Biologist Thandiwe Mweetwa was busy studying lion prides in Zambia, when she noticed something interesting: the females all seemed to give birth at approximately the same time. Naturally, Mweetwa researched this further, ultimately postulating that the lionesses actively synchronize their menstrual cycles.
And they do this, Mweetwa says, for good reason.
“Synchronized [ovulation] is thought to increase reproductive success in the pride,” she says.
In other words, having cubs at the same time means that mother lions can rely on each other to nurse, babysit, and protect the youngsters. Safety in numbers also allows more lion cubs to survive to adulthood. Predation is a threat to small, vulnerable babies in any species, but predators can only eat so many – if all the pride’s cubs are born at the same time, the likelihood is greater that more will survive. If young are born at different times throughout the year, they become a year-long food source for predators.
Even more interesting is that in the event of a cub’s death, lionesses immediately began ovulating again. This has been observed in prides where the alpha male has been killed by another male; not only does the challenger kill the alpha, he kills the pride’s young. This brings the females into heat, as they prepare to bear the new male’s offspring. Though many other animals come into heat at the same time, fewer species go into heat when their young die.
Interestingly, lionesses do not menstruate as human females do; in fact, the only mammals that have traditional “periods” are humans, primates, and a few species of bats and rodents.
So while it’s not quite the same as female roommates or coworkers having their “time of the month” at the exact same time of the month, it is close. And it’s just another reminder that no matter what we may think of ourselves, we humans are just another part of nature.