The dusky dolphin is a small cetacean that belongs to the Delphinidae family and the genus Lagenorhynchus, which also includes other five species.

It has a distribution limited to the southern hemisphere of the planet, with subpopulations scattered throughout the southeast and southwest Atlantic and Pacific oceans, including waters of Tasmania, southern Australia, New Zealand, the Chatham and Campbell Islands, South America and the Falkland Islands.

It also dwells around oceanic islands such as Tristan da Cunha, a British archipelago in the South Atlantic. Some of the countries that have dusky dolphins in their waters are Australia, Argentina, Chile, New Zealand, Peru and South Africa.

They sometimes stay close to bottlenose dolphins, but there is no evidence of interaction between the two species, unlike Risso dolphins, with whom they share feeding areas or with common dolphins that show some social contact.

This dolphin stays close to the coast, but unlike others, the coasts where they inhabit do not have warm waters. It is common to observe this cetacean on continental platforms and slopes where the waters are cold, and the currents have low temperatures, more or less of 10 to 18 Celsius degrees. The observed range of this species suggests that it limits to depths less than 200 meters and about 200 nautical miles away from the coast.

Its range of distribution goes hand in hand with the habitat that can provide them a great abundance of prey, among which is the anchovy that is found very close to the surface in shallow waters, and benthic creatures such as squids, hake and various types of fishes.

The cold habitat in which it lives does not deter humans from harming this species. Years ago, its capture was very constant in New Zealand, Peru and Chile mainly. Now, this has diminished, but its population situation, and therefore, its current state of conservation, is unknown.

Bottlenose dolphins are present in most oceans and seas of the world and adapt quickly to several types of habitat.

Their thermoregulation capacity allows them to live in waters ranging from 10 to 32 degrees Celsius, which includes temperate, tropical and subtropical areas of the Pacific, Atlantic, Indian Ocean, as well as the Mediterranean Sea and the Black Sea between Europe and Asia. The regions that avoid are the polar zones, but some individuals move through the north of Europe, whose waters have low temperatures.

In the Pacific, their distribution range is from northern Japan to Australia and from southern California to Chile in the eastern Pacific Ocean including all the vast area in the middle.

In the Atlantic ocean, they dwell from Nova Scotia to Patagonia in the West and from Norway to South Africa in the East including all the eastern coast of the United States, and the Gulf of Mexico.

Bottlenose dolphin habitat includes bays, open waters, coastal areas, lagoons, estuaries, tidal areas and shallow areas. They even venture occasionally into some rivers.

The other bottlenose species, the Indo-Pacific bottlenose dolphin, is also distributed in tropical and subtropical areas in specific regions of the ocean. This dolphin inhabits from western South Africa to Japan, including eastern and western Australia and places such as the Red Sea, Persian Gulf, Solomon Islands and the Indo-Malay archipelago.

The Indo-Pacific dolphin lives near the coasts of continental shelves, at depths of less than 300 meters and around oceanic islands. It frequently visits estuaries and coral reefs where fish banks thrive, and a significant amount of cephalopods live. Therefore it tolerates salt water and brackish waters.

In the vast ocean, all creatures are vulnerable. Bottlenose dolphins are cetaceans that rarely become prey, thanks to their size, their intelligence, the use of echolocation and their level of socialization that gives them a significant advantage by staying in groups and intimidating their opponent. However, two predators will take the smallest opportunities to feed on dolphins: killer whales and sharks.

We know that the killer whales are expert hunters, especially when they hunt in organized groups. Although there are few documented cases, these animals that are the world’s largest dolphins, attack other species of smaller dolphins, mainly young, newborn or sick. To do it they separate the mother from the calf, making impossible to the latter defend its offspring.

However, a group of orcas does not feel intimidated by a large pod of dolphins. Although there are no records of this kind of attack to bottlenose dolphins, there are videos where a pod of killer whales approaches aggressively to groups of dolphins of other species, and as if they were seals, they beat them and throw them into the air until they are stunned and finally feed on them. Several types of dolphins suffer this kind of aggression, and the bottlenose dolphins are likely part of this list.

