Species Guide: Dolphins Hunted in Taiji

Other Names: Common bottlenose dolphin

Scientific Name: Tursiops Truncatus

Body Size: 300 – 1400 lbs (136 – 635 kg)

Body Length: 6 – 13 feet (1.8 – 4 m)

Range: Temperate to Tropical, Worldwide

Range: Cool Temperate to Tropical, Worldwide

Lifespan: 40 – 60 Years

Gestation: ~12 Months

Threats: Drive Hunts, Exploitation in Captivity, Marine Pollution, Noise Pollution

In the wild, bottlenose dolphins inhabit a large part of the world’s oceans from tropical to temperate waters, and near-shore to offshore areas. Within the species, there are several different subgroups, such as coastal populations with dolphins smaller in body size, to deep diving offshore populations with more robust dolphins. Each of these populations or subgroups have a unique geographical range. They feed on a large variety of fish and invertebrates, with some populations utilizing complicated, cooperative hunting strategies (i.e. “fish whacking” and “mud ring feeding”) to forage.

Bottlenose dolphins are known to associate with family members (mothers and offspring, years after the calf matures). They have also been found to utilize signature whistles, similar to how we utilize names for each other. Spindle neurons have also been found in the brains of bottlenose dolphins, providing further evidence for mental and emotional complexity! Sadly, bottlenose dolphins are highly desired by captive facilities around the world, making them a very desirable species for live capture in Taiji’s drive hunts. In the past several seasons, bottlenose dolphins have only been subject to captive selection and not slaughter, which may be due to concerns of declining local populations.

Scientific Name: Stella coeruleoalba

Body Size: 220-350 lbs (100 – 150 kg)

Body Length:  6 – 8 feet (2.1 – 2.6 m)

Range: Temperate to Tropical, Worldwide

Lifespan: Approximately 50 Years

Gestation: 12 – 13 Months

Threats: Drive Hunts, Marine Pollution, Noise Pollution

Striped dolphins are a smaller species, and can be quite acrobatic at the surface with leaps as high as 20 feet into the air. They are widely distributed within their range, although the conservation status of individual populations is not known. Striped dolphins tend to prefer deep tropical, and warm waters near areas of upwelling, where they forage and feed on a variety of fish and cephalopods. They are capable of diving to at least 3,200 feet.

In Taiji, they look quite similar to pantropical spotted dolphins, being similar in size and basic shape. Striped dolphins can be distinguished by a slightly more robust body shape, and by their striking stripe pattern on their sides. When being chased by hunting boats, they tend to porpoise (leap with forward propulsion out of the water) at high speeds. Striped dolphins are not commonly held in captivity, although a handful of facilities claim to be “pioneering” husbandry methods of keeping them alive in concrete tanks for longer periods of time. Although sometimes captured, striped dolphins all too often fall victim to slaughter in the cove, sometimes going into mass panic during the process.

Scientific Name: Grampus griseus

Body Size: 650 – 1,100 lbs (300 – 500 kg)

Body Length: 9 – 13 feet (2.8 – 4 m)

Range: Cool Temperate to Tropical, Worldwide

Lifespan: Approximately 40 Years

Gestation: 13 – 14 Months

Threats: Drive Hunts, Exploitation in Captivity, Marine Pollution, Noise Pollution

Named after naturalist Antoine Risso, Risso’s dolphins specialize in feeding on squid, and have physical features that reflect their dietary preference. Similar to sperm whales who are also squid specialists, Risso’s dolphins only have teeth in their lower jaw. Adult Risso’s dolphins also bear a number of white scars, due to their unique skin. These scars are from hunting squid, and from social interactions with other Risso’s dolphins. Risso’s dolphins are born light grey in color, became dark grey as juveniles and then gradually become more and more white as they grow older and gain scars.

Risso’s dolphins are typically found in small pods of 3-12 individuals, but occasionally gather to form larger groups. Recent research has found that some Risso’s dolphins’ pods are often comprised of individuals of similar age, and of the same sex, and that individuals in these groups form long-term bonds. In Taiji, our team has also observed what appear to be nursery pods, or pods that are mostly made up of adult females and their calves. Like bottlenose, Risso’s dolphins have also been found to have spindle neurons, suggesting sophisticated social and cognitive abilities. Risso’s dolphins typically prefer deep, offshore waters and are capable of going on long, deep dives. They have often been documented diving for long periods of time during Taiji’s drive hunts, as the hunting fleet attempts to drive them to the cove. In recent years, Risso’s dolphins have become more common in captive facilities in some parts of the world. In drive hunts, Risso’s dolphins are subjected to both captive selection and slaughter.

