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.

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.

The false killer whale is the third largest dolphin in the world. A skeleton of this species discovered in 1843 in England was at that time the most preserved fossil of a cetacean. Owen was the first naturalist to describe it in the year 1846 and was named Phocaena crassidens. Incredibly, the fake orca was seen alive 15 years after the discovery of its skeleton.

While its current common name refers to the orca (Orcinus orca), this species and Pseudorca crassidens do not belong to the same genus and are not closely related. However, both species have similar features like the shape of the skull and the morphology of the dental pieces.

Order: Cetacea
Family: Delphinidae
Genus: Pseudorca

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

Morphology.
The shape of its body is fusiform. Slender and hydrodynamic, the false killer whale has a conical head which is devoid of a snout. Their narrow, pointed pectoral flippers have a sort of lump in the middle, so they look like elbows.

Weight and size.
The maximum length of females is approximately 5.1 meters while the largest males can measure up to 6.1 meters. Female weigh about 1,200 kilograms while males have a weight of up to 2,200 kg.

Skin Coloration.
The skin on its body is black or dark gray except for the whitish chest, and the faint light gray spots sprinkled around the neck and the head.

Distinctive characteristics.
Its elbow-shaped pectoral fins are the perfect feature to distinguish this dolphin quickly and easily from other species. The lack of snout and the almost full black color are also some unique features.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

It is possible to find false killer whales in tropical and subtropical waters of the Pacific Ocean, the Atlantic Ocean, and the Indian Ocean. Its boundaries are latitude 50° north and 52° south, so it has a wide distribution in saltwater systems, including seas and semi-closed places such as bays.

In the south, it extends from New Zealand to Chile, Australia, Peru, South Africa, Argentina and even the United States, the Bay of Biscay, the Red Sea, the Mediterranean Sea, the Sea of ​​Japan, and British Columbia. Although there are no reports of populations living in countries close to the North Pole, sightings include places like Norway and Alaska, but they are probably lost individuals because they are not cold water residents.

It has a particular preference for waters with depths of approximately 2,000 meters. It rarely approaches the coasts, and when it does, it prefers to stay close to the oceanic islands and sometimes ventures into seas or closed water systems.

WHAT DO THEY EAT? DIET AND EATING HABITS.

To hunt, a pod of 300 individuals can travel in a straight line spanning an area of ​​5 km.

The false killer whale is a carnivorous animal, but its prey is not only fish; it also includes crustaceans and cephalopods. Its size allows this dolphin to hunt some species of marine mammals successfully.

This kind of victim is common in waters of the eastern Pacific, where they have been seen attacking humpback whales calves (Megaptera novaeangliae). The following are just some of the preys that are part of its usual diet:

Yellowfin tuna (Thunnus albacares).
Albacore o longfin tuna (Thunnus alalunga)
Swordfish (Xiphias gladius).
Pacific bonito (Sarda lineolata).
Mahi-Mahi (Coryphaena hippurus).
Salmon (Genus Oncorhynchus).
Yellow Corvina (Larimichthys polyactis).
Wahoo (Acanthocybium solandri).
Japanese seabass (Lateolabrax japonicus)
Atlantic Mackerel (Scomber scombrus)
Herring (Genus Clupea)
Squid (Several species)

Sea lions (Subfamily otariinae) and probably young individuals or offspring of other dolphin species, humpback whales and sperm whales (Physeter macrocephalus).

It feeds opportunistically in coordinated groups. To hunt, a pod of 300 individuals can travel in a straight line spanning an area of ​​about 5 kilometers. It usually captures a prey near the surface, shaking it violently until dismembering it and eliminates the skin before consuming it. An interesting detail: the false killer whales share their food with their pod companions and mothers allow their offspring to feed on the prey that are inside their mouths.

HOW DO THEY BEHAVE? BEHAVIOR

This cetacean presents a very evident gregarious behavior, and they establish close ties between them. However, their pods are made up of relatively few members, about 10-50 in general, but in some regions, the groups may be more or less numerous, reaching up to 100 individuals. When they swim together, some subdivisions within the group are visible.

Social relations are long and stable throughout their life, with a minimum duration of 15 years. In Scotland, Ceylon, Zanzibar and Great Britain, numerous strandings of these cetaceans have taken place to the point of counting 800 stranded individuals in dramatic cases. It is also a species that usually stays within a particular area. For example, false killer whales in Hawaii do not move more than 500 kilometers around their area.