Regarding sharks, the most dangerous species for members of the genus Tursiops are the largest: tiger shark, sand shark, bull shark and, of course, the great white shark. It is not uncommon to observe dolphins with scars from shark attacks, which means they are not easy prey and their escape techniques often help them survive.

A study conducted in Shark Bay, Western Australia, revealed that 95 of 128 bottlenose dolphins analyzed showed scars from shark bites, mostly from tiger sharks. The frequency of new body marks and the high attack rates suggest that bottlenose dolphins are at risk in this locality more than in other parts of the world.

A few cases with rays are known. Although they are not dolphin predators because they have a diet based on small fish, mollusks, and plankton, the trauma and infections they cause with the sharp edges of their tail sometimes become deadly.

An ecological niche is a role or way of life that an organism takes within its habitat and how it adapts to meet its basic needs to survive and proliferate, through a set of conditions, resources, and interactions with others.

Two organisms can not have the same niche, as they would compete for the same resources, which would cause only the strongest to survive, leading its opponent to extinction. In nature, although there are some species whose niches overlap, they have different options that make them easier to satisfy their daily requirements.

In this sense, the niche of Orcas is quite variable. The extensive distribution of this species makes that its populations have different cultures that have evolved according to their environment. Some even think that new unidentified subspecies are wandering in the oceans right now.

The niche of these cetaceans differs more clearly in their diet. For example, North Pacific killer whales that live south of Alaska, Washington, and British Columbia and are known as residents rely on fish and squid. In contrast, orcas called transients and whose range of distribution overlaps with residents, but without interbreeding, have a diet that is based primarily on marine mammals.

The interesting thing about killer whales is that they are not limited by salinity, temperature or depth since they have the capacity to move through waters of different latitudes, the open sea or reach coastal areas with depths of only a few meters.

The five ecotypes of Antarctic killer whales and three of Pacific killer whales differ considerably in diet habits, habitat, behavior, and social structure. Therefore their niche entirely depends on the ecotype.

Indeed dolphins and all cetaceans like whales and porpoises evolved from animals that lived, reproduced and died on land. In fact, their closest relative alive is the hippopotamus, which in turn also relates them to the artiodactyls.

The common ancestor of dolphins and hippos is an animal called Pakicetus that roamed the Earth about 50 million years ago. Pakicetus had a four-leg functional anatomy, elongated snout, flexible neck and a very long tail, morphology that laid the foundation for the subsequent appearance of cetaceans.

Millions of years later, creatures like Ambulocetus and Kutchicetus emerged with body characteristics increasingly adapted to the marine world.

While the former is the commonly accepted theory, others suggest that cetaceans descend from the Mesonikia, prehistoric animals that lived on Earth about 55 million years ago. Its appearance was similar to that of a tiger, and the evolutionary change began while searching for food in the disappeared sea of ​​Thetis.

The explanations about the evolution of dolphins are:

One. The scarcity of food on land forced some coastal populations to venture into the ocean for food, which gradually adapted their anatomy to their new habitat.

Two. The other theory has to do with the climatic changes of the era, which forced them to enter the water to get a convenient place with satisfactory temperature and abundant food.

Visible evidence.

Several indicators confirm that dolphins evolved from terrestrial animals, and these are the most evident:

1. They have a robust bone structure rather than a cartilaginous skeleton like sharks or fish.

2. They are mammals because they feed their young with breast milk from the mother.

3. Dolphins breathe air like us. They can not breathe underwater like fish because they have lungs instead of gills.

4. Dolphins have vestigial bones that once were legs and pelvic bones where they were attached.

5. These cetaceans are warm-blooded.

Even that some scientists still debate about the dolphin ancestors and their relation with other species, there are enough probes to confirm that these cetaceans undoubtedly descend from terrestrial animals.

INFORMATION AND CHARACTERISTICS.

Although the common and scientific name of this toothed cetacean refers to the white color of its snout, they may or may not have the beak of this color.

