Striped dolphins (scientific name: Stenella coeruleoalaba) are among the most abundant and widespread dolphins in the world. They prefer deep tropical to warm temperate oceanic waters, and are attracted to upwelling areas, where deep, cold, nutrient-rich water rises toward the surface. and convergence zones, where ocean currents meet. [Source: NOAA]
Striped dolphins are usually found in tight, cohesive groups of about 25 to 100 individuals and have been observed breaching, jumping, and leaping over 20 feet above the surface of the water. They display a unique behavior called roto-tailing, when the animal leaps high out of the water and vigorously rotates its tail while airborne. Their estimated lifespan is up to 58 years.
Some striped dolphins have been held in captivity, but have not been successfully trained. The second part of their scientific name — “coeruleoalaba” — is derived from the Latin "caeruleus" (sky-blue) and "albus" (white). [Source: Melissa Savage, Animal Diversity Web (ADW) /=]
Striped dolphins are found worldwide and have been observed in the Mediterranean Sea, eastern and western Pacific Ocean, Atlantic Ocean, Indian Ocean, Caribbean Sea, and in the northern Gulf of Mexico. Their range includes waters off Greenland, northern Europe (United Kingdom, Denmark), the Mediterranean Sea, Japan, Argentina, South Africa, western Australia, and New Zealand. In the United States, they can be found off the west coast, in the northwestern Atlantic, and in the Gulf of Mexico. They also live in the waters off Hawaii, but do not live in the colder temperate and boreal waters of Alaska. This species has been documented outside its normal range in areas such as the Faroe Islands, southern Greenland, the Kamchatka Peninsula, and Prince Edward Island. [Source: NOAA]
Striped dolphins occupy both offshore and inshore habitats and often observed in and around reefs, They prefer tropical to warm temperate waters between 11º and 29ºC (52º and 84 F) that are oceanic and deep. They are mainly found in waters seaward of the continental shelf from 50°N to 40°S.
Websites and Resources: Britain-based Whale and Dolphin Conservation Society uk.whales.org ; 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
Stenella — Spinner, Spotted and Striped Dolphins
Striped dolphins belong to the genus Stenella, which also includes spinner dolphins and spotted dolphins and is comprised of five species of dolphins: pantropical spotted dolphins (Stenella attenuata), Atlantic spotted dolphins (Stenella frontalis), striped dolphins (Stenella coeruleoalaba), spinner dolphins (Stenella longirostris), and Clymene dolphin (short-snouted spinner dolphin, Stenella clymene. Stenella dolphins are a part of the family Delphinidae which consists of dolphins, killer, whales, pilot whales, and their relatives. Dolphins are part of the suborder Odontoceti better known as the toothed whales. They are also part of the bigger order Cetacea which is comprised of all marine mammals. [Source: Abigail Ross, Animal Diversity Web (ADW) /=]
Stenella dolphins are smaller in size compared to many other dolphins and toothed whales. They typically have beak-shaped rostrums (snouts) that vary lengths and often feed pelagic (open ocean) marine life such as lanternfish, squid, shrimp, and pelagic fishes. They're beak length can range from 11 to 20 centimeters (4 to 8 inches). All the species can be found in groups-known as pods that reach have hundreds of individuals.
Of the five species of dolphins in genus Stenella, two of the species — Clymene dolphins and Atlantic spotted dolphins — are endemic to the Atlantic Ocean, Gulf of Mexico, and Caribbean. The other three species — Pantropical spotted dolphins, spinner dolphins and striped dolphins — are found in the Atlantic, Pacific and Indian Oceans, mainly in warmer waters.
Stenella often have markings that are white or light grey in color and appear all over the back and are most numerous between the head and the dorsal fin. These markings can appear as speckles, spots, or stripes. They can also have some markings or none at all on their bottom side. Newborn Stenella they have no spots, and their coloring is often dark purplish grey. As they grow older their coloring becomes more distinctly grey, differences between the dorsal and ventral sides become more pronounced and markings appear and become bigger, more numerous and spread over larger areas. They can have dark patches or bands of color around the eyes, blowhole, fins, and tail.
