THE LONG- BEAKED COMMON DOLPHIN

 

The long-beaked common dolphin (Delphinus capensis) is a species of common dolphin. It has a more restricted range than the short-beaked common dolphin (D. delphis). It has a disjointed range in coastal areas in tropical and warmer temperate oceans. The range includes parts of western and southern Africa, much of western South America, central California to central Mexico, coastal Peru, areas around Japan, Korea and Taiwan, and possibly near Oman.^[1][3] Vagrants have been recorded as far north as Vancouver Island. They live in shallow, warmer temperature waters near the coast. They also live in the tropical and subtropical regions.^[4]

 

 

The long-beaked common dolphin is medium-sized, but smaller than the more popular bottlenose dolphin. Adults range between 1.9 and 2.5 m (6.2 and 8.2 ft), long, and can weigh between 80 and 235 kg (176 and 518 lb), although a range between 80 and 150 kg (180 and 330 lb) is more common.^[5] Males are generally longer and heavier.^[5] The color pattern on the body is unusual. The back is dark and the belly is white, while on each side is an hourglass pattern colored light grey, yellow or gold in front and dirty grey in back.^[6] This species also has a rounded melon on tops of their heads used for echolocation.^[4] It has a long, thin rostrum with up to 60 small, sharp, interlocking teeth on each side of each jaw.^[7] They have more teeth than any other delphinids.^[8]

 

The long-beaked common dolphin is medium-sized, but smaller than the more popular bottlenose dolphin. Adults range between 1.9 and 2.5 m (6.2 and 8.2 ft), long, and can weigh between 80 and 235 kg (176 and 518 lb), although a range between 80 and 150 kg (180 and 330 lb) is more common.^[5] Males are generally longer and heavier.^[5] The color pattern on the body is unusual. The back is dark and the belly is white, while on each side is an hourglass pattern colored light grey, yellow or gold in front and dirty grey in back.^[6] This species also has a rounded melon on tops of their heads used for echolocation.^[4] It has a long, thin rostrum with up to 60 small, sharp, interlocking teeth on each side of each jaw.^[7] They have more teeth than any other delphinids.^[8]

 

The long-beaked common dolphin is a member of the common dolphin genus, Delphinus within the dolphin family, Delphinidae in the cetaceans order.^[4] Until the mid-1990s, the different forms within Delphinus were not recognized as separate species, but were all considered members of the species D. delphis.^[3][5] In 1994, Heyning and Perrin^[9] did research on these species and then Kingston and Rosel^[10] confirmed there were two separate species. Currently, the two recognized species of Delphinus  are the short-beaked common dolphin (D. delphis) and the long-beaked common dolphin.^[1] The long-beaked common dolphin is generally larger with a longer beak than the short-beaked common dolphin and has a longer rostrum.

The Indo-Pacific common dolphin is sometimes considered a separate species (D. tropicalis), but is more often considered a form of the long-beaked common dolphin.^[1][3]

 

 

The long-beaked common dolphin has a varied diet consisting of small schooling fish, such as sardines, anchovies, mackerels, pilchards, mullet, drum or croaker. These dolphins may occasionally eat small cephalopods such as octopuses and squid, and more rarely eat small crustaceans like large shrimp or small crab. Since they gather in huge superpods and there is seldom enough food in one place to support all of them, smaller groups leave the main pod for a few hours to feed.^[11] They are able to dive in the water to about 900 feet (270 m) and hold their breath for up to 8 minutes to catch prey.^[4]

 

 

 

See also: Dolphin (Reproduction and sexuality)

The long-beaked common dolphin has a gestation period of 10 to 11 months typically during spring or autumn.^[4][5] The newborn calf has a length of between 80 and 100 cm (2.6 and 3.3 ft) and a weight of about 10 kilograms (22 lb).^[5] The young and juvenile dolphins coloration and patterns are darker than the adults.^[11] Typical interbirth interval ranges from one to three years.^[5] In captivity, this dolphin has hybridized with the common bottlenose dolphin (Tursiops truncatus).^[3][12] One of the hybrids has been bred back to a bottlenose dolphin, demonstrating such hybrids are fertile.^[12] The long-beaked common dolphin can live up to 40 years.^[4]

 

 

Long-beaked common dolphins are not common in human care as they are extremely difficult to keep in captivity. In the wild, however, they have been seen travelling with bottlenose dolphins, pilot whales, and yellowfin tuna.^[13]

 

 

Delphinus capensis is covered by the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia^[14] and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU).^[15] One of the main threats to the long-beaked common dolphin is fisheries. Out of 930 dolphins observed off of Peru between 1985 and 2000, 120 of them had many lacerations on their head, skin, appendages, and teeth. Most of these injuries were from fisheries-related connection.^[16] Another threat to this species is pollution because many of them have shown signs of organochlorine residue on their blubber.^[17] On the coast of California there are only about 25,000 to 43,000 dolphins and on the coast of South Africa there are 15,000 to 20,000.^[5]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Physical characteristics

 