The white-beaked dolphin is the largest member of the genus Lagenorhynchus, and it was one of the first dolphins of this genus to be scientifically recognized, back in 1846.

Order: Cetacea
Family: Delphinidae
Genus: Lagenorhynchus

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

Morphology.
It has a sturdy body, a short and thick beak and a narrow tail. It has a big and sickle-shaped dorsal fin just in the middle of its body.

Weight and size.
Adult individuals measure between 2.3 and 3.1 meters in length and weigh 180 to 354 kilograms. Males are slightly larger than females.

Skin Coloration.
It has a black or dark gray dorsal area. The sides usually have lighter stripes with different shades of light gray almost white. Its beak may exhibit a whitish color, but it can also be gray and even black.

Distinctive characteristics.
It has a white patch that starts just behind the dorsal fin and ends before the tail flukes.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

The white-beaked dolphin inhabits the waters of the North Atlantic Ocean. In the western part of this ocean it dwells from the Strait of Davis to the south of Cape Cod (Massachusetts, United States) passing through the center and the west of Greenland; In the east of the ocean is distributed from Iceland to Portugal but in the north reaching as east as the Scandinavian peninsula. Its locations include the Barents Sea, the Baltic Sea, Ireland, Canada, the Irish Sea and the United Kingdom. It also resides in the west of the Mediterranean Sea.

It inhabits the cold subpolar waters of its distribution zone, in the continental shelf, along with the edge of this and in coastal waters; Mainly in waters whose depth does not exceed 200 meters.

WHAT DO THEY EAT? DIET AND EATING HABITS.

It feeds on a large variety of mesopelagic fish mainly those that group in schools, like the capelin, haddock, hake, herring and cod. It also consumes crustaceans and cephalopods (octopus and squid), like most dolphins.

This species performs hunting techniques cooperatively on the surface of the ocean. It sometimes associates with humpback whales (Megaptera novaeangliae), Fin whales (Balaenoptera physalus) and other dolphins, including those of the species Tursiops truncatus (bottlenose dolphin).

HOW DO THEY BEHAVE? BEHAVIOR

The White-beaked dolphins create social groups composed of 5 to 50 individuals (generally less than 30), but they occasionally form larger groups of up to 1,500 dolphins. There is little information on the social structure of this species, but the separation by age and sex can occur. They sometimes mix and associate with large species like fin whales and humpback whales, and other small cetaceans, especially in the feeding areas (Reeves et al. 2002). These gregarious dolphins often perform acrobatic jumps on the surface and frequently approach ships to ride the bow waves.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

The white-beaked dolphin reaches sexual maturity when it is between 7 and 13 years old or when they grow to a length of 2.4-2.5 meters. The gestation period lasts about 11 or 12 months. Subsequently, a single offspring is born in the summer (months of May to September) measuring about 1.1-1.2 meters long.

Additional information on the reproduction of this species is so far unknown.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: “Least Concern.”

This species has been and still is hunted in the waters of the Faroe Islands, Iceland, Norway and Greenland, and even in Canada off the coast of Newfoundland, to obtain its oil and meat. Also, they are affected by the contamination of their habitats with heavy metals and organochlorines.

It is under protection by the ASCOBANS (Agreement on the Conservation of Small Cetaceans in the Baltic, North East Atlantic, Irish and North Seas) and in the Red List of the International Union for the Conservation of Nature, it appears as a species with a conservation status of “Least Concern.”

References

Jefferson, Webber, Pitman. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press, 2015. Page 282.

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 1255.

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

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

Sotalia fluviatilis

INFORMATION AND CHARACTERISTICS.

The unique name of this cetacean is pronounced “tucushi” and comes from the Tupi language, typical of South America. It is also known as gray bufeo and black bufeo in the area.

This little-known species is physically similar to the bottlenose dolphin (Tursiops truncatus) except for its size and other minor details. It is found in fresh and salty waters but is not genetically related to the South American river dolphins. Described initially in 1853, the Tucuxi is a small dolphin.

