasites such as nematodes. They also host ectoparasites such as whale lice, copepods, and barnacles. Their involvement is commensal or symbiotic relationships has not been documented.

Human Interactions: Blainville’s Beaked Whales have been subject to limited hunting historically. They are currently protected from hunting by international law. They are still at risk of vessel strikes, entanglement in marine debris, and ingestion of marine debris. From a conservation perspective Blainville’s Beaked Whale is currently considered to be of Least Concern, though in some geographical areas it is considered Data Deficient.

Synonyms:  Delphinus densirostris, Nodus densirostris, and Ziphius sechellensis.