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Moonlighting: The Effect of Moonlight on Prey Activity

Image from telegraph.co.uk

Imagine you’re stuck on the African plains at night – would you feel safer with or without the moon? Choose carefully, there are more than just lions out there.

Most people would imagine that moonless nights are safer – after all, lions need to see their prey to catch it, right? The extra light from the moon should make things more dangerous for prey. However, a new study points out a critical flaw in that logic: Wouldn’t the extra light also help the prey as well?

Turns out, each species might decide about that.

Counter to the above logic, lions tended to actually hunt less on moonlit nights, preferring the complete cover of darkness. Rodents and rabbits tended to prefer dark nights as well. Primates didn’t though – full moons correlated with more activity, not less. The researchers had originally thought that activity levels would be organized neatly into a food-chain, but what they found was that the most important factor was possibly a prey animal’s senses, not trophic level.

If you’re a sight-loving primate, for example, bright nights help you spot that creeping lion. If you’re a rabbit and depend on your ears, well, maybe that’s a good night to stay still. 

In fact, some prey species may even vary their choices based on seasonal variations and predation risk. A different study showed that snowshoe hares moved around less during bright, snowy nights than dark, snowy ones, but showed no variation during the snow-free months when, presumably, predator risks are much different.

The take-away message is that prey animals don’t just cower at any possible risk – they base their activity on measurable trade-offs and risks. The moon is bright – is my extra vision worth the risk? The moon is dark – can I depend on my ears to keep me safe?

What’s moving around out there in the night?

 
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Posted by on October 27, 2013 in Natural History

 

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Leiningen versus the Ants

One of my favorite short stories as a kid was called Leiningen versus the Ants, written by Carl Stephenson. The hero: a brooding plantation owner, the villains: ants. Thousands and thousands of angry, hungry, army ants, emerging from the jungle like an act of god. They are said to form a mile wide corridor of death, capable of stripping a horse bare of its flesh in six minutes. They form bridges and construct complicated plans to attack their prey, knocking down foliage and tree trunks to evade obstacles. Eventually Leiningen has to make a mad dash through them in order to survive.

One of the creatures bit him just below the rim of his goggles; he managed to tear it away, but the agony of the bite and its etching acid drilled into the eye nerves; he saw now through circles of fire into a milky mist, then he ran for a time almost blinded, knowing that if he once tripped and fell…. The old Indian’s brew didn’t seem much good; it weakened the poison a bit, but didn’t get rid of it. His heart pounded as if it would burst; blood roared in his ears; a giant’s fist battered his lungs.

Then he could see again, but the burning girdle of petrol appeared infinitely far away; he could not last half that distance. Swift-changing pictures flashed through his head, episodes in his life, while in another part of his brain a cool and impartial onlooker informed this ant-blurred, gasping, exhausted bundle named Leiningen that such a rushing panorama of scenes from one’s past is seen only in the moment before death.

He survives, of course, although perhaps not with all of his parts intact. Hollywood made an adaptation of this story, casting Charlton Heston as the protagonist. They also included a love interest (of course) and titled it The Naked Jungle (it premiered back in 1954).

Of course, Stephenson does make a few exaggerations. Leiningen’s ants were the wrath of an angry god, but no predator is that indomitable. An ant colony capable of creating a mile wide front would be beyond anything scientists have ever seen. And while ant armies can be very dangerous to agriculture, the creatures most at risk are the old and the newly born. Most are able to simply move out of the way (although unfortunate domestics may be trapped behind fences or pens). The only adult people at risk of attack are the sleeping or the drunk. Also, victims are not simply consumed alive, although the truth might be even more disturbing to some. Animals die when the ants move through the nose and mouth down into the lungs, either suffocating on the insects or drowning in blood.

Some animals have actually evolved specific ant defenses, as they would against any predator. West African earthworms leave the earth and escape to the trees, while land snails surround themselves in a sticky mucus bubble shield. Wasps will raise an audible alarm by beating their heads against nests, warning nest mates of the impending attack. Some wasps even try aerial harassment, grabbing and flinging ants away from the nest (although this doesn’t really work in the long run). Most animals simply flee and return to the area afterward. Although, like a forest fire, the ants’ cleansing sweep is often followed by heightened biodiversity as animals and plans file back in. Empty niches to be filled, after all.

Sources: National Geographic (2)Wikipedia, ClassicShorts.com

 
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Posted by on December 27, 2011 in Modernity

 

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