Cetaceans

Humpback whales and spinner dolphins are well known in Hawaii, but did you know at least 25 species of cetaceans can be found in our waters? The list includes: 1) several species of delphinids (dolphins) that occur both nearshore and far from the islands, 2) a diverse group of deep-diving whales (sperm and beaked), including some that are often difficult to spot and identify to species level, and 3) several species of baleen whales that most commonly occur in winter during their migration to tropical breeding grounds.

*Illustrations below are not to scale.
icons link to a species related article on the PIFSC Blog.

Delphinids (Dolphins)

Pantropical spotted dolphin (Stenella attenuata)

Pantropical spotted dolphin (Stenella attenuata). Illustration by Uko Gorter.
Pantropical spotted dolphin (Stenella attenuata). Illustration by Uko Gorter.

The pantropical spotted dolphin is found in all tropical and subtropical waters worldwide. Like other dolphins of the genus Stenella, it is a relatively small dolphin, reaching lengths of 6 to 7 ft (2 m) and weighing approximately 250 lb (114 kg) at adulthood. Individuals have long, slender, white-tipped snouts (beaks). They do not have spots at birth, but as they age, their bodies develop spots until they are almost completely covered with overlapping patterns. The pantropical spotted dolphin has a dark coloration, or cape, that extends from its head, past its dorsal fin, and mid-way to its tail. This dolphin is often in large groups of several hundred animals. It is also quite social, and tends to school with other dolphin species, including the rough-toothed dolphin, short-finned pilot whale, and spinner dolphin. In the Hawaiian Archipelago, there are genetically-distinct populations of spotted dolphins found between Hawaii Island, Maui Nui, Oahu, and offshore. Animals from each population can travel far offshore, from 120-300 miles (60-100 km), but are generally found closer to the islands.

Striped dolphin (Stenella coeruleoalba)

Striped dolphin (Stenella coeruleoalba). Illustration by Uko Gorter.
Striped dolphin (Stenella coeruleoalba). Illustration by Uko Gorter.

The striped dolphin is one of the most abundant and widespread pelagic dolphins in the world. A male can grow to a length of about 9 ft (2.7 m) and weigh up to 350 lb (160 kg), and a female can grow up to 8 ft (2.4 m) and weigh up to 330 lb (150 kg). The striped dolphin has a small- to medium-sized, robust, sleek body with a long, defined beak and round melon (forehead). Its dorsal fin is falcate (hook-shaped), tall, and located mid-back. Its body is distinguished by a complex of bold and thin stripes that branch from the eye to (1) the flipper and (2) down the side of the body to the anal region. The beak, tapered flipper, tail, and back are dark blue/gray. The area just above the side stripe is bluish or light gray and creates a contrasting shoulder blaze that curves back and up toward the animal's dorsal fin. The ventral side is white to pinkish, and much lighter than the rest of the body. The markings and coloration of this species may vary by individual and geographical location. Calves and juveniles may have more muted colorations and patterns. Like Fraser’s dolphin, the striped dolphin typically avoids vessels around Hawaii, often jumping clear of the water at high speed.

Spinner dolphin (Stenella longirostris)

Spinner dolphin (Stenella longirostris). Illustration by Uko Gorter.
Spinner dolphin (Stenella longirostris). Illustration by Uko Gorter.

The spinner dolphin is found offshore in tropical waters around the world. Like other dolphins of the genus Stenella, the spinner dolphin is relatively small, reaching lengths of 6-7 ft (2 m) and weighing approximately 130-170 lb (59-77 kg) at adulthood. They have long, slender snouts or beaks. There is a great deal of color variation of this species, between geographic regions. In Hawaii, it has a dark dorsal body, light gray sides and a white belly. The spinner dolphin is named and best known for its unique behavior of leaping into the air and spinning several times, which it does primarily to remove remoras. In Hawaii, there are several island-associated populations of the spinner dolphin throughout the archipelago. They rest in nearshore waters during the day, where they are commonly observed from shore, and then feed offshore at night as small fish and squid ascend from deeper waters toward the surface.

