Lifespan, longevity, and ageing

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Maximum longevity: 42.5 years (captivity) Observations: One captive specimen lived for 42.5 years (Richard Weigl 2005).
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Untitled

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The word "grampus" is Latin for "a kind of whale" and the word "griseus" is Latin for "gray". Pelorus Jack, a famous Risso's dolphin, had the habit of playing about ships and seemed to guide them into Pelorus Sound. It was observed for 24 years (around the turn of the century) escorting ships.

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Hans, K. 2011. "Grampus griseus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Grampus_griseus.html
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Behavior

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Risso’s dolphins use echolocation to locate, identify, and determine the distance of various objects in their environment. One of the most well-known sounds of delphinids are clicks. The clicks of Risso's dolphins have a peak frequency of 65 kHz, 3-dB bandwidths of 72 kHz, and durations of 40 to 100 Ms, all of which are consistent with other delphinids. Risso’s dolphins are also able to emit sonar clicks in the water while the majority of their forehead is above water, a characteristic unique to this species. In addition to broadband clicks, Risso's dolphins make a number of different vocalizations, including barks, buzzes, grunts, chirps, whistles, and simultaneous whistle and pulse sounds. Whistle and burst-pulse vocalizations have not been reported in other cetaceans and are thought to be unique to this species.

Communication Channels: visual ; acoustic

Perception Channels: visual ; tactile ; acoustic ; echolocation ; chemical

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Conservation Status

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Risso's dolphins are abundant and have a broad geographic range. As a result, they are classified as a species of "least concern" on the IUCN's Red List of Threatened Species. However, because little is known of current population trends, it is difficult to estimate potential conservation needs. Potential threats include direct killings for meat and oil in the Indian Ocean, and by-catch in the north Atlantic, the Mediterranean Sea, the southern Caribbean, the Azores, Peru, and the Solomon Islands. Because this species relies on echolocation to hunt, it is also thought that anthropogenic sounds may influence local populations. Recent climate change may also influence their range and abundance, however, potential effects are currently unclear.

US Federal List: no special status

IUCN Red List of Threatened Species: least concern

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Benefits

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Risso’s dolphins are sometimes a by-catch in the U.S. tuna purse seine industry, and are taken occasionally in coastal gill net and squid seining industries off the U.S. coast. They are sometimes a considered a nuisance to fisherman. Risso’s dolphins are high trophic level consumers. As a result, their tissues accumulate pollutants that are prevalent throughout their geographic range, a process known as bioaccumulation, and consuming the meat of this species could be harmful.

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Benefits

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In Indonesia and the Caribbean, Risso’s dolphins are hunted for their meat and oil. In Japan, they are taken periodically for food and fertilizer. Small numbers are sometimes collected for live exhibitions.

Positive Impacts: food ; body parts are source of valuable material

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Associations

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Risso's dolphins consume large amounts of fish, krill, crustaceans, and cephalopods and likely have a significant influence on the abundance of these animals. Risso's dolphins are one of many hosts for sea lamprey, which is common in shoreline habitat throughout north Atlantic.

Commensal/Parasitic Species:

  • sea lamprey (Petromyzon marinus)
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Trophic Strategy

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Risso's dolphins are known to prey on a mix of neritic, oceanic, and occasionally bottom dwelling organisms. Their diet consists of fish, krill, crustaceans, and cephalopods. Their most important prey item is the greater argonaut, which is also known as the paper nautilus. They often follow prey into shallow waters along the continental shelf, and prefer to feed between 600 and 800 m below the surface of the sea.

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Molluscivore )

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Hans, K. 2011. "Grampus griseus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Grampus_griseus.html
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Distribution

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Grampus griseus has an extensive distribution. The species can be found in temperate, subtropical and tropical waters of oceans worldwide.

Biogeographic Regions: indian ocean; atlantic ocean ; pacific ocean ; mediterranean sea

Other Geographic Terms: cosmopolitan

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Hans, K. 2011. "Grampus griseus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Grampus_griseus.html
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Habitat

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Risso's dolphins are pelagic, but prefer habitat on steep slopes, ranging from 400 to 1,200 meters. They are often seen near the edges of continental shelves, or near bathymetric features such as seamounts and submarine canyons. They are most commonly found in waters ranging in temperature from 59 to 68 degrees F, but will inhabit waters cold as 50 degrees F.

