(Lagenodelphis hosei)

 INFORMATION AND CHARACTERISTICS.

It is one of the most recently recognized cetaceans. The Fraser’s dolphin was scientifically described for the first time in 1956 Although the first specimen analyzed was in Borneo in 1895. During the first half of the twentieth century, the knowledge about this species came only from some bones until 1971 when scientist rediscovered the species thanks to the sighting of a live specimen in 1970.

The name of this dolphin is in honor of Francis Fraser, its discoverer in 1956.

Order: Cetacea
Family: Delphinidae
Genus: Lagenodelphis

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

This little-known dolphin is a medium-sized cetacean with a very distinctive appearance.

Weight and size.
The adult male is slightly larger than the female, so there is sexual dimorphism in the species. While females reach a maximum length of 2.6 meters, males can reach up to 2.7 meters in length. It weighs about 200 kilograms.

Morphology.
The Fraser’s dolphin body is robust and fusiform, with a postanal hump and a small beak. The pectoral flippers and the flukes of the caudal fin are triangular and pointy. The dorsal fin located in the middle of the dorsum is small, triangular and slightly curved.

Skin Coloration.
The color pattern of its body is unique to this species although it has a stripe that starts in the eyes and ends towards the anus present in other species. This band is very visible in young specimens, and it gets darker when the dolphin is older. It varies according to the habitat and the gender, and is similar to a raccoon “mask.”

The background color of the skin is bluish gray in the upper dorsal area and white or light pink in the lower ventral region.

Distinctive characteristics.
Along the lower jaw begins another light stripe that extends to the sides of the body.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

It has a pantropical distribution (tropical regions of all the continents). The Fraser’s dolphin dwells between the latitudes 30° north and 30° south in the Pacific, Atlantic, and Indian oceans but it reaches places outside of its range of distribution in Australia, France, Scotland, and Uruguay, perhaps due to climate change.

It is present in Australia, Thailand, China, Brazil, Costa Rica, Dominica, Ecuador, Senegal, Solomon Islands, Cape Verde, Taiwan, Venezuela, Argentina, Angola, Comoros Islands, Japan, Kiribati, Madagascar, South Africa, Spain, Costa Rica, Oman, Palau, French Polynesia, Panama, Micronesia, Philippines, Sri Lanka and Saint Vincent and the Grenadines.

It inhabits tropical and subtropical waters with depths greater than 1,000 meters in areas near the coasts, or areas of the continental shelf.

WHAT DO THEY EAT? DIET AND EATING HABITS.

Their diet is composed of mesopelagic fish, cuttlefish, squid and shrimp. It prefers to feed in deep areas (250-500 meters deep) and very rarely on the surface, so their food can also be benthic. It always looks for the biggest prey available.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

Both genders reach sexual maturity at about seven years of age, but possibly females can be mature a little earlier. This cetacean is polygamous, and the mothers can give birth once every two years.

Mating appears to occur during the summer months. There is no knowledge about possible courtship processes among the couple. The gestation period lasts between 10 and 12.5 months, after which the female gives birth in spring or summer to a single offspring that measures about 1 meter in length.

The life expectancy of this dolphin is approximately 16 or 17 years although in Japan an individual of 17 years and a half was found.

HOW DO THEY BEHAVE? BEHAVIOR.

It is a marine mammal that shows high sociability. The pods of this dolphin are made of 10 to 100 individuals, and sometimes they create larger groups up to 1,000 dolphins. They have no problem in associating with other species of dolphins or cetaceans, such as the melon-headed whale (Peponocephala electra) and the Short-finned pilot whale (Globicephala macrorhynchus). Seagulls can also associate with this dolphin to feed themselves.

The pods move fast, and a single Fraser’s dolphin swims in a manner described as “ostentatious” and “aggressive,” leaving a trail of foam in its wake. Pods seldom follow boats and may be timid and playful although in some areas they prove to be more accessible.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: “Least Concern.”

This species has a conservation status as “Least Concern” on the Red List of the International Union for the Conservation of Nature (IUCN). However, it continually faces the danger of bycatch. In the eastern Pacific Ocean, this dolphin often gets entangled in nets targeting tuna, but in regions near the Philippines, more than 800 dolphins are captured annually to use their meat or as bait for other species.

This dolphin does not have any known natural predator, but some think that killer whales and sharks can attack them, as in the case of other cetaceans.

Despite the threats, Fraser’s dolphins are still abundant in their range of distribution. There are no specific research or conservation strategies, but the species is in Appendix II of CITES, in the group of species which its commercial fishing requires control.

