Image of an orca and her calf from Wikimedia Commons
Orcas are one of only three species of mammals that go through menopause, including humans of course. A new study published in Current Biology may have discovered why this happens in killer whales.
Examination of 43 years worth of data collected by the Center for Whale Research and Fisheries and Oceans Canada, revealed a remarkable finding about the costs of reproduction in orcas. Older mothers tend to spend more time taking care of the family, so to speak, by making sure her offspring know where or when to find food. While this cooperative foraging behavior helps improve survival of the mother’s family, further offspring from the mother are 1.7 times more likely to die than her daughter’s offspring. This reproductive competition (or conflict) is thought to be a reason why the whales (and perhaps humans) evolved to go through menopause.
DP Croft, RA Johnston, S Ellis, S Nattrass, DW Franks, LJN Brent, S Mazzi, KC Balcomb, JKB Ford, MA Cant. Reproductive Conflict and the Evolution of Menopause in Killer. Current Biology. 27: 1-7, 2017. DOI: 10.1016/j.cub.2016.12.015