Striped Dolphin Physical Characteristics
Male striped dolphins can reach lengths of about 2.7 meters (nine feet) and weigh up to 160 kilograms (350 pounds), while females can reach up to 2.4 meters (8 feet) and 150 kilometers (330 pounds). They have a small to medium-sized, robust, sleek body with a long, defined beak and round forehead (known as a melon). This species has 43 to 50 pairs of small, sharp, conical teeth in the upper and lower jaws. Their dorsal fin is hooked, tall, and located mid-back. [Source: NOAA]
Striped dolphins are known for their distinct and striking coloration pattern, which includes bold, thin stripes that extend from the eye to the flipper and another set of stripes down the side of the body to the anal region. This unique coloration distinguishes the striped dolphin from other cetacean species and is the origin of its common name.
The striped dolphin’s beak, tapered flipper, tail, and back (or cape) 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 underside of the body 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 geographic location. Calves and juveniles may have more muted colorations and patterns. [Source:
Striped Dolphin Behavior
Striped dolphins are usually found in tight, cohesive groups averaging between 25 and 100 individuals, but they have occasionally been seen in larger groups of up to several hundred and even thousands of animals. Within these groupings, there is a complex system of individuals that may be organized by age, sex, and breeding status. Striped dolphins rarely associate with other species of whales, dolphins, and seabirds. [Source: NOAA]
Their surface behavior is often characterized as sociable, athletic, energetic, active, and nimble with rapid swimming. They can often be observed breaching (jumping out of the water), chin slaps, jumping seven meters (20 feet) above the surface and bow-riding (swimming along the wave created by a boat or ship, while often twisting and jumping). They are known for roto-tailing (a circular motion using the tail while jumping out of the water), It involves making “high arcing jumps while violently and rapidly performing several rotations with the tail before reentering the water" In the eastern tropical Pacific, field biologists and fishermen call striped dolphins "streakers" because they avoid vessels by rapidly swimming away. [Source: NOAA]
Three different kinds of groupins often occur: 1) juvenile, 2) breeding adults, and 3) non-breeding adults. Calves do not usually join the juvenile school until one or two years after weaning. When females reach the transition stage between juvenile and adult, they usually join the non-breeding adults. Only a few go straight to the breeding school. When males reach the age in which they join adult groups, roughly half join breeding groups and half join non-breeding groups. [Source: Melissa Savage, Animal Diversity Web (ADW) /=]
Stenella Dolphin Behavior
Stenella dolphins are nocturnal (active mainly at night), 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 have dominance hierarchies (ranking systems or pecking orders among members of a long-term social group, where dominance status affects access to resources or mates). [Source: Abigail Ross, Animal Diversity Web (ADW) /=]
Stenella dolphins live in pods made of individuals of both sexes and often organized by sex, age, and breeding status. They are an extremely social species, and are known for interacting with other species of whales and dolphins as well as other marine animals, and sometimes even humans. Striped dolphins tend to be less social and interact with other organisms less frequently than the other four Stenella species.
During the day Stenella dolphins stay near the surface and at night dive down to feed. They swim in zig zag or back and forth patterns moving between shallow and deeper waters, as well as engage in periods of rest. During these rest periods pods swim close to one another in a slow back and forth swaying motion. The periods of rest typically take place multiple times a day for around three to five hours at a time.
Stenella dolphins dolphins are very playful. Both calves and adults engage in playtime with each other. Play consists of jumping out of the water and flipping or spinning, as well as "roto-tailing" — jumping high above the water and rotating their tail. Striped dolphins "roto-tail" more than other species. The dolphins may use spinning to communicate with each other, or to remove parasites from their bodies. Play also consists of blowing bubbles or shooting water from the blowholes, mock chasing schools of fishes, and playing with pieces of seaweed.
Seaweed play involves picking up a piece of seaweed and placing it on a flipper, and then tossing it back and forth between their flippers, beak or tails. Most often a single dolphin plays with the seaweed but sometimes two or three dolphins all pass a piece of seaweed back and forth. More often a single piece of seaweed is shared between individuals who take turns playing with it. Some swim up to boats and ride the bow waves or surf the wake of the boats.