Order: Cetacea
Family: Delphinidae
Genus: Sotalia

The author of the image: Archilider.

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

Morphology.
The shape of its body is similar to that of the bottlenose dolphin as it is fusiform and slightly robust. It has a triangular dorsal fin slightly hooked. Its snout is long, very pronounced and narrow. Its pectoral flippers are large.

Weight and size.
It is one of the smallest cetaceans of the Delphinidae family, and there is no presence of sexual dimorphism. Adults have an average length of 2.1-2.2 meters and a weight of 35 to 55 kilograms. Individuals living in freshwater have a shorter length, estimated at 1.5 meters.

Skin Coloration.
The color of its dorsal skin varies being either bluish, gray or dark brown. The lower part of its body is white, light gray or pink and the sides are a shade between the dorsal and ventral colors. It has a dark strip blended between the snout and each of the pectoral flippers. Some populations have yellow stripes on the sides and a clear spot on the dorsal fin.

Distinctive characteristics.
Most specimens have a white patch on the tip of the snout.
There are two ecotypes of this species, one living in ocean waters of the Atlantic Ocean and another dwelling in the Amazon and Orinoco Rivers.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

The Tucuxi is a species endemic to South American waters; the tucuxi inhabits waters of Brazil, Panama, Peru, Ecuador, Colombia, Nicaragua, Venezuela and probably Honduras. Its distribution range starts from this last country or Panama and runs along the east South American coasts ending in southern Brazil.

There are two ecotypes of this species, one living in the waters of the Atlantic Ocean and other that dwells in the Amazon and Orinoco rivers. Those who live in the ocean stay near the coasts, in estuaries, and bays. The freshwater ecotype, inhabit the channels of the rivers mentioned above reaching upriver up to 2,500 kilometers in the Amazon and 250 kilometers in the Orinoco.

WHAT DO THEY EAT? DIET AND EATING HABITS.

The tucuxi is a carnivorous dolphin. It submerges for about 30 seconds to search for food, and they frequent the confluence areas because it is a zone suitable for the development of species such as plankton which in turn attracts many species of fish. Therefore, this dolphin usually goes to the confluences of bodies of water, but it also goes to places near the coasts.

Ray-finned fishes (Actinopterygii class), octopuses, squids, and shrimps are the main part of its diet. If they are in the open ocean, they prefer to feed on small fishes grouped in schools, and near the coasts, they prefer to catch pelagic or demersal fishes and cephalopods.

The tucuxi living in the Amazon consume around 28 species of fish, and within this set, they prefer those that belong to the family Curimatidae, because they represent 52 percent of their total diet.

HOW DO THEY BEHAVE? BEHAVIOR

It is considered a shy dolphin which never get close to boats or people and whose swimming is slow, but this does not mean that is “not active.” On the contrary, it spends most of the day doing activities, and its leaps out of the water are impressive. It can leap up to 1 meter out of the water and executes jumps, tumbles and blows with its pectoral flippers and the tail either alone or in coordination with other members of its pod. The only thing they do not do is riding the bow waves of boats, which is evident, as they do not come close to them.

This dolphin has a social structure based on small groups containing 2 to 6 members. In most cases, the pod is made up of 9-20 individuals for the ecotype living in freshwater and up to 50 members for those dwelling in the coastal waters of the Atlantic. Occasionally the pods associate with other species of dolphins, such as the Amazon pink dolphin (Inia geoffrensis). In any case, it seems that the adult males dominate the pods and they are the ones followed by other members.

The flood season is perfect for swimming through small tributaries, but they do not dare to leave the main river channels and enter into flooded forests. On the other hand, they communicate through whistles and clicks. Their sounds are higher than those of other dolphins, and they produce them while feeding, perhaps to call their peers.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

Researchers believe that the females of this species mate with several males in the same breeding period (polyandry). The courtship includes an aggressive behavior of males.

Both genders reach sexual maturity at six years of age. The gestation period lasts between ten and twelve months, and the calf is born at some point in the autumn. The offspring can have a length from 71 to 106 centimeters.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation status: Data Deficient.

