By Maneka Sanjay Gandhi
The moon influences life with its light. Moonlight, its presence and absence, affects reproduction, foraging, communication and other aspects of an animal’s world. Nocturnal animals can hunt or forage more easily under the light of the moon — although venturing out on moonlit nights also comes with the risk of being hunted. From prey behaviour to birdsong — lunar light affects everything.
Lions of the Serengeti in Tanzania are night predators, and are most successful in getting their prey during the darkest phases of the moon. But how does the prey react to the moon’s phases?
Scientists from Princeton University put camera traps, which spied on the lion’s favourite prey species, to see how they reacted to the moon’s phases. African buffaloes, lion prey, form herds as the moon wanes for safety in numbers. Wildebeests appear to set their plans for the entire night based on the moon’s phase. During the darkest parts of the month, they stay in a safe place where the lions are unlikely to go. As nights get brighter, wildebeests are more willing to venture into dangerous places where run-ins with lions could happen.
The routines of zebras and Thomson’s gazelles also change with the lunar cycle. These scenarios in the Serengeti demonstrate the wide-reaching effects of moonlight, a clear example of how the presence or absence of the moon can have fundamental, ecosystem-level impacts.
For nocturnal African dung beetles, moonlight is a compass. How well the insects navigate depends on the phases of the moon. Once the beetle has located a fresh heap of dung, its main objective is to roll a ball of it away as quickly as possible, to the safety of a burrow, to avoid competition from other beetles and potential predators. The quickest route away from the dung to safety is a straight line; under moonlight, the beetles make a direct getaway from the dung heap. But in the absence of moonlight the beetles roll their dung balls in confusion, often landing back into the feeding frenzy.
Doodlebugs, the larvae of dragonfly-like insects called antlions, run around sandy environments in search of places to catch prey. They dig funnel-shaped holes in the sand in which they sit and wait for prey to fall in. Doodlebugs dig bigger holes around the full moon. This could be because of the increased activity of prey when the moon brightens the night sky, creating a greater chance of catching dinner.
Scorpions have an especially unique reaction to full moon phases. The UV rays of moonlight react with a protein in scorpions that makes them glow in the dark. They hide during the full moon and hunt during the new moon’s dark period. Many nocturnal creatures become less active during a full moon period. Rattlesnakes rarely leave their burrows when the moon is full, to protect themselves from predators.
Moonlight also impacts mating behaviour. Badgers urinate to mark territory when they are getting ready to mate. They do this when the moon is new, probably because the darkness allows their prolonged mating more security from predators. During the full moon period, badger urination is much less.
Certain owl species become more active during the full moon, both in their mating calls and in showing off their feathers to potential mates – probably since owl feathers are more visible in the light of a brighter moon. On the other hand call frequencies of nocturnal seabirds are very low in moonlight and quickly increase when the moon is hidden by clouds. And, small Northern Saw-whet owls are less active during moonlit nights, in order to avoid ending up as the prey of larger owls.
The light of the moon also influences animals that are active in daytime. White-browed sparrow weavers in South Africa’s Kalahari live in family groups and sing together to defend territory. But during the breeding season, males also perform dawn solos and, when a full moon is visible, they get up even earlier and sing much longer. This reduces as the moon wanes.
For many animals, particularly birds, the moon is essential to migration and navigation. Scientists at Lund University studied European nightjars. They found that the birds begin their autumn migration southwards 10 days after the full moon – no matter where they are.
A Japanese study involving Streaked Shearwaters determined that this marine bird flies for longer periods, and lands on water more often, during nights with a full moon. However, researchers reported that sharks also take advantage of the increased light, so the shearwaters don’t remain on the water for long, in order to avoid winding up as shark prey.
Researchers find that lunar cycles affect bird hormone levels. The daily variations in melatonin and corticosterone disappear during full moons.
According to a study, by the Colorado State University Veterinary Medical Center, dogs and cats are more likely to need medical attention during the days surrounding a full moon. Cats are 23 per cent more likely to visit an emergency room during these days and dog visits increase by 28 per cent. Pets may spend more time outdoors when the night sky is brighter, increasing the chance of accidents and injuries.
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