Articles on this page are available in 2 other languages: Spanish (31), Chinese (Simplified) (4) (learn more)

Overview

Brief Summary

Description

Schools of spinner dolphins leap out of the water, twirl, and reenter with a large, noisy splashes that can be heard for long distances underwater. Usually they make several such spinning leaps in a row. The reason is a mystery. It may be to remove parasites from the skin, or to communicate with other animals in the school - or is it just for fun? Spinners are found in tropical waters worldwide. In Hawaii, they rest in shallow bays during the day, and swim out at dusk to forage in deeper waters. Groups of spinners disperse over a wide area when they are feeding, and different individuals may return to a bay in the morning. This suggests that the spinners around an island are a super-school, within which a number of sub-groups - perhaps family groups - move freely. Spinners are among the dolphins caught and killed in tuna fisheries.

Links:
Mammal Species of the World
Click here for The American Society of Mammalogists species account
  • Original description: Gray, J.E., 1828.  Spicilegia zoologica; or original figures and short systemic descriptions of new and unfigured animals, p. 1.  Treuttel, Wurtz and Co. and W. Wood, London, 8 pp.
Creative Commons Attribution 3.0 (CC BY 3.0)

© Smithsonian Institution

Source: Smithsonian's North American Mammals

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Biology

Spinner dolphins move about the oceans in schools; groups that vary in size from just a few dolphins to over a thousand. They commonly school with other species such as pantropical spotted dolphins, or small toothed whales (5). In such schools, spinner dolphins are known to undertake migrations, following prey or warm water currents (8). In Hawaii, spinner dolphins usually spend their days resting in shallow bays near deep water, and then move offshore at dusk and feed as they move substantial distances along the shore (8). Pelagic spinner dolphins feed primarily on small mesopelagic fish, squids and shrimps, and dive down to depths of 300 meters to catch their prey (8). The dwarf spinner dolphin feeds on reef fishes and other benthic organisms (7) Mating in spinner dolphins appears to be promiscuous, and like many small dolphins, true courtship behaviour can be observed, such as mutual caressing between the male and female (9). The breeding system may vary geographically, with some populations showing a greater degree of polygyny than others (10). Calves are born every three years, after a gestation period of about ten months (2). The mother nurses the calf for up to two years (2), and they form a bond that lasts a lifetime (8). Females reach sexual maturity between four and seven years, whereas males do not reach maturity until between seven and ten years (2). The purpose of the energetic spinning behaviour of the spinner dolphin is not known. It has been suggested that the large cloud of bubbles created by the powerful spin and splash landing may act as an echolocation target, to allow a widely dispersed school of dolphins to communicate (5). Another theory is that the spinning may dislodge hitch-hiking remoras, or the spinning may, at times, simply be play (5).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

WhyReef - Lifestyle

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.

Creative Commons Attribution 3.0 (CC BY 3.0)

© WhyReef

Source: WhyReef EOL content

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Description

The acrobatic spinner dolphin is the most common small cetacean in many tropical open seas, where it can be seen spinning high in the air, (hence its common name), or riding the bow waves of boats (5). The small and slender spinner dolphin varies geographically in colouration and size, but can be identified by its relatively long, slender beak and triangular dorsal fin (5). The most common colour pattern is three-part: dark grey on the back, lighter grey along the sides, and white or very light grey underneath. A darker grey stripe runs from the eye to the flipper, bordered above by a narrow, light line (2).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Comprehensive Description

WhyReef - Fun Facts

The spinner dolphin is known as an acrobat because it does many amazing jumps, spins, and flips in the air, mostly by night. But scientists aren’t sure why: some think they jump to communicate with each other, while others think they are just playing. Spinner dolphins communicate with each other and see underwater using echolocation, which means they see using sound! Here’s an example: a dolphin will make a high squeal and it will travel though the water. When it hits something (like a coral or another dolphin) it will bounce back, or echo, to the dolphin’s original location. It can then tell the distance between it and another object, or even the shape of that object, based on the way the sound returns to it!
Creative Commons Attribution 3.0 (CC BY 3.0)

© WhyReef

Source: WhyReef EOL content

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Distribution

Oceanic tropical and subtropical zones in both hemispheres. Limits are near 40ºN and 40ºS.
  • North-West Atlantic Ocean species (NWARMS)
Creative Commons Attribution 3.0 (CC BY 3.0)

© WoRMS for SMEBD

Source: World Register of Marine Species

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Range Description

The Spinner Dolphin ranges through tropical and subtropical zones in both hemispheres. Limits are near 40°N and 40°S.

