Toothed Whales: Swimming, Echolocation and Melon-Heads | Sea Life, Islands and Oceania

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TOOTHED WHALES

toothed whales

Toothed whales (also called odontocetes, scientific name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and whales possessing teeth, such as beaked whales and sperm whales. There are 73 described species of toothed whales. Toothed whales such as killer whales and sperm whales are more similar to dolphins than baleen whales such as blue whales and humpbacks.

Toothed whales first emerged during Early Oligocene Period (33 million to 23.9 million years ago). They and baleen whales (Mysticeti), which have baleen instead of teeth, are thought to have diverged around 34 million years ago. Toothed whales include sperm whales, narwhals, belugas, Baird's beaked whales, pilot whales, killer whales, bottlenose whales and dolphins and porpoises. Toothed whales range in size from the 1.4 meters (4.6 feet) and 54 kilograms (119 pounds) vaquita to the 20 meters (66 feet) and 55 t (61-short-ton) sperm whale.

Odontocetes have conical teeth designed for catching fish or squid. They have well-developed hearing, that is well adapted for both air and water, so much so that some can survive even if they are blind. Some species are well adapted for diving to great depths. Almost all have a layer of fat, or blubber, under the skin to keep warm in the cold water, with the exception of river dolphins.

Dolphins, porpoises and toothed whales generally grab their prey with their toothy jaws and swallow it whole and digest it in their multi-chambered stomachs. Toothed whales' large teeth that can slice and rip. They have throats large enough to swallow fish and squid, their main prey, or chunks of large fish or aquatic mammals. Many have scars perhaps from courtship battles between other whales.

Except for the sperm whale, most toothed whales are smaller than the baleen whales. Toothed whales have torpedo-shaped bodies with inflexible necks, limbs modified into flippers, nonexistent external ear flaps, a large tail fin, skulls with small eye orbits and eyes on the sides of their heads . With the exception of sperm whales, they have bulbous heads. Many have long beaks. [Source: Wikipedia]

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures

Toothed Whale Characteristics

Toothed whale teeth are comprised of cementum cells overlying dentine cells. Cementum is calcified or mineralized tissue covering teeth. Unlike human teeth, whose exposed parts outside the gum are mostly enamel,, the exposed parts of toothed whale teeth are mostly cementum. The teeth differ considerably among the species. Some dolphins have more than 100 teeth in their jaws. At the other extreme are narwhals have a single long tusk and the almost toothless beaked whales with tusk-like teeth only in males. Not all species are believed to use their teeth for feeding. For instance, the sperm whale likely uses its teeth for aggression and showmanship.

Toothed whales have a two-chambered stomach similar ones in terrestrial carnivores. Breathing involves expelling stale air through a a single blowhole (many baleen whales have two) followed by inhaling fresh air into the lungs. Exhalations through the blowhole produce upward steamy spouts. Spout shapes differ among species, which serves as a means of identification. The spout only forms when warm air from the lungs meets cold air, thus does not form in warmer climates.

Almost all whales and dolphins have a thick layer of blubber. In species that live polar regions, the blubber can be as thick as 28 centimeters (almost a foot). In addition to providing warmth, this blubber help with buoyancy, offers some protection from predators, provides energy and nutrition during times when food is scarce. Calves are born with only a thin layer of blubber, but some species compensate for this with thick lanugos (soft, fine hair covering that cover a fetus while inside the uterus and after birth)..Toothed whales have also evolved the ability to store large amounts of wax esters in their adipose tissue, an adaption that allows them to make deep dives. Species that have the highest amounts of wax esters in their blubber are also the species that can dive the deepest and for the longest amount of time.

Toothed whale eyes are relatively small for animals of their size, but most species have fairly good eyesight. Their eyes are on the sides of their head, so their vision consists of two fields, rather than a binocular view as humans have. Olfactory lobes are absent in toothed whales. Unlike baleen whales, they lack the vomeronasal organ, suggesting they have no sense of smell. It is believed that toothed whales don’t have a good sense of taste either, as their taste buds are atrophied or missing altogether. However, some dolphins have preferences for different kinds of fish, indicating some sort of taste or taste-like mechanism.

