It is known that in the animal world — among tens of thousands of mammals, birds, fish and amphibians — only a few individuals reach adulthood. Moreover, after losing the ability to bear offspring (menopause), survive, not all females. However, according to a study published in the journal PNAS, menopause has its advantages, and use them not only people. So, cetaceans, including belugas, narwhals and orcas are attracted to help in the upbringing of offspring grandmothers. It turned out that menopause dramatically increases the survival chances of the young generation.
Another confirmation of the “grandmother hypothesis”
By studying the data on populations of killer whales in Washington state in the United States and British Columbia in Canada, the researchers found that the mortality rate of newborn calves increased immediately after the death of the grandmothercompared to the pups whose grandmothers were alive. Research suggests that orcas Mature age, which do not multiply, increase the chances of offspring survival. Scientists came to the conclusion that the life of the grandmother after menopause is important for her family group. Moreover, the results of the study can be an important factor in assessing future populations of these mammals. Note that today the population of whales continues to decline, so the researchers believe that the role of grandmothers is likely to become even more important. Female orcas reach sexual maturity around 10 years and cease to reproduce at the age from 30 to 40 years. While in the wild they can live much longer: from 80 to more than 100 years.
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Previous studies showed that a limited reproductive period entails less competition for the search of sustenance for offspring. It turned out that grandmothers, whales are seen as leaders. Moreover, they know best hunting grounds, and equipment.
These benefits can be attributed to “grandmother hypothesis,” which suggests that menopause creates generation wiser family members, which contributes to the overall well-being of their relatives. However, researchers believe that it is not so easy, as in other animals, such as elephants, there are also grandmothers who care for their grandchildren. However, they do it for their own children.
The study team found that within two years after the death of the maternal grandmother, the probability of young orcas dying was 4.5 times higher than orcas live with their grandmothers in postmenopausal women, and 1.5 times higher than that of the orcas, whose grandparents were in the reproductive age.
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Scientists believe that when grandparents support their own children, their movement and activities is limited and unable to support the same as orcas in postmenopausal women. Perhaps menopause has evolved in killer whales for these reasons. To better understand the relationship between different generations of killer whales, in the future, scientists intend to use drones.