The time of the year that the moon is at its brightest, roundest and fullest has finally come! Today is the Mid-Autumn Festival, one of the loveliest Chinese festivals. For Chinese families, it’s a day for family gathering, moon-gazing and of course, indulging in delicious mooncakes.
When it comes to Mid-Autumn Festival, what comes to your mind must be mooncakes, lanterns, and (maybe) the legends related to it. However, this post is not going to be about any of them! Because today, October 4th, is also World Animal Day! World Animal Day is a social movement which aims to raise the status of animals in order to improve welfare standards around the globe, making the world a better place for all animals (find out more here: https://www.worldanimalday.org.uk/). So, to celebrate both the Mid-Autumn Festival and World Animal Day, let us tell you about the story of the moon and the animals associated with it ~
Chapter 1: The Time Keeper
Most animals, including humans, have bodily rhythms governed by the sun. However, the moon also controls several mysterious circadian clocks in many animals, both marine and land, and especially nocturnal creatures.
How does the moon clock work? The moon provides time cues to animals via two ways: changes in moonlight and tides. These two environmental cycles are the result of the lunar cycle (the number of days required for the Moon to orbit around the Earth) and the lunar day (the number of hours required for the Moon to travel by the same spot on Earth). These environmental changes can be perceived by animals and plants, cueing them to behave in certain ways and perform certain activities at certain timings to survive in the wild.
During full moon, corals are all ready to make babies
For hundreds of species of corals, the full moon sets the great atmosphere for lovemaking. Corals keep close watch for changes in moonlight. As the full moon arrives, corals release huge amounts of eggs and sperm into the water at the same time – a mass-spawning event and one at the most massive scale on Earth. This mass coral spawning event just happened in Singapore in April 2017!
Researchers had found that corals are able to perceive the blue region of the visible light spectrum and are extremely sensitive to the spectra that match that of the blue moonlight. By synchronizing spawning, the free-floating sperm and eggs have a higher chance to come into contact with one another and undergo fertilisation in the vast ocean. This lovemaking event always occurs on or near a full moon.
Turtles ride waves onto shore during high tide to lay eggs
While the moonlight tells corals when to spawn, tidal changes inform sea turtles on when to lay their eggs. Females of most species come ashore at night during high tide to lay their eggs on the beach.
Light changes during the lunar cycle not only represent time cues to many species, but also affect the animals’ use of senses.
Chapter 2: The Compass
Not only do species rely on moonlight to tell time, some also use the moon to navigate their way to find food and go back home!
“Just keep walking, just keep walking”
Under a dark night sky, newly hatched baby sea turtles depend on moonlight reflecting off the ocean surface to guide them toward the sea. Just in August, 32 Hawksbill turtle hatchlings were sighted at Each Coast Park, trying to find their way to the sea!
Besides sea turtles, dung beetles also use polarized moonlight as a compass to roll its ball of poop in a straight line in order to escape competitors.
Chapter 3: A fine dinner under the moonlight
Dining under the moonlight may be a romantic scene to us, but how is it like in the animal kingdom?
Let’s play hide and seek
Full moons shine extra light onto the landscape. Many predators in the animal kingdom take advantage of this, and find it easier to spot and hunt their prey. Nightjars and owls were found to be more efficient in foraging when there is moonlight, and avoid activity at dark nights. It may seem that predators have an edge as the moon brightens. However, many prey have also stepped up their game. During bright nights, prey dramatically reduce their night activity and go into hiding. There are also prey which find it easier to detect and evade predators, and are daring enough to increase activity levels. Doodlebugs, the larvae of dragonfly-like insects called antlions, dig bigger holes to trap insect prey during full moon nights as the prey are more active.
Chapter 4: Losing the moonlight
Light is important to both humans and wildlife. Lightbulbs are seen as one of the greatest inventions of all time. However, in today’s world, our use of light has become so excessive that it is disrupting the natural patterns of light and dark, altering the behaviour of wildlife and functions of ecosystems. The baby sea turtles found at East Coast Park were found to be circling on the beach. The bright streetlights were distracting the hatchlings, and they were unable to follow the moonlight to the sea.
Every flip of a light switch is contributing to altering natural patterns of mating, migration, feeding, and pollination, at a rate which species are unable to adapt. Not only does ecological light pollution affect wildlife, studies have shown that it has profound impacts on human health too. Nocturnal light disrupts our sleep and confuses our circadian rhythms. After all, humans are animals as well.
As you enjoy your mooncakes and appreciate the full moon tonight (if it is visible), we hope that this post will increase your appreciation of the importance of the moon to both humans and wildlife, and encourage you to reduce and fight light pollution!
Happy Mid-Autumn Festival! 中秋节快乐！
Bogard, P. (2013). Bringing Back the Night: A Fight Against Light Pollution. Retrieved from: https://e360.yale.edu/features/bringing_back_the_night__a_fight_against_light_pollution
Poppick, L. (2013). How the Moon Affects the Nocturnal World. Retrieved from: https://www.livescience.com/37927-how-moon-affects-nocturnal-animals.html
Grant, R.A., et al. (2009). The lunar cycle: a cue for amphibian reproductive phenology? Retrieved from: http://www.amphibianark.org/pdf/Husbandry/The%20lunar%20cycle%20a%20cue%20for%20amphibian%20reproductive%20phenology.pdf
Kronfeld-Schor, N., et al. (2013). Chronobiology by moonlight. Retrieved from: http://rspb.royalsocietypublishing.org/content/royprsb/280/1765/20123088.full.pdf
Hansford, D., et al. (2017). Sex, Death, and Pollination: How the Moon Changes Life on Earth. National Geographic. Retrieved from: http://news.nationalgeographic.com/2017/07/moonlight-behavior-circadian-chronobiology-earth-live-animals/
Tan, R. (n.d.). Mass Coral Spawning. Retrieved from: http://wildshores.blogspot.sg/search/label/coral%20spawning#.WdMwaWiCzIU
SeaWorld Parks & Entertainment. (n.d.). Sea Turtles Reproduction. Retrieved from: https://seaworld.org/animal-info/animal-infobooks/sea-turtles/reproduction/
Words by: Ho Lijean