Mesoplodon hectori

Geographic Range

Mesoplodon hectori is distributed in oceans throughout the Southern Hemisphere.

• Biogeographic Regions
• ethiopian ethiopian
  • native native
• neotropical neotropical
  • native native
• australian australian
  • native native

Habitat

Mesoplodon hectori is found in pelagic oceanic waters in the Southern Hemisphere, primarily in cold temperate waters between 35° South and 55° South. Beached specimens have been found in Argentina, the Falkland Islands, South Africa, Chile, New Zealand, and Tasmania. One beached specimen was found 80 km north of Rio Grande in Southern Brazil, the northernmost sighting of this whale. These whales may undergo a slight seasonal migration to cooler waters during summer months. They seem to prefer colder shelf-edge or canyon habitats. They can dive to a depth of 5.75 km but, on average, they dive to a depth of 3.5 km.

• Habitat Regions
• temperate temperate
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic

Physical Description

Hector's beaked whales can be distinguished from other species of Mesoplodon by the shape of the mandibles, the shape of the rostrum, and the position of its single pair of teeth in the lower jaw. This species has a narrower premaxillary crest than other Mesoplodon species. The teeth are triangular and positioned near the tip of the lower jaw. Other species, such as Mesoplodon mirus and Mesoplodon pacificus also have teeth close to the tip of the jaw, but the morphology of their teeth differs from that of M. hectori in that M. mirus has smaller and more conical teeth than M. hectori , and the teeth of M. pacificus are sloped forward at a 45° angle. The teeth of M. hectori are not sloped forward in this manner. The dorsal fin is small and rounded and the tail flukes are straight-edged and broad.

This species is the second smallest of all beaked whales, second only to pygmy beaked whales ( Mesoplodon peruvianus ). No subspecies or polymorphisms of M. hectori are known to exist. Males and females do not differ in size, but they do have different color patterns. Dorsally, males are dark grey with a lighter grey ventral zone. Females, on the other hand, are light grey dorsally and white ventrally. Both males and females tend to have white lower jaws.

Additionally, while males have a single pair of teeth (tusks) in the lower jaw, females and juveniles usually do not. This dimorphism is consistent with other species of Mesoplodon . Males of this species tend to have extensive scarring as a result of aggressive intrasexual encounters where teeth are used to establish breeding hierarchies. Males also tend to have increased ossification of the rostrum, which may allow them to aggressively contact each other with the tops of their rostra without risking damage to the rostrum. Because so few specimens have been found alive, there is virtually no information on the average mass or basal metabolic rate of these animals. However, one study suggests that M. hectori can reach up to 800 kg.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes colored or patterned differently
• ornamentation ornamentation

Reproduction

Little information is known about their mating system. Scholars suggest that the mating behaviors of beaked whales may be similar to those of other toothed whales . Because toothed whales tend to live in small groups that occupy thousands of square miles of ocean. When individuals of the opposite sex do come across each other, they take advantage of the meeting by emitting a series of physical and hormonal cues to indicate readiness to breed. However, no research exists to suggest that Mesoplodon hectori follows these same mating patterns.

Researchers have documented that beaked whales, including species of Mesoplodon , use their teeth to defend their mates and territory from other males and to establish breeding hierarchies. Although little is known about the specific mating system of Mesoplodon hectori , the presence of scarring on some beached male specimens suggests that males may also engage in this intrasexual aggression, most likely to defend females and territories.

Although little information exists about the reproductive behavior of Mesoplodon hectori , studies of other Mesoplodon species suggests that breeding most likely occurs between October and December. Calves of other Mesoplodon species are usually born in February or March in areas much shallower than their normal habitats. Hector's beaked whales may follow this breeding pattern. Mothers most likely give birth to a single calf. Mesoplodon species in general have gestational periods averaging 12 months, but virtually no information exists as to how long the specific gestation period is for M. hectori . At birth, calves are 190 to 202 centimeters long. Research on other Mesoplodon species suggests that sexual maturity may occur anywhere from 9 to 12 years old for females and males, but no specific information exists for this species. At the time of weaning, juveniles are estimated to be about 3 meters in length. Other reproduction information is not reported in the literature.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

All cetaceans share a similar style of parental investment. The mother nurses the young. If she lives in a group, the mother and her entire pod teach the young how to avoid predators and to feed. However, because Mesoplodon hectori is thought to be a relatively solitary species, the mother may be the only adult in charge of socializing her young. No other information about parental investment in M. hectori has been documented.