The false killer whale performs some acrobatic jumps, including riding the bow waves of the boats and jumping out of the water. On the other hand, this dolphin communicates with its mates through whistles, squeals and pulsating sounds of frequencies above 100-130 kilohertz.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

The false killer whale can mate throughout the year if the individual is already sexually mature. Females reach maturity between 8 and 11 years while males reach maturity at 8 to 10 years of age. Both are polygamous and have a very low reproduction rate because mothers have offspring only every seven years.

Mating occurs when a male detects receptivity of a female. If there is not conception in the first ovulation, the female keeps the ovulation until it is pregnant.

The gestation period lasts 11-12 months, and after that time the calf is born with a length of about 2 meters. The mother feeds the offspring for 18-24 months, after which it can consume solid foods.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation status: Data Deficient.

Bycatch (mainly in Japan and Indonesia), reduction of prey availability, pollution of coastal waters and killing by fishers who consider it a competitor for fish, put this cetacean on a bad conservation perspective.

The number of individuals that exist is not known, in fact, the Red List of the International Union for Conservation of Nature does not have enough data to evaluate their conservation status.

Their inclusion in Appendix II of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) implies a better regulation for this species.

References

http://www.iucnredlist.org/details/18596/0

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

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 405.

Gerardo Ceballos. Mammals of Mexico. JHU Press, Oct 9, 2014

Dolphins will circle protectively around the weak members of the pod, and viciously attack anything that approaches in a threatening manner. And they can kill sharks. Most predators take one look, and then just swim away.

Like any animal, dolphins are sometimes victims to other species that seek to feed on them or get some other benefit from their body. But besides humans and other aquatic animals, they have a small number of natural enemies. In fact, some species do not have any.

In fact, the natural predators of dolphins kill very few specimens compared to the deaths of those predators who do not belong to their aquatic environment.

PREDATORS IN THEIR NATURAL HABITAT

Orcas (Orcinus orca) and large sharks dispute the title of “The most dangerous predator of dolphins,” and is that both, with their size and other physical characteristics and, of course, their natural need to feed on meat, find dolphins attractive.

Killer whales.
For some species, this mammal is the most deadly predator, and it is also a dolphin! Orcas feed on a wide variety of fish, mollusks, and crustaceans, but if they find a dolphin, they do not hesitate to grab it and feed on it. They usually catch the smallest individuals, the small species or the young.

Sharks.
It is common that sharks kill dolphins. Usually we hear that sharks are the mortal enemies of dolphins, but in reality, this is only because of their feeding instinct and not a particular “hate” or antagonism towards dolphins.

The smallest species are a common prey of bull sharks (Carcharhinus leucas), dusky sharks (Carcharhinus obscurus), tiger sharks (Galeocerdo cuvier) and great white sharks (Carcharodon carcharias). The most vulnerable dolphins are usually young and calves.

In some regions, sharks are the most dangerous group of predators that dolphins have to face, such as on the east coast of the United States. Sharks have species preferences; For example, bottlenose dolphins (Tursiops truncatus) are the favorite of the sharks mentioned above.

Killer whale – Apex predator.

Some researchers suspect that the attacks on dolphins do not always intend to kill for food, but only to defend what they consider their territory. However, scars on the skin of dolphins indicate that bites are evidence that sharks strike from below and behind the dolphins.

A surprising fact for many people, regarding the relationship between dolphins and sharks, is that they can tolerate each other perfectly in the same area and feed on the same bank of fish. Sometimes they completely ignore each other despite being a few meters apart.

But dolphins also defend themselves. Although they usually avoid sharks or flee from them, if necessary, they show aggression and show their most powerful defense system: The pod! When the group is together and alerted, sharks prefer to go away and avoid the pod which can quickly kill him.

Bottlenose dolphins sometimes attack these predators by striking their bodies with the caudal fins (tails). However, this defensive behavior is not very common with sharks.

THE MOST DANGEROUS PREDATOR

As with most species today, their most dangerous threat is the man. Sometimes, humans kill dolphins not because they are a source of food, but because they prey on the same fish species than humans. Therefore, many fishers have killed dolphins only because they are a competition for the fish.

In some countries, people eat cetaceans, including dolphins. In Japan, the meat of some species is seen as a delicacy and can cost up to $25 USD a pound.

In Peru and some other Latin American countries where the fish is becoming scarce due to overfishing or environmental conditions such as El Niño, desperate fishers have turned to catch dolphins and porpoises to sell them in fish markets.

Even more, there are some countries like the Faroe Islands, where killing and eating cetaceans, including dolphins, is a longstanding cultural tradition.

The presence of humans on Earth does not give dolphins many possibilities to survive. In the dynamic predator-prey, one side has to die so the other lives, but what happens when it is not about survival, but about business?

