“It’s a beautiful story, a very clear example of how the presence or absence of the moon can have fundamental, ecosystem-level impacts.”
On the eve of the 50th anniversary of the Apollo 11 moon landing, lunar science is still capable of surprise. Moonlight, as Science News reported this past weekend, shapes how many animals move, behave and plant the seeds for future generations.
Just one example: Twice a month, from March through August — right now, in other words — hundreds of thousands of California grunion, silvery sardine lookalikes, beach themselves in the sand late at night and plant their eggs, which will hatch 10 days later. The incoming tide will wash the hatchlings out to sea, and their new home. The mating ritual is timed to the tides, with the hatching coinciding with the peak high tide, every two weeks.
As science now knows, the ultimate force choreographing this dance is the moon.
Another example: lions.
On the other side of the world, in Botswana, nature filmmakers and National Geographic Explorers-in-Residence Beverly Joubert and Dereck Joubert noted years ago how lions become more active under the full moon. Under the light of a full moon, lions even going as far as to tackle elephants — who are more comfortable in daylight — if they’re hungry enough and desperate enough, and if they sense an opportunity for the taking. The Jouberts were the first explorers to capture their strange find on film.
Hyenas are active at night, too, all the more so under a full moon, as the Jouberts recounted in their 1997 book Hunting with the Moon: The Lions of Savuti, one of the classics of African wildlife photography.
True, it’s no surprise to scientists who study lions in the Serengeti — or anyone else, for that matter — that lions are more active at night, especially under a full moon. Cats are nocturnal, for the most part, after all.
What behavioural science has found interesting of late, though, is how the lions’ prey respond to the ever-changing threat at night, as the moon waxes
and wanes.
A 2016 study that involved some 200 camera traps over an area the size of Los Angeles found that wildebeest avoid places where lions are known to congregate on the darkest nights, when there is little moonlight to see by.
Another prey animal, the buffalo, were shown to huddle in ever larger herds on the darkest nights.
Different species, the researchers found, make different risk assessments, depending on the changing light, and modify their behaviour accordingly. (The study findings, co-authored by University of Minnesota ecologist and lion expert Dr. Craig Packer, were published in the science journal Ecology Letters in 2017. https://onlinelibrary.wiley.com/doi/abs/10.1111/ele.12832)
There’s more, too. The light of the moon influences the movement of the annual migrations in the Serengeti-Mara ecosystem. River crossings, which take place in daylight for the most part, have been known to occur on nights when there is a full moon to see by.
Behavioural scientists are constantly looking to find a human connection — whether the moon affects such human triggers as
emotion and aggression, aside from that which is the stuff of Hollywood movies. That said, behavioural ecologist Davide Dominoni, of Scotland’s University of Glasgow, cautions against jumping to easy-to-reach conclusions.
“It’s really hard to find definitive answers because most of the studies are correlational,” he told Science News.
A correlation could be real, or due to some other factor — a common mistake in “junk science,” which seeks to find a human connection where there may be none. Until scientific researchers come up with a way to determine with hard evidence how the moon affects human behaviour one way or the other, it will remain the stuff of fevered speculation.