True's Beaked Whale

True's beaked whale (Mesoplodon mirus) is one of 21 species of beaked whales (Hyperoodontidae or Ziphiidae), medium-sized whales with distinctive, long narrow beaks and dorsal fins which are set far toward the posterior. This species is a marine mammal within the order of cetaceans.

True's beaked whale is a toothed whale and can be recognised as such by the single blowhole as well as the presence of teeth (rather than baleen). Because of the highly disjunctive distribution patches of True's beaked whale, it is possible that the northern and southern hemisphere temperate ocean populations are actually distinct species or subspecies. Threats to the species include bycatch and underwater noise pollution.

Did You Know? • True's beaked whales receive their common name from Frederick W. True, who was a curator at the Smithsonian Institution, and described the species from an animal that stranded on a beach in North Carolina (Reeves et al. 2002). • Animals living in the northern hemisphere have different coloration from those living in the southern hemisphere. Status MMPA - True's beaked whales, like all marine mammals, are protected under the MMPA. CITES Appendix II - throughout its range Taxonomy Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Cetacea Family: Ziphiidae Genus: Mesoplodon Species: mirus Species Description True's beaked whales are little known members of thebeaked whale family (Ziphiidae). As adults, True's beaked whales can reach lengths of 15.5-17.5 ft (4.8-5.4 m) and weigh at least 2,200-3,000 lbs (1,020-1,400 kg). Females may be slightly larger than males. Adult males can be distinguished from females and juveniles by a pair of teeth visible on the tip of the lower jaw. The mouthline is typically straight or slightly curved. True's beaked whales have a relatively small to medium-sized body with a moderately short beak, as well as a rounded sloping melon. They have a small, wide-based, slightly "falcate" "dorsal" fin located far down (about two-thirds) the animal's back. Their coloration varies from gray to brown on the dorsal side with a paler ventral side. The coloration in the southern hemisphere is different from animals in the northern hemisphere. Individuals in the southern hemisphere have more white coloration on their back, tailstock and underside. Mature males may have more linear scarring covering the body than other animals. The linear scars are probably the result of males battling for access to females during mating. 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. Few have been seen alive at sea. 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. When observed, True's beaked whales are usually alone or in small, closely associated groups averaging 2-6 animals. While diving, they use suction to feed on small fish and cephalopods (e.g., squid) in deep waters. This species has been known to breach and occasionally display surface active behaviors. Very little is known about reproduction in True's beaked whales. Females generally give birth to a single newborn calf that is about 6.5-8 ft (2.0-2.5 m) long and weighs about 300 lbs (136 kg). The estimated lifespan of this species is unknown. Habitat True's beaked whales prefer deep warm temperate waters of the North Atlantic Ocean as well as at least two other areas in the Southern Hemisphere (e.g., Indian Ocean). Distribution True's beaked whales occur throughout the northern and southern hemispheres. Their range includes areas off of Nova Scotia (Canada), Ireland, Europe, the Canary Islands, Bermuda, Florida, and the Bahamas in the Atlantic, as well as off the coasts of Brazil, Madagascar, South Africa, and southern Australia. There are no known seasonal movements or migrations for this species. Population Trends For management purposes, True'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. There are insufficient data to determine the population trends for this species. The status of this stock is unknown, but is considered "strategic." Threats May be sensitive to underwater sounds and anthropogenic noise. Anthropogenic noise levels in the world's oceans are an increasing habitat concern, particularly for deep-diving cetaceans like True's beaked whales that use sound to feed, communicate, and navigate in the ocean. Previously, incidentally taken (by catch) in fisheries using driftnets and gillnets off the U.S. Atlantic coast, but no recent reports exist Conservation Efforts The International Union for Conservation of Nature and Natural Resources (IUCN's) Red List of Threatened Species considers this species "Data Deficient" due to insufficient information on population status and trends. Regulatory Overview This species is protected under the Marine Mammal Protection Act of 1972, as amended. References: Reeves, R. R., P. A. Folkens, et al. (2002). Guide to Marine Mammals of the World. New York, Alfred A. Knopf. p.276-277.

Stranding Distribution Inhabits the temperate waters of the North Atlantic. Although there is considerable overlap, it appears to prefer slightly colder waters than M. europaeus. Most stranding records are from the western North Atlantic, with the relatively few strandings in the eastern North Atlantic focused around Ireland and France. The northernmost record is from Saint Ann's Bay, Nova Scotia and southernmost from San Salvador Island, Bahamas. It has been reported in the Gulf of Mexico, but further verification of its occurence in this area is needed. From strandings in South Africa and South Australia it is evident that this species is also distributed in the warm temperate waters of the southern Indian Ocean. There appears to be a distributional break in the tropical Atlantic Ocean.

Tooth position A single pair of anteriorly inclined teeth are positioned at apex of the mandible. Tooth exposure Nearly all of erupted teeth in adult males are exposed above the gumline, Teeth do not erupt in females or juveniles. Tooth shape Teeth are oval in cross section and much less transversely flattened than other Mesoplodon species.

True's beaked whales are not known to differ substantially from other species of Mesoplodon, although they have a slightly bulging forehead and prominent beak. These beaked whales are characterized by the position of the mandibular teeth at the very tip of the lower jaw. The teeth are oval in cross-section, lean forward, and are visible outside the closed mouth of adult males. Can be confused with: At sea, True's beaked whales are difficult to distinguish from other species of Mesoplodon. The only other species in which males have oval teeth at the tip of the lower jaw is Longman's beaked whale; whose appearance is not known.

Both sexes are known to reach lengths of slightly over 5 m. Weights of up to 1 400 kg have been recorded. Newborns are probably between 2 and 2.5 m.

There is almost no information available on the natural history of this species of beaked whale.Stranded animals have had squid in their stomachs.

An individual of this species was taken off Nova Scotia in 1938, but no other exploitation is known. IUCN: Insufficiently known.

True's beaked whale (Mesoplodon mirus) is a medium-sized whale in the genus Mesoplodon. It is native to the northern Atlantic Ocean. The common name is in reference to Frederick W. True, a curator at the United States National Museum (now the Smithsonian).

scattered in all oceans

Temperate waters of both sides of the North Atlantic, and temperate waters of the Southern Hemisphere (known from South Africa and Australia).

Data Deficient (DD)