References

http://www.iucnredlist.org/details/11140/0

http://www.cms.int/reports/small_cetaceans/data/L_hosei/L_hosei.htm

http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/frasersdolphin.htm

https://en.wikipedia.org/wiki/Fraser%27s_dolphin

]]> https://www.dolphins-world.com/atlantic-white-sided-dolphin-lagenorhynchus-acutus/ Tue, 25 Apr 2017 20:02:06 +0000 http://www.dolphins-world.com/?p=2953 Photo by Anna. This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.

Lagenorhynchus acutus

INFORMATION AND CHARACTERISTICS.

The Atlantic white-sided dolphin is one of the six species of the genus Lagenorhynhus, which is well known to fishers and whalers of the North Atlantic ocean for many years. The word acutus in Latin means “sharpened,” a term referring to their sharp dorsal fin.

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

Morphology.
The Atlantic white-sided dolphin has a sturdy body with a thick, but very short snout and a wide tail. It has a curved and sickle-shaped dorsal fin that can reach up to 50 centimeters of height in the largest individuals. The long pectoral flippers protrude in the lower part of their body with a length of 30 cm. It has 30 to 40 pairs of pointed teeth in each row.

Order: Cetacea
Family: Delphinidae
Genus: Lagenorhynchus

Weight and size.
Females are significantly smaller than males. The latter can reach a length up to 3 meters, but their average length is between 2.5 and 2.8 meters. Females reach up to 2.7 meters, although their average length is between 1.9 and 2.5 meters. The weight of both genders is between 200-230 kilograms.

Skin Coloration.
This dolphin is one of the most colorful cetaceans alive. The Atlantic white-sided dolphin has a complex color pattern on its skin, characterized by featuring a black color on the dorsal area, both fins, and the flippers, and white color in the ventral and genital regions and part of the sides. It has a section of light gray skin from the eyes to the base of the tail and an ochre patch on both sides, over the black part of the dorsal area but near the tail. From the snout to the eyes it also has the dark color that extends in the form of a mask, but only in the upper jaw, as the lower jaw has the same light gray color than the ventral region.

Distinctive characteristics.
The main feature to distinguish this species from others is its coloring pattern and, in particular, the ochre patch on both sides near the tail.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

This dolphin is native to the North Atlantic Ocean, and its distribution only comprises the subpolar waters. Its habitat range starts from the region of New England (United States) in the west to France in the east reaching the north Greenland, Iceland, the British islands and all the Scandinavian peninsula. This species is common in the waters around the Hebridean islands, in the North Sea and the northern Islands of the Baltic Sea.

It inhabits open, temperate and cold waters of the platform and the continental slope in waters that have about 40-270 meters deep and temperatures of 6° to 20° Celsius. Also, it prefers habitats of low salinity.

WHAT DO THEY EAT? DIET AND EATING HABITS.

The Atlantic white-sided dolphin bases its diet on several species of fish and cephalopods as well as some species of crustaceans. In fact, their diet has variations because it depends on the geographic region where this cetacean dwell and the season of the year.

It shows a cooperative behavior to catch prey more efficiently and look for large schools of fish. It also associates occasionally with Fin whales (Balaenoptera physalus), Long-finned pilot whales (Globicephala melas) and humpback whales (Megaptera novaeangliae). But this dolphin does not hesitate to separate from its group if it has to feed more efficiently.

Their most common prey:

Fish
– Silver hake (Merluccius bilinearis).
– Atlantic mackerel (Scomber scombrus).
– Atlantic herring (Clupea harengus).
– Silvery pout (Gadiculus argenteus).
– Blue whiting (Micromesistius poutassou).

Cephalopods
– Northern shortfin squid (Illex iilecebrosus).

Crustaceans.
– Shrimp.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

The reproduction of this species is similar to that of other dolphins, with differences in the gestation period and the age of sexual maturity. The female reaches maturity between 6 and 12 years of age at an approximate length of 1.94-2.22 meters. For its part, the male reaches maturity between 7 and 11 years or 2.1-2.4 meters in length.

The details of courtship and mating are still unknown. The female gives birth to one offspring of 1.1 meters long approximately every two years, from May to August or from June to July after a gestation period of 10-11 months. The mother breastfeeds the calf for about 12-18 months.

HOW DO THEY BEHAVE? BEHAVIOR.

Lagenorhynchus acutus is a gregarious, sociable and playful species. It groups in pods of 30 to 50 individuals that can join with other groups to make superpods of 500 and up to a few thousand dolphins. In some remote parts of Canada, the groups are smaller, composed of 6-8 dolphins. This species can associate with bottlenose dolphins (Tursiops truncatus), and fin and humpback whales. In the North Sea associations of Atlantic white-sided dolphins with white-beaked dolphins (Lagenorhynchus albirostris) are sometimes formed.