Without a doubt, humans are the biggest predator of dolphins. Their commercial activities endanger the life of these cetaceans directly and indirectly. Let’s look at some:

Dolphin Hunting.

The highest numbers of dolphin killings are in Asia, Africa, and South America. Dolphin meat is consumed in several parts of the world even though it is suspected to have high concentrations of mercury. Thousands of dolphins die every year, and the annual slaughter in Japan is infamously known. Sadly, dolphins put little or no resistance when massacred by humans.

Bycatch.

Tragically, the largest group of dolphins killed by man are those killed by accident or incidentally during large-scale fishing operations. Dolphins and other cetaceans that swim into these nets following fish, become entangled and drown when they can’t reach the surface to breathe or tear off parts of their body in their struggles to escape.

Dolphins die when incidentally caught by gillnets and trawl nets, without the intention to hunt these cetaceans.

Fishers have found that tuna swim beneath dolphins in high numbers, so they get caught when nets are deployed to catch tuna. Though the surviving dolphins are released, estimations indicate that at least 30 million dolphins have been killed in this way since the observations began in the 1960s.

Reduction of the habitat.

The construction of structures and the contamination reduces the number of healthy habitats turning some of them unsuitable. Intimately linked to pollution.

Pollution.

Every day millions of gallons of polluted water, toxic substances such as pesticides, heavy metals, plastic trash and hundreds of other hazardous materials are released into the ocean and the rivers. Their habitat becomes contaminated and causes illness and death. Especially, river dolphins are dangerously threatened by pollution because most of the rivers where the five river dolphin species live have high concentrations of pollutants.

Unintentional deaths.

Other unfortunate accidents are also deaths by collision against propellers or any other parts of boats.

References

https://en.wikipedia.org/wiki/Dolphin

https://seaworld.org/en/animal-info/animal-infobooks/killer-whale/diet-and-eating-habits

http://www.tandfonline.com/doi/abs/10.1080/13880291003705145

]]> https://www.dolphins-world.com/dolphins-in-the-military/ Thu, 27 Apr 2017 05:34:08 +0000 http://www.dolphins-world.com/?p=142 It might seem taken from a Hollywood movie, but it’s true: many dolphins are trained to work for military purposes. Obviously, this has nothing to do with their normal behavior, but their ability to learn and their intelligence makes them perfect targets to be used by man to achieve specific purposes.

The United States and Russia (the former Soviet Union) are the countries that have made these cetaceans authentic soldiers, but it is the American country that has the longest history with this practice. Incidentally, the most commonly used species is the bottlenose dolphin (Tursiops truncatus).

THE REASON

In the 1960s, the United States Navy implemented the Navy’s Marine Mammal Program to

(a) investigate the ability to swim and dive of the cetaceans to apply the knowledge to their naval structures and

b) to study the characteristics of echolocation that allowed them to design efficient methods for detecting objects in the water.

Their sense of echolocation makes dolphins perfect for locating objects underwater, one of the main tasks performed by these cetaceans for the military.

Although the U.S. Navy not only trained dolphins as they also used sea lions (Subfamily Otoriinae) and beluga whales (Delphinapterus leucas), dolphins were especially helpful during the Cold War, Vietnam War, Gulf War and recently In the Iraq war. When they realized their ability to learn and their sense of echolocation, the rest is history.

For its part, the USSR made use of the dolphins to perform tasks similar to those of the US Navy dolphins. However, the collapse of its political system resulted in the elimination of the military programs involving dolphins.

Those responsible for theses programs affirm that dolphins are the perfect animals for their needs. They are intelligent, can adapt to a different environment and the continuous contact with humans and therefore they are easy to train.

THE HOMEWORK

Their sense of echolocation makes dolphins perfect for locating objects underwater, one of the main tasks performed by these cetaceans for the military. Their responsibilities are varied, but each dolphin has a particular job, and they do not perform general tasks so while some are trained to detect objects, others learn how to patrol specific areas.

The set of tasks that dolphins perform in the military includes:

– Detection, location, and marking of mines buried in the seabed of shallow water.

– Detection, localization, and recovery of lost objects.

– Watching ports or specific areas.

– Detecting intruders in a limited area.

However, some analysts think that they could put mines on foreign ships and they could be used to attack and perhaps kill foreign divers.

These last two activities are controversial because although the armed forces deny such activities, some think that it is pretty obvious that they use dolphins in such way.

A dolphin named KDog work in the Persian Gulf during the Iraq War /U.S. Navy photo by Photographer’s Mate 1st Class Brien Aho.

