Hubbs' beaked whale

Species (main)

Published: May 3, 2011, 12:00 am

Updated: May 29, 2011, 8:09 am

Topics:

Species (main) Marine Ecology (main) Oceans and seas (main)

Hubbs' beaked whale. Source: Wildwhales.org

Hubb's beaked whale (scientific name: Mesoplodon carlhubbsi ) is one of 21 species of beaked whales (Hyperoodontidae or Ziphiidae), medium-sized whales with distinctive, long and narrow beaks and dorsal fins set far back on their bodies. They are marine mammals within the order of cetaceans.

Size comparison of an average human against Hubbs' beaked whale. Source: Chris Huh

Conservation Status: Data Deficient

Scientific Classification Kingdom: Animalia Phylum:--- Chordata Class:------ Mammalia Order:-------- Cetacea Family:-------- Hyperoodontidae Genus:--------- Mesoplodon Species:--------Mesoplodon carlhubbsi (Moore, 1963)

Common Names: Bering Sea beaked whale Hubb's beaked whale Hubbs' beaked whale Sabre-toothed Beaked Whale Arch-beaked whale Archbeaked whale Hubbs's beaked whale

Hubbs’s beaked whale is another little-known species. Beaks of squids and otoliths (inner ear particles) of some deepwater fish, some of which could have come from the stomachs of the squids, were found in the stomachs of a few stranded individuals along the California coastline.

Scars on the skin have been noted, and may be evidence that males fight each other. The jaws of this species may be adapted to fighting: they are made of very compact bone, denser than any other mammalian tissues, including teeth.

In North American populations, females are thought to calve in mid-summer, but little is known about reproduction in this species.

Physical Description

Overview anatomical features are an endothermic metabolism and bilateral symmetry. Generally, the whales in the genus Mesoplodon are relatively small in stature. The maximum adult length ranges from 4.3 meters to 6.3 meters. Males of this species can reach a maximum body mass of 1500 kilograms. These whales have small heads, large thoraxes and abdomens, and short tails (as compared to other toothed whales).

Mesoplodon species also have a pair of throat grooves. These are found on the ventral side of the head between the lower jaws. A notch occurs in the center of the flukes. The flipper has a short phalangeal portion. This is typical of the family Ziphiidae.

The dorsal fin is small and sub-triangular. It is positioned about two-thirds of the way back on the animal.

There is a pronounced sexual dimorphism evinced by coloration and patternation, with the male being more colorful. Adult male Hubb's beaked whale are usually dark gray to black except for two white patches on the head. One patch covers the tip of the rostrum and lower jaw back to the posterior border of the teeth. The other patch occurs in a roughly circular pattern, about 30 centimeters in diameter, centered around the blowhole. The functional teeth in males are large and straight-sided. They are located near the middle of the mouth. These remain exposed when the mouth is closed.

Adult female Hubb's beaked whale are usually medium-gray on the dorsal surface of their bodies. Their sides are a lighter shade of gray. The belly is white. Also, the area of the body just posterior to the flipper, termed the flipper pocket, is darker in color than the surrounding body. The front half of the rostrum and lower jaw are lighter in color than the rest of the head.

The functional teeth of females are smaller than those of the males. They often don’t erupt above the gums. In both sexes of Mesoplodon carlhubbsi, the bottom side of the flukes is lighter in color than the top side. They also have concentric striations that radiate anteriorly from the terminal caudal vertebrae. (Nowak and Paradiso, 1991; Ridgway and Harrison, 1989)

Behavior

Detailed data are lacking on the behavior of Hubb's beaked whale. In fact, for most members of the genus, there are few accounts of sightings in wild, so what follows are chiefly generalizations for the genus. Key behaviors of the species are: diurnal; motile; nomadic; and social.

Mesoplodon species are usually seen in small groups. During one particular sighting, there were reported pairs of animals that were swimming about twenty feet apart. These groupings may show some resemblance to a social structure. The social structure seems to be composed of both small and large animals that traveled together. This is similar to the social structure observed in other species of odontocetes.

A pod of Stejneger's beaked whale was seen with members traveling abreast of one another, almost touching in some cases. They appeared to be highly cohesive and to move in unison. The pod dove several times, but apparently did not dive very deep and spent a lot of time at the surface of the water. When the animals surfaced from a dive, they often rolled slowly. These animals have a low, inconspicuous blow, and this might account for the low number of sightings. Or, the infrequency of sightings may be related to their rarity.