Risso’s dolphins are present year round throughout most of their geographic range. Residents of the northern-most parts of their range migrate seasonally between summering and wintering grounds For example, populations off the coast of northern Scotland during the summer, migrate to the Mediterranean during the winter, and populations off the coast of California during the summer, migrate to Mexican waters during winter.

Range depth: 400 to 1,200 m.

Habitat Regions: temperate ; tropical ; saltwater or marine

Aquatic Biomes: pelagic ; benthic ; coastal

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Hans, K. 2011. "Grampus griseus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Grampus_griseus.html
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Life Expectancy

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On average Risso's dolphins live at least 30 years.

Average lifespan
Status: wild:
30 years.

Average lifespan
Status: wild:
20.0 years.

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Hans, K. 2011. "Grampus griseus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Grampus_griseus.html
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Morphology

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Risso's dolphins have blunt, squarish heads and lack the beak typical of other delphinids. The dorsal fin is tall and falcate, and their flippers are long, pointed, and recurved. The anterior part of the body is very robust, tapering to a narrow tailstock. Adults range from 2.6 to 4 m in length, with an average body mass around 400 kg. The sexes are similar in size. Newborns range from 1.1 to 1.5 m in length and average 20 kg at birth. Along the body axis on the melon (i.e., beak, eyes, blowhole) there is a slight concave groove which is a unique characteristic of this species. Sexual dimorphism has not been reported in this species.

The youngest calves range in colour from iridescent gunmetal grey to fawn-brown dorsally and are creamy-white ventrally. Pale ochre-yellow highlights accentuate the muzzle. A white anchor-shape patch between the flippers resembles the chest chevron seen on pilot whales but is typically brighter and more extensive. Calves become silver-grey, then darken to nearly black, retaining the ventral patches of white. As animals age further, their heads, abdomens, and flanks lighten. (Nishiwaki 1972, Kruse et al. 1999, MMSC 1996,

This species displays highly variable coloration. The youngest calves range in colour from iridescent gunmetal grey to fawn-brown dorsally and are creamy-white ventrally. Pale ochre-yellow highlights accentuate the muzzle. A white anchor-shape patch between the flippers resembles the chest chevron seen on pilot whales but is typically brighter and more extensive. Calves become silver-grey, then darken to nearly black, retaining the ventral patches of white. In older animals, lip colour frequently contrasts with the surrounding background. Coloration fades with age, and some adults appear almost completely white due to the linear scarring that accumulates on individuals over time. These distinctive scars accumulate primarily on the animals' dorsal and lateral surfaces and have been hypothesized to result from the combined effects of lack of repigmentation of damaged tissue and a slower healing process than that observed in animals such as bottlenose dolphins. Scarification can be caused by other Risso's dolphins, predators (e.g., cookie cutter sharks), prey, or by parasites like sea lamprey. Intraspecific, tooth rake, scars tend to be long and parallel and may act as an indicator of male fitness during aggressive social interactions.

Risso's dolphins lack teeth in their upper jaws, but have 2 to 7 pairs of sharp peg-like teeth in their lower jaw, which are specialized for capturing prey, fighting predators, and competing with conspecific for mates and resources. Evolutionary retention of these teeth may be partly due to their significance in male-male interactions.

Risso's dolphins may be confused with bottlenose dolphins, false killer whales, and killer whales due to the shape and size of their dorsal fin. However, their blunt heads and extensive scarring make them unmistakable.

Range mass: 300 to 500 kg.

Range length: 2.6 to 5 m.

Average length: 2.8 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

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Hans, K. 2011. "Grampus griseus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Grampus_griseus.html
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Kelsey Hans, University of Michigan-Ann Arbor
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Associations

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There is no information available regarding predators specific to Risso's dolphin.