Stenella longirostris longirostris occurs mainly around oceanic islands in the tropical Atlantic, Indian, and western and central Pacific east to about 145°W (Rice 1998). However, the distribution in the Atlantic is not well known, especially in South American and African waters; the known range can be expected to expand considerably in those areas with increased attention to the cetacean faunas there. The southernmost record is from New Zealand, more than 2,000 km south of what is thought to be the normal range but still well north of sub-Antarctic waters (Perrin and Gilpatrick 1994).

Stenella longirostris orientalis inhabits pelagic waters of the eastern tropical Pacific (ETP) east of about 145°W, from 24°N off Baja California south to 10°S off Peru, but exclusive of the range of the following subspecies (Perrin 1990).

Stenella longirostris centroamericana is found in coastal waters over the continental shelf of the ETP, from the Gulf of Tehuantepec in southern Mexico southeast to Costa Rica (Perrin 1990).

Stenella longirostris roseiventris is distributed in shallow waters of inner Southeast Asia, including the Gulf of Thailand, the Timor and Arafura Seas off northern Australia, and other similar shallow waters off Indonesia and Malaysia. It is replaced in deeper and outer waters by the larger pelagic subspecies S. l. longirostris (Perrin et al. 1999, Kahn pers. comm. to W. Perrin 2007).

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states. States within the hypothetical range but for which no confirmed records exist are included in the Presence Uncertain list.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Distribution in Egypt

Red and Mediterranean Sea.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Bibliotheca Alexandrina

Source: Bibliotheca Alexandrina - EOL Ar

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Geographic Range

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 )

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

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).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Range

The spinner dolphin inhabits most tropical waters of the world, and can also occur in sub-tropical and warm temperate waters (2), approximately between 30 to 40 degrees north and 20 to 30 degrees south (5). At present, four subspecies are recognised (6) (7): S. l. longirostris (Gray's spinner dolphin), which occurs in all tropical seas; S. l. orientalis (Eastern spinner dolphin), found in open waters of the eastern tropical Pacific; S. l. centroamericana (Costa Rican or Central American spinner dolphin), which inhabits continental shelf waters off western Central America and southern Mexico (6); and S.l. roseiventris, (dwarf spinner dolphin) which inhabits shallow waters of Southeast Asia (7).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Physical Description

Morphology

Physical Description

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.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Size

Size in North America

Length:
Range: "1.3-2.4 m "

Weight:
Range: 22-75 kg
Creative Commons Attribution 3.0 (CC BY 3.0)

© Smithsonian Institution

Source: Smithsonian's North American Mammals

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Length: 220 cm

Weight: 78000 grams

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
In most tropical waters, nearly all records of spinner dolphins are associated with inshore waters, islands or banks. Around Hawaii Sspinner Dolphins depend on the availability of sheltered shallow bays for use as resting areas during the day. In the ETP, however, Spinner Dolphins occur in very large numbers on the high seas many hundreds of kilometers from the nearest land. Spinner Dolphins favour a specific habitat in the ETP, called by oceanographers "tropical surface water;" it is typified by unusual conditions of shallow mixed layer, shoal and sharp thermocline, and relatively small annual variation in surface temperature (Reyes 1991, Perrin and Gilpatrick 1994). There they are often found in close association with Pantropical Spotted Dolphins, Yellowfin Tuna (Thunnus albacares) and birds of several species. The dwarf form of the Spinner Dolphin in Southeast Asian waters apparently inhabits a shallow coral reef habitat (Perrin and Gilpatrick 1994). In the north-central and western Gulf of Mexico, Stenella longirostris is found over intermediate bottom depths, its distribution overlapping with that of purely pelagic and purely coastal species (Davis et al. (1998).

Most Spinner Dolphins feed predominantly at night, on small (<20 cm) midwater fish of many different families (including myctophids), squids, and sergestid shrimps (Perrin et al. 1973; Dolar et al. 2003). Dwarf Spinner Dolphins are exceptional, however; they feed (presumably during daylight hours) on small, reef-associated organisms (benthic reef fishes and invertebrates) (Perrin et al. 1999).

