Peponocephala electra

Geographic Range

Peponocephala electra is found in warm, deep, tropical, and subtropical oceanic waters between 40⁰ North and 30⁰ South, with most animals concentrated between 20⁰ North and 20⁰ South. While Peponocephala electra is most commonly found in the Philippine Sea, its range includes the Gulf of Mexico, Senegal, the Arabian Sea, the Bay of Bengal, the South China Sea, Taiwan, southern Honshu, the Hawaiian Islands, and Baja California Sur; and south to Espiritu Santo in Brazil, Timor Sea, northern New South Wales, and Peru. This range is extremely similar to that of Feresa attenuata . There have also been reports by Mignucci et al. (1998) of Peponocephala electra in the Caribbean sea. Other sources report individuals seen as far out of the typical range as southern Japan, Cornwall in England, Cape Province in South Africa, and Maryland in USA. These individuals most likely come from populations in adjacent warmer waters and represent extreme cases of migration.

• Biogeographic Regions
• indian ocean
  • native native
• atlantic ocean atlantic ocean
  • native native
• pacific ocean pacific ocean
  • native native

Habitat

The distribution of the rare, reported sightings of melon-headed whales suggest that they are found primarily in equatorial and subtropical waters from the continental shelf seaward. They seem to be found in deeper waters.

• Habitat Regions
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic

Physical Description

Melon-headed whales are mostly dark grey, with a faint, darker gray cape that narrows at the head on the dorsal side. Often, they have a distinct dark eye patch that widens as it extends from the eye toward the melon. The lips are often white. Additionally, white or light grey areas are common in the throat region, from the blowhole to the top of the melon, and on the ventral side. The bodies of melon-headed whales are shaped like torpedos and are similar in size to pygmy killer whales , making it difficult to distinguish between the two in the field. The head of Peponocephala electra is shaped like a rounded cone, but lacks the clearly defined beak often seen in dolphins. The beak is longer and more slender than that of dolphins and it lacks the typical saddle or cape markings seen in many dolphins. The head is narrow and tapers, but the bump of the melon gives it a curved profile. The flippers are relatively long, estimated to be about 20% of the body length. They are smoothly curved and sharply pointed at the end. This creates an obvious distinction from the rounded flippers of pygmy killer whales . The dorsal fins of P. electra are distinct, curved in the middle of the back with a pointed tip, and shaped very much like the dorsal fin of bottlenose dolphins . Additionally, P. electra has 82 vertebrae, the first 3 are fused together. Melon-headed whales have 20 to 25 teeth in each upper toothrow, compared to 8 to 13 in pygmy killer whales . The teeth of P. electra are small and slender while those of pygmy killer whales are larger and more robust. This difference in dentition is the key identifier between pygmy killer whales and melon-headed whales. Peponocephala electra is small to medium sized, averaging 2.6 meters in length in both males and females (no sexual dimorphism exists). The maximum length is about 2.75 meters, and the average length at birth is estimated to be 1 to 1.12 meters. The average weight is 228 kg (maximum 275 kg). At birth, the average young weights about 15 kg. The basal metabolic rate of Peponocephala electra is not known. In the wild, melon-headed whales have a lower fin, no patch on the chin, and a pointed, rather than rounded, flipper compared to pygmy killer whales . Melon-headed whales look around with their head out of the water, but do not sit up as high as other species. Nevertheless, it is difficult to distinguish melon-headed whales from pygmy killer whales .

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

• Sexual Dimorphism
• sexes alike

Reproduction

Nothing is known about the mating systems of Peponocephala electra or its close relatives.

Little is known about the reproduction of Peponocephala electra . Little or nothing is known about the breeding habits, breeding season, or breeding interval of melon-headed whales. Calving appears to peak in either early spring in the low latitudes of both hemispheres or in July and August in higher latitudes, but it seems calves are born year round and most data are inconclusive. Nothing is known of the birthing habits of melon-headed whales (their close relatives, pygmy killer whales , generally have only 1 calf). The length of gestation is not known, but probably about 12 months. Mass at birth is estimated to be between 10 and 15 kg, averaging around 12 kg. Nothing is known about the time to weaning specifics or independence. It is estimated that maturity is reached by about 4 years of age for both males and females.

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

Little is known of the parental habits of Peponocephala electra , but it is assumed that mothers care for and nurse her young until they reach independence. As in other whale species , young are capable of swimming soon after birth.