The tucuxi has a conservation status of “Data Deficient” in the Red List of the International Union for the Conservation of Nature (IUCN). The size of the total population is unknown, but it is true that it is vulnerable to the effects of human activities such as:

– Bycatch.
– Direct hunting.
– Prey Overfishing.
– Habitat Contamination.
– Acoustic pollution.
– Boat collisions.
– Construction of dams that reduce and segment their distribution.

This dolphin is in Appendix II of the CMS (Convention on Migratory Species) for animals in need of conservation agreements and in Appendix I of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora), which contains species with a higher danger of extinction and whose trade is prohibited. Also, the International Whaling Commission (IWC) initiated a plan called Project Sotalia with the aim of studying this species thoroughly.

References

http://www.iucnredlist.org/details/190871/0

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 1188.

http://animaldiversity.org/accounts/Sotalia_fluviatilis/

http://www.arkive.org/tucuxi-dolphin/sotalia-fluviatilis/

INFORMATION AND CHARACTERISTICS.

This dolphin is one of two species of the genus Lissodelphis. It is a toothed cetacean found only in the southern hemisphere. Bernard Germain de LacépèdeIt described this species in 1804 based on a specimen he saw near the island of Tasmania.

PHYSICAL DESCRIPTION.

Morphology.
This dolphin has the thinnest body of all cetaceans. Its body, incredibly hydrodynamic, is similar to the one of the northern right whale dolphin (Lissodelphis borealis) with a slender shape, a short snout and lacking the dorsal fin. It has a tilted forehead instead of rounded like most species and pectoral flippers with a sickle shape.

Weight and size.
The adult dolphin measures 1.8-2.9 meters in length and weighs between 60 and 100 kilograms. The sexual dimorphism is very slight, being the male bigger than the female.

Order: Cetacea
Family: Delphinidae
Genus: Lissodelphis

Skin Coloration.
The body of this cetacean is bicolor. The dorsal area is black from the forehead to the tail lobes. The white color starts from the snout and continues to the belly and up to the middle of both sides. The pectoral flippers are usually gray, and some individuals exhibit small white patches on the head.

Distinctive characteristics.
Their coloring pattern and the lack of dorsal fin are the main distinguishing features. There may be confusion with the northern right whale dolphin because they have a similar appearance, but the difference between them lies in the fact that the sides of this dolphin are entirely black, and the snout is not white as the southern species. Besides, the distribution area of each species is far from each other.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

It has a circumpolar distribution only in waters of the southern hemisphere, between the Antarctic Convergence and the Subtropical Convergence. Its limits are between latitudes 30° south and 65° south, being the north of Peru the northmost limit of its distribution.

It is present in countries such as Australia, Chile, Argentina, New Zealand, Uruguay, South Africa, Mozambique, and Peru.

It is a pelagic dolphin that prefers high seas and only approaches the coasts if the waters are deep on the edge of the continental shelf. The temperatures of their cold habitats range between 1° and 20° Celsius degrees.

WHAT DO THEY EAT? DIET AND EATING HABITS.

Studies of the stomach of specimens of this species report a carnivorous diet in which mesopelagic fish, crustaceans, and cephalopods have preponderance. Their preys commonly inhabit depths between 200 and 1,000 meters.

Given its thin and hydrodynamic body, most scientists think that this dolphin is quick and agile to capture its prey, but if it feeds on the surface or in lower layers of the water column, it is still unknown.

Some of its favorite prey are lanternfish (Myctophidae), bigeye tuna (Thunnus obesus), squid, shrimp and species of the family Euphausiacea, which includes several species of krill.

HOW DO THEY BEHAVE? BEHAVIOR

It is a highly gregarious species which the creation of pods influence its social and individual behavior. A pod of Lissodephis peronii is usually composed of more than 100 members and may have up to 1,000 members. However, the average number of dolphins in a group is around two hundred.