Toothed Whale Swimming and Diving

pilot whales

Whales, dolphins, and porpoises have two flippers on the front, and a tail fin. These flippers contain four digits. Although toothed whales do not possess fully developed hind limbs, some, such as the sperm whale, possess discrete rudimentary appendages, which may contain feet and digits. [Source: Wikipedia]

Toothed whales are fast swimmer. Sperm whale, for example, can travel at speeds of up to 35 kilometers per hour (22 miles per hour). The fused neck vertebrae in toothed whales increases stability when swimming at high speeds but decreases flexibility, rendering them incapable of turning their heads. When swimming, toothed whales rely on their tail fins to propel them through the water. Flipper movement is continuous. They swim by moving their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering. Some species log out of the water, which may allow them to travel faster. Most species have a dorsal fin.

Many toothed whales are adapted for diving to great depths, but many porpoises and dolphins are not. In addition to their streamlined bodies, they can slow their heart rate to conserve oxygen; blood is rerouted from tissue tolerant of water pressure to the heart and brain among other organs; haemoglobin and myoglobin store oxygen in body tissue; and they have twice the concentration of myoglobin than haemoglobin. Before going on long dives, many toothed whales exhibit a behaviour known as sounding; they stay close to the surface for a series of short, shallow dives while building their oxygen reserves, and then make a sounding dive.

Pilot whales are also famous for stranding themselves en masse on beaches. Often those that are rescued beach themselves again. Scientists are still unable to explain why the strand themselves. False killer whales are dolphins. They are slimmer and darker than killer whales. A mass stranding of 800 of them occurred off the coast of Argentina in the mid-1940s.

Toothed Whale Sounds and Communication

All toothed whales and dolphins produce sound to communicate, navigate and locate prey. They all have a melon, a lens of fatty tissue used in navigation and finding prey and produce a wide range of sounds, including whistles, oinks, squawks, squeaks, blats and chirps. Exactly how they make the noises is still unclear. The clicking noises are used for echolocation (emitting sound waves and sensing their reflections to determine the location of objects). A single click is an intense form of energy that lasts less than 1/10,000th of a second yet contains a startling range of frequencies, most of them too high for humans to hear. The sounds emerge from the forehead as a beam, with many toothed whales and dolphins being able to focus or widen the beams with their melon. Some clicks are so loud they can temporarily deafen a person.

Toothed whales are capable of making a broad range of sounds using nasal airsacs located just below the blowhole. Roughly three categories of sounds can be identified: 1) frequency-modulated whistles, 2) burst-pulsed sounds, and 3) clicks. Dolphins communicate with whistle-like sounds produced by vibrating connective tissue, similar to the way human vocal cords function, and through burst-pulsed sounds. The clicks are directional and are used for echolocation, often occurring in short series called click trains. The click rate increases when approaching an object of interest. Toothed whale biosonar clicks are amongst the loudest sounds made by marine animals.

Toothed whales are well adapted to hear sounds at ultrasonic frequencies, as opposed to baleen whale who generally hear sounds within the range of infrasonic frequencies. The ears of whale and dolphins are adapted for their marine environment. Humans have a middle ear which aid in the collection of sounds. In whales, instead of sound passing through the outer ear to the middle ear, whales receive sound through the throat, from where it passes through a low-impedance, fat-filled cavity to the inner ear. The ear is acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater.

Toothed Whale Echolocation

Toothed whales do not rely on sight, but rather on their sonar to hunt prey. Echolocation also allowed toothed whales to dive deeper in search of food, with light no longer necessary for navigation. This opened up new food sources for them as they evolved. Toothed whales echolocate by creating a series of clicks emitted at various frequencies. Sound pulses emitted through their melon-shaped foreheads reflected off objects, and retrieved through the lower jaw.

With echolocation, the melon sends out high-frequency clicks and focuses outgoing sounds. The skull of creatures with a melon will have a large depression. The melon size varies between species, the bigger it is, the more dependent they are on it. A beaked whale, for example, has a small bulge sitting on top of its skull, whereas a sperm whale's head is filled mainly with the melon. The melon evolved from a sac off the main nasal passage and is used for moving air back and forth to create sound vibrations. The lower jaw helps catch returning vibrations. Zoe Cormier wrote in for BBC Earth: By vibrating the 'phonic lips' on their nasal bulbs at the top of their heads, they channel beams of sound through the melon (the globe of oily tissue in their forehead) towards their prey, and by picking up the echoes that bounce back (mostly through the jaw), can figure out not just the location of a fish, but also how big it is. [Source: Zoe Cormier, BBC Earth]

Stephen Rossiter, an expert on bats at Queen Mary University of London, told the BBC, that insect-eating bats which live in caves and hunt at night and during dusk echolocate like like toothed whales can dolphins, They emit high-pitched chirps in a rapid fire burst, and by listening to the echoes can locate prey and navigate through their habitat. He said, “You can see how echolocation would evolve if you’re in a dark environment like a cave or the deep ocean – there are in fact many blind humans who have learned how to echolocate, and even normal sighted people can tell if they are in a huge chamber or a crowded room just by listening to the acoustics,” he says. “But while bats have a typical mammalian ear, cetaceans have a much more specialised system.”

