The findings have been described in detail in the journal Current Biology, and it sheds more light on the competition and cooperation that the killer whales have to endure within their respective pods and how it results in early menopause. These new findings come from 43 years of data collected on the whales.
"At the start of her reproductive life, a female's relatedness to males in her local group is relatively small, because her father is from a different social group," the study showed. "As a female reproduces, her sons will remain in her group, increasing her overall age-specific local relatedness."
Killer Whales have a lifespan of around 90 years, but reach menopause in their 30's to 40's. This means that they are only fertile for only about half of their lives.
Two groups of killer whales were taken for the study over a four-decade period. Scientists found out that if a female whale gave birth in old age, the kid whale's chances of making it to 15 years of age were slim, compared to the daughter's child of childbearing age.
The competition for a whale mother for food against her own daughter and grandchild may be responsible for this evolution of menopause to the mother.
On the other hand, male whales go to other pods to mate, so that means that as a female whale continues aging, she becomes more related to the other members of the pod, as the study explains. This is another reason the menopause kicks in early.