• Parental Investment
• precocial precocial
• 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

Little is known about the lifespan or longevity of Peponocephala electra . The longest known lifespan in the wild is over 30 years, but the exact age is not known. There are no individuals in captivity, nor have there ever been.

Behavior

Melon-headed whales are highly social and travel in large pods, usually of 100 to 500 individuals. Pods have been known to be as large as 2000 individuals. They typically move at high speeds, making low, shallow leaps out of the water regularly, creating lots of spray, and occasionally bow-ride for short periods of time (but they are usually wary of boats). They often travel with other species including Fraser’s , spinner , and spotted dolphins. When traveling in groups, melon-headed whales are often tightly packed and change their course frequently. Occasional stranding has been reported from Moreton Island and Crowdy Heads, Australia; Malekoula Island, Vanuatu; the Seychelles; Aoshima, Japan; Piracanga Beach, Brazil in 1990; the Kwajalein Atoll; and Tambor, Costa Rica. Although they are difficult to distinguish at a distance, once melon-headed whales are stranded they are easy to identify, as the teeth are unmistakable. Most of the information about this species comes from stranded individuals, as individuals are rarely seen in the wild. Currently, there are no data regarding migration; however, melon-headed whales most likely do not migrate.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• nomadic nomadic
• sedentary sedentary
• social social

Home Range

Nothing is known of territorial behavior. Migration is not likely.

Communication and Perception

Melon-headed whales make sounds similar to the whistles and clicks of bottlenose dolphins .

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic

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

Food Habits

Melon-headed whales typically feed on squid and small fish, but detailed information is lacking.

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

• Animal Foods
• fish
• mollusks

Predation

Little is known about predators of Peponocephala electra . Their medium to large size prevents them from attracting many predators, but perhaps large sharks or cetaceans would not be deterred by size alone. No specific predators are known.

Ecosystem Roles

Peponocephala electra is an important predator of fish and squid in pelagic waters.

Economic Importance for Humans: Positive

Melon-headed whales are important members of pelagic ecosystems. Humans occasionally catch them in fisheries, especially near the island of St. Vincent in the Caribbean, in the Japanese dolphin drive fishery, near Lamalera, Indonesia, near Sri Lanka, and in the Philippines. However, the number of Peponocephala electra taken each year is small. For instance, during the 1982 fishing season only 4 melon-headed whales were taken. Once caught, melon-headed whales are used for bait or for consumption. These whales are typically caught and killed with hand harpoons or toggle-head harpoon shafts shot from spear guns.

• Positive Impacts
• food food

Economic Importance for Humans: Negative

There are no known adverse effects of Peponocephala electra on humans. Since they are so uncommon and swim in such deep water, it is rare that they collide with a boat, get tangled in nets, or disrupt fisheries.

Conservation Status

Peponocephala electra is categorized as a species of “least concern” by the IUCN Red List. A taxon is “least concern” when it is considered widespread and abundant. Melon-headed whales are classified by CITES as an Appendix II species. They are not hunted specifically, but are accidentaly caught in fishing nets or occasionally hunted by fisheries in coastal Japan. Peponocephala electra is not listed on the other conservation sites.

Other Comments

The classification of melon-headed whales has been debated throughout history, as their relationships to dolphins and pilot or killer whales are unclear.

Melon-headed whales are also known by the common names little killer whales and many-toothed blackfish. They are known commonly as elektra tmavá, plískavice Elektra, or plískavice tmavá in Czech, and calderón in Spanish.

The first known specimens are 2 skulls described by Gray in his 1846 report and he named them “electra” from the Greek word “Elektra”, meaning amber, because of the amber color of the bones. A third skull was found in Hawaii in 1848 and a fourth in Magras in 1869. It was not until 1963 that a live specimen was caught at Sagami Bay in Honshu, Japan. The once extremely rare species began to appear in more abundance as more than 500 were seen in Suruga Bay in Japan in 1951 and 250 were caught. The genus was officially named “Peponocephala” based on the Greek words “peponis”, a melon, and “kephalos”, a head (Dutton 1981).

Overall, very little information is available for this species due to the small number of individuals observed.

Additional Links

Encyclopedia of Life

Contributors

Nicole Jacqueline Armbruster (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor, Tanya Dewey (editor), Animal Diversity Web.

References

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