Systems
  • Marine
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

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

Aquatic Biomes: benthic ; coastal

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Depth range based on 1117 specimens in 4 taxa.
Water temperature and chemistry ranges based on 1065 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 9.374 - 29.364
  Nitrate (umol/L): 0.035 - 11.982
  Salinity (PPS): 32.337 - 39.872
  Oxygen (ml/l): 4.235 - 6.648
  Phosphate (umol/l): 0.097 - 0.932
  Silicate (umol/l): 0.777 - 7.399

Graphical representation

Temperature range (°C): 9.374 - 29.364

Nitrate (umol/L): 0.035 - 11.982

Salinity (PPS): 32.337 - 39.872

Oxygen (ml/l): 4.235 - 6.648

Phosphate (umol/l): 0.097 - 0.932

Silicate (umol/l): 0.777 - 7.399
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

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).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

The spinner dolphin is typically thought of as a tropical high seas species, but it also inhabits shallow reef areas, coastal areas, and subtropical and warm temperate waters (5) (7).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Migration

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.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Trophic Strategy

Food Habits

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 )

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

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).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Associations

WhyReef - Menu

Spinner dolphins eat fresh, medium-sized fish that school together. Their excellent communication skills allow them to confuse their prey by hunting in groups. They also like to eat squid and shrimp. Since spinner dolphins only eat meat, they are carnivores.
Creative Commons Attribution 3.0 (CC BY 3.0)

© WhyReef

Source: WhyReef EOL content

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Population Biology

Global Abundance

10,000 to >1,000,000 individuals

Comments: See TRENDCOM.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

General Ecology

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.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Life History and Behavior

Cyclicity

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

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Reproduction

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)

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

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).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Evolution and Systematics

Functional Adaptations

Functional adaptation

Noise stuns prey: spinner dolphin
 

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

   
  "Whales may use ultrasonic noise like a stun gun against fish…Working with captive Hawaiian spinner dolphins (Stenella longirostris), California University cetologist Prof. Ken Norris found that when they direct ultrasonic beams at a shoal of fish, they can stun or even kill some of them. The beams may cause the fishes' air-filled swimbladders to resonate so intensely that their body tissues also vibrate, disorienting them." (Shuker 2001:23)
  Learn more about this functional adaptation.
  • Shuker, KPN. 2001. The Hidden Powers of Animals: Uncovering the Secrets of Nature. London: Marshall Editions Ltd. 240 p.
Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© The Biomimicry Institute

Source: AskNature

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
DD
Data Deficient

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
Bearzi, G., Bjørge, A., Forney, K.A., Hammond, P.S., Karkzmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y. , Wells, R.S. & Wilson, B.

Reviewer/s
Rojas-Bracho, L. & Smith, B.D.

Contributor/s

Justification
The eastern Spinner Dolphin population has ceased to decline but shows no clears signs of recovery. While there are few estimates of abundance and takes available in regions other than the eastern tropical Pacific, they are taken throughout their range by a diverse number of direct and indirect fisheries; some of these indirect takes may evolve into directed takes. Annual takes on the order of hundreds or thousands have been reported from countries in the Indian Ocean. These kills may comprise a large proportion of the global population. More information is needed before the possibility of a global decline of 30% or more can be eliminated.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Status in Egypt

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

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Bibliotheca Alexandrina

Source: Bibliotheca Alexandrina - EOL Ar

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

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

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

National NatureServe Conservation Status

United States

Rounded National Status Rank: NU - Unrankable

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

NatureServe Conservation Status

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.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Status

Classified as Data Deficient (DD) on the IUCN Red List (1), and is listed on Appendix II of CITES (3). The eastern tropical Pacific and Southeast Asian populations are listed on Appendix II of CMS (4).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Population

Population
There were about 801,000 (CV=37%) whitebelly spinners (S. l. orientalis X S. l. longirostris intergrades) in the ETP in 2000 (Gerrodette et al. 2005). The eastern spinner dolphin (the population most heavily impacted by the ETP tuna fishery) numbered about 613,000 (CV=22%) in 2003, and despite large reductions in the kill is recovering at an estimated rate of only 1.1% per year, an estimate that is not statistically different from zero (Gerrodette and Forcada 2005). There are estimated to be 11,971 (CV=71%) spinner dolphins in the northern Gulf of Mexico (Waring et al. 2006), and 3,351 (CV=74%) in Hawaiian waters (Barlow 2006). There are no abundance estimates for the dwarf subspecies. Dolar et al. (1997) estimated abundance in the southern part of the Sulu Sea and north-eastern Malaysian waters at 4,000 individuals. For the southeastern Sulu Sea, Dolar et al. (2006) estimated abundance at about 31,000 (CV=27%) Spinner Dolphins. The numbers listed above add up to more than a million spinner dolphins: numerous other regional populations in the Atlantic, Indian and Pacific Oceans have not been surveyed.