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Hans, K. 2011. "Grampus griseus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Grampus_griseus.html
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Reproduction

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There is no information regard the mating system of Grampus griseus. However, other Cetaceans tend to be either polygynous and polyandrous.

There is little information available regarding reproductive behavior in Grampus griseus. Most females are sexually mature by 8 to 10 years old, however, size is often a better indicator of sexual maturity than age in marine cetaceans. Most males reach sexually maturity at a length of 2.6 to 2.8 m. Gestation lasts 13 to 14 months, and average mass of newborns calves is 20 kg. Weaning is complete by 12 to 18 months after parturition. Breeding and calving occur year-round, but peak during summer and winter in the north Atlantic and eastern Pacific, respectively.

Breeding season: Grampus griseus breeds year round, but peaks seasonally depending on hemisphere.

Range gestation period: 13 to 14 months.

Range weaning age: 12 to 18 months.

Range age at sexual or reproductive maturity (female): 8 to 10 years.

Key Reproductive Features: year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous

Average number of offspring: 1.

Female Risso's dolphins are the primary care givers to calves, and paternal care, which is rare in other cetaceans, has not been documented in this species. Newborns are precocial and begin swimming immediately after birth. Mother-calf pods form, and young usually do not leave the group until a few years before sexual maturity. Alloparental care has been recorded amongst females. Often, while a calve's mother is foraging for food, another female provides care.

Parental Investment: precocial ; female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); post-independence association with parents

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Hans, K. 2011. "Grampus griseus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Grampus_griseus.html
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Biology

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Risso's dolphin feeds largely on squid, although other cephalopods are also taken, as well as fish and crustaceans (2). Like most dolphins, this species is a highly social animal, typically occurring in groups of between 3 to 50 individuals (2), and may mix with different species of cetaceans (whales and dolphins) (8). When groups are hunting they spread out into a long line (5). This species tends to ride alongside or in the wake of boats, and young individuals often breach (clear the water), slap their flippers on the surface of the water or 'spyhop' (lift their heads clear of the water) (5). A number of sounds are produced, including characteristic 'signature whistles' (6), many of these vocalisations are important in detecting prey through echolocation (8).
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Conservation

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A UK Biodiversity Action Plan priority species, Risso's dolphin is protected in UK waters by the Wildlife and Countryside Act 1981 and the Wildlife (Northern Ireland) Orders, 1985; it is illegal to intentionally kill, injure, or harass any cetacean (whale or dolphin) species in UK waters (4). The Agreement on the Conservation of Small Cetaceans in the Baltic and North Seas (ASCOBANS) has been signed by seven European countries, including the UK. Provision is made under this agreement to set up protected areas, promote research and monitoring, pollution control and increase public awareness (4).
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Description

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Risso's dolphin is a large, stocky species with a blunt head (2). They are easily recognised as they are heavily scared and become whiter with age as the number of scars increases (2). Calves are born with grey skin that turns chocolate brown as they age (5), eventually they take on the adult colouring of a grey back and white underside with darker flippers and tail (5). The scars are thought to be caused by the teeth of other Risso's dolphins, due to playing or fighting, however it is also thought that some of the scars are the result of squid bites (2). The tall, centrally positioned sickle-shaped dorsal fin is even taller and more erect in adult males than in females (7).
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Habitat

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Shows a preference for deep, warm temperate and tropical waters in offshore areas (6). Risso's are fairly abundant, with wide distribution. They prefer deep off shore waters, but can be seen close to shore around oceanic islands. In Britain and Ireland most records are within 11 km of the coast (9).
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Range

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Widely distributed, inhabiting tropical and warm temperate waters of both hemispheres (6). In UK waters the main concentration is around the Hebrides, but the species also occurs around the Northern Isles and in the Irish Sea. It is also quite common in south-east and western Ireland (4).
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Status

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Classified as Least Concern (LC) on the IUCN Red List (1). Listed on Annex IV of the EC Habitats Directive, and Appendix II of the Bonn Convention (North and Baltic Sea populations), and Appendix III of the Bern Convention (3). All cetaceans (whales and dolphins) are listed on Annex A of EU Council Regulation 338/97; they are therefore treated by the EU as if they are included in CITES Appendix I, so that commercial trade is prohibited. In the UK all cetaceans are fully protected under the Wildlife and Countryside Act, 1981 and the Wildlife (Northern Ireland) Order, 1985 (4).
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Threats

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This dolphin is vulnerable to hunting (5) and environmental change, chemical and noise pollution (8), and entanglement in fishing nets, which results in drowning (5).
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Distribution in Egypt

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Mediterranean and Red Sea.

