Biologists studied the demographic dynamics in the southern resident population of killer whales living in the Pacific Ocean near
Southern resident killer whale population since 1976is under the supervision of the Center for Whale Research. In their work, scientists analyzed data on the number of children of different sexes in adult killer whales, collected over the entire period of observation.
The analysis showed a strong negative correlationbetween the number of sons females have and the probability of giving birth to a new child. Each surviving cub reduced the chances of giving birth to a new child by almost 50% on average. At the same time, the negative correlation persisted when children reached adulthood.
Killer whales are distinguished by an amazing sociala system in which both males and females stay with their mother for life. At the same time, biologists have long known that female killer whales continue to patronize their adult sons, who rely on the protection of the mother in dangerous situations. But until now it was not known what the price of such care was.
The amount of costs that women incur,to take care of her mature sons is really amazing. Females gain an evolutionary advantage if their sons can successfully breed. Our results show that these benefits are enough to outweigh the large personal costs.
Michael Weiss, researcher at the University of Exeter and the Whale Research Center and co-author of the paper
Scientists note that understanding how the reproductive principles of killer whales are arranged will help to better plan measures to restore the population of these mammals.
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