THE PROCESS

The ways in which dolphins perform their tasks are fascinating. Their echolocation allows the detection of rare material either from a mine or other object when the “clicks” emitted bounce back in the material and return to them. Tom Lapuzza, a spokesman for the US Marine Mammal Program, says that dolphins can differentiate objects and even distinguish one metal from another.

Dolphins trained for attacking humans is a task not admitted by the Navy. Although some analysts think is pretty evident.

Dolphins can patrol a zone 24 hours a day every day. If a dolphin detects an intruder in protected waters, the cetacean touches a sensor installed on a boat to alert the personnel and they place a device that produces noise or light on the nose of the dolphin, then the dolphin swims towards the trespasser and touches it with his nose showing the location of the intruder. Sometimes they can also mark it for identification.

The mine detection process is similar. When the dolphin locates an explosive, it places around a series of buoys to mark the location. Then, the dolphin or other trained marine mammal lays particular devices to grab the object without any danger.

Attacking humans, as mentioned, is a task not admitted by the Navy. But the suspicions arise from an activity in which dolphins are trained to shoot the strangers using a device that could fire a bullet of carbonic acid installed in an injection needle. This weapon, placed in the head of the animal, is fired as it touches the human diver. Do not forget that these are only speculations from some analysts, so far.

In return for their performance, dolphins get food.

CONSEQUENCES

The use of dolphins for military tasks has had a lot of criticism from the animal protectors and the society in general. The arguments are:

– Dolphins are kept in captivity, away from their habitat and stopping or modifying their natural behaviors as socialization and reproduction.

– They are exposed to abnormal conditions to test their adaptability and resistance and to somewhat extreme circumstances.

– They are subject to greater stress than in the wild. It reduces their life expectancy.

– They are put in danger being in contact with the hazardous materials.

– They can easily be a target and eliminated by the enemy as they would be considered soldiers as well.

Instead, those responsible for military programs ensure that dolphins are kept in optimal health conditions because they have exceptional medical care and balanced nutrition.

However, it is a controversial subject that generates several opinions and organizations like the Whale, and Dolphin Conservation Society (WDCS) oppose firmly.

PRIVATE DOLPHIN

We’ve heard for years that Dolphins are incredibly intelligent creatures. It turns out that they are smart enough to serve in the United States Navy, and have been doing so since 1960 when the Navy decided to study their underwater sonar capabilities to learn how to design better methods for detecting objects in the ocean. The Navy also realized that they could find out how to improve the speed of their boats and submarines by studying how dolphins can swim fast and dive deep.

The research ended up going much further than that. Dolphins have been trained to perform several tasks, including delivering equipment to underwater personnel, locating and retrieving lost objects, and guarding boats and submarines. They have been trained to detect enemy swimmers, and this was the case in both the Vietnam war, as well as the Persian Gulf war. The Dolphins patrol around boats and submarines and use their natural sonar to alert their trainers when enemy swimmers are detected. They could even tag the enemy swimmer with a marker so soldiers could spot and apprehend them.

Dolphins even do underwater surveillance for the Navy, by holding cameras in their mouths or attached to the dorsum and have been used to detect and mark underwater mines as well.

The Navy began the studies of dolphins in 1960, but the Marine Mammal Program began its first military project until 1965. The first project was called Sea Lab II, and a dolphin named Tuffy was trained to dive 200 feet below the surface of the ocean off the coast of La Jolla, California, to deliver mail and tools to personnel.

The Marine Mammal Program has gone through many changes since 1965. From 1965 to 1975, Navy used dolphins in the Vietnam war. During this time, the Navy was steadily building up a team of dolphins, and the program had over 100 dolphins during the 1980’s. With the end of the Cold War, the government reduced the budget for the Marine Mammal Program, however, between 1986 and 1988, six Navy dolphins were sent to the Persian Gulf to protect US flagships from enemy swimmers and mines. They also escorted Kuwaiti oil tankers through dangerous waters. In 1992, the program became declassified.

With the cutbacks and the declassification of the program, the Navy explored the possibility of returning the dolphins to the wild but found that this would be a complicated process that would not be economically feasible. The Navy contacted several marine parks but got few requests for the cetaceans. In 1994, they sent three dolphins to a Sanctuary near Key West, Florida. Two were released into the wild by the owner of the sanctuary, without the proper permits, and this caused quite a bit of controversy. Two weeks later, the Navy recaptured the Dolphins and kept the three cetaceans in its facilities, assuming their care and responsibility for the rest of their natural lives.

The most recent use of Navy dolphins was during the war on terrorism, in Operation Enduring Freedom. Again, the Navy dolphins were used to guard ships against enemy swimmers and locate and mark mines. The Navy also uses whales and sea lions in their programs.