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Status in Egypt

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Accidental?

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Brief Summary

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Risso's dolphins are often covered with scars. The older the dolphin, the more scratches on its body. These scars are probably caused by the teeth of other Risso's dolphins, made during fights or while playing. Squid can also leave scars, when they are caught and eaten by the animal. Risso's dolphins prefer warm water, but occasionally there are reports of one swimming in the northern North Sea.
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Diagnostic Description

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Risso's dolphins are robust blunt-headed animals without distinct beaks.

The flippers are long, pointed, and recurved; the dorsal fin is tall and falcate. Risso's dolphins have mouthlines that slope upward.

One of the most distinctive features is a vertical crease on the front of the melon. However, at sea, the best identification character is the coloration and scarring.

Adults range from dark grey to nearly white, but are typically covered with white scratches, spots, and blotches. The chest has a whitish anchor-shaped patch, and the appendages tend to be darker than the rest of the body. Young animals range from light grey to dark brownish grey and are relatively unmarked.

The teeth are also unique; there are 2 to 7 pairs in the front of the lower jaw and usually none in the upper jaw. Some or all of the teeth may be worn-down in, or missing from, adults.

Can be confused with: Risso's dolphins are generally easy to identify when seen at close range; however, from a distance they may be confused with other large delphinids with a tall dorsal fin (such as bottlenose dolphins, false killer whales, and killer whales). When visible, the light, extensively scarred bodies and squarish heads of Risso's dolphins make them unmistakable.

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Marine mammals of the world. Jefferson, T.A., S. Leatherwood & M.A. Webber - 1993. FAO species identification guide. Rome, FAO. 320 p. 587 figs. . 
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Size

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Newborns are 1.2 to 1.5 m long and adults range up to at least 3.8 m long. Weights of up to 400 kg have been recorded, and the maximum may be near 500 kg.
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Marine mammals of the world. Jefferson, T.A., S. Leatherwood & M.A. Webber - 1993. FAO species identification guide. Rome, FAO. 320 p. 587 figs. . 
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Brief Summary

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These large dolphins are often seen surfacing slowly, although they can be energetic, sometimes breaching or porpoising, and occasionally bowriding. Herds tend to be small to moderate in size, but groups of up to 4 000 have been reported. Risso's dolphins commonly associate with other species of cetaceans. Hybrids between this species and the bottlenose dolphin have been recorded, both in captivity and in the wild. In the North Atlantic, there appears to be a summer calving peak.

Risso's dolphins feed on crustaceans and cephalopods, but seem to prefer squid. Squid bites may be the cause of some of the scars found on the bodies of these animals.

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Marine mammals of the world. Jefferson, T.A., S. Leatherwood & M.A. Webber - 1993. FAO species identification guide. Rome, FAO. 320 p. 587 figs. . 
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Benefits

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Risso's dolphins have been taken in small numbers, (both incidentally and intentionally) in drive, gillnets, seine, and harpoon fisheries throughout the species' range. In Sri Lanka, they are apparently the second most commonly taken cetacean in fisheries, providing fish and meat for human consumption and fish bait; stocks there may be adversely affected. IUCN:

Insufficiently known.

