Like us, spinner dolphins are mammals, which means their females give birth! They are pregnant for about 10 months, and give birth to one calf (that’s a baby dolphin) at a time. Dolphin mothers have to take care of calves, nursing them for 7 months.

Spinner dolphins can be found in tropical seas all over the world, almost always in groups called pods. It is common for pods to include around 200 dolphins, but some have had up to 1,000 dolphins! Sometimes, spinner dolphins will also group with other dolphins and even other animals in the sea, like tuna.

Red and Mediterranean Sea.

Spinner dolphins are found in the tropical and subtropical waters in the Atlantic, Indian and Pacific oceans. They can also be found in some warm temperate areas. Spinner dolphins often occur near islands (Klinowska 1991).

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Tropical, subtropical, and, less often, warm temperate regions of Atlantic, Pacific, and Indian oceans (Leatherwood and Reeves 1983). Costa Rican spinner occurs primarily less than 80 km from shore along the western coast of Central America (7-18 degrees north latitude). Eastern spinner ranges from southwestern coast of Baja California south to the equator and offshore to about 145 degrees west longitude. Whitebelly spinner occupies much of the equatorial Pacific, well offshore, extending south to 20 degrees south latitude off western South America, north to 20 degrees north latitude west of Mexico, and west almost to the Hawaiian Islands. Eastern and whitebelly spinners overlap greatly in range. See Leatherwood and Reeves (1983) and IUCN (1991).

Spinner dolphins are six to seven feet long and have a three part color pattern on their bodies. The pattern consists of a dark gray back, a pearl-gray side panel, and a white belly. Males possess a postanal hump and are generally larger than the females (Norris, 1991). Spinner dolphins that live farther away from land are morphologically different from those that live close to land (Norris et al, 1994).

Range mass: 55 to 75 kg.

Length: 220 cm

Weight: 78000 grams

• Marine

Stenella longirostris is mostly pelagic. It does spend time in both shallow waters and deeper water farther from land.

Aquatic Biomes: benthic ; coastal

Habitat Type: Marine

Comments: Primarily inhabiting pelagic inshore waters or banks, but may occur hundreds of kilometers from land in waters with specific characteristics of shallow mixed layer, shoal and sharp thermocline, and low annual variation in temperature (Perrin 1998). During daily rest period in Hawaii, occupies atoll lagoons or certain coves, or swims over shallow sandy areas (usually <50 m deep) (Norris and Dohl 1980).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Spinner dolphins are carnivorous. They eat mesopelagic fish and epipelagic and mesopelagic squid and shrimp (Klinowska, 1991). Most of the prey they eat are vertically migrating species (Norris et al., 1994).

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore )

Comments: Diet in eastern tropical Pacific: small (<20 cm), mainly mesopelagic fishes, epipelagic and mesopelagic squid, and sergestid shrimps (Perrin 1998; Leatherwood and Reeves 1983). In Hawaii, feeds on scattering layer fishes, squid, shrimp (Norris and Dohl 1980).

10,000 to >1,000,000 individuals

Comments: See TRENDCOM.

Commonly in herds of up to 200, sometimes up to 1000+ (Leatherwood and Reeves 1983). Frequently associates with spotted dolphin in eastern Pacific and with other oceanic dolphin and small-medium whales elsewhere. In Hawaii, herds are fluid in size and composition.

Comments: Daily cycle in Hawaii: nighttime feeding, morning approach to shore, morning-midday rest, travel to feeding areas at dusk (Norris and Dohl 1980).

Spinner dolphins are polygynandrous. The male senses when the female is ready to mate and pursues her. Mating happens within the school with no real mate selection.

Mating System: polygynandrous (promiscuous)

Spinner dolphins mate when their hormone levels are high, which is one or two times a year. The male swims upside down underneath the female and inserts his penis into the female's reproductive tract (Norris, 1991). Males reach sexual maturity at about 10-12 years old, while the females' age at sexual maturity ranges from 5.5-10 years old. Adult females give live birth to one calf every 2 or 3 years. Gestation period averages 10.6 months (Klinowska, 1991).

Breeding interval: Adult females give birth to one calf every 2 or 3 years

Breeding season: Spinner dolphins mate when their hormone levels are high, which is one or two times a year

Average number of offspring: 1.

Average gestation period: 10.6 months.

Range weaning age: 7 (low) months.

Average weaning age: 7 months.

Range age at sexual or reproductive maturity (female): 5.5 to 10 years.