References

Judith Janda Presnall. I Wonder…Can Navy Dolphins Work for the Army?: Educational Version. Learning Island.

John M. Kistler. Animals in the Military: From Hannibal’s Elephants to the Dolphins of the U.S. Navy: From Hannibal’s Elephants to the Dolphins of the U.S. Navy. ABC-CLIO, 2011.

Jay Griffiths. Savage Grace: A Journey in Wildness. Counterpoint, 2015.

Dolphins are highly sociable mammals that establish close links with other individuals of the same species and even with dolphins of other species sometimes. They seem to show empathic, cooperative, and altruistic behaviors.

Most species live in groups called pods composed of 2 to 30 dolphins as the number varies, but in some areas with abundant food, many pods can merge forming superpods with more than 1,000 members.

Dolphins depend on this interaction for hunting, mating and defending themselves. In some cases, these superpods include more than one species of cetaceans that seem to interact well together.

PODS, THE REASON

Why do dolphins group? They have several reasons to join, besides following a sample learned since they born. Small dolphin species gather into multi-member pods as a way to compensate for their size when facing predators.

In this sense, these groups provide protection to an animal that does not have large jaws or razor sharp teeth. When Dolphins are together, it is easier for them to survive if they cooperate with each other, either through communication or intimidating the predator if it is a large number of individuals.

DYNAMIC OF THEIR SOCIAL STRUCTURES

It seems that dolphins are free spirits. Studying the dynamic of the social composition of the pods, scientists discovered that when dolphins belong to a group, nothing binds them to it in a matter of space and time, this means that they can move freely to different pods that are in their vicinity, then the movement of members is continuous.

This type of social network is flat and open, and scientists found no evidence of a rigid, closed or semi-closed structure, so dolphins do not have permanent “membership” in any pod.

These open associations are another indication of their high intelligence since these actions require a lot of brain capacity. Likewise, the hydrodynamic shape of their body supports the need to move continuously between several groups of different environments.

Even though pods do not lack social hierarchy, this depends on the species. For example, bottlenose dolphins (Tursiops truncatus) establish dominance biting, chasing and striking their tails or fins against the surface of the water. The marks of teeth remain in the skin of the dolphins and are practically in all the species meaning that confrontations are also part of their life. That is why, when they want to demonstrate “who rules here,” they may not be so charming as usual but more aggressive than we think.

On the other hand, the composition and structure of the groups depend on certain circumstances: age, sex, family ties, reproductive condition and even the history of associations. Studies on the behavior of dolphins indicate that dolphins can have preferences for meeting with particular individuals and that they can be remembered and recognized after experiencing extended periods of separation. Amazing, right?

Dolphin social structure.

TYPES OF PODS

The characteristics of the groups differ according to the number of members and the circumstances mentioned above. Dolphins do not behave the same when they change from one pod to another.

There are three types of pods:

Nursery groups (mothers-offspring).
A calf stays with its mother from birth up to a few years after weaning. Usually, the mother’s bond with her son is very close and continues until the young dolphin is 6 or 8 years old. Since offspring are vulnerable, the females with calves join and form groups where they help each other to feed and protect their offspring. If a young female gets pregnant, she can return to her natal pod to give birth and care for her calf along with her female relatives, forming a multigenerational group.

The males usually do not get close to these groups.

Juvenile pods.
When reaching a certain age, both males and females leave their breeding group and join with other young dolphins, but curiously, they go to the group of their mothers occasionally for a while and then return to their youth group.

Two male dolphins can stay together for 10, 15 or 20 consecutive years.

The members of these groups are engaged in socializing with others and establishing a preamble to mating. Genres, however, are not intimately related for extended periods of time and once a female becomes pregnant, she joins the nursery group.

Adult males.
The structure of the male pods is very complex and similar to a human male group, you will see why.

Often males are related to 2 or 3 individuals of the same gender and create partnerships for cooperation purposes. Two male dolphins can stay together for 10, 15 or 20 consecutive years. The smaller groups have the objective of cooperating to ensure the mating of the others with a specific female. The larger groups make alliances with other herds of males to defend themselves but also to compete. They continue moving from pod to pod throughout their lives.

INTERNAL SOCIAL STRUCTURE

Males are dominant in all groups, but there is no evidence of strong social bonds between them and females. An example of social interaction and their high intelligence is the regular playing activities they perform. Juvenile and adult dolphins often chase each other and toss items such as seaweed back and forth.

Most experts believe that the social relationships formed by dolphins are long lasting.

Dolphins often have close body contact with other dolphins through rubbing, petting, and even hitting each other.