Sperm Whales

sperm whales

Sperm whales (Scientific name: Physeter catodon) are the largest toothed whales. They have one of the widest global distributions of any marine mammal species. They are found in all deep oceans, from the equator to the edge of the pack ice in the Arctic and Antarctic. They spend more time in warm waters than baleen whales because they feed mainly on squid which are widely distributed around the globe. [Source: National Geographic, December 1984; National Geographic, November 1995]

Sperm whales get their name from the waxy, milky, white oil that comes from the whale’s head that reminded whalers of, yes, sperm. This substance,, spermaceti, was used in oil lamps, lubricants, and candles. Whaling greatly reduced the sperm whale population. Whaling is no longer a major threat and its population is still recovering. The sperm whale is listed as endangered under the Endangered Species Act and depleted under the Marine Mammal Protection Act. [Source: NOAA]

Estimates of the number of sperm whales varies greatly. According to one estimate around 600,000 sperm whales remain today, about two thirds of their former numbers. According to another estimate there are as many as 2 million of them. There are dwarf sperm whales.

Sperm whales can reach a length of 18 meters and weigh 70 tons. They have a large head that occupies nearly a third of the whale’s length and vestigial hind limb passed down to them by their terrestrial ancestors. Sperm whales can reach speed of 32 kilometers per hour (20 miles per hour) and dive to depths 2,000 meters 6,500 feet) in search of prey. They often stay submerged for more than an hour. Their lifespan is thought to be around 60 years. The maximum known life span is 77 years.

Orcas (Killer Whales)

Orcas (also known as killer whales) are actually a kind of a dolphin. One of the most recognizable marine mammals, with their distinctive black and white bodies, they are the fastest marine mammal and the supreme predator of the sea. The have been timed at 55.5 kilometers per hour (34.5 mph) and have been observing taking on great white sharks, winning decisively, and attacking and feeding on mako sharks, blue whales, gray whales and sperm whales. [Source: Douglas Chadwick, National Geographic, April 2005]

Orcas (Scientific name: Orcinus orca) are arguably the most popular and closely-watched whales in the world. Their name “killer whale” is derived from early descriptions of them as “whale killers” or “killers of whales.” The name orca, which has become fashionable in recent years, is derived from the species scientific name, “ Orcinus orca”. It is not a name some Pacific Northwest Indian tribe gave the whale but rather Latin for “whale from the underworld of the dead.” People that are fond of orcas tend to call them orcas while those that are less fond of them or don’t care call them killer whales.

Orcas are the largest member of the Delphinidae family, or oceanic dolphins. Members of this family include pilot whales, , whose common names contain "whale" instead of "dolphin." The fossil history of orcas dates to the Pliocene Period (5.4 million to 2.4 million years ago), with the oldest fossils being about five million years old. Teeth, partial skulls, jaw bones, and periotic bones (mammal's ear bones) have been found in Japan, Hungary, Italy, and South Africa. [Source: Emily Burnett, Animal Diversity Web (ADW)]

Pilot Whales

short-finned pilot whales

Pilot whales are cetaceans (whales and dolphins) belonging to the genus Globicephala. There are two species — long-finned pilot whales (Globicephala melas) and short-finned pilot whales (Globicephala macrorhynchus). The two are difficult to tell part at sea. Analysis of the skulls is the best way to distinguish between them. Combined the two species range nearly worldwide, with short-finned pilot whales living in tropical and subtropical waters and long-finned pilot whales living in colder waters. Pilot whales are among the largest of the oceanic dolphins. Only orcas are bigger. They and other large members of the dolphin family are also known as blackfish. [Source: Wikipedia]

Pilot whales feed primarily on squid, but they also eat large demersal fish such as cod and turbot. They are gregarious and often remain with their birth pod throughout their lifetime. Short-finned pilot whales are one of the few mammal species in which females experience menopause. Humans and orcas are the only other known animals whose females go through it.

