About the Species
Striped dolphins 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.
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.
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). NOAA Fisheries is committed to conserving striped dolphins, and our scientists and partners use a variety of innovative techniques to study and protect this species.
Striped dolphins are abundant and widespread in offshore U.S. waters and throughout the world. NOAA Fisheries estimates population size for striped dolphin stocks in its stock assessment reports.
Male striped dolphins can reach lengths of about 9 feet and weigh up to 350 pounds, while females can reach up to 8 feet and 330 pounds. They have a small to medium-sized, robust, sleek body with a long, defined rostum 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.
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 rostrum, tapered pectoral fins or flippers, 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 than adults.
Behavior and Diet
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 groups, 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.
Their surface behavior is often characterized as sociable, athletic, energetic, active, and nimble with rapid swimming. They can often be observed breaching, roto-tailing (a circular motion using the tail while jumping out of the water), jumping, and leaping 20 feet above the surface. In the eastern tropical Pacific Ocean, field biologists and fishermen call striped dolphins "streakers" because they avoid vessels by rapidly swimming away.
Striped dolphins feed throughout the water column on a diverse diet of fish and cephalopods (e.g., squid and octopus). They are capable of diving to at least 2,300 feet.
Where They Live
Striped dolphins prefer tropical to warm temperate waters (52 to 84° F) that are oceanic and deep. They are mainly found in waters seaward of the continental shelf from 50° North to 40° South and are often linked to upwelling areas and convergence zones.
Striped dolphins are found worldwide. 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 Hawai‘i, 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, Denmark’ southern Greenland; the Kamchatka Peninsula, Russia; and Prince Edward Island, Canada.
Lifespan & Reproduction
The estimated lifespan of striped dolphins is up to 58 years. They become sexually mature when they reach about 7 feet in length—between the ages of 5 and 13 years for females and 7 and 15 years for males. Their mating system is generally unknown, but is thought to be polygynous, meaning one male mates with more than one female. Every 3 to 4 years, females give birth to a single 3-foot-long calf during the summer or autumn after a gestation period of about 1 year. Lactation lasts 12 to 18 months.
Entanglement in Fishing Gear
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.
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 (e.g., organochlorines) and fewer available prey. Environmental toxins and contaminants lower their disease immunity.
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.
In the Spotlight
Like all marine mammals, the striped dolphin is protected under the Marine Mammal Protection Act. NOAA Fisheries is working to conserve this species to ensure populations remain stable.
Reducing Entanglement in Fishing Gear
Striped dolphins are caught as bycatch in fishing gear, leading to serious injuries and even deaths. NOAA Fisheries works with fishermen, industry, non-government organizations, and academia to find approaches and strategies for reducing bycatch in U.S. fisheries.
Overseeing Marine Mammal Health and Stranding Response
We work with volunteer networks in all coastal states to respond to marine mammal strandings including all dolphins and porpoises. When stranded animals are found alive, NOAA Fisheries and our partners assess the animal’s health and determine the best course of action. When stranded animals are found dead, our scientists work to understand and investigate the cause of death. Although the cause often remains unknown, scientists can sometimes attribute strandings to disease, harmful algal blooms, vessel strikes, fishing gear entanglements, pollution exposure, and underwater noise. Some strandings can serve as indicators of ocean health, giving insight into larger environmental issues that may also have implications for human health and welfare.
Marine Mammal Unusual Mortality Events
Striped dolphins have never been part of a declared unusual mortality event. Under the Marine Mammal Protection Act, an unusual mortality event is defined as "a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response." To understand the health of marine mammal populations, scientists study unusual mortality events.
Implementing the Dolphin-Safe/Tuna Tracking and Verification Program
Dolphins, like other marine mammals, may become bycatch in fisheries. Some species of tuna aggregate beneath schools of certain dolphin stocks. In some parts of the world, this close association led to the fishing practice of encircling a dolphin school to capture the tuna concentrated below. The Dolphin Protection Consumer Information Act established a national tuna tracking program to ensure that tuna imported into the United States meets certain requirements to ensure the safety of dolphins during tuna fishing operations.
Striped dolphins are protected under the Marine Mammal Protection Act.
In 1999, the United States signed on to the Agreement on the International Dolphin Conservation Program (AIDCP). In addition to other requirements, the AIDCP mandates the establishment of an international tuna tracking program for tuna caught in the eastern tropical Pacific Ocean. The program helps minimize dolphin deaths during fishing for tuna destined for canning. The International Dolphin Conservation Program Act (PDF, 19 pages) amended the MMPA to make the objectives and requirements of the AIDCP legally effective in the United States.
Key Actions and Documents
NOAA Fisheries and our partners are committed to research to help us further understand striped dolphins.
Determining the size of striped dolphin populations helps resource managers gauge the success of NOAA Fisheries’ conservation measures. Our scientists collect and present these data in annual stock assessment reports.
NOAA Fisheries conducts research cruises to collect information on dolphin stocks, such as habit preferences and feeding ecology. For example, our scientists estimate the abundance of striped dolphins and other cetaceans using oceanic research vessels to perform large-scale line-transect surveys. Information from this research can be used in management actions to protect these animals.