Striped Dolphin

(Stenella coeruleoalba)

INFORMATION AND CHARACTERISTICS.

The striped dolphin is among the most studied members of the Delphinidae family and is very abundant in the oceans. In 1833, the botanist Franz Meyen described the species and named it Delphinus Coeruleoalbus from the study of a specimen from Rio de la Plata.

Order: Cetacea
Family: Delphinidae
Genus: Stenella

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

There is a slight variation in the body of the populations of the striped dolphin, but it is only in the shape of the skeleton and not the external appearance.

Morphology.
Its fusiform body is robust but able to perform graceful movements. It has a narrow, long and prominent snout, a rounded forehead because of the pronounced melon, long and narrow pectoral flippers and a curved dorsal fin located in the center of the dorsal area.

Weight and size.
It is a medium-sized dolphin. The adult male has a length of 2.6 meters and a weight of 160 kilograms. The female measures up to 2.4 meters and weighs about 150 kg.

Skin Coloration.
The dorsal region is blue or blue-gray, and the lower ventral area is lighter blending from light gray to whitish. There is a pattern of dark stripes extending from the eyes to the flippers and another set that begin near the eyes and end in the anus. On the sides, there is an area of light skin before the start of the caudal fin, but the pectoral flippers are dark.

Distinctive characteristics.
The easiest way to recognize a striped dolphin is observing the coloring pattern of its body.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

This dolphin inhabits the temperate and tropical waters of the Atlantic, Pacific, and Indian Oceans, the Mediterranean Sea, the Caribbean Sea, the Black Sea and the Gulf of Mexico. Its distribution range is between latitudes 50° north and 50° south. It dwells in waters of the United States, Belize, Mexico, China, Costa Rica, Australia, Brazil, Dominican Republic, Guatemala, India, Indonesia, France, Senegal, Uruguay, Philippines, Sri Lanka, Portugal, Qatar, Greenland, French Polynesia, Mozambique, New Zealand, Barbados, Cuba, Germany and many others.

Its habitats are waters with temperatures ranging from 10° to 26° Celsius degrees but tend to avoid waters that are less than 20° Celsius. Commonly it thrives in areas of upwelling and convergence. It is a dolphin mainly pelagic.

WHAT DO THEY EAT? DIET AND EATING HABITS.

The diet of the striped dolphin is not the same in all the regions where it lives. It is a carnivorous animal that feeds mainly on bony fish, cephalopods, and crustaceans. The prey of this dolphin is small animals, measuring 6 to 30 centimeters in length.

The population of the Mediterranean Sea consumes almost entirely cephalopods, octopus, and squid. Those living off the coasts of Japan and South Africa prefer to eat lanternfish (Myctophidae family), and in the northeastern Atlantic, the diet of striped dolphins is 56 percent cephalopods, 39 percent fish, and 5 percent crustaceans. Again, lanternfish are the favorites of this population, but the cod fish is also appreciated.

It has an opportunistic feeding style and can look for its food in any area of ​​the water column. If necessary, it submerges to depths of 200 to 700 meters. The decomposition of the food found in the stomach of some specimens studied suggests that these dolphins wait for the sunset or the early night to carry out their feeding activities.

HOW DO THEY BEHAVE? BEHAVIOR

The striped dolphin groups in pods of 100 to 500 individuals organized by age, gender and reproduction status. However, sometimes they form larger groups with thousands of dolphins.

The division in the society of these dolphins is in groups of young individuals, adults in breeding age, and non-breeding adults. The association with other species of dolphins or animals is rare.

It is a very active, energetic and extremely agile dolphin. It can jump out of the water, ride the bow waves of boats, spin in the air and perform a particular movement that consists of jumping quickly and turning several times in the air before diving back into the ocean. On the other hand, its capacity of communication is similar to the one of other dolphins, based on the emission of clicks, squeals, and whistles.

The striped dolphin performs some seasonal travels related to warm ocean currents, with differences between populations. For example, the dolphins of the Mediterranean Sea move north as soon as they feel that the temperature of the ocean begins to rise.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

Females reach sexual maturity at the age of five, but this can extend until they reach 13. In the case of the males, sexual maturity occurs between 7 and 15 years.

Mating seasons differ between regions. The dolphins living in the Mediterranean sea commonly mate during the fall; While populations dwelling in the Northwest Pacific breed during the winter months. A female has offspring every four years, but this is only an estimate and may be less or more time.

The gestation period of a striped dolphin lasts between 12 and 13 months, after which a single offspring is born, measuring between 90 and 100 centimeters. Summer and fall are the seasons with more births. The caring mother, nurses its calf for 12 -13 months.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: Least Concern.

The striped dolphin is the target of some fisheries that seek to get their meat or keep them away from the boats, as the cetacean can approach to “steal” fish. Japan is the country with the largest direct catches, with numbers ranging from 600 to 800. In the Mediterranean Sea, the number of dolphins captured is lower. In this case, they hunt these dolphins for human consumption.

Another threat is bycatch in several parts of the world. The problem is that some fishing is illegal and there are not records of all deaths. In the western Pacific Ocean, the deaths of dolphins trapped are numerous: from 2,000 to 4,000 individuals.

Overfishing, contamination of their habitat and noise pollution complete the range of threats. Nevertheless, it is on the Red List of the International Union for the Conservation of Nature (IUCN) as “Least Concern.”

In the United Kingdom, the striped dolphin is under the protection of the UK Biodiversity Action Plan and the Wildlife and Countryside Act of 1981. Also, it is in the Agreement on the Conservation of Small Cetaceans in the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS).

References

http://www.iucnredlist.org/details/20731/0

http://www.cms.int/reports/small_cetaceans/data/S_ceoruleoalba/s_coeruleoalba.htm

Jefferson, Webber, Pitman. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press, 2015. Page 261.

http://www.fao.org/fishery/species/3596/en

]]> https://www.dolphins-world.com/atlantic-humpback-dolphin-sousa-teuszii/ Tue, 25 Apr 2017 17:37:03 +0000 http://www.dolphins-world.com/?p=2947 Photo by Greg Schechter from San Francisco, USA. This file is licensed under the Creative Commons Attribution 2.0 Generic license.

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