The animals were named "pilot whales" because pods were believed to be "piloted" by a leader. They are also called "pothead whales" and "blackfish". The genus name is a combination of the Latin word globus ("round ball" or "globe") and the Greek word Kephale ("head"). Fossils of an extinct relative, Globicephala baereckeii, have been found in Pleistocene Period (less than two million years old) deposits in Florida. Another Globicephala dolphin was discovered in Pliocene Period (5.4 million to 2.4 million years Pliocene strata in Tuscany, Italy,

Pilot whales are infamous for stranding themselves on beaches. The reason behind this is still not completely understood, but damage to the mammal’s inner ear (their principal navigational sonar) by ocean noise-pollution from cargo ships or military exercises may play a part.

False Killer Whales

False killer whales (Scientific name: Pseudorca crassidens) are a separate species of whale that are more dolphin-like, slimmer and darker than orcas. Sometimes off of Hawaii they gather in the hundreds. A mass stranding of 800 of them occurred off the coast of Argentina in the mid-1940s. The oldest estimated age of false killer whales (based on growth layers in teeth) is 63 years for females and 58 years for males. [Source: NOAA]

False killer whales are social animals found globally in all tropical and subtropical oceans. They are top predators that primarily hunt fish and squid. Occasionally they take marine mammals such as seals and sea lions. Among the fish they eat are salmon, bonito mahi mahi, yellowfin tuna yellowtail and perch. To catch some of these fish requires speed and skill. Remains of humpback whale have been found in their stomachs. False killer whales feed both during the day and at night, hunt in dispersed subgroups, and converge when prey is captured. Prey sharing has also been observed among individuals in the group. False killer whales can dive for up to 18 minutes and swim at high speeds to capture prey at depths of 300 to 500 meters.

False killer whales often leap completely out of the water, particularly when attacking certain prey species. In Hawaii, they are also known to throw fish high into the air before consuming them. According to Animal Diversity Web: They have been observed catching a fish in their mouth while completely breaching the waters' surface. They have also been seen shaking their prey until the head and entrails are shaken off. They then peel the fish using their teeth and discard all the skin before eating the remains. Some mothers will hold a fish in the mouth and allow their calf to feed on the fish. This food manipulation is rare in cetaceans.

False killer whales are found throughout the Atlantic, Pacific, and Indian Oceans between the latitudes 50º north and 52º degrees south. They generally prefer offshore waters that are deeper than 100 meters (3,300 feet) and inhabit depths of zero to 2000 meters (6561 feet) and frequently dive of 500 meters (1640 feet). False killer whales have been observed as far south as New Zealand, Peru, Argentina, South Africa, and the north Indian Ocean. They also range from Australia, the Indo-Malayan Archipelago, Philippines, and north to the Yellow Sea. They have been observed in northern latitudes in the Sea of Japan, coastal British Columbia, the U.S. east coast, the Bay of Biscay, and have been spotted in the Red and Mediterranean Seas. Many pods live near the Gulf of Mexico and surrounding the Hawaiian Islands. [Source: Kevin Hatton, Animal Diversity Web (ADW) /=]

False Killer Whale Characteristics

false killer whale

False killer whales are large members of the dolphin family. They range in weight from 916 to 1842 kilograms (2018 to 4056 pounds) and range in length from 3.5 to 6.1 meters (11.5 to 20 feet). Males are larger than females and males and females have different shapes. Adult females reach lengths of five meters (16 feet), while adult males are almost 6.1 meters 20 feet) long. In adulthood, large false killer whales weigh around 1,360 kilograms (3,000 pounds). False killer whales are is often mistaken for short-finned pilot whales and long-finned pilot whales. They inhabit the same regions and look kind of similar. To distinguish between them pilot whales are larger with obvious dorsal fin differences.[Source: Kevin Hatton, Animal Diversity Web (ADW) /=]

The body of false killer whales is black or dark gray, although lighter areas may occur ventrally (on its underside) between the flippers or on the sides of the head. The species is large and slender, and males are slightly larger than females. They have a small conical head without a beak. The front of an adult male’s head hangs over the lower jaw to a greater extent than in females and is flattened in older males. The pectoral fins or flippers have a distinct central hump creating an S-shape along the outer edge. The dorsal fin is located in the middle of the back and generally curves backward. In Hawaiian waters, dorsal fin shapes show a lot of variability, often caused by injury from fishery interactions. Scientists can photo-identify individual whales through unique natural markings, such as scars to false killer whales’ dorsal fins or scars from cookie cutter sharks. These prominent markings to the body and dorsal fin help distinguish one whale from another.