COMMUNICATION, THE GROUND FOR SOCIALIZATION.

Dolphins communicate with their pods usually through whistles. Each dolphin has a unique whistle that identifies it with other members of its group. If an individual is in distress, it uses a particular sound that indicates help is needed, so the pod responds quickly.

SOCIAL ACTIVITY BEYOND LIMITS.

Although it would be normal that dolphins socialize only with their kind, the interest of some species of dolphins to interact with humans is evident. In the wild, dolphins are extremely curious, and they will often engage in contact with people if a chance comes up. In captivity, dolphins are very attached to the people that usually interact with them, like trainers or researchers.

References

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

Karen Pryor, Kenneth S. Norris. Dolphin Societies: Discoveries and Puzzles. University of California Press, 1998.

https://link.springer.com/chapter/10.1007/978-1-4757-9909-5_7#page-1

http://www.cbmwc.org/wp-content/uploads/2012/01/Social-structure-of-bottlenose-dolphins-in-Cardigan-Bay-by-Cally-Barnes.pdf

]]> https://www.dolphins-world.com/ganges-river-dolphin/ Thu, 27 Apr 2017 05:27:28 +0000 http://www.dolphins-world.com/?p=111 Author of the picture: Whymper and P. Smit Lydekker, Richard. This work is in the public domain.

Ganges River Dolphin

(Platanista gangetica gangetica)

INFORMATION AND CHARACTERISTICS.

It is one of two subspecies of the South Asian river dolphin (Platanista gangetica), and it has the title of the national aquatic animal of India, where is also called Ganges susu or shushuk.

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

The Ganges River dolphin and its closely related subspecies, the Indus River dolphin, have an appearance quite different from that of oceanic dolphins. Specifically, this species has the following characteristics:

Morphology.
It has a robust body with an asymmetrical skull, a protruded front, and a very flexible neck. Its long snout measures almost 20 percent of its body length and in adult females is even longer than that of the males. It has a small crest on the melon.

The dorsal fin is a little triangle with a broad base, and the longer pectoral flippers are flat. Its eyes are tiny.

Order: Cetacea
Family: Platanistidae
Genus: Platanista
Species: Platanista gangetica

Weight and size.
An adult has a length between 2 and 2.2 meters, and it has an approximate weight of 51-89 kilograms.

Skin Coloration.
The body has a dark gray or brown color, with a lighter color in the ventral area.

Distinctive characteristics.
It’s hard to differentiate a Ganges River dolphin from an Indus River dolphin, but the former species has a slightly longer tail than that of its relative.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

The Ganges River dolphin distribution is limited to the east of India. It inhabits the freshwater system Ganges-Brahmaputra-Megna (GBM) and the Karnaphuli-Sango river systems, and their tributaries, which run through Nepal, Bhutan, and Bangladesh.

It Inhabits large sections of these rivers or their tributaries from the tidal zone to the foothills of the Himalayas, the Cachar Hills (District of India) and the Garo Hills of Meghalaya (Indian state). During the flooding season, this dolphin leaves the main canals and reach the temporary tributaries and flooded lowlands.

It is most frequently found in bodies of countercurrent water located between the convergence of channels and meanders (pronounced curves) and occasionally go to channels and reservoirs. Their habitat has a depth of 3 to 9 meters, and water temperatures between 8 and 33 Celsius degrees.

WHAT DO THEY EAT? DIET AND EATING HABITS.

The Ganges River dolphin has a carnivorous diet which includes a large variety of fish and invertebrate animals; perhaps it is also capable of consuming birds and turtles. These are some of their usual prey:

– Common carp.
– Gobio.
– Prawn.
– Freshwater sharks.
– Mahseer fish (Family Cyprinidae).
– Shrimp.

Although it has visible teeth in the jaws, it does not use them to chew but to hold their prey firmly. Its eyes are not useful to find food because in the muddy waters of its habitat they are not required, that is, it is an animal functionally blind, so it uses echolocation to detect prey.

This dolphin usually swims with a fin touching the riverbed to feel the sediments since animals hide there. Its snout is very useful for this. Once it finds a suitable prey, it holds the victim with the jaws and begins to swallow it whole starting from the head so that the scales (if the prey has them) do not hurt its throat.

It does not always look for food at the riverbed. Its most common practice is finding a school of fish near the surface and drag them to the bottom to eat them.

HOW DO THEY BEHAVE? BEHAVIOR.

The maximum speed that this dolphin reaches when swimming in its natural habitat is 27 kilometers per hour.

