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.

What does this have to do with the dolphins in the wild? Well, thinking that dolphins are non-human people means to consider them beings with rights protected by the laws in a similar way to humans, that is, they must be treated as equals and not as inferiors, which questions their capture and slaughter, as it should be considered murder. In this way, the captivity of dolphins ideally would be reduced.

Ethics as a philosophy prizes the right of people’s freedom and this should be the same in the Animal Kingdom, but it has not been so, and many dolphins have spent their lives, sometimes their whole, living in harsh conditions and without the possibility to experience the freedom of their species.

Life in captivity is not as fun as it seems in dolphinariums.

While even the best aquariums restrain freedom, we have to be aware that not all places that keep dolphins have the best conditions for them. In general, life in captivity is not as fun as it seems in top notch dolphinariums. In fact, there are some differences between dolphins living in those facilities and dolphins in the wild. These discrepancies seem to be always better for free dolphins which make us think that all animals are born free, and although humans use them for various purposes, usually with an ulterior economic end, life in the wild is ideal for them because:

To start with the most evident, free dolphins have hundreds of miles to swim in the ocean, explore and live for a long time. Captive dolphins have ponds or water bodies of several meters, which they can not leave unless their holders decide otherwise, very much like a prison. What about those dolphins that instinctively perform migrations?

Free dolphins born, grow, reproduce and die according to their nature and instincts. Captive dolphins are forced to do several things, for example, they may be induced to mate, to consume a certain food or behave in a particular way.

Free Dolphins retain their physical characteristics unless they are injured, but in captivity, they exhibit an atrophied dorsal fin, that is, it bends downward, perhaps because they spend only 20 percent of their time underwater compared to the 80 percent of the time that free individuals spend.

Normally dolphins have a relatively long life in their natural habitat, but in captivity, both the longevity and the chances of survival reduce. These cetaceans may die during their capture or their transfer as a result of an inadequate supervision of the transport structures or as a result of accidents. In general, captive dolphins live fewer years than their free counterparts.

Dolphins Swimming in the Ocean.

Although dolphins can resist the transportation, their anatomy is not designed to withstand the weight of their body caused by gravity on land. Internal organs or bones like the rib cage can get damaged by carrying them out of the water.

There is no certainty about the proper treatment of captive dolphins unless specific investigations are performed. Therefore, it all depends on the conscious of the people who capture them. While not all are ruthless, we know the where money is involved, some people sacrifice the security and comfort of the dolphins to get higher profits.

Some people argue that in captivity dolphins are safe from predators such as killer whales and sharks, that they have guaranteed food every day and that they have the medical attention of professional veterinarians in case of injury or illness. However, we must not forget that they are animals perfectly adapted to the aquatic life and all that this entails, like the large space in the ocean, the diversity of food and the chance of socializing.

The social life of dolphins and the tight bonds between them is also a major concern for dolphins in captivity as confined they have no contact with other mates or at most with a few of them also in the same conditions.

Conservationists argue strongly about all this, but the release of the captive dolphins is still unlikely.

Humans are a sociable species, we also depend on relations and connections with others to survive, and we all know that most lonely people is not happy and sometimes they have depression and other consequences related to that loneliness. As we are aware, one of the main characteristics of dolphins is their social behavior, so the answer to this is pretty obvious. Dolphins belong to the wild.

WILD DOLPHINS

While the demand for dolphins increases for attractions like swim with dolphins or Dolphin Assisted Therapy (DAT) programs, more and more dolphins are kept in captivity.

Some scientists claim that dolphin research is progressing in great strides, but critics believe that keeping wild dolphins in captivity is cruel and should be stopped.

When contrasting wild dolphins to dolphins in captivity, there are vast differences in behavior, but the high cost of studying wild dolphins has made that scientific data available comes mainly from those in captivity.

Wild dolphins can travel up to 40 miles every day and are constantly on the move, foraging for food, playing and fighting within their pods. Sometimes they submerge to great depths and are hard to follow.

The need for continuous movement of Wild dolphins is one of the reasons that critics of captivity use as arguments to request the release of these dolphins.

The process to capture wild dolphins has traumatic effects on them. Statistics show that 53% of the dolphins that survive the process will die within the first three months.

DOLPHINS IN CAPTIVITY

Regardless that the dolphins we see in captivity seem to be happy, scientists believe that their boredom eventually leads to their premature deaths. Dolphins in captivity, spend only 20% of their time under the surface contrasting with the dolphins in the wild that can be up to 80%.

Activities like beaching themselves in aquatic shows are against their nature because the dolphins in the wild would never beach themselves. Scientists believe that this is extremely harmful because resting on their bellies over a hard surface, will eventually damage their internal organs.

At least 50% of the dolphins in captivity will die in less than seven years. Chlorine poisoning, diseases, and stress-related illnesses are the main reasons that cause the death of those in captivity.

Sometime during the capture process, dolphins are herded towards the shore, separating those still swimming with their mothers from the pod. They are then trussed in a sling and carried from the water to a transport vehicle. Research proves this procedure is very traumatic to dolphins.

US government researchers have found that mortality rates in bottlenose dolphins rise six-fold immediately after capture.

Experience have shown that Dolphins in captivity do not live more than a few years. However, better caring procedures and advanced veterinary medicine, have helped them to live longer, sometimes as long as the dolphins in the wild. Scientists have not figured out yet why dolphins in captivity live less, as most wild animals in captivity, protected from their natural predators will always outlive their counterparts in their natural environments.

Many animal conservation groups are demanding the release of dolphins in captivity, but while there is profit involved, this will be difficult to achieve.

References

Use of Marine Mammals in Swim-with-the-dolphin Programs (FL,HI): Environmental Impact Statement, Volume 1. 1990.

http://us.whales.org/wdc-in-action/end-captivity

http://us.whales.org/faqs/captivity

Janet Mann. Cetacean Societies: Field Studies of Dolphins and Whales. University of Chicago Press, 2000.