Population Trend
Unknown
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

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.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Threats

Major Threats
The association of Spinner Dolphins with Spotted Dolphins and Yellowfin Tuna results in their entanglement in tuna purse seines in the ETP. This is the second-most important species of dolphin involved in the tuna fishery (after the pantropical spotted dolphin) (Gerrodette 2002). The population of the eastern Spinner Dolphin subspecies S. l. orientalis is estimated to have been reduced by 65% by the tuna fishery kills (Reilly et al. 2005). Since the Inter-American Tropical Tuna Commission (IATTC) implemented per-vessel mortality limits on the international fleet, the mortality for the eastern and whitebelly forms combined decreased, to 389 in 2005 (IATTC 2006). Although current mortality is greatly reduced, the eastern form appears to be recovering slowly. Potential factors such as fishery-related stress, unobserved mortality due to calf separation and orphaning during fishing operations (Archer et al. 2001), possible mortality by small vessels that do not carry observers, and under-reporting of mortality have been suggested as possible reasons the eastern Spinner’s slow recovery (Gerrodette and Forcada 2005).

Throughout their range, Spinner Dolphins are taken as bycatch in purse-seine, gillnet, and trawl fisheries (Perrin et al. 1994, Donahue and Edwards 1996), often in high numbers. Spinner Dolphins are the most abundant dolphin in the Indian Ocean (Balance and Pitman 1998) and are taken throughout the region. In the Indian Ocean, annual takes of hundreds of Spinner Dolphins have been reported bycaught in the few fisheries that have been examined in India (Lal Mohan 1994), and annual takes in the thousands have been reported in Sri Lanka (Leatherwood and Reeves 1991, Lal Mohan 1994). Takes in other areas are unknown, but may be substantial. Unknown numbers have been taken in the tuna purse-seine fishery in the eastern Atlantic (Donahue and Edwards 1996) and in small-scale gillnet fisheries in the western Atlantic (Siciliano 1994). Dolphins taken incidentally in the Philippines and Venezuela are utilized for shark bait and human consumption (Dolar et al. 1994, Perrin and Gilpatrick 1994). Dwarf Spinners are caught incidentally in shrimp trawls in the Gulf of Thailand (Perrin et al. 1999). There are likely to be undocumented fisheries interactions off West Africa (Jefferson et al. 1993; Perrin and Gilpatrick 1994). Zerbini and Kotas (1998) report on by-catches in Brazilian drift-net fisheries and Cockcroft (1990) on animals entangled in shark nets off KwaZulu-Natal, South Africa.

In some cases, human use of by-caught Spinner Dolphins has led to direct fisheries. Direct kills occur in several areas, including the Caribbean, Sri Lanka, the Philippines (Dolar 1994), Taiwan, and Indonesia (Perrin and Gilpatrick 1994; J. Wang pers. comm., Kahn 2004). Spinners may also be so taken in West Africa (Van Waerebeek et al. 1999).

Tourist development may affect the habitat and viability of spinner dolphins in some regions, for example at Fernando de Noronha Island, Brazil (Reyes 1991), in Hawaii (Lammers 2004) and in Bali, Indonesia (T. Jefferson pers. comm.). The habit of resting in shallow coastal waters during the day leads to problems of harassment by dolphin-watching boats.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

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.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Spinner dolphins in the eastern tropical Pacific have been killed incidentally since the early 1960s by tuna purse seine fisheries. They were caught in such large numbers that the population of S. l. orientalis was reduced to less than one third of its original size (5). Following raised awareness of the number of dolphins killed in tuna purse seine fisheries, measures were implemented to reduce dolphin by-catch. Today spinner dolphins continue to be killed in this way, although in greatly reduced numbers (6). However, continued chase, capture and release of large numbers in the fishery may be preventing the population from recovering (11). In Sri Lanka and the Philippines, large numbers of spinner dolphins have also been captured in gillnets and killed by harpoons for the past 20 years (6), and local harpoon fisheries exist in several more locations throughout the world. Incidentally captured dolphins are consumed by local people, or used as shark bait, and this has led to the development of markets and fisheries directed at dolphins (5) (8). The takes in these fisheries may be unsustainable (5).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

WhyReef - Threats

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.