This dolphin has a shy, quiet and rather passive behavior. It swims alone or with 1 or 2 more individuals (pods may have 2-10 members) and rarely gather in large groups although some people report sightings of groups with up to 30 members. It is probably a semi-gregarious and territorial animal since sometimes it chases other dolphins aggressively. Their leaps out of the water are related to reactions to aggressions or external disturbances.

The primary function of the sense of echolocation in this species is searching for food rather than communicating. An unusual behavior observed in this species is the habit of swimming sideways, especially to the right. The reason is unknown. The maximum speed that reaches when swimming in its natural habitat is 27 kilometers per hour.

During the rainy season, this dolphin ventures into the tributaries of the river and returns to the main canals in the winter.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

The Ganges River dolphin mates throughout the year and not in any specific season. The first breeding occurs between six and ten years of age and females give birth once every 2 or 3 years. It is a relatively large interval that, together with the late maturation, produce a low natality rate that does not contribute to increasing the number of individuals in the wild.

It is not known the process of courtship and mating, and a calf is born 8 to 12 months after the intercourse more frequently between December and January and between March and May. Maternal care is presumed to be similar to that of other dolphin species, but in this case, after weaning (1 year after birth), the offspring do not maintain ties with its mother.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation status: “Endangered.”

As is frequently the case in the world of dolphins, the greatest threat to this species are humans who, looking for their meat and oil, have hunted them for many years putting them close to extinction.
According to the Red List Of the International Union for the Conservation of Nature (IUCN), this subspecies has a conservation status of endangered.

These dolphins do not have many predators in their habitat, so most of their threats are anthropogenic like:

– Dam construction.
These structures separate different populations of the same species which reduces the genetic diversity and the amount of mature individual available to mate.

– Bycatch.
They are sometimes trapped or entangled in fishing nets and other devices which are not intended to hunt these cetaceans.

– Pollution.
The contamination of the Ganges river comes from chemicals, garbage, residual waters and industry spills.

There are less than 2,000 Ganges dolphins left in the wild and a few time to help them survive in this challenging context. But the cause is not entirely lost, as the Indian Wildlife Protection Act looks for the protection of this species as a priority. Also, international organizations such as the WWF (World Wide Fund for Nature) have established programs to move from theory to practice and reduce the degradation of this dolphin’s habitat.

References

http://www.iucnredlist.org/details/41758/0

Rashmi Sanghi. Our National River Ganga: Lifeline of Millions. Springer Science & Business Media,  2013.

http://s3.amazonaws.com/academia.edu.documents/46348097/Sources_and_Accumulation_of_Butyltin_Com20160608-24155-1njpezf.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1489183099&Signature=0jehfoy3PH4ix9VZ15G6QKFQMVU%3D&response-content-disposition=inline%3B%20filename%3DSources_and_accumulation_of_butyltin_com.pdf

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

http://animaldiversity.org/accounts/Platanista_gangetica/

All the information we have about dolphins is thanks to the countless studies, tests, and research that some scientists have performed. In fact, new reports, papers, and conclusions come out every year that mentions the outcome of a given study that expands the understanding of the complex world of dolphins.

These mammals were known in the ancient classical civilizations and in others that had contact with the sea. Today it is assumed that they were attracted to this beautiful, docile and almost friendly animal as much as we do. The seventeenth century brought a new era of individuals interested in the life of plants and animals, and from then on began a period of more thorough research performed under an organized structure and later with the scientific methodology.

The knowledge about dolphins got during centuries was transferred hand to hand among the famous naturalists. Many species of dolphins were discovered and described for the first time during the nineteenth century, such as the Peale’s dolphin (Lagenorhynchus australis), the White-beaked dolphin (Lagenorhynchus albirostris), Hector’s dolphin (Cephalorhynchus hectori) and the Long-beaked common dolphin (Delphinus capensis).

According to estimations, 130 dolphins are in possession of the US Navy.

The scientists in the twentieth century discovered new species, and as they got new information, they restructured some taxonomies. With time, investigators sometimes realized that a subspecies existed not previously considered as such or that newly-known characteristics were inconsistent with the assigned taxonomic family of a species. Further research also made them aware of the intelligence potential of these cetaceans.

In this regard, the US Navy has developed leading research programs since the 1950s. The most obvious example is the Marine Mammal Research Program (1960), whose objective was to learn about the sense of echolocation and to know the morphology of these mammals thoroughly, with the intention to get the knowledge from them and apply it to technologies at the service of humans.

Dolphin research is still relevant for the Navy. To get an idea, in 2007 they spent about $ 14 million on marine mammal research that includes training activities. The number of dolphins in possession of the US Navy is estimated to be 130.