False killer whales have a more slender build than other dolphins and they have tapering heads and flippers. Their flippers average about one-tenth of the head and body length and have a distinct hump on the leading margin of the fin. There is a definite median notch on their flukes and they are very thin with pointed tips. False killer whales also have 16 to 22 teeth. The skulls of females range in length from 55 to 59 centimeters (1.8 to 1.95 feet), while males are 58 to 65 centimeters (1.9 to 2.1 feet). They have 47 to 52 vertebrae: seven cervical, 10 thoracic, 11 lumbar, and 20 to 23 caudal vertebrae. They have 10 pairs of ribs. /=\

False Killer Whale Behavior

False killer whales are motile (move around as opposed to being stationary), nomadic (move from place to place, generally within a well-defined range), social (associates with others of its species; forms social groups) and colonial (living together in groups or in close proximity to each other). [Source: Kevin Hatton, Animal Diversity Web (ADW) /=]

False killer whales are gregarious and form strong social bonds. They are often found in relatively small subgroups of a single to a few individuals that are associated with a larger aggregation that may spread over tens of kilometers. These strong social bonds between groups and dispersion into small subgroups likely help them find prey. When they capture prey, many individuals tend to converge, and their prey items may be shared among several animals in the group. [Source: NOAA]

False killer whales are found in groups ranging from just a few individuals to hundreds of individuals. In Hawaii, these larger aggregations may include 40 to 50 animals altogether, whereas larger groups have been observed in other regions. In these large groups they are sometimes separated into smaller groups or pods, which average about 18 members (typically 10 to 30). Pods contained members of all ages and both sexes. In some regions, false killer whales are also found with other whales and dolphins, most notably bottlenose dolphins.

False killer whales ride in the wakes and bow waves of ships. They prefer faster-moving ships, but will ride the bow waves on any vessel. They are one of the few large mammals that leap out of the water over the wake of the ship. They are also known to strand in groups as well. Large strandings have been reported on beaches in Scotland, Ceylon, Zanzibar and along the coasts of Britain. It is thought that stranded groups might have been chasing groups of seals or sea lions into the shallower waters and became stuck. /=\

false killer whale

False Killer Whale Mating, Reproduction and Offspring

False killer whales are viviparous, meaning they give birth to live young that developed in the body of the mother. They engage in year-round breeding and employ sexual induced ovulation (release of a mature egg from the ovary) Females give birth every seven years, on average. The breeding season is from year-round, but peaks December to January and again in March. The number of offspring is one. The gestation period ranges from 11 to 15.5 months. Lactation and nursing occurs for 1.5 to 2 years. Females reach sexual maturity at eight to 11 years. Males reach sexual maturity at eight to 10 years. [Source: Kevin Hatton, Animal Diversity Web (ADW) /=]

False killer whales are polygynandrous (promiscuous), with both males and females having multiple partners. In this species and a few others in the family Didelphinidae, if the female doesn't conceive after the first ovulation, she will keep ovulating until she does conceive. After giving birth, the female will not breed for a long time. Female false killer whales enter menopause and become less reproductively successful between 44 and 55 years old. [Source: NOAA]

Young are precocial. This means they are relatively well-developed when born. During the pre-fertilization, pre-birth and the pre-weaning stages provisioning and protecting is done by females. After false killer whales calves are born, they are cared for and nursed by their mother for up to 24 months. Young are capable of swimming on their own shortly after birth. Young are likely to remain in the same social group with their mother beyond weaning. The post-independence period is characterized by the association of offspring with their parents. There is an extended period of juvenile learning.

