So you're out walking in the bush somewhere in Africa, let's say Tanzania, one evening after dusk. It's not really late, but there's no moon in the sky yet because it rises later in the days right after the full moon.
If you're smart, you go home.
Otherwise, you're likely to be a lion's evening meal
A new study that looked at lion predatory behavior over the lunar cycle found that lions were more likely to attack and eat humans successfully in the ten days after a full moon, in the evening, when it's darkest and when humans are most likely to be out and about, and when lions are at their hungriest, according to Science.
The study, led by Craig Packer of the University of Minnesota Twin Cities campus, looked at the relationship between lunar cycles, lion attacks and lion feeding behavior, according to Science News. Researchers used records of more than 1,000 lion attacks on Tanzanian villagers between 1988 and 2009. Nearly two-thirds of the attacks were fatal, and most occurred after dark. The researchers could figure out a precise time of day for 474 attacks, and found that they occurred mostly between 6 p.m. and 9:45 p.m.
The most striking finding was the fact that the attacks were up to four times more likely on the ten nights after the full moon.
Hourly attack rates were 2–4 times higher in the first 10 days after the full moon (when the moon does not rise until after sunset) than in the 10-day period before the full moon (when the moon is 30–100% illuminated and above the horizon at sunset)
The reasoning goes like this: lions are least successful at getting and eating prey during the full moon, when it's bright out. Lions like to hunt in the dark, and they have more success in the dark because their prey has difficulty seeing them. But when the moon is full, it's very easy for the prey to spot the lions, making it harder for the lions to get something to eat. By looking the belly size of the lions, the researchers saw clearly that during the evenings of the full moon, the lions weren't getting much to eat, and they were getting hungry.
At the same time, humans usually take shelter at night. So they're only out and about for a certain amount of time in the evening before they go back to their shelters. After a full moon, as it is waning, it doesn't appear until well after dusk, which near the equator occurs early even in summer, according to the Guardian. Peak danger times for humans are therefore the active hours after sunset.
So, one the one hand, you have hungry lions, and on the other hand, you have humans going about their business in darkness.
As Packer explains, according to the Guardian:
"People start out at moderate danger during days 0-4, when the moon is only a sliver and sets shortly after sunset.
"Danger then declines as the moon gets brighter each evening, with very few attacks in the nights just before the full moon. Then, wham, danger spikes as those hungry lions can now operate in darkness for the rest of the lunar cycle.
"The post-full-moon spike is restricted to relatively few hours of full darkness before the largish moon rises later in the evening."
Packer points out that perhaps this phenomenon has contributed to the human fear of the dark, and the deep-rooted beliefs that exist about the danger of the full moon, according to Science:
"There's bound to have been an effect of moonlight on our psychology because of these risks," he says. "The full moon definitely is a loud and clear harbinger."
In other words, it's not actually the full moon that's dangerous; it's what comes after.