- Aquatic Biomes
Generally, the whales in the genus Mesoplodon are small. The maximum adult length ranges from 4.3 meters to 6.15 meters. Males of this species can reach a maximum weight of 1500 kg. These whales have relatively 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.
Adult maleare 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 femaleare 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.
- Sexual Dimorphism
- sexes colored or patterned differently
- male more colorful
- Range mass
- 1500 (high) kg
- 3303.96 (high) lb
- Average mass
- 1500 kg
- 3303.96 lb
- Range length
- 4.3 to 6.15 m
- 14.11 to 20.18 ft
There is not much data available on the development of. The mean length at birth is estimated to be 2.50 meters for . However, this is based on extrapolation as 40-48% of the maximum reported length of females in the species. (Ridgway 1989). can reach a maximum length of about 530 cm along with an average of about 1500 kg. (Nowak 1991).
The mating system of these whales has not been characterized in the literature.
There is not much data available on reproduction in. 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 in the entire genus Mesoplodon. Young are likely precocial, and able to follow the mother from birth.
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- The breeding interval for these whales is unknown, but is certainly no more than once per year.
- Breeding season
- Breeding probably occurs in the summer.
- Average number of offspring
- Average gestation period
- 12 months
Young are most likely precocial and able to follow their mother through the water from birth. As in all mammals, the mother provides milk for the developing young, although the period of nursing in this species is not known. It is not known what role males may play in parental care.
- Parental Investment
No data has been found regarding the lifespan, or longevity, of (Loughlin and Perez, 1985). This paucity of data is common for the genus.
Data are lacking on the behavior of. In fact, for most members of the genus, there are few accounts of sightings in wild, so what follows is mainly generalizations for the genus.
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 M. stejnegeri 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 sitings. 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 (Heynig, 1984; Loughlin and Perez, 1985; Nowak and Paradiso, 1991; Ridgway and Harrison, 1989). Heynig (1984) hypothesized that the dense structure of the adult male rostrum serves to reinforce the rostrum when fighting occurs.
The home range of these animals is not known.
Communication and Perception
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.
produces pulses and whistles to communicate. Their typical frequency range for pulses are 0.3-2, 0.3-80+ kHz, with the dominant frequencies occurring in the range of 0.3-2 kHz. The typical frequency range for whistles is 2.6-10.7 kHz.
In addition to vocal communication, it is likely that (Richardson, 1995), like other mammals, uses both visual and tactile signals.
- Animal Foods
No information has been found regarding predation in.
No information has been found regarding the ecosystem roles of (Nowak and Paradiso, 1991). However, it is likely that as large marine predators, these whales have some regulating influence on their prey populations, primarily fish and squid.
Economic Importance for Humans: Positive
Very small numbers of (Nowak and Paradiso, 1991)are taken by commerical fisheries.
- Positive Impacts
Economic Importance for Humans: Negative
No information has been found regarding any negative economic impact of this species on humans. It is unlikely that there is even much interaction between humans and this species, asis typically found far from shore in deep waters.
It is difficult to evaluate the population size of species like, 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.
Althoughis not considered endangered or threatened by the U.S. governement, this species is still protected by U.S. laws and regulations.
Cetaceans fall under the responsibility of the National Marine Fisheries Services. This is a category under the Department of Congress.
According to the National Environmental Policy Act of 1969 (NEPA), there are major implications with regard to noise and its effects on marine mammals. Studies of noise effects have been done to provide the data needed for impact statements in regards to its effects on marine mammals. NEPA is the U.S. legislation under which Environmental Assessments and Impact Statements are required.
The U.S. Marine Mammal Protection Act of 1972 (MMPA) promotes the conservation of marine mammal populations and their habitats. They established a stand on the “taking of marine mammals.” “Taking” can be defined as including harassment as well as hunting, capturing, and killing. There are some exceptions to “taking”, however. It is allowed during scientific research as long as a scientific research permit is obtained. Also excused is the unintentional harassment of small numbers of marine mammals by human activities. An incidental take authorization must be obtained in this case.
In 1994, amendments were made to the MMPA. Harassment was defined as “any act of pursuit, torment, or annoyance which has the potential” to a) “injure a marine mammal or marine mammal stock in the wild,” or b) “disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns including, but not limited to, migration, breathing, nursing, breeding, deeding, or sheltering.”
Specifically, because of the limited scale of which Mesoplodon species are directly taken, and the “lack of effect that any kind of regulation would have on these kinds of subsistence fisheries,” there has been no known effort to regulate the take of these animals. (Richardson, 1995; Ridgway and Harrison, 1989)
Nancy Shefferly (editor), Animal Diversity Web.
Julie Mann (author), California State University, Sacramento, James Biardi (editor), California State University, Sacramento.
- Pacific Ocean
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
uses sound to communicate
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
- active during the day, 2. lasting for one day.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
- internal fertilization
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
- native range
the area in which the animal is naturally found, the region in which it is endemic.
generally wanders from place to place, usually within a well-defined range.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats fish
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
- saltwater or marine
mainly lives in oceans, seas, or other bodies of salt water.
- seasonal breeding
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- young precocial
young are relatively well-developed when born
Heynig, J. 1984. Functional Morphology Involved in Intraspecific Fighting of the Beaked Whale, *Mesoplodon carlhubbsi*. Canadian Journal of Zoology, 62: 1645-1654.
Loughlin, T., C. Johnson, A. Rugh, D. Rugh. 1982. Observations of *Mesoplodon stejnegeri* (Ziphiidae) in the Central Aleutian Islands, Alaska. Journal of Mammalogy, 63: 697-700.
Loughlin, T., M. Perez. 1985. Mesoplodon stejnegeri. Mammalian Species, 250: 1-6.
Nowak, R., J. Paradiso. 1991. Walker's Mammals of the World, 5th Edition. Maryland: The Johns Hopkins University Press.
Reynolds III, J., S. Rommel. 1999. Biology of Marine Mammals. London: Smithsonian Institution Press.
Richardson, W. 1995. Marine Mammals and Noise. California: Academic Press.
Ridgway, S., R. Harrison. 1989. Handbook of Marine Mammals. London: Academic Press Limited.