But other governmental and non-governmental organizations have carried out remarkable studies in the field and even collaborated with each other. Many research institutes have different approaches, some move from theory to action, implementing rescue or conservation programs.

OBJECTIVES OF DOLPHIN RESEARCH

Most of the research focus on the following aspects:

– Genetic data of dolphins.
– Behavior.
– Social structure.
– Brain, intelligence, and communication.
– Taxonomy.
– Discovery of new species.
– The impact of anthropogenic activities on the species.
– Preservation and conservation.

Research involves a series of studies that include practical activities, which require a highly coordinated team. It includes reviewing previous studies, analyzing findings, and even rearranging information, which sometimes leads to changes in the taxonomy of some species of dolphins.

MORE RESEARCH

Today we have a lot of information about dolphins since they are one of the most studied animals probably because their intelligence and some similar characteristics to humans make them grab the focus.

Some of the research recently published is:

US researchers led by Dr. Jason Bruck of the University of Chicago stated in 2013 that dolphins have the longest social memory of all non-human beings. They can remember individuals even after 20 years since their last interaction and in the opinion of these scientists, this is the result of the close social relations established between them.

Although it was an issue that was already suspected, researchers from the University of Saint Andrews in Scotland, brought to light in 2013 a study that proves once again that each dolphin differentiates from the others by emitting a characteristic whistle. In human words, a kind of a particular name. According to Dr. Vincent Janik, dolphins responded to their “name” during the tests when the researchers made their whistling sound through underwater speakers.

A study by the Dolphin Research Center in Grass Keys, Florida, released in 2013, reported that dolphins could solve problems in the same way humans do because they can make decisions and guess. They not only react to stimuli.

Dolphins have culture; an aspect believed to be exclusive to man. Observations concluded this when seeing bottlenose dolphins (Tursiops truncatus) using marine sponges in their snout to protect it by feeding on rough surface areas. Subsequently, the researchers realized that mothers transmitted this behavior to their offspring and they learned in consequence.

The former is a great discovery because transferring knowledge among generations is probably one of the main things that made humans reach the fantastic development that we have now. Therefore, even in a basic way, demonstrating this behavior put dolphins in a whole new level.

Research is ongoing. There is still much to discover despite being activities that involve a lot of time, work, and money. However, understanding their life can generate human awareness and improve conservation efforts.

US NAVY LEADS THE WAY

Although we’ve been fascinated by dolphins for thousands of years, it wasn’t until approximately the 1940’s that research in the field of marine mammals began. While there are hundreds, perhaps thousands of research projects currently being conducted on dolphins, the largest project is the one undertaken by the U.S. Navy.

The U.S. Navy Marine Mammal Research Program started to work with dolphins in the late 1950’s to analyze their hydrodynamic properties and their biosonar. The hope was that dolphins could be trained to locate and retrieve lost objects from the ocean using their capabilities. In the early 1960’s, John Ci. Lilly and several other scientists discovered that dolphins possessed an intelligence level they believed was second only to that of man and that dolphins could learn how to complete tasks quickly and efficiently. It was at this point that the Navy launched a secret research program on dolphins.

Over the next 29 years, the U.S. Navy officially had over 240 dolphins in their research program. The types of dolphins included were Atlantic Bottlenose and Pacific white-beaked dolphins and Beluga, Killer and Pilot whales. For over four years, from 1965 to 1969, the Navy used acoustic signals to give commands to the cetaceans in exchange for fish. The Dolphins soon learned to retrieve mines even more efficiently than Navy scuba divers.

In a “top secret operation,” Six Pacific Bottlenose Dolphins were airlifted by the Navy to the Persian Gulf in 1987 where they were used to detect missiles and mines as well as for underwater surveillance. In 1988, trainers who had been working with these dolphins on the Navy project came forward with claims of abuse and carelessness of the dolphins in the Navy’s programs, but despite these allegations, the Navy Research Program continued. Since that time, the Navy has admitted that the Dolphins were also present in the Vietnam and the Persian Gulf War.

The Navy employs the Marine Mammal Productions Inc. to catch and transport the animals. They are sent to Seaco Inc. in San Diego, California for their initial training and then deployed to bases in Hawaii, San Diego, and Key West. The number of dolphins currently involved in the Navy programs is at least 130.

References

Thomas I. White. In Defense of Dolphins: The New Moral Frontier. John Wiley & Sons, 2009.

John M. Kistler. Animals in the Military: From Hannibal’s Elephants to the Dolphins of the U.S. Navy: From Hannibal’s Elephants to the Dolphins of the U.S. Navy. ABC-CLIO, 2011.

Judith Janda Presnall. In Defense of Dolphins: The New Moral Frontier. Learning Island.