Moonlight Can Be A Benefit For Some Prey Species
October 22, 2013

Not All Prey Falls Victim To Moonlight

Lee Rannals for – Your Universe Online

According to a new study published online recently in the Journal of Animal Ecology, not all animal species are negatively affected by moonlight.

One prevailing theory in ecology is that moonlight increases predation risk, but Laura Prugh, a wildlife biologist at the University of Alaska, Fairbanks, says that is not always the case.

"Ecologists have long viewed the darkness of a moonless night as a protective blanket for nocturnal prey species," Prugh said in a press release. “The theory that moonlight increases predation risk ignores the fact that prey animals also have eyes, and they often use them to detect predators."

While moonlight may help some predators find prey, it could also help some animals seek out approaching predators. In order to get down to the bottom of how animals are affected by moonlight, researchers compiled its effects as reported in existing studies of 58 nocturnal mammal species.

Researchers found that species ranged widely in their affinity for moonlight, from the moon-loving lemurs to the lunar-phobic kangaroo rats in the southwestern United States.

"Contrary to the expectation that moonlight increases predation risk for all prey species, however, moonlight effects were not clearly related to trophic level and were better explained by phylogenetic relatedness, visual acuity and habitat cover," the authors wrote in the journal.

Prey animals that use vision as their main sensors system were generally more active during bright nights, while prey species that relied on senses like smell were generally less active. Predators such as African lions were also less active on moonlit nights.

"Moonlight is indeed risky for some prey species, but only those that use vision as a backup system rather than their first line of defense," said Prugh. "Our synthesis shows that moonlight can benefit visually oriented prey.”

This study is the first to examine how moonlight can affect a diversity of species. Nearly half of all mammals are nocturnal, and the moon is constantly changing its face every month.

“Our results suggest that moonlight alters predator-prey relations in more complex ways than previously thought,” Prugh said in a press release. “Do lunar cycles affect population growth rates? How do artificial lights affect the hunting success and vulnerability of nocturnal species? These are important questions that we do not currently have answers to."