Study Finds Post-Menopausal Killer Whales Vigilantly Shield their Sons against Aggressors

**Post-Menopausal Killer Whales Protect Sons from Injuries in Fights**

A recent study has discovered that post-menopausal killer whales exhibit protective behavior towards their sons during fights with other whales. The research revealed that males displayed fewer tooth-rake marks, which are scars caused by the scraping of teeth across another whale’s skin, when their mother was present and no longer breeding. However, this protective effect did not extend to daughters. This study sheds light on the potential evolutionary advantages of menopause in killer whales and other species that experience this phenomenon.

**Understanding Post-Reproductive Females**

Charli Grimes, a whale researcher at the University of Exeter and the first author of the study, explained that the primary motivation behind the research was to comprehend the ways in which post-reproductive females contribute to the well-being of their offspring. Grimes stated, “Our results highlight a new pathway by which menopause is adaptive in killer whales.”

**The Longevity of Female Killer Whales**

In the wild, female killer whales can live up to 90 years, with an average of 22 years after reaching menopause. Scientists have long been intrigued by the fact that humans and certain whale species spend a significant portion of their lives not reproducing. Previous studies have demonstrated that post-menopause killer whale mothers enhance the lifespans of their offspring and grand-offspring by sharing food and leading their pods to plentiful fishing areas. This latest research indicates that experienced female mothers also assist their sons in navigating social relationships.

**Analysis of Southern Resident Killer Whales**

The researchers conducted an analysis of nearly 7,000 photographs of southern resident killer whales, a population that resides off the Pacific coast of North America and has been tracked for over 50 years. These killer whales primarily consume salmon and have no natural predators except for humans. Thus, tooth marks on their skin are evidence of aggressive encounters with other killer whales, which can result in significant injuries.

The study found that males whose post-menopausal mothers were present exhibited fewer signs of aggressive encounters. However, this protective effect was not observed in daughters and only occurred after mothers had ceased breeding. The exact mechanisms through which mothers protect their sons remain unclear, but conflicts often revolve around competition for mates. Grimes speculated that mothers may utilize their heightened knowledge of other social groups to help their sons navigate risky interactions or signal them to avoid conflicts. Alternatively, mothers may directly involve themselves in conflicts.

**The Parallels Between Humans and Whales**

Professor Darren Croft, also from the University of Exeter, highlighted the intriguing similarities between humans and killer whales. He stated, “Just as in humans, it seems that older female whales play a vital role in their societies – using their knowledge and experience to provide benefits including finding food and resolving conflict.”

**The Evolutionary Significance of Protective Behavior**

From an evolutionary standpoint, it is logical for whale mothers to prioritize their sons. Grimes explained, “Males can breed with multiple females, so they have more potential to pass on their mother’s genes. Also, males can mate with females outside of their social group, which means the responsibility of raising the calf falls on another pod.” In killer whales, adult offspring typically remain in the same social group as their mothers, and mating occurs sporadically during interactions with other pods. Consequently, adult sons and daughters typically live with their mothers until the mothers die. This behavior results in close, long-lasting relationships between mother and son.

**Conclusion**

In conclusion, the study reveals the protective behavior of post-menopausal killer whale mothers towards their sons during fights with other whales. While this behavior provides evolutionary advantages for offspring, such protection is not extended to daughters. The research emphasizes the critical role that experienced female mothers play in their societies, using their knowledge and experience to provide various benefits. The study’s findings provide valuable insights into the adaptive nature of menopause in killer whales and shed light on the parallels between human and whale behavior.