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The killer whale -

The killer whale or orca is the largest member of the oceanic dolphin family. It is one of the world’s most powerful predators and is recognizable by its distinctive black body with white markings.

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Lack of knowledge -

Pods of these majestic creatures can be found in every major ocean on Earth. And yet, until recently, we understood very little about this fascinating species.

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The CRW study -

It is thanks to the work of the Center for Whale Research (CRW) that we have begun to understand more about killer whales and their way of life.

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The CRW study -

The CWR conducted a study of a single population of killer whales that inhabit the ocean just off the coast of British Columbia and Washington State in North America.

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Major finding -

A major finding from the study was the importance of the role played by the grandmother of the killer whale family, which is difficult to overstate.

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The life cycle -

Killer whale grandmothers all start out, of course, as calves. They are born into their mother’s family group, which is otherwise known as a "matriline."

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The matriline -

Killer whale matrilines do everything together: they play, they hunt, and they communicate with each other via a set of calls unique to their own family.

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Exceptional -

The killer whale species is very unusual because both sons and daughters spend their whole lives with their mothers’ families.

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Intra-matriline communication -

Different matrilines do interact with each other, however: in addition to having its own set of calls, each matriline can communicate with others via a dialect.

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Social creatures -

Killer whales are in fact very sociable creatures, and there is a lot of interaction between matrilines. And when females are around 15 years old, they begin to mate with the males they meet.

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Fear of commitment? -

However, they don’t enter into long-term relationships. Shortly after mating, the female returns with her calves to her mother’s family and the male goes back to his mother.

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Baby machines -

Female killer whales continue to give birth every seven or eight years (on average) until they are 40. At this point, they go through menopause.

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The menopause -

Animals that go through menopause are extremely rare. Females who continue to live a long time after they stop reproducing are almost unheard of in animals other than humans. With the exception of the killer whale, the only other non-human species whose females are known to go through menopause is the short-finned pilot whale.

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Why does menopause exist? -

Scientists are unsure as to the reason why menopause exists for these three species. According to Darren Croft of Exeter University, there are a number of theories.

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Theory 1 -

One theory says that there is no real reason for the females of these species to live long after they stop reproducing, and that it’s simply an evolutionary accident.

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Theory 2 -

However, Croft insists that this is not the case. There is another theory that takes into account the concept of the ‘granny effect.’

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The ‘granny effect’ -

The ‘granny effect’ theory suggests that older females stop reproducing so that they are able to take better care of the children and grandchildren they already have.

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The ‘granny effect’ -

The argument is that by doing so, they stop passing on their genes directly but continue to do so indirectly by ensuring the survival of their existing offspring.

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Theory 3 -

Another theory suggests that females of certain species go through menopause because they cannot compete with their daughters’ reproductive ability.

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Findings -

One study of a killer whale pod showed that the offspring of older mothers were 1.7 times more likely to die than the offspring of younger mothers.

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The matriarch -

Whatever the reason that they stop reproducing, it is after menopause that the female orca really comes into her own, taking the lead in the all-important hunt for fish.

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The diet of a killer whale -

The killer whale diet consists mainly of salmon, but they do also eat other species of fish and animals. The grandmother shows her family the good places to find food.

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The diet of a killer whale -

She is an experienced hunter herself and shares around 90% of the salmon she catches. The older she gets, the more important her role becomes.

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Dwindling salmon reserves -

The killer whale matriarch’s experience and input is all the more important given the overfishing and habitat destruction that has almost wiped out the salmon population.

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Dwindling salmon reserves -

Severely-reduced salmon supplies mean that killer whales are facing an almost constant threat of starvation. The whales studied by the CWR are critically endangered.

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Action needed -

The grandmother orcas are doing the best they can, but if we are to ensure the survival of the species, something must be done to revive the salmon population.

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Going forward -

More studies like that conducted by the CWR will also help us anticipate the vulnerabilities of killer whales to human interference and thus help us to ensure their survival.

Sources: (TED-Ed) (The Guardian)

See also: Amazing animals under threat of extinction

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