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Marine mammals of the world. Jefferson, T.A., S. Leatherwood & M.A. Webber - 1993. FAO species identification guide. Rome, FAO. 320 p. 587 figs. . 
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Risso's dolphin

provided by wikipedia EN

Risso's dolphin (Grampus griseus) is the only species of dolphin in the genus Grampus. It is commonly known as the Monk dolphin among Taiwanese fishermen. Some of the closest related species to these dolphins include: pilot whales (Globicephala spp.), pygmy killer whales (Feresa attenuata), melon-headed whales (Peponocephala electra), and false killer whales (Pseudorca crassidens).[4]

Taxonomy

Risso's dolphin is named after Antoine Risso, whose description formed the basis of the first public description of the animal, by Georges Cuvier, in 1812. Another common name for the Risso's dolphin is grampus (also the species' genus), although this common name was more often used for the orca. The etymology of the word "grampus" is unclear. It may be an agglomeration of the Latin grandis piscis or French grand poisson, both meaning big fish. The specific epithet griseus refers to the mottled (almost scarred) grey colour of its body.

Description

 src=
Illustrations by Edward Drinker Cope in 1876

Risso's dolphin has a relatively large anterior body and dorsal fin, while the posterior tapers to a relatively narrow tail. The bulbous head has a vertical crease in front.[5]

Infants are dorsally grey to brown and ventrally cream-colored, with a white anchor-shaped area between the pectorals and around the mouth. In older calves, the nonwhite areas darken to nearly black, and then lighten (except for the always dark dorsal fin). Linear scars mostly from social interaction eventually cover the bulk of the body; scarring is a common feature in toothed whales, but Risso's dolphin tend to be unusually heavily scarred.[6] Older individuals appear mostly white. Most individuals have two to seven pairs of teeth, all in the lower jaw.[5]

Length is typically 10 feet (3.0 m), although specimens may reach 13.12 feet (4.00 m).[7] Like most dolphins, males are typically slightly larger than females. This species weighs 300–500 kilograms (660–1,100 lb), making it the largest species called "dolphin".[8][9]

Range and habitat

 src=
A Risso's dolphin swims off Morro Bay

They are found worldwide in temperate and tropical waters, in the Indian, Pacific and Atlantic Oceans, also the Persian Gulf, Mediterranean and Red Seas, but not the Black Sea (a stranding was recorded in the Sea of Marmara in 2012[10]). They range as far north as the Gulf of Alaska and southern Greenland and as far south as Tierra del Fuego.[5]

Their preferred environment is just off the continental shelf on steep banks, with water depths varying from 400–1,000 m (1,300–3,300 ft) and water temperatures at least 10 °C (50 °F) and preferably 15–20 °C (59–68 °F).[5]

The population around the continental shelf of the United States is estimated to be in excess of 60,000. In the Pacific, a census recorded 175,000 individuals in eastern tropical waters and 85,000 in the west. No global estimate exists.

Ecology

 src=
Risso's dolphin off Port San Luis, Harford Pier, at Avila Beach, California.

They feed almost exclusively on neritic and oceanic squid, mostly nocturnally. Predation does not appear significant. Mass strandings are infrequent.[5] Analysis carried out on the stomach contents of stranded specimens in Scotland showed that the most important species preyed on in Scottish waters is the curled octopus.[11]

A population is found off Santa Catalina Island where they are sympatric with short-finned pilot whales (Globicephala macrorhynchus) and both species feed on the squid population. Although these species have not been seen to interact with each other, they take advantage of the commercial squid fishing that takes place at night. They have been seen by fishermen to feed around their boats.[12] They also travel with other cetaceans. They surf the bow waves of gray whales, as well as ocean swells.[5]

Risso's dolphins have a stratified social organisation.[13] These dolphins typically travel in groups of between 10 and 51, but can sometimes form "super-pods" reaching up to a few thousand individuals. Smaller, stable subgroups exist within larger groups. These groups tend to be similar in age or sex.[14] Risso's experience fidelity towards their groups. Long-term bonds are seen to correlate with adult males. Younger individuals experience less fidelity and can leave and join groups. Mothers show a high fidelity towards a group of mother and calves.[13] But, it is unclear whether or not these females stay together after their calves leave or remain in their natal pods.