Rough-toothed dolphin (Steno bredanensis)

Rough-toothed dolphin (Steno bredanensis). Illustration by Uko Gorter.
Rough-toothed dolphin (Steno bredanensis). Illustration by Uko Gorter.

The rough-toothed dolphin is found primarily in deep waters through tropical and warmer temperate regions of the world. In Hawaiian waters, it is found both in island-slope and offshore waters. A relatively small dolphin, it reaches a length of 8.5 ft (2.6 m) and weight of 350 lb (160 kg). Its small head and long beak form no crease at the melon (forehead). Its dorsal fin, located mid-back, is relatively large and tall, and it has relatively large pectoral flippers. The rough-toothed dolphin has a body color that is blotchy gray with a darker dorsal cape that is narrow between the blowhole and dorsal fin. Older individuals have white lips and extensive, irregular, ventral spots and blotches. Although typically found in small groups from 2-15 individuals, large groups (over 100) have been documented in Hawaiian waters.

Bottlenose dolphin (Tursiops truncatus)

Bottlenose dolphin (Tursiops truncatus). Illustration by Uko Gorter.
Bottlenose dolphin (Tursiops truncatus). Illustration by Uko Gorter.

The bottlenose dolphin inhabits almost everywhere; from offshore pelagic waters to secluded bays and estuaries, and from tropical to temperate waters. The bottlenose dolphin has a short, thick beak and a robust body with a light ventral to a dark-gray dorsal coloration. This dolphin has adapted for many marine environments, and body size and coloration can vary between inshore and offshore forms. Inshore animals are generally smaller and lighter in color, while offshore animals are larger and darker and have smaller flippers. Their adult bodies range in length from 6 to 12.5 ft (1.8-3.8 m), with males slightly larger than females. Adults weigh from 300-1400 lb (136-635 kg). In the Hawaiian Archipelago, there are small and genetically-distinct populations of bottlenose dolphins around each of the main islands (Hawaii Island, Maui Nui, Oahu, and Kauai), as well as a separate offshore population. Offshore animals in Hawaiian waters are typically covered with light colored scars from cookie-cutter shark bites.

Fun facts: “Flipper” was a bottlenose dolphin that was domesticated and trained to perform for television. Bottlenose dolphins have been known to attack sharks!

Risso's dolphin (Grampus griseus)

Risso's dolphin (Grampus griseus). Illustration by Uko Gorter.
Risso's dolphin (Grampus griseus). Illustration by Uko Gorter.

The Risso's dolphin generally prefers deeper offshore waters and can be found in the temperate and tropical zones of all the world’s oceans. This dolphin has a robust body with a narrow tailstock and can reach lengths of approximately 8.5-13 ft (2.6-4 m) and weigh 660-1100 lb (300-500 kg). Males and females are usually about the same size. They have a bulbous head with a vertical crease, and an indistinguishable beak. They have a tall, falcate (sickle-shaped) dorsal fin located mid-way down the back. Calves have a dark cape and saddle, with little or no scarring on their bodies. As the Risso's dolphin ages, its coloration lightens from black, dark-gray or brown to pale-gray or almost white. Their bodies are usually heavily scarred, with scratches from teeth raking between individuals, as well as circular markings from its prey (e.g., squid), cookie-cutter sharks (Isistius brasiliensis), and lampreys. Mature adults swimming just under the water's surface appear white.

Fraser's dolphin (Lagenodelphis hosei)

Fraser's dolphin (Lagenodelphis hosei). Illustration by Uko Gorter.
Fraser's dolphin (Lagenodelphis hosei). Illustration by Uko Gorter.