If a dolphin is alone without company, it shows a relative shyness and avoids the ships. On the other hand, if a dolphin is with its pod, it shows more activity and dynamism. They can jump and hit the water with their belly or tail and create disturbances on the surface of the ocean due to the massive number of individuals in the pods.

Pods usually submerge for more than 6 minutes, but a single dolphin only dives for a very short time, so it tends to surface every 10 seconds or so. When swimming slowly, it only keeps the spiracle and part of the head out of the water; this is usually done while resting or during periods of low activity.

To date, there is no significant data on the existence of migration patterns, although it is likely that during the spring and summer they move northwards.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

There is a lack of information about most of the breeding habits of the southern right whale dolphin, but research suggests that males reach sexual maturity when they have a length of 2.51 meters and females are sexually mature with an approximate length of 2.18-2.28 meters.

The birth season is not known although in winter and spring more calves are seen, so perhaps the births occur around those seasons.

A calf can measure 0.86 meters in length and weigh about 5 kilograms at birth. Its longevity is approximately 42 years in the wild.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: Data Deficient.

It is true that there are more doubts than confirmed facts about this species. In fact, not even the International Union for Conservation of Nature (IUCN) has sufficient data to assess its conservation status which has a “Data deficient” classification due to the lack of information about the species.

However, this does not mean that the southern right whale dolphin is out of danger as this species has several threats, most of them derived from human activities. In Peru and Chile they have been caught for consumption, and in other regions, bycatch is common when these cetaceans become entangled in gillnets, particularly those trying to catch swordfish.

There are no specific conservation efforts for the Southern right whale Dolphin yet, but CITES has included it in Appendix II of endangered species where this organization lists the animals whose commercial trade must follow strict regulations.

References

Jefferson, Webber, Pitman. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press, 2015. Page 306.

http://www.iucnredlist.org/details/12126/0

http://www.cms.int/reports/small_cetaceans/data/L_peronii/l_perronii.htm

http://www.fao.org/fishery/species/18218/en

INFORMATION AND CHARACTERISTICS.

Delphinus delphis is probably one of the most common species of dolphin, and it has a broad distribution around the world. The naturalist Carlos Linnaeus was the first person to describe this short-beaked cetacean in 1758. It is probably the most abundant dolphin on the ocean.

Order: Cetacea
Family: Delphinidae
Genre: Delphinus

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

It is a medium-sized dolphin, similar to other common dolphin species.

Weight and size.
The sexual dimorphism is slight since males are larger and heavier than females. The average length is 1.52-1.82 meters, and the weight is 100-136 kilograms.

Morphology.
Its fusiform body has a long snout (even though is shorter than that of the Delphinus capensis) and a rounded melon. The Short-beaked common dolphin has a dorsal fin almost triangular, with a curved inclination. The pectoral flippers and the flukes of their caudal fin are small.

Skin Coloration.
Its coloring pattern features a dark dorsal area and a white ventral region. From the end of the beak starts a layer of dark color that extends toward the dorsal fin and the sides, forming a “V.” From the lower jaw to the flippers, there is a narrow black stripe, and a dark patch is around the eyes. Along the sides, there is a thick band of light color that does not become white.

Distinctive characteristics.
The shape of the coloring pattern is its most distinctive sign. To distinguish it from Delphinus capensis, which is very similar, the size of the beak is the main feature that makes them different.

> Short-beaked common dolphin characteristics.
> Short-beaked common dolphin – Delphinus delphis.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

This dolphin inhabits all tropical, subtropical and warm seas of the world, especially in the Pacific and Atlantic oceans. In the south of Australia. In the western Atlantic it extends from Newfoundland to Florida in the United States; From Norway to West Africa in the eastern Atlantic, from Canada to Chile in the eastern Pacific Ocean; In the central region of this ocean and around New Caledonia, New Zealand and Tasmania. It has a presence in a few closed seas: the Sea of ​​Japan, the Sea of ​​Ojotsk (Asia) and the Black Sea.