Creative Commons Attribution 3.0 (CC BY 3.0)

© WhyReef

Source: WhyReef EOL content

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Management

Conservation Actions

Conservation Actions
The species is listed in Appendix II of CITES.

Spinner Dolphins, as with other species impacted by the ETP tuna purse-seine fishery are managed both nationally by the coastal countries and internationally by the IATTC. The IATTC has imposed annual stock mortality limits on each purse seine and promulgated regulations regarding the safe release of dolphins (Bayliff 2001).

The species is composed of several subspecies and regional populations. The conservation status of each of these should be assessed. The available estimates of abundance and removals suggest that some of them may fall into a Threatened category.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

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

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Conservation

The eastern tropical Pacific and Southeast Asian populations of the spinner dolphin are listed on Appendix II of the Convention on Migratory Species (CMS). This means that the spinner dolphin is a migratory species that needs, or would significantly benefit from international co-operation, and the convention encourages the range states to conclude global or regional agreements (4). The spinner dolphin is also listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that international trade in this species should be carefully regulated (3). The value of dolphins as a tourist attraction offers countries and communities an incentive to protect these beautiful animals. Fernando de Noronha National Marine Park; (an archipelago off equatorial Brazil) was established in 1988, to provide nominal protection to spinner dolphins and support dolphin watching tourism (12), and it has been reported that in Zanzibar, the value of spinner dolphins for tourism far exceeded that of using them as bait for sharks (8). It is hoped that with meaningful laws, the will and resources to enforce them, continued attention by non-governmental organizations and efforts to make the public aware of the intrinsic value of their endemic dolphins (13), this charismatic species will continue spinning in our oceans forever.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Positive

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

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Economic Uses

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

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Risks

IUCN Red List Category

Data Deficient (DD)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
Creative Commons Attribution 3.0 (CC BY 3.0)

© WoRMS for SMEBD

Source: World Register of Marine Species

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Wikipedia

Spinner dolphin

The spinner dolphin (Stenella longirostris) is a small dolphin found in off-shore tropical waters around the world. It is famous for its acrobatic displays in which it spins along its longitudinal axis as it leaps through the air. It is a member of the family Delphinidae of toothed whales.

Taxonomy[edit]

The spinner dolphin is sometimes referred to as the long-snouted dolphin, particularly in older texts, to distinguish it from the similar Clymene dolphin, which is often called the short-snouted spinner dolphin. The species was described by John Edward Gray|John Gray in 1828. The four named subspecies are:

  • Eastern spinner dolphin (S. l. orientalis), from the tropical eastern Pacific.
  • Central American or Costa Rican spinner dolphin (S. l. centroamericana), also found in the tropical eastern Pacific.
  • Gray's or Hawaiian spinner dolphin (S. l. longirostris), from the central Pacific Ocean around Hawaii but represents a mixture of broadly similar subtypes found worldwide.
  • Dwarf spinner dolphin (S. l. roseiventris), first found in the Gulf of Thailand.

The species, though, displays greater variety than these subspecies might indicate. A hybrid form characterized by its white belly inhabits the eastern Pacific. Other less distinct groupings inhabit other oceans.

The zoology comes from the Latin term for long-beaked.

Physical description[edit]

The spinner dolphin is a small cetacean with a slim build. Adults are typically 129–235 cm long and reach a body mass of 23–79 kg.[3] This species has an elongated rostrum[4] and a triangular or subtriangular dorsal fin.[4] Spinner dolphins generally have tripartite color patterns. The dorsal area is dark gray, the sides light gray, and the underside pale gray or white.[5] Also, a dark band runs from the eye to the flipper, bordered above by a thin, light line. However, the spinner dolphin has more geographic variation in form and coloration than other cetaceans. In the open waters of eastern Pacific, dolphins have relatively small skulls with short rostra.[4] A dwarf form of spinner dolphin occurs around southeast Asia.[6] In these same subspecies, a dark dorsal cape dims their tripartite color patterns.[7] Further offshore, subspecies tend to have a paler and less far-reaching cape.[8] In certain subspecies, some males may have upright fins that slant forward.[7] Some populations of spinner dolphin found in the eastern Pacific have bizarre backwards-facing dorsal fins, and males can have strange humps and upturned caudal flukes.[9]