Fraser's dolphin generally occurs in tropical and sub-tropical waters and may be much more common in the Pacific than in the Atlantic and other oceans. Fraser’s dolphin has a stocky or chunky body and a small distinct beak. The dorsal fin, located midway down its back, is relatively small, slightly falcate (sickle-shaped), and triangular in shape, and the flippers and flukes are also small when compared to other dolphin species. Fraser's dolphin is recognized by a distinct dark (usually black or gray) lateral stripe along its flank from eye to flipper and anus and reminds some people of a raccoon or bandit-like mask. The stripe may vary based on geography and gender. The dorsal side of the animal is a bluish or brownish gray and the ventral side is usually pale white or pink. Adults are about 6-9 ft (2-2.7 m) long and weigh 350-450 lb (160-210 kg). Males are generally slightly longer, weigh more, and have more distinct color patterns than females. Fraser’s dolphin is not commonly seen on the island slopes of Hawaii, but are common in offshore pelagic waters. Like the striped dolphin, it often appears to flee from boats, porpoising clear of the water at high speed.

Melon-headed whale (Peponocephala electra)

Melon-headed whale (Peponocephala electra). Illustration by Uko Gorter.
Melon-headed whale (Peponocephala electra). Illustration by Uko Gorter.

The melon-headed whale lives in deep tropical and sub-tropical waters all over the world. It can reach a length of 9 ft (2.7 m) and weight of 460 lb (210 kg). It has a small head with a rounded melon (forehead) and no discernible beak. Its dorsal fin is relatively large and it has pointed, tapering flippers (pectoral fins). Its body has a dark, dorsal cape with a diffuse boundary, and it has dark areas on the side of its face that are not always readily apparent. The melon-headed whale is extremely gregarious, and often seen in groups of 100 to over 500 animals. In Hawaii, there are two populations of melon-headed whales: one found only near-shore around the northern tip of Hawaii Island, and the other more broadly, including in deep nearshore and offshore waters.

Pygmy killer whale (Feresa attenuata)

Pygmy killer whale (Feresa attenuata). Illustration by Uko Gorter.
Pygmy killer whale (Feresa attenuata). Illustration by Uko Gorter.

The pygmy killer whale has a pantropical range and is rarely found near the coast except in areas where deep waters come close to the shore, such as oceanic islands like Hawaii. This whale can reach a length of 8.5 ft (2.6 m) and weight of 380 lb (170 kg). It has a small head with a rounded melon (forehead) extending in front of its mouth with no discernible beak. It has relatively long, tapering flippers (pectoral fins) with rounded tips. Its body color is dark with some small white areas on the lips and belly. Easily confused with melon-headed whales, the best ways of distinguishing between the two species at sea are by finding the pygmy killer whale’s frequent paired white tooth rakes, and the clear demarcation between the darker cape and lighter lateral pigmentation. There are resident populations of this species off Oahu, Penguin Bank, and Hawaii Island.

False killer whale (Pseudorca crassidens)

False killer whale (Pseudorca_crassidens). Illustration by Uko Gorter.
False killer whale (Pseudorca crassidens). Illustration by Uko Gorter.

The false killer whale lives in warm temperate and tropical waters throughout the world. It is a large member of the dolphin family. Females reach lengths of 15 ft (4.5 m), while the largest known male was almost 20 ft (6 m). In adulthood, a false killer whale can weigh approximately 1500 lb (700 kg). It has a small conical head without a beak. Its dorsal fin is tall and its pectoral flippers have a distinctive hump or bulge in the middle of the front edge. The false killer whale has dark coloration except for some lighter patches near the throat and middle chest. Its body shape is more slender than other large delphinids. In Hawaii, there are three populations of the false killer whale: one broadly distributed pelagic population, one island-associated population in the northwestern Hawaiian Islands, and one island-associated population in the main Hawaiian Islands. The main Hawaiian Islands insular population is very small and is considered endangered under the Endangered Species Act. The false killer whale is known to take bait and catch off fishing hooks, a behavior that sometimes leads to getting hooked or entangled. For the pelagic population, this depredation and hooking is common enough that fishermen, researchers, the National Marine Fisheries Service, and the State of Hawaii developed a Take-Reduction Plan to reduce the number of interactions between false killer whales and the longline fishery to ensure conservation of the false killer whale population.

Short-finned pilot whale (Globicephala macrorhynchus)

Short-finned pilot whale (Globicephala macrorhynchus). Illustration by Uko Gorter.
Short-finned pilot whale (Globicephala macrorhynchus). Illustration by Uko Gorter.