It inhabits coastal areas or the high sea as long as the water temperature is 10 to 28° Celsius. It dwells along the continental slope, in waters with depths ranging from 200 to 2,000 meters and has a preference for the marine areas where the upwelling occurs and for the seamounts and escarpments.

WHAT DO THEY EAT? DIET AND EATING HABITS.

Small fish such as herring, sardines, hake, and anchovy are an important part of their diet, also cephalopods which include octopus and squid. They consume crustaceans to a lesser extent. In total, an adult dolphin consumes more than 8 kilograms of food per day.

It feeds mostly at night, and it has cooperative hunting strategies. When a group of dolphins is looking for food, each member submerges for up to 8 minutes to detect prey. If they are successful and find a school of fish or any other prey, they can perform two hunting strategies:

1.- Individually, these dolphins approach the center of the school of fish and chase them. Before the prey escapes, they catch it.

2.- Dolphins dive towards a school of fish chasing them to guide them towards the surface of the water. They prefer to feed at night because they wait for the prey that migrates to the surface every night.

The whole hunting process takes about 1 hour, and they can submerge up to 200 meters deep during the process.

HOW DO THEY BEHAVE? BEHAVIOR

It is very rare to find a Short-beaked common dolphin alone. These dolphins are very social which can be seen in all their daily activities like eating, traveling and even breathing. The pods are very numerous and are composed of 10 to 500 individuals but, as in other species, they usually associate with other pods forming large temporal groups of thousands of dolphins. Its association with other species of cetaceans like the pilot whales (Genus Globicephala) is also common.

This species is a perfect example of a playful dolphin. It jumps, hits the water with its flippers, and spin in the air for several hours. Without a doubt, their favorite game is to ride the bow waves of boats. Its swimming speed reaches up to 60 kilometers per hour.

Short-beaked common dolphin – Delphinus delphis.

It shows great empathy for its peers. When a member of the pod is sick or injured, another dolphin helps him to float and breathe, a fact that demonstrates their capacity for bonding. This dolphin can remember its mates even though it has been a long time since they separated and experiences joy and excitement. In the same way, if one dies or separates, it shows sadness.

Individuals in some regions migrate seasonally in a process induced by the temperature increase of the surface water.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

An unusual fact about the reproduction of this dolphin is that, although it is usual to have only one offspring, there are some cases of births with 2 and up to 3 dolphins, when in other species this happens much less frequently.

Males reach sexual maturity between 12 and 15 years of age, but females are mature when they reach 85 percent of their final size and if they have ovulated at least once in their lifetime. But the sexual maturity and the interval of births vary considerably among populations since in some parts these dolphins reach maturity at 2.7 years; In the eastern Pacific Ocean females give birth every three years, but in the Black Sea they can do it every year.

Their sexual habits are not only for reproduction. They can participate in activities that provide pleasure for themselves or their peers. During spring and autumn, males begin to courtship females with actions involving physical contact and approach, then both mate. Females have a gestation period of 10-12 months.

From the moment of its birth, the offspring is of vital importance for the mother and the pod; It swims next to its mother and separates just a few feet from it as it grows. Weaning occurs when offspring are between 5 and 19 months of age.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: “Least Concern.”

By-catch with longlines, gillnets, and trawls constitutes the greatest threat to the survival of this species. In Asia and areas of the Mediterranean Sea, is hunted for human consumption to prepare some little-known dishes, but also for its oil. Additionally, the chemical contamination and the human disturbance of their habitat are also important factors, although fortunately the species still has a conservation status of “Least Concern” on the Red List of the International Union for Conservation of Nature.

The species has the safeguard of the Marine Mammal Protection Act of 1972. In the United Kingdom, killing cetaceans is banned by the law. Seven European countries signed the Agreement on the Conservation of Small Cetaceans in the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS). Also, there are plans to create protected areas for this dolphin and to control the pollution of its habitat.

References

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 255.

Mammals in the Seas: Small cetaceans, seals, sirenians and otters. Food & Agriculture Org., 1978.

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

http://www.iucnredlist.org/details/6336/0