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Wildlife camera study finds tropical forest mammals shy away from the moonlight

Beware of the full moon: Tropical forest mammals shy away from the moonlight
Pacas are lunar phobic and less active when there is more lunar/moon illumination. Taken by a wildlife camera. Credit: TEAM - Tropical Ecology Assessment and Monitoring Network.

A recent study using automatic wildlife cameras across three continents has shed light on how the moon's phases affect the behavior of tropical forest mammals. Half of the species studied altered their activity levels or timing, or both, in response to the full moon.

The findings, in the journal Proceedings of the Royal Society B: Biological Sciences, suggest that even in some of the darkest places on Earth—the floors of —the moon's phases can influence animal behavior. This impact could be even more pronounced in degraded and fragmented forests.

"Imagine playing hide-and-seek in a dark room, and then somebody lights a candle," says Richard Bischof, professor at the Norwegian University of Life Sciences (NMBU).

"The light, even if it is weak, may make it easier for you to find your way around the room."

"But if you are the one hiding, you suddenly become a lot easier to detect."

In the same way, extra light changes the conditions for predators and their prey inhabiting tropical forests. But the stakes are much higher.

Half of the species had a reaction

In the study, an international team of researchers analyzed 2.1 million images from wildlife cameras from 17 protected forests on three continents. The wildlife images are collected by the Tropical Ecology Assessment and Monitoring Network.

In total, 86 were recorded; 12 species displayed a strong avoidance of moonlight during the night, while only three species exhibited a strong attraction to moonlight.

"These were the species with the most pronounced reactions," Bischof explains.

"However, half of all the species responded to lunar phases. Either by changing their nocturnal habits, altering their overall activity levels, or both."

Avoidance of the full moon was more common, exhibited by 30% of all species, compared to 20% of species that showed attraction. Nocturnal species, especially rodents, were over-represented among species that avoided the full moon.

Beware of the full moon: Tropical forest mammals shy away from the moonlight
Armadillo. Armadillos are lunar phobic and less active when there is more lunar/moon illumination. Taken by a wildlife camera. Credit: TEAM - Tropical Ecology Assessment and Monitoring Network.

What is the problem?

Surely, moonlight is a . Why should we worry about how animals respond to it?

"The key takeaway from our research is that light affects animal behavior," Bischof says.

"It raises further questions about how changes in illumination affect species activity."

Other conditions that increase at floors include changes in canopy cover due to logging, and artificial illumination, such as road lights and buildings.

Tropical forests, which harbor a substantial portion of Earth's biological diversity, are being cleared, fragmented, and degraded at an alarming rate. This not only results in direct habitat loss and modification, but also in reduced canopy cover.

"Areas affected by artificial illumination due to urbanization also continue to increase."

More light—less activity

Despite humanity's massive impact on the globe, we still know remarkably little about the implications of illumination on the activity of most mammals.

The higher prevalence of avoidance of the moon in the study suggests there may be more losers than winners when illumination increases in tropical forests.

Moreover, almost all species that responded negatively to moonlight did so, at least in part, by reducing their overall activity during periods with a full moon.

Beware of the full moon: Tropical forest mammals shy away from the moonlight
Peccaries are lunar philic and shift their activity towards nights with high lunar illumination. Taken by a wildlife camera. Credit: TEAM - Tropical Ecology Assessment and Monitoring Network.

"If these results extend to artificial light, loss of dark nights could curtail the amount of time animals invest into foraging and other important activities," Bischof comments.

"There is a risk that we are fundamentally altering both species composition and species interactions in tropical forest communities through light conditions alone."

The influence of natural and artificial light raises important questions and concerns in wildlife conservation and ecosystem functioning.

Halloween is just around the corner; and as it turns out, the moon's influence extends beyond spooky tales and into the dark midst of our tropical forests. Recognizing this can help us shape more effective conservation strategies for the future.

More information: Richard Bischof et al, The moon's influence on the activity of tropical forest mammals, Proceedings of the Royal Society B: Biological Sciences (2024).

Journal information: Proceedings of the Royal Society B

Provided by Norwegian University of Life Sciences

Citation: Wildlife camera study finds tropical forest mammals shy away from the moonlight (2024, October 16) retrieved 2 June 2025 from /news/2024-10-wildlife-camera-tropical-forest-mammals.html
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