• Parental Investment
• precocial precocial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Because fewer than 30 specimens of Mesoplodon hectori have been found – and of those, only a few found alive – there’s very little information on longevity. However, based on longevity data from other members of the genus, this species may be a long-lived species, living at least to its early 30's and potentially even longer. Other than these speculations, there is no research on longevity in the wild for this species. No attempts to keep M. hectori in captivity have been documented.

Behavior

Because toothless specimens of Mesoplodon hectori can feed, scholars suggest that the teeth are not involved in feeding and have most likely been retained for male-male competitions. Males are oftentimes found with teeth marks on their backs and flanks, leading many scholars to suggest that males engage in aggressive intrasexual encounters to defend their territories and mates. In these interactions, males swim towards each other and use the momentum to create linear wounds by dragging their teeth along each other’s side. Males will most likely accrue these bites as they age and engage in more aggressive encounters. Additionally, Mesoplodon hectori may engage in aggressive encounters with Isistius ; one specimen of M. hectori was found to have what were tentatively classified as bite marks from these cookie-cutter sharks.

Most sightings of live and beached specimens of M. hectori suggest that this species generally occurs singly, but researchers have seen pairs on occasion. Furthermore, one study of beaked whales found that other species of Mesoplodon may live in small groups, while other genera of beaked whales tend to live in much larger groups. Therefore, there is still considerable contention over the size of social groups. Hector's beaked whales may live in small social groups, but the sighting of single whales suggests that they may also be a largely solitary species. Additionally, while species of Mesoplodon are known to flee from boats, there have been numerous occasions in which M. hectori has approached boats and even allowed researchers to take skin samples. This species is particularly hard to detect because it does not “blow,” although no information exists as to why these animals are so inconspicuous when they surface. The average dive for Mesoplodon is about 20 minutes long.

Most species of Mesoplodon tend to live near other genera of beaked whales, such as Ziphius and Hyperoodon , so it is possible that M. hectori comes into contact with other beaked whales. However, because Mesoplodon species occupy a separate dietary niche, M. hectori most likely does not compete with other beaked whales for food.

• Key Behaviors
• natatorial natatorial
• motile motile
• nomadic nomadic
• migratory migratory
• solitary solitary

Home Range

While some research suggests that Mesoplodon hectori may engage in seasonal migration, evidence from other beaked whales shows long-term fidelity to specific locations; for example, one species of Mesoplodon was sighted in the same location over a period of fifteen years. Although no documentation of the home range of M. hectori exists, these clues from other species may help identify some of this species' behavioral patterns, but there is still not enough evidence to discern whether this species diverges from or aligns with the norms of other species in its genus. Australian researchers estimate the area of occupancy of these whales to be greater than 2000 square kilometers, but a more conservative estimate of home range has not yet been made.

Communication and Perception

Echolocation has been identified as a feeding behavior of this species, but high-frequency echolocation of up to 120 Hz may also be used for social communication. Mesoplodon hectori may also use non-echolocating sounds ranging from 1 to 16 kHz to communicate with other individuals. Other species of beaked whales whistle in a way that researchers suggest serves a social function, although the nature of that social function is not yet clear. Although the group size of M. hectori is still unclear, the presence of both high-frequency echolocation and non-echolocating sounds may bolster the hypothesis that this species is not a completely solitary species but instead lives in small groups where communication is necessary.