Striped Dolphin Perception and Communication
Like other dolphin, striped dolphins sense using vision, touch, sound, vibrationss, chemicals and echolocation (emitting sound waves and sensing their reflections to determine the location of objects) and communicate with vision, sound, vibrations and choruses (joint displays, usually with sounds, by individuals of the same or different species). [Source: Abigail Ross, Animal Diversity Web (ADW) /=]
Stenella dolphins communicate using a wide range of auditory cues and sounds, as well as using some visual cues and echolocation. Their main sources of communication are auditory sounds and acoustic signaling. They make a variety of sounds including whistles, clicks, click trains (repetitions of multiple clicks), squeaks, squeals, squawks, barks and chirps. Used in mating, hunting and prey spotting, as well as predator avoidance, acoustic signals consist of patterns that rise and fall in a synchronous manner.
Dolphins use echolocation to scan the environment, find prey, avoid predators, find other dolphins, and detect objects from a distance. They perform echolocation by sending out a series of clicks, which create sound waves that travel until bouncing off an object and then come back to the dolphin, providing information about composition of the object and how far away it is.
Striped Dolphin Feeding and Predators
Striped dolphins feed throughout the water column on a diverse diet of fish and cephalopods (such as, squid and octopus). Capable of diving to at least 700 (2,300 feet), they are known for being opportunistic feeders. Stomach contents examinations have revealed mainly cephalopods, crustaceans, and bony fishes. There are regional variations. Mediterranean striped dolphins seem to prey primarily on cephalopods (50-100 percent of stomach contents), while northeastern Atlantic striped dolphins most often prey on fish, frequently cod. The ranges of observed prey indicate that striped dolphins primarily feed in pelagic (open ocean) or benthopelagic (on or near the bottom in the open ocean) zones of the ocean, often along the continental slope (at the edge of the continental shelf where the ocean floor plunges steeply four to five kilometers), [Source: Melissa Savage, Animal Diversity Web (ADW) /=]
Stenella dolphins feed mostly at night on prey from mesopelagic area of the open ocean at depths between 200 meters and 1000 meters. Their prey often migrate vertically towards the surface at night. Stenella dolphins diet consists of a wide variety of small fishes, cephalopods, mollusks, crustaceans and other small invertebrates. Typical prey includes squids, shrimp, lantern fish, conger eels, flounder, jacks, needlefish and octopuses. Some have preferences for certain prey, but most tend to feed on anything eatable that passes their way.
Pods of dolphins engage in cooperative hunting for their prey. They are able to catch their prey by surrounding them, and then taking turns swimming at and grabbing the surrounded prey. [Source: Abigail Ross, Animal Diversity Web (ADW) /=]
Stenella dolphins are considered apex predators and do not have very many predators except sharks, killer whales, false killer whales and short finned pilot whales. Among the individuals that are most at risk are pregnant females, lactating females, young calves and juveniles. Sharks and whales preying on dolphins harass the dolphins and attempt to subdue and separate their prey from the pod and killing it by biting and removing chunks of flesh from their prey. Adult dolphins protect calves by engaging in group chasing of the nearby predator and harassing and pestering them until the predator leaves.