In each pod, there may be division according to age and sex. One hypothesis indicates that smaller groups are formed to facilitate feeding tasks while large groups are created to travel. In fact, some believe that this dolphin performs seasonal movements heading south in the winter and north in the summer within its distribution range.

The Atlantic white-sided dolphins enjoy performing acrobatic jumps and frequently ride the bow waves of boats and splash their tails on the surface of the water.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation status: Least Concern (LC).

In earlier times the species was hunted in Norway, and at present, this happens in Canada, the Faroe Islands, and Greenland. For this reason, direct hunting is an important threat to the survival of this dolphin, although fortunately it still has large populations.

The primary threats to this species are:

– Direct hunting.
– Bycatch in fishing nets.
– Pollution of their habitat with chemicals.
– Climate change and its repercussions on the ocean conditions.
– Massive dolphin stranding.

The conservation status of this species on the Red List of the International Union for Conservation of Nature (IUCN) is “Least Concern.” In 2006, the National Marine Fisheries Service (NMFS) implemented the Atlantic Trawl Gear Take Reduction Team to reduce bycatch of several cetacean species, including the Atlantic white-sided dolphin.

References

http://www.iucnredlist.org/details/11141/0

http://www.fisheries.noaa.gov/pr/species/mammals/dolphins/atlantic-white-sided-dolphin.html

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009.

Sousa teuszii

INFORMATION AND CHARACTERISTICS.

The Atlantic humpback dolphin is a toothed cetacean native to, of course, waters of the Atlantic Ocean but whose populations are at least 2,000 kilometers apart from each other. This species is a close relative of the Chinese white dolphin (Sousa chinensis).

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

Morphology.
Sousa Teuszii is a robust dolphin, with a narrow and mid-sized snout and rounded head because of his big melon. It has a very pronounced hump on which it raises a broad and rounded dorsal fin. It has a wide caudal fin with a notch in the center.

Order: Cetacea
Family: Delphinidae
Genus: Sousa

Weight and size.
Males of the Atlantic Humpback Dolphin are larger than females, and the length of an adult is 1.8-2.6 meters. The weight is around 100-139 kilograms.

Skin Coloration.
The back and sides of the animal have a slate gray color while the belly is light gray.

Distinctive characteristics.
Undoubtedly, its most striking feature is the hump on the back on which the dorsal fin is.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

The Atlantic hunchback dolphin inhabits warm, tropical waters of the eastern part of this ocean, in the west coast of the African continent from Morocco to Angola.

It dwells in coastal and shallow waters about 2 kilometers from the coast, in bays, deltas, estuaries with mangroves, canals, and rivers within its range of distribution although it does not go upriver far from the ocean. It is not a river dolphin.

Despite its preference for shallow waters, it is possible that this dolphin stays around reefs to take shelter from predators and to swim along the seabed.

WHAT DO THEY EAT? DIET AND EATING HABITS.

This cetacean feed on fish, crustaceans, and cephalopods. Among their favorite prey are mullets, breams, herrings, sardines and squids.

Their feeding habits vary according to their habitat but usually coordinate with a pod to capture their prey. In Mauritania, it associates with local fishers to catch mullets, in Senegal it enters the brackish water channels when the tide rises and returns to the ocean when the tide get low. In any case, its echolocation plays a crucial role in the detection of their food.

HOW DO THEY BEHAVE? BEHAVIOR.

The behavior of this dolphin does not seem to have much in common with that of other curious and energetic dolphins. On the contrary, it is a slow-moving species that swim at about 5 miles per hour. During the day, it swims alone or in groups of 5 to 7 individuals, but the maximum number of members in a pod is around 25.

It is quite shy and does not intend to establish contact with humans, and it even avoids boats. It reaches the surface to breathe every minute but can be under the water for up to 3 consecutive minutes. It can perform acrobatic jumps, but it is not very common to see it doing it. It communicates by whistles and a kind of squealing.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

The Atlantic humpback dolphin is a polygamous animal that mates with multiple partners throughout its life. Most of the information on the reproductive habits of this dolphin are hypotheses created from their closest relatives, the other members of the genus Sousa.

It is unknown at what age they reach sexual maturity, but many individuals begin to reproduce between four and eight years of age. A specific mating season is unknown, although, due to the number of births between March and April and an apparent gestation period of 12 months, males and females breed during the summer months, as the Chinese white dolphin (Sousa Chinensis chinensis).