• Communication Channels
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• ultrasound ultrasound
• echolocation echolocation
• chemical chemical

Food Habits

Although little is known about the specific feeding behavior of Mesoplodon hectori , researchers suggest that Mesoplodon species are piscivores. Among the genera of beaked whales ( g.Hyperoodon >, Mesoplodon , and Ziphius ), Mesoplodon species tend to eat the most fish – and their prey tends to be smaller than those of the other two genera. Mesoplodon species also eat cephalopods. Most prey is benthic or benthopelagic, meaning that it lives at or near the ocean floor, usually between 200 and 2000 meters in depth. Mesoplodon species are generalist feeders, in that they eat whatever prey is locally abundant.

Mesoplodon hectori is most likely a suction feeder like other species in the genus. Powerful muscles at the back of the tongue work in tandem with pleated throat grooves to allow the mouth to distend and create a vacuum that sucks prey into the mouth, prey that is then swallowed whole. Some scholars believe that Mesoplodon suction feeding is an adaptation to eating squid in particular.

Like all species of Mesoplodon , this species most likely uses echolocation to locate prey. When searching for food, Mesoplodon emits high-frequency clicks to detect squid and other small marine creatures. A study of foraging Mesoplodon revealed that these beaked whales tend to click only at depths between 200 and 1267 meters and they click continuously once at those depths. Even though specific studies with M. hectori have not been conducted, it is likely that this species uses echolocation to forage in a similar fashion to other members of Mesoplodon .

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • molluscivore molluscivore

• Animal Foods
• fish
• aquatic crustaceans
• other marine invertebrates

Predation

Little is known about the predators or anti-predator adaptations of Mesoplodon hectori . Some research suggests that Orcinus orca may occasionally prey on this species, but no definitive evidence exists to verify this claim.

Ecosystem Roles

Beaked whales are some of the most numerous cetaceans in their geographic range and are important “apex” predators as a result. However, little is known about the specific ecological role Mesoplodon hectori plays in its marine ecosystem.

Hector's beaked whales may play host to a number of parasites. In 2005, a female specimen was found to have a species of Sarcocystis in her skeletal muscle as well as a species of Tetrabothrius and a species of Bolbosoma in her intestinal tract. A beached male concurrently analyzed was found to have Braunina cordiformis in his stomach. Both specimens also had a species of Anisakis in their digestive tracts. Neither individual died from these parasites, and researchers concluded that the presence of the stomach parasites, presumably acquired through consuming intermediary hosts, is most likely common and non-fatal for M. hectori .

Economic Importance for Humans: Positive

Some specimens of Mesoplodon hectori may have been captured by opportunistic whalers over a hundred years ago. However, their general elusiveness means that few, if any, modern incidences of human exploitation have been reported because few people have encountered this species alive.

• Positive Impacts
• body parts are source of valuable material
• research and education

Economic Importance for Humans: Negative

There are no documented cases of negative interactions between humans and Mesoplodon hectori .

Conservation Status

Even though there have been only a handful of sightings of Mesoplodon hectori at sea, this species does not classify as vulnerable, threatened, or endangered on any of the major lists. Individuals of many Mesoplodon species have gotten entangled in offshore fishing nets over the last twenty years, and M. hectori may be at risk for entanglement as well.

Additional Links

Encyclopedia of Life

Contributors

Jasmine Reid (author), Yale University, Rachel Racicot (editor), Yale University, Eric Sargis (editor), Yale University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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Gales, N., M. Dalebout, J. Bannister. 2002. Genetic Identification and Biological Observation of Two Free-Swimming Beaked Whales: Hector’s Beaked Whale (Mesoplodon hectori, Gray, 1871), and Gray’s Beaked Whale (Mesoplodon grayi, Von Haast, 1876). Marine Mammal Science , 18(2): 544-551. Accessed April 11, 2012 at http://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.2002.tb01055.x/pdf .

Johnson, M., P. Madsen, W. Zimmer, N. Aguilar de Soto, P. Tyack. 2004. Beaked Whales Echolocate on Prey. Proceedings: Biological Sciences , 271: S383-S386. Accessed May 01, 2012 at http://www.jstor.org/stable/4143015 .

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