Striped Dolphin Mating and Reproduction
Striped dolphins are viviparous, meaning they give birth to live young that developed in the body of the mother, and engage in seasonal breeding. Females typically give birth every three to four years. The breeding season is in the winter and early summer in the western north Pacific, while it occurs in the fall in the Mediterranean. Usually one calf is born during the summer or autumn. The gestation period ranges from 12 to 13 months. Fetuses grow at an approximate rate of 0.3centimeters a day. Females reach sexual maturity at five to 13 years. Males reach sexual maturity at seven to 15 years. [Source: Melissa Savage, Animal Diversity Web (ADW) /=\, NOAA]
The age of sexual maturity is quite variable within sexes. Males reach sexual maturity between the ages of seven and 15, and females become sexually mature between five and 13 years of age. The mating season of the striped dolphin is in the winter and early summer in the western north Pacific, while it occurs in the fall in the Mediterranean (Archer and Perrin, 1999). The gestation period of striped dolphins lasts 12-13 months. Females typically have a four year calving interval, having a resting period of approximately 2-6 months between lactation and the next mating (Calzada et al., 1996). /=\
The mating system of striped dolphin is generally unknown, but is thought to be polygynous, meaning one male mates with more than one female. Male and female Stenella dolphins (spinner, spotted and striped dolphins) seeking mates engage in playful activities with each other such as chasing each other and making lots of noises that include whistles, clicks, and burst-pulse signals. Males often gently tap their fins on the fins and belly of females, and then rub, nudge, and gently bite the female. To impregnate the female the male moves below the female with his belly up, so that male and female are belly to belly when sexual intercourse occurs. Intercourse is typically very quick, lasting only a few seconds or a few minutes. [Source: Abigail Ross, Animal Diversity Web (ADW) /=]/=\
Female Stenella dolphins have an estrous cycle, which is similar to the menstrual cycle of human females. Reproduction is characterized by three stages: calving, lactation, and a period of inactivity or estrus. Because their gestation period is around 12 months the mating and calving seasons are around the same time. There are two primary seasons for mating and calving — the spring and the fall. However times of high reproductive activity can vary from year to year, and may occur during the summer.
Striped Dolphin Offspring. Parenting and Development
Striped dolphin parental care is provided by females. During the pre-fertilization, pre-birth and pre-weaning stage provisioning and protecting is done by females. Stenella dolphins are cooperative breeders (helpers provide assistance in raising young that are not their own) with females in a pod often helping to take care of calves that are not their own.
Young are precocial. This means they are relatively well-developed when born. At birth, striped dolphins are 90 to 100 centimeters (2.9 to 1.2 feet) long, differing slightly between regions, and weigh approximately 11.3 kilograms (25 pounds) Lactation lasts 12 to 18 months. The average weaning age is 16 months.
Striped dolphins become sexually mature when they reach about 2.2 meters (7 feet) in length. There is an extended period of juvenile learning. It takes calves about one to three years to reach the juvenile stage. While calves are nursing they tend to stay close to their mothers. Females can be pregnant and lactating at the same time, and gives birth to only one calf per pregnancy.
Striped Dolphins, Humans, Threats and Conservation
Striped dolphins are not endangered. They are abundant and widespread in offshore U.S. waters and throughout the world. They are designated as a species of least concern on the International Union for Conservation of Nature (IUCN) Red List and have no special status on Trade in Endangered Species (CITES), which places them in Appendix II, which lists species not necessarily threatened with extinction now but that may become so unless trade is closely controlled. Striped dolphins in the United States are not endangered or threatened. Like all marine mammals, they are protected under the Marine Mammal Protection Act (MMPA). One distinct population segment is protected by Specially Protected Areas and Wildlife (SPAW) Annex II
Striped dolphins have provided entertainment to sailors and whale watchers as they flip, twist, and breach and ride waves created by ships and boats. They are sometimes hunted for meat in certain regions. Striped dolphins compete with humans over prey such as anchovies, tuna, and cod. Fisherman have killed striped dolphins caught in their fishing nets. The number of striped dolphins killed in the western Pacific was estimated at 14,000 each year between 1950 and 1969 but after dolphin saving measures were introduced the number of deaths decreased to between 2,000 and 4,000 per year. [Source: Melissa Savage, Animal Diversity Web (ADW) /=]
Threats to striped dolphins include entanglement in fishing gear, hunting, chemical contaminants, and disease. In the early 1990s, more than 1,000 striped dolphins died in the Mediterranean Sea from a morbillivirus epizootic — a temporary, highly contagious, widespread, and lethal disease outbreak — that may have been triggered by pollution (such as, organochlorines) and fewer available prey. Environmental toxins and contaminants lower their disease immunity. [Source: NOAA]
One of the main threats to striped dolphins is becoming entangled or captured in commercial fishing gear such as trawls, gillnets, purse-seine nets, and hand-harpoons. Striped dolphins have been subjected to drive hunts in Japan and taken in Sri Lanka and the Caribbean. During the mid-20th century, as many as 21,000 animals were caught and killed each year.
Image Sources: 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