The short-finned pilot whale is widespread and abundant throughout the world’s tropical and warm temperate oceans. The short-finned pilot whale’s tropical and warm temperate distribution compliments that of its cool-water relative, the long-finned pilot whale. It is a larger member of the dolphin group reaching average lengths of 12 ft (3.7 m) for females and 18 ft (5.5 m) for males with maximum male size of 24 ft (7.3 m). There are two forms (possibly sub-species) in the North Pacific, and those in Hawaiian waters are the smaller form, reaching a maximum length of about 18 ft (5.5). Adult weight is 2200-6600 lb (1000-3000 kg). It has a bulbous melon head with no discernible beak. Its dorsal fin is located far forward on the body and has a relatively long base. Its body is dark gray (often appearing black), and while some pilot whales have a large gray saddle behind the dorsal fin (the form found in Hawaiian waters does not).

Killer whale (Orcinus orca)

Killer whale (Orcinus orca). Illustration by Uko Gorter.
Killer whale (Orcinus orca). Illustration by Uko Gorter.

The killer whale is considered the most widespread cetacean, found in all parts of the oceans. It is most abundant in colder waters, but also occur at lower densities in tropical, subtropical, and offshore waters. It is black on its dorsal side with a white ventral side, white patches near its eyes, and a highly variable gray or white saddle behind the dorsal fin; these markings are unique across individuals and populations. The species shows considerable size dimorphism. Adult males develop larger pectoral flippers, dorsal fins, tail flukes, and girths than females. Female killer whales reach sexual maturity when they grow to about 15-18 ft (4.6-5.4 m) long, depending on geographic region. Different sub-species of killer whales specialize in foraging exclusively on fish or on other marine mammals. The killer whale is relatively rare in Hawaii, and appears to be a generalist in Hawaiian waters, feeding on sharks, cephalopods, and other marine mammals.

Deep-Diving Whales

Sperm whale (Physeter macrocephalus)

Sperm whale (Physeter macrocephalus) male. Illustration by Uko Gorter.
Sperm whale (Physeter macrocephalus). Illustration by Uko Gorter.

The sperm whale inhabits all oceans of the world. It is the largest of the odontocetes (toothed whales) and the most sexually-dimorphic cetacean, with males considerably larger than females. Adult females may grow to lengths of 36 ft (11 m) and weigh 15 tons (13,600 kg), while adult males reach about 52 ft (16 m) and may weigh as much as 45 tons (40,800 kg). The sperm whale is distinguished by its extremely large head, which takes up to 25-35 percent of its total body length. It is the only living cetacean that has a single blowhole asymmetrically situated on the left side of its head near the tip. Sperm whales have the largest brain of any animal (on average 17 lb, 7.8 kg, in mature males); however, compared to its large body size, the brain is not exceptional in size. There are between 20-26 large conical teeth in each side of the lower jaw. The teeth in the upper jaw rarely erupt and are often considered to be vestigial. It appears that teeth may not be necessary for feeding, since they do not break through the gums until puberty, if at all, and healthy individuals have been caught that have no teeth. The sperm whale is mostly dark gray, but oftentimes the interior of the mouth is bright white, and some have white patches on the belly. Its flippers are paddle-shaped and small compared to the size of the body, and its flukes are triangle-shaped. It has a small dorsal fin that is low, thick, and usually rounded. In Hawaii, large groups of sperm whales generally consist of adult females and their offspring, while adult males generally roam alone. Sperm whales are listed as endangered under the Endangered Species Act.

Dwarf sperm whale (Kogia sima)

Dwarf sperm whale (Kogia sima). Illustration by Uko Gorter.
Dwarf sperm whale (Kogia sima). Illustration by Uko Gorter.