Melon-Headed Whales

Melon-headed whales (Scientific name: Peponocephala electra) are robust, small whales found primarily in deep, tropical waters worldwide. They are social animals and often occur in groups of hundreds to over 1,000 individuals. They likely maintain a matrilineal social structure, where females remain in groups with their mother and sisters and males move between groups. At birth, melon-headed whales are approximately one meter (3 feet) long and grow to three meters (9.3 feet) long. Melon-headed whales typically feed on squid, small fish, cuttlefish,and shrimp. Their lifespan is around 45 years.[Source: NOAA]

Also known as little killer whales and many-toothed blackfish, melon-headed whales can be easily confused with pygmy sperm whales and false killer whales, to whom they are closely related. The classification of melon-headed whales has been a matter of debate for some time as their relationships to dolphins, pilot whales and orcas is unclear. The first known specimens are two skulls described in 1846 and named “electra” from the Greek word “Elektra”, meaning amber, because of the amber color of the bones. They were once thought to be an extremely rare species, But then more than 500 were seen in Suruga Bay in Japan in 1951, of which 250 were caught. Their perceived rarity was probably the result of them living places not frequented by Europeans. The genus was officially named “Peponocephala” based on the Greek words “peponis”, a melon, and “kephalos”, a head. Overall, little is known about them as only a small number of individuals has been observed. [Source: Nicole Jacqueline Armbruster, Animal Diversity Web (ADW) /=]

Melon-headed whales are found primarily in deep waters throughout tropical and subtropical areas of the world at latitudes between 40º North and 30º South, with most concentrated between 20º North and 20º South. They are most commonly seen in the Philippine Sea, the Gulf of Mexico, the Arabian Sea, the Bay of Bengal, the South China Sea and off Senegal, Taiwan, southern Honshu (Japan), the Hawaiian Islands and southern Baja California. They have been observed as far south as Espiritu Santo in Brazil, the Timor Sea, northern New South Wales, and Peru. This range is extremely similar to that of pygmy killer whales. [Source: Nicole Jacqueline Armbruster, Animal Diversity Web (ADW) /=]

melon headed whale

In the United States, there are four distinct populations. Based on photo identification, satellite telemetry tag, and genetic research, we believe there are two populations of melon-headed whales in Hawaii — a large population that moves frequently among the islands that utilizes deep waters (4,600 to 6,000 feet deep), and a small population resident to the island of Hawaii that uses shallower waters (500 to 1,300 feet deep). There is also a population that lives in the Gulf of Mexico and the offshore waters of the southeastern United States. [Source: NOAA]

Melon-Headed Whale Physical Characteristics

Melon-headed whales ate small to medium sized. They range in length from 1.4 to 2.75 meters (4.7 to 9 feet), with their average length being 2.6 meters (8.5 feet). They reach weights of 275 kilograms (605.73 pounds), with their average weight being 210 kilograms (460 pounds). Both sexes are roughly equal in size and look similar. Males are somewhat bigger. [Source: Nicole Jacqueline Armbruster, Animal Diversity Web (ADW) /=]

Melon-headed whales have a small head with a rounded melon and no discernible beak. Their dorsal fin is relatively large and they have pointed, tapering flippers (pectoral fins). Their body color is dark gray, with a large faint, darker gray dorsal cape that narrows at the head on the dorsal side and dark areas on the side of the face that are not always easy to see. . Often, they have distinct dark eye patches that widens as they extend from the eye toward the melon. The lips are often white. White or light grey areas are common in the throat region, from the blowhole to the top of the melon, and on their bottom side. [Source: NOAA /=]

According to Animal Diversity Web : 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 melon-headed whales 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 percent 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 Melon-headed whales 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, Melon-headed whales has 82 vertebrae, the first three are fused together. /=\

Melon-headed whales have 20 to 25 teeth in each upper tooth row, compared to eight to 13 in pygmy killer whales. The teeth of Melon-headed whales 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. 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. Even so, it is difficult to distinguish melon-headed whales from pygmy killer whales. One of the best ways to tell them from other species is to look at their teeth, which are unmistakable, but usually you can’t them when they are moving at high speeds in the sea. /=\

Melon-Headed Whale Behavior

Melon-headed whales are diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), nomadic (move from place to place, generally within a well-defined range), sedentary (remain in the same area), and social (associates with others of its species; forms social groups). [Source: Nicole Jacqueline Armbruster, Animal Diversity Web (ADW) /=]

Melon-headed whales typically feed on squid, small fish, cuttlefish,and shrimp. They make fast, low shallow leaps from the water as they swim. They tend to rest in the morning, socialize in the afternoon, and hunt for food at night. They are often seen moving at high speeds,, creating lots of spray, and occasionally bow-ride on boats for short periods of time but overall they are wary of boats.