On some adult male odontocetes, scarring is noticeable. The scars are presumably due to intraspecific mating combat, and are believed to be inflicted with the mouth closed. This information was based on a study of scars in Mesoplodon carlhubbsi. Heynig (1984) hypothesized that the dense structure of the adult male rostrum serves to reinforce the rostrum when fighting occurs. (Heynig, 1984; Loughlin and Perez, 1985; Nowak and Paradiso, 1991; Ridgway and Harrison, 1989)

Communication

Most odontocete whistles are narrowband sounds. The frequency pattern can be unmodulated, trilled, ascending, descending, ascending-descending, descending-ascending, or slowly wavering. A whistle can consist of one of these sound patterns that is given once or repeated. It can also consist of a series of sounds of several types. The amplitudes of the ascending and descending portions can vary over the duration of a whistle. Whistles can have a varying number of breaks and segments in one whistle or be continuous. The initial, final, maximum and minimum frequencies, as well as the duration and level, may vary for any one species.

Hubb's beaked whale produces pulses and whistles to communicate. Their typical frequency range for pulses are 0.3-2, 0.3-80+ kilohertz (kHz), with the dominant frequencies occurring in the range of 0.3-2.0 kHz. The typical frequency range for whistles is 2.6-10.7 kHz. Loud man-made sounds that propagate underwater, such as boat engine noise or sonar, has the potential to interfere with species communication.

In addition to vocal communication, it is likely that Mesoplodon carlhubbsi, like other mammals, uses visual, acoustic and tactile signals. (Richardson, 1995) These three mechanisms are not only operative as perception/communication channels, but chemical perception is operative as a perception channel for this species.

Reproduction

Key reproductive features are: Iteroparous; Seasonal breeding; Gonochoric/gonochoristic/dioecious (sexes separate); Internal fertilization; Viviparous. However, the apecies mating system has not been characterized in detail within the literature. There is relatively detailed data available on reproduction in Hubb's beaked whale.

Birth usually occurs during the summer, after a twelve month gestation. According to Reynolds and Rommel (1999), “The timing of events in the reproductive cycle for all cetaceans is clearly geared to optimize the seasonal changes in environmental conditions to benefit the ecology of the species and favor maximal survival of the young."

The litter size is most likely one offspring per birth within the entire genus Mesoplodon. Young are thought to be precocial, and able to follow the mother from birth. As for other mammals, the mother provides milk for the developing young, although the period of nursing in this species is not known. It is also not known what role males may play in parental care.There are scant data available on the timing of weaning, independence, or reproductive maturity for this species. (Loughlin et al., 1982; Nowak and Paradiso, 1991; Reynolds III and Rommel, 1999)

Distribution and Movements

Mesoplodon carlhubbsi, or Hubb’s beaked whale, is found in the temperate waters of the North Pacific. Hubb's beaked whale ranges from Japan to British Columbia and California. The northernmost sighting occurred in Eastern North Pacific, near Prince Rupert, British Columbia. The southernmost record occurred southwest of San Clemente Island, California. Here, a rostral portion of a skull was found by the submersible “Deep Sea.” (Nowak and Paradiso, 1991; Ridgway and Harrison, 1989)

Habitat

Hubb's beaked whale seems to prefer deep marine water far from coastal zones. Their typical pelagic habitat is the deep, subarctic marine current system. (Ridgway and Harrison, 1989); however, they are found in both temperate and polar regimes.

Feeding Habits

The diet of Hubb's beaked whale includes squid, other cephalopods, mollusks and fish. According to Ridgway and Harrison (1989), it is believed that Hubb's beaked whale feeds mainly on squid, which habit is characteristic of beaked whales. However, all information is based on stranded animals. It is possible that the stranded individuals might not be representative of the whole population. (Nowak and Paradiso, 1991; Ridgway and Harrison, 1989)

Threats and Conservation Status

It is difficult to evaluate the population size of species like Mesoplodon carlhubbsi, because they occur far from shore, and because they are not very conspicuous animals. Although they are sighted infrequently, as are most members of the genus, it is difficult to tell whether the low incidence of sightings is due to rarity of animals, or is simply an artifact of their unobtrusive behavior in a remote habitat.

However, all species of Cetacea are listed by CITES as being on Appendix II unless listed on Appendix I. This places all Mesoplodon species on Appendix II.

The IUCN Red List adds:

Hubbs' beaked whale has occasionally been taken by Japanese whalers in several small cetacean fisheries. Whale meat products from this species are occasionally found for sale on the Japanese market (Dalebout et al. 2001). Incidental catches in drift gill-nets occur sporadically off the coast of California.

This species, like other beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006).

Evidence from stranded individuals of several similar species indicates that they have swallowed discarded plastic items, which may eventually lead to death (e.g. Scott et al. 2001); this species may also be at risk.

IUCN Red List classifies this beaked whale as Data Deficient; the US Federal List indicates no special status for M. carlhubbsi, while CITES lists this taxon in Appendix II.

References

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Citation

Encyclopedia of Life (2011). Hubbs' beaked whale. ed. C. Michael Hogan. Encyclopedia of Earth. National Council for Science and Environment. Washington DC. Retrieved from http://editors.eol.org/eoearth/wiki/Hubbs'_beaked_whale