The dwarf sperm whale occurs in tropical and temperate latitudes worldwide and is most common along the waters of the continental shelf edge and the slope. It can reach lengths of up to about 9 ft (2.7 m) and weigh between 300-600 lb (135-270 kg). This species has a small compact body that tapers near the tail, and has a dorsal fin located midway down the back. Like the pygmy sperm whale, it tends to lie almost motionless at the surface. It can best be distinguished from the pygmy sperm whale at the surface by its relatively larger dorsal fin in comparison to the amount of visible back. The shape of the dorsal fin varies from falcate (sickle-shaped) and pointed to triangular depending on the individual. The head is sometimes described as shark-like due to a conical pointed snout and a small narrow distinctive underslung lower jaw. On the throat below the jaw may be several short longitudinal grooves or creases. Its "bulging" eyes are dark with a light circular mark above them. Behind the eye is a pale false gill marking, which looks similar to a fish's gill cover. Like its larger cousin the sperm whale, the dwarf sperm whale has a spermaceti organ and single blowhole situated slightly to the left side of the body. While at the surface, it has a low, flat, profile due to the level position of the head and back. The skin is brownish to dark bluish-gray on the dorsal side, and whitish to pinkish on the ventral side, giving the animal a counter-shading effect. The dwarf sperm whale is a deep-diver and is very hard to see at the surface, especially when the water is not calm.

Pygmy sperm whale (Kogia breviceps)

Pygmy sperm whale (Kogia breviceps). Illustration by Uko Gorter.
Pygmy sperm whale (Kogia breviceps). Illustration by Uko Gorter.

The pygmy sperm whale occurs in tropical and temperate latitudes worldwide and is thought to reside primarily seaward of the continental shelf. This species has a small, compact body that tapers near the tail and has a small, low, rounded, dorsal fin located slightly posterior of the mid-point of the back. The smaller, more posterior dorsal fin is the best way of distinguishing this species from dwarf sperm whales, and they have a relatively larger head. The shape of the dorsal fin varies depending on the individual. The head is sometimes described as "shark-like" due to a conical, pointed snout, and a small narrow, distinctive, underslung lower jaw. Unlike the dwarf sperm whale, this species does not have irregular grooves or creases on the throat. The pygmy sperm whale lacks teeth in its upper jaw, but have 10-16 pairs of teeth in the lower jaw that fit into sockets in the upper jaw. Its "bulging" eyes are dark with a light circular mark above and around them. Behind the eye is a pale false gill marking, which looks similar to a fish's gill cover. Like its larger cousin the sperm whale, the pygmy sperm whale has a spermaceti organ and single blowhole situated slightly to the left side of the body. At the surface, it has a low profile due to the level position of its head and back. The skin is wrinkled (only when closely observed) and is brownish to dark bluish-gray on the dorsal side. The ventral side is paler with whitish to pinkish coloration that gives the animal a counter-shading effect.

Blainville's beaked whale (Mesoplodon densirostris)

Blainville's beaked whale (Mesoplodon densirostris). Illustration by Uko Gorter.
Blainville's beaked whale (Mesoplodon densirostris). Illustration by Uko Gorter.

Blainville’s beaked whale occurs in tropical to temperate waters worldwide. It is generally found in deep, offshore waters of the continental shelf and often associated with steep underwater geological structures such as banks, submarine canyons, seamounts, and continental slopes. The adult Blainville's beaked whale reaches lengths of approximately 15 ft (4.7 m) and weights of 1800-2300 lb (820-1,030 kg). Males can be easily distinguished from females and juveniles by a pair of large visible tusk-like teeth that erupt and point forward from the heavily arched lower jaw. Females and juveniles have teeth as well, but they remain hidden beneath the gum tissue of the mouth, and their jawline is less-curved. Blainville's beaked whale has a relatively medium-sized, round body with a small, wide-based, slightly falcate (sickle-shaped) dorsal fin located far down (about two-thirds) the animal's back. The whale's head has a low, sloping forehead and indistinct melon. Its color varies from dark gray to brownish and bluish. The face and ventral side is pale gray or white, giving it a counter-shading appearance. The skin is covered with linear and oval-shaped scars and other markings. Blainvilles' beaked whale, like all beaked whales, is typically a deep-diver and can spend 45-90 min underwater at a time. It is regularly sighted in island-slope waters roughly 1600-3300 ft (500-1000 m) deep. Their sounds can be easily identified when they echolocate on prey.