Range age at sexual or reproductive maturity (male): 10 to 12 years.

Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Females nurse their calves for at least seven months.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

Gestation averages 10.6 months in Gulf of Mexico. Produces one young every 2-3 years (although pregnancy rate has declined in exploited populations (Chivers and DeMaster 1994, cited in Perrin 1998). Young are weaned at age >7 months, usually 1-2 years (Perrin 1998). Males are sexually mature at 10-12 years, females at 5.5 years (eastern Pacific) or 7-10 years (Gulf of Mexico).

The members of spinner dolphin pods stun and capture fish by emitting ultrasonic beams.

Occur frequently in the Red Sea near Marsa Alam, but not clear whether they breed.

The major threat to spinner dolphins is getting caught in tuna nets. There is also habitat destruction in some areas due to tourism. Spinner dolphins are protected in some countries. In the United States, special efforts have been made to monitor and reduce deaths due the tuna industry (Klinowska, 1991).

IUCN Red List of Threatened Species: data deficient

United States

Rounded National Status Rank: NU - Unrankable

Rounded Global Status Rank: G5 - Secure

Reasons: Widespread and abundant. Populations in eastern Pacific have declined significantly in past 40 years, but decline may have stabilized recently; threatened by continuing mortality associated with commercial fishing, most notably tuna purse seines.

Global Short Term Trend: Relatively stable (=10% change)

Comments: Significant declines in eastern Pacific populations occurred in the 1960s through the 1980s; trends uncertain since then (Perrin 1998). These declines the result of mortality associated with purse-seine tuna fishery; estimated kill in 1986 was 31,000 (IUCN 1991). These populations, which originally numbered in the millions, have been reduced to hundreds of thousands (e.g., declined from 1,000,000 in 1975 to around 300,000 in the early 1980s); despite some evidence of the beginning of a trend towards recovery in recent years (600,000 in mid-1980s), kill rates are high and efforts to reduce them have been less successful than previously thought (IUCN 1991). The northern whitebelly spinner stock (north of 1 degree south latitude) declined from about 1.25 million in 1976 to around 500,000 in the early 1980s, with possibly some increase since; southern whitebelly spinner stock (south of 1 degree south latutude) declined from perhaps 500,000 in the late 1970s to about 100,000 in the early 1980s and possibly may have recovered to around 250,000 by the mid-1980s (IUCN 1991). Elsewhere in the range, generally regarded as common, though information is needed regarding the status of a recently described form in the Gulf of Thailand.

Degree of Threat: C : Not very threatened throughout its range, communities often provide natural resources that when exploited alter the composition and structure over the short-term, or communities are self-protecting because they are unsuitable for other uses

Comments: See Trend.

Since spinner dolphins swim with tuna, they sometimes get caught and die in tuna fishing nets. But many humans have changed the way they fish, and use dolphin safe tuna nets.

Some people catch them to eat or to use as bait, but they are more valuable to people alive. Many people like to watch them swim and jump, especially tourists. Tourists pay to watch them swim, and local people can use the money to keep their home and dolphins safe. This is called Ecotourism.

Needs: Further action to reduce kills associated with purse-seine tuna fishery is urgently needed (IUCN 1991).

Spinner dolphins attract tourists for dolphin watching. They are also subject to scientific investigation because of their remarkable capacity to learn.

Comments: Relatively small numbers are taken in small cetacean fisheries in some parts of the range; uses include consumption by humans (IUCN 1991).

Comments: Three subspecies are recognized in Perrin (1998): the nominate S. l. longirostris in the tropical Atlantic, Indian and western, southern and central Pacific Ocean; and two in the eastern tropical Pacific: Central American spinner dolphin (S. l. centroamericana) and eastern spinner dolphin (S. l. orientalis).

A recently described dwarf form (S. l. roseiventris) of this species occurs in shallow waters of inner Southeast Asia, including the Gulf of Thailand, Timor Sea, and Arafura Sea, and possibly also the Java Sea and other shallow waters throughout inner Indonesia and Malaysia (Perrin et al. 1999). Mead and Brownell (in Wilson and Reeder 2005) did not recognize this as a valid subspecies.

Another form (the "Whitebelly Spinner") is thought to be the result of intergradation between the two eastern Pacific forms and the pantropical S. l. longirostris. Perryman and Westlake (1998) identified another form ("Tres Marias spinner dolphin") along the edge of the continental shelf north of Cabo Corrientes, Mexico.