Melon-headed whales often occur in pods (groups) of hundreds to over 1,000 animals. Pods as large as 2000 individuals have been reported. Smaller, coordinated subgroups are common within the larger groups. They are often associated with schools of Fraser's dolphins and have been sighted in mixed schools with spinner dolphins, bottlenose dolphins, rough toothed dolphins, short-finned pilot whales, and spotted dolphins. [Source: NOAA]

Melon-headed whales sense using vision, touch, sound, echolocation (emitting sound waves and sensing their reflections to determine the location of objects) and chemicals usually detected by smell. They communicate with vision, touch and sound. Melon-headed whales make sounds similar to the whistles and clicks of bottlenose dolphins. 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. There is little data regarding migration. It is likely that their movements are defined by searches for food rather than seasonal migrations. /=\

Strandings of melon-headed whales have been reported at 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. Because these whales are difficult to distinguish at sea but are easy to identify after they have stranded, a lot of what is known about them comes from stranded individuals,

Melon-Headed Whale Mating, Reproduction and Offspring

Melon-headed whales are viviparous, meaning they give birth to live young that developed in the body of the mother. Little is known about their breeding habits. When the breeding season is is unknown. Calving appears to take place in early spring in the low latitudes of both hemispheres and in July and August in higher latitudes, but there is also evidence that calves are born year round. The average number of offspring is one. [Source: Nicole Jacqueline Armbruster, Animal Diversity Web (ADW) /=]

Female melon-headed whales reach sexual maturity at approximately 7 years of age while males mature later, between 12 and 15 years of age. The gestation period is approximately 12 months and females give birth every three to four years. [Source: NOAA]

Little is known of the parental habits of Melon-headed whales, but it is assumed that mothers care for and nurse her young until they reach independence. Young are precocial. This means they are relatively well-developed when born. As in other whale species, young are capable of swimming soon after birth. During the pre-fertilization, pre-birth, pre-weaning and pre-independence stages provisioning and protecting are done by females. At birth, the average young weighs about 15 kilograms.

Melon-Headed Whales, False Killer Whales, Humans and Conservation

False killer whales are generally not considered to be endangered but data is lacking on them and some populations suc as those around Hawaii are threatened. The Convention on International Trade in Endangered Species (CITES) places them in Appendix II, which lists species not necessarily threatened with extinction now but that may become so unless trade is closely controlled. False killer whales hunted in Indonesia, Japan, and the West Indies. Fishery interactions is one of the main threats facing this species. False killer whales are known to depredate (take fish and bait off of fishing lines), which can lead to hooking and/or entanglement. This is especially a concern for false killer whales that interact with the Hawaii longline fishery. [Source: NOAA]

Melon-headed whales are not endangered. They are designated as a species of least concern on the International Union for Conservation of Nature (IUCN) Red List. The Trade in Endangered Species (CITES) places them in Appendix II, which lists species not necessarily threatened with extinction now but that may become so unless trade is closely controlled. Like all marine mammals, they are protected under the Marine Mammal Protection Act. [Source: NOAA *]

Population estimates for melon-headed whales vary by location, ranging from approximately 400 individuals in the Hawaiian Islands to 45,000 individuals in the eastern tropical Pacific. Melon-headed whales have been hunted by humans near the island of St. Vincent in the Caribbean, in the Japanese dolphin drive in Taiji, near Lamalera, Indonesia, near Sri Lanka, and in the Philippines. Some hunting may still occur but the number of whales taken each year is small. For example, in 1982, only four melon-headed whales were recorded as being taken. They are used for bait rather than consumed. These whales are typically caught and killed with hand harpoons or toggle-head harpoon shafts shot from spear guns in the Philippines. [Source: Nicole Jacqueline Armbruster, Animal Diversity Web (ADW) /=]

Threats to melon-headed whales include entanglement in fishing gear and ocean noise. They are also occasionally caught incidentally in tuna purse seine nets in the eastern tropical Pacific and drift net fisheries in the Philippines, Indonesia, India, Malaysia, West Africa, and the Caribbean. Underwater noise threatens whale populations, interrupting their normal behavior and driving them away from areas important to their survival, such as feeding and breeding grounds. Increasing evidence suggests that exposure to intense underwater sound in some settings may cause some whales to strand and ultimately die. In Japan, heavy metal and man-made chemical concentrations (perfluorocarbons and flame retardants) in melon-headed whales have increased over time. Concentrations of polychlorinated biphenyls (PCB) in melon-headed whales in Hawaii and Japan are at levels thought to cause toxic effects. **

Image Source: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated June 2023