Cuvier's beaked whale (Ziphius cavirostris)

Cuvier's beaked whale (Ziphius_cavirostris). Illustration by Uko Gorter.
Cuvier's beaked whale (Ziphius cavirostris). Illustration by Uko Gorter.

Cuvier's beaked whale is a member of the beaked whale family (Ziphiidae). It is found in all oceans of the world, except the polar regions of both hemispheres, and is the most widely distributed of all beaked whales. Cuvier’s beaked whale prefers deep water of over 3300 ft (1000 m) and avoids shallow coastal areas. It can reach lengths of about 15-23 ft (4.5-7 m) and weigh 4000-6800 lb (1850-3100 kg). Males and females are similar in size. This medium-sized whale has a round and robust body, with a triangular falcate (sickle-shaped) dorsal fin located far down the animal's back. The head is a sloping concave-shape with no obvious melon (forehead), an indistinct beak, and a large slit-like blowhole. The jaw-line is slightly upturned giving the whale a "smiling" appearance. The profile of the head is sometimes described as goose-like. The teeth of Cuvier’s beaked whale are located at the tip of the bottom jaw. Like most other beaked whale species, the teeth only erupt from the gums in adult males and they are used for fighting among males. A Cuvier's beaked whale's body has variable coloration that ranges from dark gray to a reddish-brown, with a paler counter-shaded underside. The reddish-brown coloration is caused by the infestation of microscopic diatoms and algae. The body is often covered with linear scratches and oval-shaped scars. As this species grows older, they become paler, develop a more significant indentation on the top of the head and accumulate more scarring (especially males). There is a whitish coloration on the face and dark-colored patch around the eye. Fun Fact: Cuvier’s beaked whale can hold its breath over two hours.

Longman's beaked whale (Indopacetus pacificus)

Longman's beaked whale (Indopacetus pacificus). Illustration by Uko Gorter.
Longman's beaked whale (Indopacetus pacificus). Illustration by Uko Gorter.

Longman’s beaked whale occurs in tropical waters of the Indian and Pacific Oceans. As an adult, it can reach an estimated length of about 20-30 ft (6-9 m). Its weight is unknown. Compared to other tropical beaked whales, this species is relatively large. Longman's beaked whale has a large, robust body with a fairly large, falcate (sickle-shaped) dorsal fin located far down its back. This species has dark, small, rounded, narrow flippers that fit into a depression on either side of the body. It has a well-defined melon that is almost perpendicular to its long, tube-shaped beak. A crease may distinguish the melon from the beak. As it grows older, the melon develops into a steeper, more bulbous shape that may hang over the beak. It is typically found in much larger groups than other species of beaked whales in Hawaii, numbering from 30 to over 100 individuals.

Baleen whales

Minke whale (Balaenoptera acutorostrata)

Minke whale (Balaenoptera acutorostrata). Illustration by Uko Gorter.
Minke whale (Balaenoptera acutorostrata). Illustration by Uko Gorter.

The minke whale is among the most widely distributed of all the baleen whales. It occurs in the North Atlantic and North Pacific, from tropical to polar waters. Generally, they inhabit warmer waters during winter and travel north to colder regions in the summer. This whale is frequently observed in coastal or shelf waters. It has a relatively small, dark, sleek body that can reach lengths of up to about 35 ft (10.7 m) and weigh up to 20,000 lb (9200 kg). Females may be slightly larger than males. The minke whale has a fairly tall, falcate (sickle-shaped) dorsal fin located about two-thirds down its back. The body is black to dark grayish/brownish in color with a pale chevron on the back behind the head and above the flippers and a white underside, giving it a counter-shading appearance. It also has a large white patch on its flipper. Calves are usually darker in coloration than adults. Minke whales make very strange sounds, with different sounds in different geographic regions. Minke whale sounds in Hawaii and through much of the Pacific are called boings.

Bryde's whale (Balaenoptera edeni)

Bryde's whale (Balaenoptera_edeni). Illustration by Uko Gorter.
Bryde's whale (Balaenoptera edeni). Illustration by Uko Gorter.

