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.

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/killer-whale/ Thu, 27 Apr 2017 05:27:50 +0000 http://www.dolphins-world.com/?p=1263 Killer Whale

(Orcinus Orca)

INFORMATION AND CHARACTERISTICS.

Although it is commonly named “killer whale,” environmentalist are trying to change this name because there are two inaccuracies in it: it is not a whale, and much less a killer. The Orca is a toothed cetacean member of the genus Delphinidae, so it is the largest dolphin in the world.

Although it is also a powerful predator that even attacks sharks, it is not a human killer. Attacks have occurred but only from specimens in captivity victims of stress and confusion.

Order: Cetacea
Family: Delphinidae
Genus: Orcinus

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

Orcas are considered monotypic, that is, they belong to a single species although in recent years some scientists think that the smaller orcas of Antarctic waters are a subspecies. There are several ecotypes result of one of the largest distribution of all mammals, in fact, just after humans.

Weight and size.
Orcas exhibit sexual dimorphism since males are larger than females. Adult males reach a length of 6 to 8 meters and weigh about 6 tons; while females have a length about 5-7 meters and weigh about 3 to 4 tons. The maximum registered length in an orca is 9.8 meters.

Morphology.
It is a huge and bulky cetacean that has a shape similar to the other dolphin species. It has a strong skeleton and the skin covered with collagen fibers. Both genders have a round head with a big forehead and pectoral flippers similar to paddles. Its dorsal fin is also large: in males can measure up to 1.8 meters while that of females reaches between 70 and 80 centimeters and is more curved. The caudal fin has two flukes and measures 1.8 meters wide.

It has 10 centimeters long teeth covered with enamel; those in the front can lean forward when the orca holds a prey. Orcas have excellent senses of sight, hearing and touch.

It is the largest mammal predator and feeds on a wide variety of large or small animals.

Skin Coloration.
An Orca is easily recognizable by its black and white color pattern. The dorsal area is black but changes to white from the lower jaw passing through all the ventral part up to the anus. Above the eyes, it has a white patch. Its flippers are also black, and it has a gray saddle patch in the dorsal area just behind the dorsal fin. Orcas show this coloration pattern after one year of age.

Distinctive features.
The color pattern is unique to each specimen. Also, the gray patch behind the dorsal fin called “saddle” got this name because of its apparent resemblance to such supportive structure.

Orcas – Orcinus orca.

WHERE DO THEY LIVE? HABITAT AND DISTRIBUTION.

The orca distribution is incredibly broad, ranging from the polar waters to the equator in the open ocean or closed systems such as the Gulf of Mexico, the Gulf of California, the Persian Gulf, the Mediterranean Sea and the Red Sea. They are distributed in all the oceans of the world although they have a preference for cold regions. They live in waters with depths of 20 to 60 meters, and occasionally there are sightings along the coasts. After humans, killer whales are the most distributed mammals on the Earth.

The list of countries they inhabit is very long but includes:
Canada, France, Greenland, Portugal, Iceland, Ireland, Italy, Oman, Pakistan, India, Vietnam, Yemen, Bangladesh, Benin, Brunei, Cambodia, United Arab Emirates Uruguay, Venezuela, Mexico, Costa Rica, Dominican Republic, Singapore, Saint Vincent and the Grenadines, China, Japan, Philippines, Jamaica, Honduras, Ecuador, Colombia, Antigua and Barbuda, Russia, Papua New Guinea, Madagascar, Haiti and Brazil.

Orcas can inhabit deep or shallow waters as well as visit bays, estuaries, and even rivers. They dwell in all kind of marine aquatic habitats.

WHAT DO THEY EAT? DIET AND EATING HABITS.

It is the largest mammal predator and feeds on a wide variety of large or small species, warm-blooded or cold-blooded, whether dangerous or not. Orcas do not discriminate. A daily intake of 45 kilograms may include seals, sea lions, fishes, squids, turtles, birds (even penguins), sea otters and even animals considered as predators like sharks. Killer whales even prey on baleen whales or dolphins.

When orcas consume small prey, they swallow it completely, but they have to split the large ones into smaller pieces before ingesting them, which usually do it by shaking the victim violently. They have several hunting strategies depending on the type of prey and the region they inhabit. For example, in the North Pacific, they feed on some fish, seabirds, and sharks.

Cooperative hunting is a demonstration of their sociability and their intelligence. First, a group of orcas follow a prey and corner it. When the prey is exhausted, the orcas give the victims powerful blows with their tail before eating them.

Orcas in the wild.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

Killer whales have a polygamous reproduction system, and both genders mate with multiple individuals throughout their life. Females are sexually mature at an age ranging from 6 to ten years, and males between 10 and 13 years. Both can mate at any time of the year although in the northern hemisphere this occurs more frequently during October and March.

After a gestation period of 14-18 months, the mother gives birth to one calf; this happens one time every 3-8 years until the female turns 40 years old. A mother provides dedicated maternal care because the breeding depends entirely on her for feeding and protection. When the calf is 1 or 2 years old, it is weaned but continues in its native pod.

HOW DO THEY BEHAVE? BEHAVIOR.

It is a sociable species with a complex social structure. They live, reproduce and feed in pods of up to 40 or 50 members forming temporal superpods with more members sometimes. In general, these pods have 20 percent of mature males, 20 percent of offspring and 60 percent of females and young males. Orcas always stay in the mother’s group.