Ecology[edit]

The spinner dolphin lives in nearly all tropical and subtropical waters between 40°N and 40°S.[10] The species primarily inhabits coastal waters, islands, or banks. However, in the eastern tropical Pacific, dolphins live far from shore.[11] Spinner dolphins may use different habitats depending on the season.[12]

The spinner dolphin feeds mainly on small mesopelagic fish, squids, and sergestid shrimps, and will dive 200-300 m to feed on them.[13] Spinner dolphins of Hawaii are nocturnal feeders and forage in deep scattering layers, which contain many species. The dwarf spinner dolphin may feed mostly on benthic fish in reefs and shallow water.[6] Off Oahu, Hawaii, spinner dolphins forage at night and cooperatively herd their prey into highly dense patches.[14] They swim around the prey in a circle and a pair may swim through the circle to make a catch.[14] Spinner dolphins are in turn preyed on by sharks. Other possible predators include the killer whale, the false killer whale, the pygmy killer whale and the short-finned pilot whale.[15] They are susceptible to parasites, both external ones like barnacles and remoras, and internal ones, like nematodes, trematodes, cestodes and acanthocephalans.[4]

Behavior and life history[edit]

In certain regions, such as Hawaii and northern Brazil, dolphins spend the daytime resting in shallow bays near deep water.[16] At dusk, they travel offshore to feed. They travel along the shore during foraging trips, and the individuals that occupy the same bay may change daily.[16] Some individual dolphins do not always go to a bay to rest; however, in Hawaii, dolphins do seem to return to the same site each trip.[17] Spinner dolphins live in an open and loose social organization.[18] The spinner dolphins of Hawaii live in family groups, but also have associations with others beyond their groups.[4] Mothers and calves form strong social bonds. Spinner dolphins seem to have a promiscuous mating system, with individuals changing partners for up to some weeks. A dozen adult males may gather into coalitions[disambiguation needed].[18] Vocalizations of spinner dolphins include whistles, which may be used to organize the school, burst-pulse signals, and echolocation clicks.[19] The spinner dolphin has a 10-month gestation period, and mothers nurse their young for one to two years. Females are sexually mature at four to seven years, with three-year calving intervals, while males are sexually mature at seven to 10 years.[4] Breeding is seasonal, more so in certain regions than others.[4]

Spinning behavior[edit]

Spinner dolphins are known for their acrobatics and aerial behaviors. A spinner dolphin comes out of the water front first and twists its body as it rises into the air.[20] When it reaches its maximum height, the dolphin descends back into the water, landing on its side.[20] A dolphin can make two to 5.5 spins in one leap; the swimming and rotational speed of the dolphin as it spins underwater affects the number of spins it can do while airborne.[20] These spins may serve several functions.[20] Dolphins may also make nose-outs, tail slaps, flips, head slaps, "salmon leaps", and side and back slaps.

Conservation status[edit]

Tens of thousands of spinner dolphins, mostly eastern and white-bellied varieties, were killed in the 30 years after purse seine fishing for tuna began in the 1950s.[4] The process killed probably half of all eastern spinner dolphins. They have also been contaminated by pollutants such as DDT and PCBs.[4] Spinner dolphins, as with other species affected by ETP tuna purse-seine fishing, are managed nationally by the coastal countries and internationally by the IATTC. The IATTC has imposed annual stock mortality limits on each purse seine and promulgated regulations regarding the safe release of dolphins.[2]

The eastern tropical Pacific and Southeast Asian populations of the spinner dolphin are listed on Appendix II[21] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), since they have an unfavourable conservation status or would benefit significantly from international co-operation organized by tailored agreements.[22]

In addition, the spinner dolphin is covered by Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU)[23] and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU).

Spinner dolphins in Hawaii have multiple daily visits to their near-shore resting grounds. The Big Island, Hawaii, on the Kona Coast is a popular area for spinner dolphins. Boats take people out daily to snorkel and interact with the local dolphin population.