Bryde's (pronounced "broo-duhs") whale is found worldwide in tropical to temperate waters, rarely seen at latitudes greater than 35° N or S. This whale is a member of the baleen whale family and can reach lengths of about 40-55 ft (13-16.5 m) and weigh up to about 90,000 lb (40,000 kg). Males are usually slightly smaller than females. Bryde's whale is a large animal (considered medium-sized for balaenopterids) that has a sleek body that is dark gray (dorsal side) and white (ventral side). It looks similar in to the sei whale, but can be distinguished by three prominent longitudinal ridges located on its rostrum in front of the blowhole. The sei whale, like other rorquals (baleen whales with throat grooves), has a single median ridge on its rostrum. The head of Bryde's whale makes up about one quarter of the whale's entire body. It has an erect, falcate (sickle-shaped) dorsal fin located far down the animal’s back and broad flukes. On each side of a Bryde's whale’s mouth are 250-410 gray-colored coarse baleen plates (generally less than 40 cm long). Between 40-70 ventral pleats are located on the animal's underside. Bryde's whale is the only species of baleen whale known to occur in Hawaii year-round, though still is rarely spotted nearshore.

Sei whale (Balaenoptera borealis)

Sei whale (Balaenoptera borealis). Illustration by Uko Gorter.
Sei whale (Balaenoptera borealis). Illustration by Uko Gorter.

The sei whale occurs worldwide, from subtropical or tropical waters to high latitudes, and inhabits both shelf and oceanic waters. This large animal can reach lengths of about 40-60 ft (12-18 m) and weigh 100,000 lb (45,000 kg). Females may be slightly longer than males. The sei whale has a long, sleek body that is dark bluish-gray to black in color and pale underneath. The body is often covered in oval-shaped scars (probably caused from cookie-cutter shark and lamprey bites) and sometimes has subtle "mottling" pattern. This species has an erect falcate (sickle-shaped) dorsal fin located about two-thirds down the animal’s back. It often looks similar in to Bryde's whales, but can be distinguished by the presence of a single ridge located on the animal's rostrum instead of the three ridges that the Bryde’s whale has on its rostrum. The sei whale has 219-410 baleen plates that are dark in color with gray/white fine inner fringes in its enormous mouth. It also has 30-65 relatively short ventral pleats that extend from below the mouth to the naval area. The number of throat grooves and baleen plates may differ depending on geographic population. Sei whales are listed as endangered under the Endangered Species Act.

Fin whale (Balaenoptera physalus)

Fin whale (Balaenoptera physalus), left side. Illustration by Uko Gorter.
Fin whale (Balaenoptera physalus), left side. Illustration by Uko Gorter.
Fin whale (Balaenoptera physalus), right side. Illustration by Uko Gorter.
Fin whale (Balaenoptera physalus), right side. Illustration by Uko Gorter.

The fin whale occurs in all major oceans, usually in temperate to polar latitudes (and less commonly in the tropics). It tends to concentrate in coastal and shelf waters, but can also be found in the deep ocean. It is the second-largest species of whale, with a maximum length of about 75 ft (22 m) in the Northern Hemisphere, and 85 ft (26 m) in the Southern Hemisphere. The fin whale shows mild sexual dimorphism, with females measuring longer than males by 5- 10 percent. Adults can weigh between 80,000 and 160,000 lb (40-80 tons). It has a sleek, streamlined body with a V-shaped head. It has a tall, falcate (sickle-shaped) dorsal fin, located about two-thirds of the way back on the body, that rises at a shallow angle from the animal's back. The species has a distinctive coloration pattern: the back and sides of the body are black or dark brownish-gray, and the ventral surface is white. The unique, asymmetrical head color is dark on the left side of the lower jaw, and white on the right side. Many individuals have several light-gray, V-shaped "chevrons" behind its head, and the underside of the tail flukes is white with a gray border. The fin whale is also rarely seen in Hawaii, likely because it is generally here in the winter when migrating from feeding grounds further north. Like the blue whale, the fin whale can be easily identified from its songs, and long-term acoustic recordings of regular winter visitors suggest the characteristics of an individual’s songs provides clues on where it is from. Fin whales are listed as endangered under the Endangered Species Act.