A female usually has one offspring which at birth, it has a length of approximately 1 meter and weighs between 9 and 11 kilograms. 24 to 48 months later the mother weans her calf, but they can stay together for more time. After 4 or 5 years, the calf separates from its mother and joins another pod of dolphins.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

The Atlantic humpback dolphin has a conservation status of “Vulnerable” in the Red List of the International Union for the Conservation of Nature (IUCN) as its coastal habitat, very close to human populations, makes this species prone to be affected by the Anthropogenic activities.

Conservation status: “Vulnerable.”

In its natural habitat, this dolphin only has to be aware of the orcas that can feed on them, but this cetacean usually shelters in coral reefs avoiding them. On the other hand, its greatest threats are those related to man, and are the following:

– Hunting.
In some parts of West Africa, native communities catch this dolphin for human consumption.

– Bycatch.
In the coastal waters of Senegal, Gambia and other African countries, populations of this species are already scarce, because for many years the entanglement in fishing nets has caused bycatch which still happens today.

– Reduced food availability.
Overfishing affects the availability and abundance of their usual prey, which can fragment the food chain.

– Destruction and degradation of their habitat.
The destruction of mangroves and the contamination of coastal waters directly affect the survival of this dolphin.

– Boat collisions.
As they dwell close to the coast and the marine traffic in their distribution range is high, they are continuously hit by boats and propellers causing life-threatening injuries.

CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) included the Atlantic humpback dolphin in Appendix I of the most endangered species, and therefore the organization prohibits commercial hunting of this dolphin.

References

Distribution, status, and biology of the Atlantic humpback dolphin, Sousa teuszii (Kükenthal, 1892)

http://www.iucnredlist.org/details/20425/0

http://animaldiversity.org/accounts/Sousa_teuszii/

http://www.fao.org/fishery/species/18237/en

(Stenella frontalis)

The Atlantic spotted dolphin is very long, with a size of about 7 ½ feet when fully mature. They can weigh from 240 to 360 with the males being much larger than the females. They develop unique spots all over their bodies as they get older. Young ones don’t have any spots and those that are mature may only have a handful. It is for this reason that the Atlantic spotted dolphin is often misidentified.

The top of their bodies are a dark gray or a dark black. Underneath it is a white or cream color. On the dark part of their bodies they will have white spots and on the whitish areas they will develop dark colored spots.

Distribution

The Atlantic spotted dolphin is only found in the ocean. They are known to live in a variety of locations including the oceans around the United States, Africa, Europe, the Bahamas, and the Gulf of Mexico. They have significantly increased in numbers in the Bahamas. There are now hundreds of them when only a couple of decades there were less than 100 there. It is estimated that there are more than 100,000 Atlantic spotted dolphins out there.

Some of them that live along the Gulf of Mexico do migrate annually. Others tend to move long distances each day but not out of a need to follow a migration pattern.

Behavior

They are excellent when it comes to communication. They use a variety of loud clicks and whistles to talk with each other. They form groups of about 50 and they are also known to move around with other species of dolphins without any conflicts among them. There is a hierarchy among these dolphins that depends upon many factors including their size, age, and gender.

They are extremely protective of their young and will help each other to care for them. They also tend to do their best to protect the pregnant females from enemies including sharks.

Diet and Feeding

Their main food sources include octopus and various types of small fish. Most of the time they will fish at night. They also tend to hunt in groups as they have a tactic that allows them to get their prey into a big circle. Then they are able to come at these schools of fish from all angles.

Reproduction

There isn’t too much known about the reproductive habits of these dolphins. It is estimated that it takes 11 months from mating to birth. They are born without any spots but about one year of age they begin to develop. It is along this same period of time that the mothers will stop offering milk to them.

Conservation

One of the biggest threats to the Atlantic spotted dolphin is the amount of pollution that is found in their natural environment. Many types of efforts have been initiated to help clean up these bodies of water. At the same time educating the public about not polluting has also helped to reduce it. Still, there is plenty more than has to be done in order to resolve the problem.

Human interaction

This particular species of dolphin is very timid. They have been known to come right up to humans that are visiting the areas of the Bahamas. This has become one of the main tourist attractions in that area.

Many of them are killed annually due to illegal hunting by fisherman. They want to reduce the number of them so they can produce more product in their fishing nets. Others are accidentally captured in those nets so they may drown or become severely injured.

References

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 54.

Jefferson, Webber, Pitman. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press, 2015.

http://www.iucnredlist.org/details/20732/0

http://www.cms.int/reports/small_cetaceans/data/S_frontalis/s_frontalis.htm