EXETER, England, Jan. 13 (UPI) -- Conflicts between mother and daughter killer whales may explain why the females of the species experience menopause, researchers say.
In a study published in the journal Current Biology, a research team found younger females are more likely to successfully reproduce than their older counterparts. Scientists say this trend has influenced mothers to turn away from reproduction and focus on raising their younger family members instead.
"Our previous work shows how old females help, but not why they stop reproducing," University of Exeter researcher Darren Croft said in a press release. "Females of many species act as leaders in late life but continue to reproduce. Our new work provides a mechanism that can explain why old females stop [reproducing] -- they lose out in reproductive competition with their daughters."
Prior scholarship established older females tend to take up strong leadership roles in their social groups, but did not explain why they would experience menopause and stop reproducing altogether.
Female killer whales typically begin reproducing at the age of 15, and stop once they reach their 30s or 40s. The species can live to be over 90 years old.
During the research, the scientists used a unique long-term dataset on wild resident killer whales in the Pacific Northwest. According to the data, older females are more closely related to their kinship group than younger females are. Calves born to older females were 1.7 times more likely to die.
The team says their findings suggest reproductive selection tends to favor younger females when they breed at the same time as their older counterparts. This characteristic influences older females to compete less, and cooperate more with their social groups.
To follow up on their study, the researchers plan to use underwater drones to observe the animals more closely.