Behavior

Natural Resources Wales work on the conservation of Risso's dolphins around Bardsey Island, Wales

Social behavior

Risso's dolphins do not require cutting teeth to process their cephalopod prey, which has allowed the species to evolve teeth as display weapons in mating conflicts.[6]

Reproduction

Gestation requires an estimated 13–14 months, at intervals of 2.4 years. Calving reaches seasonal peaks in the winter in the eastern Pacific and in the summer and fall in the western Pacific. Females mature sexually at ages 8–10, and males at age 10–12. The oldest specimen reached 39.6 years.[5]

Risso's dolphins have successfully been taken into captivity in Japan and the United States, although not with the regularity of bottlenose dolphins or orcas. Hybrid Risso's-bottlenose dolphins have been bred in captivity.

Human interactions

Like other dolphins and marine animals, there have been documentations of these dolphins getting caught in seine-nets and gillnets across the globe.[4] Many of these incidents have resulted in death.[14] Small whaling operations have also been cause of some of these deaths. Pollution has also affected many individuals who have ingested plastic. Samples from these animals shows contamination within their tissue.[4]

In Ireland, though not apparently in England, Risso's Dolphin was one of the royal fish which by virtue of the royal prerogative were the exclusive property of the English Crown.[15]

Conservation

The Risso's dolphin populations of the North, Baltic, and Mediterranean Seas are listed on Appendix II[16] 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 organised by tailored agreements.[17]

In addition, Risso's dolphin is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS),[18] the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS),[19] the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU)[20] and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU).[21]

Risso's dolphins are protected in the United States under the Marine Mammal Protection Act of 1992. Currently, Japan, Indonesia, the Solomon Islands, and The Lesser Antilles hunt Risso's dolphins.[14]

Strandings

At least one case report of strandings in Japan's Goto Islands has been associated with parasitic neuropathy of the eighth cranial nerve by a trematode in the genus Nasitrema.[22] There was a recent reporting of a juvenile male Risso's dolphin that was stranded alive on the coast of Gran Canaria on 26 April 2019. This was the first documented case of capture myopathy and stress cardiomyopathy in a male juvenile Risso's dolphin that has received rehabilitation.[23]