Blue whale (Balaenoptera musculus)

Blue whale (Balaenoptera_musculus). Illustration by Uko Gorter.
Blue whale (Balaenoptera musculus). Illustration by Uko Gorter.

The blue whale is found worldwide and inhabits coastal, shelf, and oceanic waters. The blue whale is generally smaller in the Northern Hemisphere than it is in the Southern Hemisphere. In the North Atlantic and North Pacific, it can grow up to 90 ft (27 m), but in the Antarctic, it can reach up to 110 ft (33 m) and weigh more than 330,000 lb (150,000 kg). Like with other baleen whales, the female blue whale is somewhat larger than the male. The blue whale has a long body and comparatively slender shape, a broad, flat rostrum when viewed from above, a proportionately smaller dorsal fin than other baleen whales, and a mottled gray color pattern that appears light blue (hence, the "blue" whale) when seen through the water. We rarely see blue whales in Hawaii because they generally only visit in the winter when survey conditions are rough. Blue whale calls are easy to identify, and its very low-frequency repeated songs can propagate long distances underwater making it possible to track the presence of this species using acoustic recorders. Blue whales are listed as endangered under the Endangered Species Act.

Humpback whale (Megaptera novaeangliae)

Humpback whale (Megaptera_novaeangliae). Illustration by Uko Gorter.
Humpback whale (Megaptera novaeangliae). Illustration by Uko Gorter.

The humpback whale is found worldwide in all major oceans from the equator to polar latitudes. It is well known for its long pectoral fins, which can be up to 15 ft (4.6 m) in length. These long fins give it increased maneuverability; they can be used to slow down or even go backwards. Similar to all baleen whales, adult females are larger than adult males, reaching lengths of up to 52 ft (16 m). Its body coloration is primarily dark grey, but individuals have a variable amount of white on their pectoral fins and belly. This variation is so distinctive that the pigmentation pattern on the undersides of its flukes is used to identify individual whales, similar to a human fingerprint. The humpback whale is highly migratory; it feeds during summer in mid and high latitudes, and mate and give birth during winter in tropical or subtropical waters, often concentrated around islands or reef systems. There are at least 14 separate populations of humpbacks whales throughout the world and some are still recovering from whaling or other impacts. Humpbacks in Hawaii are not listed as endangered under the Endangered Species Act.

Fun fact: Each winter, over 10,000 humpback whales migrate to Hawaiian waters to mate and give birth.

North Pacific right whale (Eubalaena japonica)

North Pacific right whale (Eubalaena japonica). Illustration by Uko Gorter.
North Pacific right whale (Eubalaena japonica). Illustration by Uko Gorter.

The North Pacific right whale, as its name implies, is found only in the North Pacific, where these whales occur as two populations: a western population centered around the Okhotsk Sea and an eastern population found primarily in the Bering Sea and Gulf of Alaska. Right whales are among the largest of the baleen whales and can reach up to 60 ft (18 m), with females being larger than males, as is the case with other baleen whales. Right whales have a very distinct V-shaped blow that can reach up to 16 ft (5 m), making them quite visible at a distance. They are all black, have a flat back with no dorsal fin, and have an enormous head, almost a third of the length of their body, that is characterized by a highly-curved jawline and the presence of callosities (patches of roughened skin). Right whales are unlikely to be confused with any other species in Hawaii; however, their presence in Hawaii is extremely rare, with the last confirmed sighting (of a whale from the eastern population) occurring in 1996. Right whales are migratory and feed at high latitudes, but it is unknown where eastern North Pacific right whales breed and to what degree, if any, their breeding areas include Hawaiian waters. Unfortunately, eastern North Pacific right whales failed to recover from the impacts of commercial and illegal Soviet whaling and have been estimated to number just over thirty individuals. Right whales are listed as endangered under the Endangered Species Act, and the eastern population is considered the most endangered large whale population in the world.

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All photos were taken with research permit.