Scientific Name: Peponocephala electra

Body Size: 350 – 460 lbs (160 – 210 kg)

Body Length: 7 – 9 feet (2.3 – 2.7 m)

Range: Tropical to Subtropcal, Worldwide

Lifespan: Approximately 40 Years

Gestation: 12 – 13 Years

Threats: Drive Hunts, Marine Pollution, Noise Pollution

Despite their name, melon-headed whales are part of the oceanic dolphin family. They are mostly black or dark grey in body color. They are very similar in appearance to another dolphin species- pygmy killer whales- and are often mistaken for them at sea. Pygmy killer whales were once mistakenly driven to the cove by the dolphin hunting fleet in Taiji, and were soon after released upon correct identification. The easiest way to tell the two species apart is the head shape; melon-headed whales have a more triangular, sloped head that becomes pointed near their mouth, whereas pygmy killer whales’ heads are more rounded and bulbous.

Melon-headed whales often occur in pods numbering hundreds of individuals, and are thought to maintain a matrilineal social structure. They sometimes associate with other dolphin species. Melon-headed whales tend to prefer deep waters, often diving several hundred feet on foraging dives. Along with rough-toothed dolphins, melon-headed whales were added to Taiji’s drive hunt quota in 2017.  Melon-headed whales are not commonly held in captivity, although they are sometimes subject to capture in Taiji’s drive hunts. This species all too often falls victim to slaughter in the cove, huddling together and nudging one another during their final moments together.

Scientific Name: Stenella attenuata

Body Size: 200 – 260 lbs (90 – 120 kg)

Body Length: 5 – 8 feet (1.6 – 2.6 m)

Range: Tropical to Subtropcal, Worldwide

Lifespan: Approximately 40 Years

Gestation: ~11 Months

Threats: Drive Hunts, Exploitation in Captivity, Marine Pollution, Noise Pollution

Pantropical spotted dolphins are a smaller dolphin species and are mainly found in tropical waters around the world. As their name suggests, they are have a spotted, freckle-like pattern as adults. As calves, pantropical spotted dolphins are born without spots. They slowly become more spotted as they grow older, with lighter spots on their dark grey area of their backs, and dark spots on the lighter areas of their belly. They are similar in size to striped dolphins. In addition to the difference in pattern, pantropical spotted dolphins are slightly more slender in body shape. Pantropical spotted dolphins are quite social, and are often found in large pods of hundreds of individuals. They are also sometimes sighted with other dolphin species. They are capable of diving several hundred feet, with maximum recorded depths over 1,000 feet!

In the past few seasons, pantropical spotted dolphins have only been subjected to captive selection in Taiji’s drive hunts. They are becoming increasingly common in captive facilities in some parts of the world. Our cove monitor team has observed several deceased pantropical spotted dolphins being removed from Taiji’s sea pens, indicating that some of them perish after the traumatic capture process.

Scientific Name: Steno bredanensis

Body Size: 200 – 340 lbs (90 – 155 kg)

Body Length: 6 – 8 feet (2.1 – 2.6 m)

Range: Tropical to Subtropical, Worldwide

Lifespan: Approximately 40 Years

Gestation: Unknown

Threats: Drive Hunts, Exploitation in Captivity, Marine Pollution, Noise Pollution

At a distance, rough-toothed dolphins have a similar appearance to bottlenose dolphins, but upon a closer look there are some unique differences. Unlike most beaked dolphin species, rough-toothed dolphins have no demarcation between their melon (forehead) and beak. Their melon slopes into their beak, giving them an almost “prehistoric” look. Rough-toothed dolphins also have a lighter underside, which extends to their throat, lower jaw and sometimes the edges of their upper jaw. Some interesting behaviors have been observed in this species in the wild, such as caring for sick individuals, supporting dead individuals for hours, or even several days. Our Cove Monitor team has observed them swimming in tight together, shoulder to shoulder around the hunters’ divers during high tension moments of the capture process. There is a lot that is yet to be discovered about rough-toothed dolphins.

Along with melon-headed whales, rough-toothed dolphins were added to Taiji’s drive hunt quota in 2017. The quota for this species has been quite low for each season they’ve been listed, and they have only been the target of live-capture for the aquarium trade.