See also

References

  1. ^ Mead, J.G.; Brownell, R. L. Jr. (2005). "Order Cetacea". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 723–743. ISBN 978-0-8018-8221-0. OCLC 62265494.
  2. ^ Taylor, B.L.; Baird, R.; Barlow, J.; Dawson, S.M.; Ford, J.; Mead, J.G.; Notarbartolo di Sciara, G.; Wade, P. & Pitman, R.L. (2012). "Grampus griseus". IUCN Red List of Threatened Species. 2012: e.T9461A17386190. doi:10.2305/IUCN.UK.2012.RLTS.T9461A17386190.en.
  3. ^ William Perrin (2014). Perrin WF (ed.). "Grampus Gray, 1828". World Cetacea Database. World Register of Marine Species. Retrieved 16 March 2015.
  4. ^ a b c Baird, Robin (2008). Encyclopedia of Marine Mammale 2nd edition. Academic Press. pp. 975–976. ISBN 9780123735539.
  5. ^ a b c d e f g Baird, Robin W. (2009). Perrin, William F.; Wursig, Bernd; Thewissen, J. G. M. (eds.). Encyclopedia of Marine Mammals (2nd ed.). Burlington Ma.: Academic Press. p. 975. ISBN 978-0-12-373553-9. Archived from the original on 9 November 2009.
  6. ^ a b MacLeod, Colin D. (January 1998). "Intraspecific scarring in odontocete cetaceans: an indicator of male 'quality' in aggressive social interactions?". Journal of Zoology. 244 (1): 71–77. doi:10.1111/j.1469-7998.1998.tb00008.x. ISSN 0952-8369.
  7. ^ "Grampus griseus – Risso's dolphin". Animal Diversity Web.
  8. ^ American Cetacean Society Fact Sheet – Risso's Dolphin Archived 11 July 2007 at the Wayback Machine
  9. ^ Risso's Dolphin. Whale Web. Retrieved 22 September 2015.
  10. ^ First stranding record of a Risso’s Dolphin (Grampus griseus) in the Marmara Sea, Turkey (pdf). Retrieved 6 September 2017
  11. ^ MacLeod, C.D.; Santos, M.B.; Pierce, G.J. (2014). Can habitat modelling for the octopus Eledone cirrhosa help identify key areas for Risso's dolphin in Scottish waters? (PDF) (Report). Scottish Natural Heritage Commissioned Report. 530. Scottish Natural Heritage. Retrieved 24 December 2016.
  12. ^ Shane, Susan H. (1995). "Behavior patterns of pilot whales and Risso's dolphins off Santa Catalina Island, California" (PDF). Aquatic Mammals. 21 (3): 195–197 – via Aquatic Mammals Issue Archives.
  13. ^ a b Hartman, K. L.; Visser, F.; Hendriks, A. J.E. (14 March 2008). "Social structure of Risso's dolphins (Grampus griseus) at the Azores: a stratified community based on highly associated social units". Canadian Journal of Zoology. 86 (4): 294–306. doi:10.1139/Z07-138. ISSN 0008-4301.
  14. ^ a b c "Risso's dolphin, Open Waters, Marine mammals, Grampus griseus at the Monterey Bay Aquarium". montereybayaquarium.org. Retrieved 27 April 2018.
  15. ^ Ball, F, Elrington "History of Dublin" Volume 5 (1917) Alexander Thom and Co. Dublin< p.49
  16. ^ "Appendix II Archived 11 June 2011 at the Wayback Machine" 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.
  17. ^ Convention on Migratory Species page on the Risso's dolphin. Cms.int (25 June 1998). Retrieved 22 September 2015.
  18. ^ Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas. Ascobans.org. Retrieved 22 September 2015.
  19. ^ Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area. Accobams.org. Retrieved 22 September 2015.
  20. ^ Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region. Pacificcetaceans.org. Retrieved 22 September 2015.
  21. ^ Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. Cms.int. Retrieved 22 September 2015.
  22. ^ Morimitsu, T; Kawano, H; Torihara, K; Kato, E; Koono, M (1992). "Histopathology of eighth cranial nerve of mass stranded dolphins at Goto Islands, Japan". Journal of Wildlife Diseases. 28 (4): 656–8. doi:10.7589/0090-3558-28.4.656. PMID 1474668.
  23. ^ Câmara, Nakita; Sierra, Eva; Fernández, Antonio; Arbelo, Manuel; Bernaldo de Quirós, Yara; Arregui, Marina; Consoli, Francesco; Herráez, Pedro (29 January 2020). "Capture Myopathy and Stress Cardiomyopathy in a Live-Stranded Risso's Dolphin (Grampus griseus) in Rehabilitation". Animals. 10 (2): 220. doi:10.3390/ani10020220. ISSN 2076-2615. PMC 7070958. PMID 32013196.
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Risso's dolphin: Brief Summary

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Risso's dolphin (Grampus griseus) is the only species of dolphin in the genus Grampus. It is commonly known as the Monk dolphin among Taiwanese fishermen. Some of the closest related species to these dolphins include: pilot whales (Globicephala spp.), pygmy killer whales (Feresa attenuata), melon-headed whales (Peponocephala electra), and false killer whales (Pseudorca crassidens).

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Distribution

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in all oceans
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van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO). van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO). IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species. North-West Atlantic Ocean species (NWARMS) North-West Atlantic Ocean species (NWARMS)
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Jacob van der Land [email]

Distribution

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Georges Bank, on the continental shelf and shelf edge waters
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van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO). van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO). IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species. North-West Atlantic Ocean species (NWARMS) North-West Atlantic Ocean species (NWARMS)
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Mary Kennedy [email]

Habitat

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temperate to tropical, oceanic
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van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO). van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO). IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species. North-West Atlantic Ocean species (NWARMS) North-West Atlantic Ocean species (NWARMS)
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Jacob van der Land [email]

IUCN Red List Category

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Least Concern (LC)
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van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO). van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO). IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species. North-West Atlantic Ocean species (NWARMS) North-West Atlantic Ocean species (NWARMS)
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William Perrin [email]