Orca mothers are known to be very devoted to their offspring, especially their sons. But new research suggested that they also play a protective role for their adult sons, shielding them from conflicts and injuries caused by other orcas.
This behavior may help explain why orcas are one of the few animals that undergo menopause, and how they maintain their complex social structure.
How orca moms keep their sons out of trouble
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Orca mothers and sons have a strong bond that lasts throughout their lives.
Sons often stay close to their mothers, even when they are fully grown and capable of breeding. Mothers help their sons find food, especially salmon, which is their main prey, as per Phys.org.
They also provide social support and guidance, helping them navigate the challenges and opportunities of living in a large and dynamic group of orcas.
But orca mothers do more than just feed and nurture their sons.
They also protect them from harm, according to a new study by researchers from the University of Exeter, the University of York, and the Center for Whale Research.
The study examined the tooth rake marks on the bodies of orcas, which are scars left by the teeth of other orcas during fights or rough play.
These marks can indicated the level of aggression and competition within a group, as well as the risk of injury and infection.
The researchers found that adult male orcas had fewer tooth rake marks if their mothers were still alive in their old age, compared to those whose mothers had died.
This suggested that older orca mothers may intervene in conflicts involving their sons, either by physically shielding them from attacks or by signaling them to avoid risky situations.
This protection may increase the survival and reproductive success of their sons, as well as reduce stress and promote cooperation within the group.
Orca mothers are not only protective of their sons but also selective about when to have them. Orca females stop reproducing around the age of 40 but can live up to 90 years in the wild, as per Insider.
This means that they spend more than half of their lives in a post-reproductive state, which is very rare among animals. Only humans and a few other whale species share this trait.
Scientists have long wondered why orca females undergo menopause, and what benefits it may bring to them and their offspring.
One hypothesis is that it is an adaptation to avoid reproductive conflict with their daughters, who also breed within the same group.
By stopping reproduction, older orca females avoid competing with their daughters for mates and resources and instead focus on helping their existing offspring survive and reproduce.
Another hypothesis is that it is an adaptation to enhance the transmission of their genes to future generations.
By living longer and helping their sons breed with multiple females from other groups, older orca females can increase the spread of their genes across different populations.
They can also pass on their knowledge and experience to their offspring and grand-offspring, enhancing their survival skills and social bonds.
Both hypotheses suggested that menopause is a result of natural selection favoring older orca females who invest more in their offspring than in themselves.
This investment may take different forms, such as feeding, teaching, supporting, and protecting. By doing so, older orca females increase the fitness of their offspring, especially their sons, who depend on them more than their daughters.