Images[edit]

See also[edit]

References[edit]

  1. ^ Mead, J. G.; Brownell, R. L., Jr. (2005). "Order Cetacea". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. pp. 723–743. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  2. ^ a b Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B. (2008). Stenella longirostris. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 7 October 2008.
  3. ^ Perrin, W. F, Dolar, MLL, Chan, CM, and Chivers, SJ (2005). Length-weight relationships in the spinner dolphin, Marine Mammal Science 21:765-778.
  4. ^ a b c d e f g h i Perrin WF (1998) "Stenella longirostris". Mamm Spec 599: 1-7.
  5. ^ WF Perrin, (1972) "Color patterns of spinner porpoises (Stenella cf. S. longirostris) of the eastern Pacific and Hawaii, with comments on delphinid pigmentation". Fish. Bull. (US) 70: 983-1003.
  6. ^ a b William F Perrin, Nobuyuki Miyazaki, Toshio Kasuya (1989) "A dwarf form of the spinner dolphin (Stenella longirostris) from Thailand". Marine Mammal Science 5(3): 213-227.
  7. ^ a b Perrin WF (1990) "Subspecies of Stenella longirostris (Mammalia: Cetacea: Delphinidae)". Proc Biol Soc Washington 103 (2): 453- 463.
  8. ^ WF Perrin, PA Akin, (1991) "Geographic variation in external morphology of the spinner dolphin Stenella longirostris in the eastern Pacific and implications for conservation". Fishery Bulletin 89:411-428.
  9. ^ Nelson, Bryan (November 2011). "Why does this dolphin have its fin on backwards?". Retrieved January 2013. 
  10. ^ Jefferson TA, Leatherwood S, Webber MA (1993) FAO Species identification guide. Marine mammals of the world. UNEP/FAO, Rome, 320 pp.
  11. ^ David WK Au and Wayne L. Perryman (1985) Dolphin habitats in the eastern tropical Pacific. Fishery Bulletin 83:623-643.
  12. ^ Fiedler, P. C., and S. B. Reilly. (1994) "Interannual variability of dolphin habitats in the eastern tropical Pacific. II: effects on abundances estimated from tuna vessel sightings, 1975 - 1990". Fishery Bulletin 92:451-463.
  13. ^ Dolar MLL, Walker WA, Kooyman GL, Perrin WF (2003) "Comparative feeding ecology of spinner dolphins (Stenella longirostris) and Fraser's dolphins (Lagenodelphis hosei) in the Sulu Sea". Mar Mamm Sci 19: 1-19.
  14. ^ a b Benoit-Bird K, Au W (2003) "Hawaiian spinner dolphins aggregate midwater food resources through cooperative foraging". Acoust Soc Am 114: 2300.
  15. ^ Norris KS, Würsig B, Wells RS, Würsig M (1994) The Hawaiian spinner dolphin. U Cal Press, Berkeley, Cal., USA.
  16. ^ a b Wursig B, Wells RS, Norris KS Würsig M, "A spinner dolphins day" pp. 65-102. in: Norris KS, Würsig B, Wells RS, Würsig M (1994) The Hawaiian spinner dolphin. U Cal Press, Berkeley, Cal., USA.
  17. ^ Marten K, Psarakos S (1999) "Long-term site fidelity and possible long-term associations of wild spinner dolphins (Stenella longirostris) seen off Oahu, Hawaii". Mar Mamm Sci 15: 1329-1336.
  18. ^ a b Norris KS, Johnson CM, Schools and schooling, pp 234-242 in Norris KS, Würsig B, Wells RS, Würsig M (1994) The Hawaiian spinner dolphin. U Cal Press, Berkeley, Cal., USA.
  19. ^ Brownlee SM, Norris KS. "The acoustic domain" in Norris KS, Würsig B, Wells RS, Würsig M (1994) The Hawaiian spinner dolphin. U Cal Press, Berkeley, Cal., USA.
  20. ^ a b c d Frank E Fish, Anthony J Nicastro, Daniel Weihs (2006) "Dynamics of the aerial maneuvers of spinner dolphins", Journal of Experimental Biology 209(4):590-598.
  21. ^ "Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009.
  22. ^ Convention on Migratory Species page on the Spinner dolphin, Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia
  23. ^ Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region
Creative Commons Attribution Share Alike 3.0 (CC BY-SA 3.0)

Source: Wikipedia

Unreviewed

Article rating from 0 people

Average rating: 2.5 of 5

Names and Taxonomy

Taxonomy

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.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Disclaimer

EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.

To request an improvement, please leave a comment on the page. Thank you!