Scientific Name: Lagneorhynchus obliquidens

Body Size: 200 – 375 lbs (90 – 170 kg)

Body Length: 5 – 8 feet (1.7 – 2.5 m)

Range: Temperate, North Pacific Ocean

Lifespan: Approximately 40+ Years

Gestation: 11 – 12 months

Threats: Drive Hunts, Exploitation in Captivity, Marine Pollution, Noise Pollution

Pacific white-sided dolphins were named for their distinct coloring. With a name that’s a mouthful, they are sometimes alternatively called “lags,” short for their scientific name. The easiest way to identify them at sea is by their dual-toned dorsal fin, which is dark grey on the front half and light grey on the back half. Some populations of Pacific white-sided dolphins are thought to be migratory, residing in cooler waters during summer months and temperate waters in the winter months.

Pacific white-sided dolphins are in high demand for captivity facilities, making them a capture target in Taiji’s drive hunts. They are not typically found in local waters until towards the end of the hunting season in February. Unlike other species that are driven into the cove, Pacific white-sided dolphins are typically hunted utilizing an offshore netting method, where a pod is enclosed in nets just outside of the Taiji harbor. This is thought to be done to avoid injuries they could sustain from panic and attempts to escape the rocky shallows of the cove. The stress in offshore netting is still immense, as evidenced by injuries on the dolphins, and blood on some of the gear used for capture documented by our Cove Monitor team. In February of 2020, one Pacific white-sided dolphin died during a capture process and was discreetly tied to the corner of a sea pen, while the rest of the pod was captured and several members were placed in the pen alongside it.

Scientific Name: Globicephala macrohynchus

Body Weight: 2,200 – 7,000 lbs (1.1 – 3.5 tons)

Body Length: 12 – 24 feet (3.5 – 7.3 m)

Range: Warm Temperate and Tropical, Worldwide

Lifespan: Approximately 60 Years

Gestation: 12 – 16 Months

Threats: Drive Hunts, Exploitation in Captivity, Marine Pollution, Noise Pollution

There are two species of pilot whale: long-finned pilot whales and short-finned pilot whales. Both species are very similar in appearance but inhabit different areas. No long-finned pilot whales live near Taiji, and only short-finned pilot whales are on the drive hunt quota. Pilot whales primarily feed on squid, and have been found to dive over 3,000 feet when foraging. Pilot whales are long-lived, slow to reproduce, and incredibly social. They tend to stay together in matrilineal family groups consisting of 15-30 individuals. They are believed to form intense bonds with each other, remaining with their closest family members for life. Some researchers believe pilot whale matrilines may have distinct dialects, similar to pod-specific dialects of orcas. Pilot whales are occasionally involved in mass strandings. Although causes for stranding remain unclear, family groups strand together. There are many things we are still learning about the details of pilot whale intelligence, but recent evidence has found that long-finned pilot whales have the highest number of neocortical neurons of any species known to date! In Taiji, pilot whales are subjected to both captive selection and slaughter.

Scientific Name: Pseudorca crassidens

Body Size: 1 – 2 tons

Body Length: 13 – 19 feet (4 – 6 m)

Range: Tropical to Warm Temperate, Worldwide

Lifespan: 60 – 70 Years

Gestation: 14-16 Months

Threats: Drive Hunts, Exploitation in Captivity, Marine Pollution, Noise Pollution

False killer whales do not outwardly resemble killer whales (orcas), but were named after so the skull similarities between the two species. False killer whales more closely resemble pilot whales in appearance, but are more long and slender in body shape and have differently shaped dorsal and pectoral fins. False killer whales are known to form strong social bonds, with pod sizes ranging from around 10 individuals, to larger aggregations of a couple hundred individuals. Some fascinating behaviors have been observed in wild false killer whales as well. A well studied population of false killer whales near New Zealand has been observed forming partnerships with bottlenose dolphins. These two populations have been seen hunting together, socializing, traveling and resting together over long periods of time (as much as several years) and over long distances.

False killer whales are desired by captive facilities, and have been the subject of live capture in Taiji, and other (now defunct) drive hunt sites in Japan. SeaWorld and Sea Life Park are among the US facilities that have obtained false killer whales acquired in drive hunts. Although they remain on the drive hunt quota, false killer whales have not been hunted in Taiji since 2015. There are concerns for the health of local populations, although the exact cause of their recent absence from drive hunts is not known.