In some cases, an elementary unit may consist of a mature female, her adult offspring and the offspring of her daughters. Sometimes, some pods have a small number of members but with no close links.

On the other hand, killer whales can communicate through various sounds that other orcas in the pod recognize even though they are several kilometers away. Jaw claps, pulsed calls, pops, and whistles, are part of their communication sounds as well as echolocation clicks.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

State of conservation: Data deficient.
* But the population of some regions is in danger of extinction.

For centuries, orcas have frequently been hunted for oil and meat. Now, commercial fishing is not a significant hazard, but bycatch is. Also, they are very vulnerable to the contamination of their habitat as nocive chemicals can penetrate their skin and tissues; Consequently, this affects their reproductive and survival capabilities.

While there isn’t an assessment of the conservation status of the entire species, the population of some regions is in danger of extinction, such as that of British Columbia and Washington, in the United States. For this reason, CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) has included the species in Appendix II of the species whose trade is controlled. The IUCN Red List does not have enough data to establish it in a category.

In 2008, NOAA (National Oceanic and Atmospheric Administration) through the National Marine Fisheries Service announced a Recovery Plan for Southern Resident Orcas to improve the living conditions of these cetaceans.

References

http://www.iucnredlist.org/details/15421/0

http://www.nmfs.noaa.gov/pr/species/mammals/whales/killer-whale.html

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 650.

Ford, Ellis, Balcomb. Killer Whales: The Natural History and Genealogy of Orcinus Orca in British Columbia and Washington. UBC Press, 2000.

Dolphins have a social structure which makes them swim and live together in small groups called pods or herds. (Names of animal groups).

The best defense mechanism that dolphins have is their social organization and the strong bonds between them. The primary purpose of pods, composed of about 12 dolphins is the protection of the members.

These groups make sharks, the only predator that dolphins have to face, to avoid approaching the pod.

When threatened or attacked, dolphins use their speed and agility hit predators.

Large species of sharks, eat small species of dolphins or calves. Also, occasionally killer whales eat small dolphins too.

The larger dolphins are apex predators which mean that they are at the top of the chain food.

The only predator that the small species of dolphins or calves have in the ocean are the large species of sharks.

Besides, there are no constant threats in the sea.

Sometimes, killer whales attack or eat dolphins, but this is not a standard behavior. In fact, killer whales belong to the family of oceanic dolphins too.

However, the most dangerous predators that dolphins have today are humans, and although we are not in the sea, we kill more dolphins (and sharks) than any other animal in the ocean.

killer whale factsKiller whales, also known as Orcas (Orcinus orca) are fascinating creatures that attract a great deal of attention from marine biologists, as well as the general public.

Orcas are Apex predators and adults do not have any other threat in ocean than humans, Research is always being done about Killer Whales, and new facts about their habits, socialization, intelligence, and travel patterns are discovered continuosly.

Here are the top facts that make this cetacean so unique to the general public as well as to the scientists.

• Killer Whales are one of the fastest creatures in the sea, traveling up to 30 miles per hour.
• Killer Whales are able to control the flow of blood to their hearts and brains, which keeps them from suffering from a lack of oxygen when they are deep underwater.
• Killer Whales eat up to 5% of their body weight each day. This averages out to over 500 pounds of food for each Orca.
• Killer Whales do most of their socialization within their own pods. However, pods do socialize with other pods as well.
• When breeding, Killer Whales do not breed with relatives. They only breed with killer whales that are not closely related to them within their own pods.
• Killer Whales are called “Killer Whales” because they feed on other dolphins and smaller whales, not because they kill people. They are also know as orcas.
• The only recorded instances of a killer whale attacking a human being have been of attacks by Orcas held in captivity. No killer whale that lives in the wilds has ever attacked a human being.
• Killer Whales eat up to 5% of their body weight each day. This averages out to over 500 pounds of food”.

• Every Killer Whale has a mark behind it’s dorsal fin that is totally unique. These marks are used by humans to distinguish one killer whale from another, just as humans each have their own specific characteristics that make our appearances different from every one else’s.
• Killer Whales use vocalization to communicate with each other, but each pod has it’s own unique ‘accent,’ which makes it easy for Orcas to identify members of their own pods.
• Pods of killer whales are found in all oceans in the world, but the greatest numbers are found in cooler waters.
• Killer Whales are actually dolphins. In fact, they are the largest dolphins in existence, and can be up to 30 feet or more in length, and weigh up to 12,000 pounds.
• Killer Whale brain is five times larger than a humans. They are very social, intelligent, and curious. killer whales brains that have been studied with microscopes have proven to be as structured and developed as the human brain.
• Killer Whales have very organized and complex social structures, and divide themselves in pods, which operate as human families do. They protect their young, ill, and injured within their pods.
• Killer Whales spend 60% of their time foraging for food. killer whales do not migrate, but they have been known to travel hundreds of miles to find fresh food that is in ‘season.’
• Life expectancy of a Killer Whale in the wild is 50 – 60 years for males, and up to 90 years for females, however, Killer Whales held in captivity have not lived longer than 30 years, and the average life expectancy for captive Orcas is only 20 years.
• Female Killer whales usually do not breed until they are between the ages of 12 and 16 years old. Their gestation period is 15 – 17 months, as opposed to 9 months for humans. They nurse their calves for up to 2 years. On an average, each female Orca that lives in the wilds will have approximately five calves during her lifetime.