The long-beaked common dolphin is medium-sized, but smaller than the more popular bottlenose dolphin. Adults range between 1.9 and 2.5 m (6.2 and 8.2 ft), long, and can weigh between 80 and 235 kg (176 and 518 lb), although a range between 80 and 150 kg (180 and 330 lb) is more common.^[5] Males are generally longer and heavier.^[5] The color pattern on the body is unusual. The back is dark and the belly is white, while on each side is an hourglass pattern colored light grey, yellow or gold in front and dirty grey in back.^[6] This species also has a rounded melon on tops of their heads used for echolocation.^[4] It has a long, thin rostrum with up to 60 small, sharp, interlocking teeth on each side of each jaw.^[7] They have more teeth than any other delphinids.^[8]

 

Taxonomy

Delphinus c. tropicalis in the Red Sea

The long-beaked common dolphin is a member of the common dolphin genus, Delphinus within the dolphin family, Delphinidae in the cetaceans order.^[4] Until the mid-1990s, the different forms within Delphinus were not recognized as separate species, but were all considered members of the species D. delphis.^[3][5] In 1994, Heyning and Perrin^[9] did research on these species and then Kingston and Rosel^[10] confirmed there were two separate species. Currently, the two recognized species of Delphinus  are the short-beaked common dolphin (D. delphis) and the long-beaked common dolphin.^[1] The long-beaked common dolphin is generally larger with a longer beak than the short-beaked common dolphin and has a longer rostrum.

The Indo-Pacific common dolphin is sometimes considered a separate species (D. tropicalis), but is more often considered a form of the long-beaked common dolphin.^[1][3]

Behavior

Delphinus capensis with whale watching vessels off Kochi, Japan

Long-beaked common dolphins can live in aggregations of hundreds or even thousands.^[3] Within these large groups, smaller subgroups of 10 to 30, related in either sex or age, typically are found.^[4] They sometimes associate with other dolphin species, such as pilot whales.^[3] They have also been observed bow riding on baleen whales, and they also bow ride on boats.^[3] Breaching behavior and aerial acrobatics are common with this species.^[5]

 

Diet

 

The long-beaked common dolphin has a varied diet consisting of small schooling fish, such as sardines, anchovies, mackerels, pilchards, mullet, drum or croaker. These dolphins may occasionally eat small cephalopods such as octopuses and squid, and more rarely eat small crustaceans like large shrimp or small crab. Since they gather in huge superpods and there is seldom enough food in one place to support all of them, smaller groups leave the main pod for a few hours to feed.^[11] They are able to dive in the water to about 900 feet (270 m) and hold their breath for up to 8 minutes to catch prey.^[4]

 

Reproduction

 

 

See also: Dolphin (Reproduction and sexuality)

The long-beaked common dolphin has a gestation period of 10 to 11 months typically during spring or autumn.^[4][5] The newborn calf has a length of between 80 and 100 cm (2.6 and 3.3 ft) and a weight of about 10 kilograms (22 lb).^[5] The young and juvenile dolphins coloration and patterns are darker than the adults.^[11] Typical interbirth interval ranges from one to three years.^[5] In captivity, this dolphin has hybridized with the common bottlenose dolphin (Tursiops truncatus).^[3][12] One of the hybrids has been bred back to a bottlenose dolphin, demonstrating such hybrids are fertile.^[12] The long-beaked common dolphin can live up to 40 years.^[4]

 

Relationship to humans and other species

 

Long-beaked common dolphins are not common in human care as they are extremely difficult to keep in captivity. In the wild, however, they have been seen travelling with bottlenose dolphins, pilot whales, and yellowfin tuna.^[13]

 

Conservation

 

Delphinus capensis is covered by the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia^[14] and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU).^[15] One of the main threats to the long-beaked common dolphin is fisheries. Out of 930 dolphins observed off of Peru between 1985 and 2000, 120 of them had many lacerations on their head, skin, appendages, and teeth. Most of these injuries were from fisheries-related connection.^[16] Another threat to this species is pollution because many of them have shown signs of organochlorine residue on their blubber.^[17] On the coast of California there are only about 25,000 to 43,000 dolphins and on the coast of South Africa there are 15,000 to 20,000.^[5]

 

 

 

 Binomial name

 

 Delphinus capensis

Gray, 1828

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

THE LA. PLATA DOLPHIN

 

The La Plata dolphin, franciscana or toninha (Pontoporia blainvillei) is a species of river dolphin found in coastal Atlantic waters of southeastern South America.^[4] It is a member of the Inioidea group and the only one that lives in the ocean and saltwater estuaries, rather than inhabiting exclusively freshwater systems. Commercialized areas that create agricultural runoffs and industrialized zones can affect the health of the La Plata dolphin, especially in regards to their contributions of waste and pollution, which can lead to habitat degradation and poisoned food among other concerns. ^{[citation needed]}

The La Plata dolphin is the only species in its genus, Pontoporia, and is often placed in its own family, Pontoporiidae. It was first described by Paul Gervais and Alcide d'Orbigny in 1844 (the species epithet blainvillei commemorates the French zoologist Henri Marie Ducrotay de Blainville). The La Plata dolphin is also widely known as the Franciscana (the Argentine and Uruguayan name), a name that has been adopted internationally. Other common names are the toninha (the Brazilian name) and cachimbo.

