Calay News
A new study published in the journal Current Biology reveals that female orcas that have reached menopause show protective behavior towards their male sons in fights but not towards their daughters. Menopause is very rare in the natural world, and this fact piqued the interest of researcher Charli Grimes, who led the study. Killer whales are one of the few species, along with humans, to experience menopause, which raises the question of how and why this phenomenon occurs.
The study focused on a population of killer whales in the Pacific Ocean, along the North American coasts. Orcas live in female-led family groups, usually led by a grandmother with her male and female offspring and her daughters’ pups. Males often breed with females from other groups but return to their family cell and remain close to their mother for their entire lives. Orcas can live to be 90 years old, 20 of which are after menopause.
For the study, the researchers examined tooth marks on killer whales, which are wounds caused by bites during fights or horseplay. These tags help quantify social interactions, and thousands of photos of orcas taken since 1976 were analyzed for the study. Males living with a mother who had reached menopause were found to have fewer teeth marks than those living with a mother who was still capable of reproducing, suggesting that postmenopausal mothers are more protective of their male offspring.
Although exactly how mothers protect their young has not been established, it is speculated that they could use their knowledge of other orca groups to avoid problematic specimens or intervene during a fight by using their vocalizations to restrain their young. Daughters, on the other hand, did not show fewer bite marks when their mother was around, as they are probably less involved in fights, and the mother may be more protective of the sons, increasing the chance of passing on the genes from her.
The protection of mothers towards their children after their reproductive stage is an established phenomenon in humans, and this study shows that it also occurs in orcas. Previous research has shown that elderly orcas share food and pass on feeding knowledge to their offspring, contributing to the survival of their grandchildren. The study will continue to use drones to observe orca behavior and gain a deeper understanding of how they protect their young.
