True's Beaked Whale

About the Species

True’s beaked whales are little known members of the beaked whale family, Ziphiidae. They can be found in deep, warm, temperate waters of the North Atlantic Ocean as well as at least two other areas in the Southern Hemisphere. They receive their common name from Frederick W. True, a curator at the Smithsonian Institution, who described the species from an animal that stranded on a beach in North Carolina.  

There is little information on the abundance of True’s beaked whales worldwide. The beaked whale family is cryptic and skittish, and distinguishing between species in the field can be challenging.  

Like all marine mammals, True’s beaked whales are protected under the Marine Mammal Protection Act and face threats from human-caused ocean noise. True’s beaked whales are considered “data deficient” by the International Union for Conservation of Nature’s list of threatened species, meaning that there is not enough information to assess their population status.  

Status

NOAA Fisheries estimates population size for True’s beaked whales in its stock assessment reports. A stock is a group of animals that occupy the same area and interbreed. Due to the rarity of sightings at sea, there is little information on the abundance of this species worldwide. Thus, data are insufficient to estimate population size or trends.

Appearance

True's beaked whales have a relatively small- to medium-sized body with a moderately short beak, as well as a rounded, sloping forehead (known as a melon). They have a small, wide-based, slightly hooked dorsal fin located far down their back. Their coloration varies from gray to brown on the dorsal side with a paler ventral side. In the field, they are distinguished from Gervais’ beaked whales (which are similar in appearance) by the pale coloration across their melon and lack of a dark, defined dorsal stripe. 
 
True’s beaked whales in the Southern Hemisphere have more white coloration on their back, tailstock, and underside than those in the Northern Hemisphere. Mature males may have linear scarring covering their body from battling other males for access to females during mating. This species 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. 
 
As adults, True's beaked whales can reach lengths of 15.5 to 17.5 feet and weigh from 2,200 to more than 3,000 pounds. Females may be slightly larger than males. Mature males can be distinguished from females and juveniles by a pair of teeth visible on the tip of their lower jaw. The mouthline is typically straight or slightly curved. 

Behavior and Diet

When observed, True's beaked whales are often alone or in small, closely associated groups averaging five to six 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. 

Even when dead, many species of beaked whales (especially those in the genus Mesoplodon) are difficult to distinguish from one another because they lack easily discernible or apparent physical characteristics. At sea, they are also challenging to observe and identify to the species level because of their cryptic, skittish behavior; low profile; and small, inconspicuous blow at the water’s surface. Therefore, much of the available characterization for beaked whales is to the genus level only.  

Where They Live

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). Their range, which is mostly known from strandings, includes areas off of Nova Scotia (Canada), Bay of Biscay, Ireland, Europe, the Azores, the Canary Islands, Bermuda, Florida, and the Bahamas in the Atlantic, as well as off the coasts of Brazil, Madagascar, South Africa, New Zealand, and southern Australia. It is unknown whether this species migrates or exhibits seasonal shifts in habitat use.

Lifespan & Reproduction

The lifespan of this species is unknown, and very little is known about their reproduction. Females generally give birth to a single calf that is about 6.5 to 8 feet long and weighs about 300 pounds.

Threats

Ocean Noise  

Deep-diving cetaceans like True’s beaked whales use sound to feed, communicate, and navigate in the ocean. This species may be sensitive to underwater sounds and human-made noise. Sound pollution threatens them by interrupting their normal behavior and driving them away from areas important to their survival, such as breeding and feeding waters.

Scientific Classification

Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Cetacea
Family	Ziphiidae
Genus	Mesoplodon
Species	mirus