The La Plata dolphin weighs up to 50 kilograms (110 lb), and lives for up to 20 years. Sexual maturity is reached between two and three years. Females have a two-year reproductive cycle. Calves are 70 to 75 cm when born after a gestation of 10–11 months. Calves are weaned at a year old.^[5] Females may be giving birth by the age of five.

The La Plata dolphin reaches sexual maturity around two to three years for both sexes, but some populations have shown as long as five years. Although it is difficult to observe La Plata dolphins, the reproductive patterns of one population of La Plata near Brazil was studied extensively. A majority of the dolphins observed were born around September to February, during the austral spring and summer. La Plata dolphin has an average gestation period of about 11 months.

 

Smaller testes indicate less importance of sperm competition when considering mating strategies, and La Plata dolphins generally have smaller testes. However, data reveals that the size of an individual's testes has seasonal variation which indicates their breeding season, but there is still research needed to further this observation. The size of La Plata testes in relation to their body mass may reveal that they primarily perform serial monogamy. This does not directly indicate that La Plata are purely monogamous, but that they may remain with one partner during a breeding season or a portion of that season.

There is evidence that suggests that La Plata have a reproductive cycle of two years; however, more is required to make any legitimate claims.^[6]

The animal is very inconspicuous—it moves very smoothly and slowly—and can be difficult to spot unless estuary conditions are very calm. It will commonly swim alone or in small groups. Exceptional groups as large as 15 have been seen. La Plata dolphins are bottom feeders and gut inspections have revealed they eat at least 24 different species of fish, depending on which species are most common. They will also take octopus, squid and shrimp. They are, in turn, hunted by killer whales (orcas) and several species of sharks (such as tiger sharks, sand tiger sharks, broadnose sevengill sharks, hammerhead sharks (Sphyrna), and requiem sharks Carcharhinus).^[7]

The La Plata dolphin is found in the coastal Atlantic waters of southeastern South America, including the Río de la Plata estuary. Its distribution ranges from the Tropic of Capricorn near Ubatuba, Brazil, south to Península Valdés, Argentina. It is the only member of the river dolphin group that lives in the ocean and saltwater estuaries, rather than freshwater. Although some members of the species do spend portions of their lives outside of river systems, many individuals live their entire lives within rivers, never venturing into the ocean proper.^[8]

 

 

The species has been observed in Miramar, Buenos Aires Province, Rio Negro Province, Bahia Rosas swimming in small groups. Their reported range is from the opening of the Doce River, Regencia, Espirito Santo, Brasil to Peninsula Valdes in Chubut Province, Argentina.^[8]

When along the Brazilian coast, the species is usually reported in depths ranging from 8 to 30 meters, and up to 35 for accidental captures.^[9][10] However, there are a few reports of individual further away from the shore.^[11]

The La Plata dolphin is affected by factors like habitat destruction and water pollution. Plastic debris and synthetic material has been found in the stomach contents of these animals. More research is necessary to determine whether or not these factors negatively affect the health of La Plata dolphins.^[2] 90% of the population in Guanabara Bay was lost in three decades.^[12] La Plata also faces threats from fishing nets and other types of fishing gear that they get caught in while searching for prey.

 

 

Commercialized areas often have agricultural runoff or industrial zones that are harmful to the species's health. Waste and pollution from these areas lead to habitat degradation and toxic chemicals in fish that dolphins feed on.^[13]

Since the La Plata dolphin is a small mammal and their habitat is regularly hunted by sharks and killer whales, they are generally quiet in nature and inhabit shallow coastal waters.^[14]

The La Plata dolphin is listed as "Vulnerable" in the IUCN Red List of Threatened Species.^[2] However, the Franciscana is a particular conservation concern because of its restricted distribution and vulnerability to incidental capture in fishing gear. Large numbers are killed in gillnets. Although the largest documented catches in the 1970s were in Uruguay, catches in recent decades have also been high in southern Brazil and Argentina. Scientists from all three countries have voiced their concerns, and asked for international assistance in highlighting the plight of the dolphin (see Reeves et al., pg. 53).

 

 

The species is listed on Appendix I^[15] and Appendix II^[15] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix I^[15] as this species has been categorized as being in danger of extinction throughout all or a significant proportion of its range. CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them. It is listed on Appendix II^[15] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.

 

 A young La Plata dolphin was rescued in 2011 off Montevideo, Uruguay.^[16] In February 2016 a young dolphin died on the beach of Santa Teresita, Argentina. Reports circulated internationally that the dolphin's death resulted after being passed around by a crowd who were posing for selfies with it.^[17][18] However, an interview by the photographer of the images, Hernan Coria, contradicted such claim.^[19]

 

 

 

 

 

 

 

 

 

 

 

 

 

 La Plata dolphin range