Date: May 8, 2010

Title: How Lunar Cycles Affect Wildlife

Podcaster: Wild Ideas

Organization: Wild Ideas…the Podcast by The WIlderness Center

http://www.wildernesscenter.org

Description: It’s a surprising how much effect the moon –its light, its tides — has on the earth and some creatures. Look at how the behavior of owls and their prey, the ocean’s deep scattering layer, horseshoe crabs/shorebirds, and even corals are affected by the lunar cycle.

Bio: WIld Ideas…the Podcast is your own nature talk! Observations of everyday nature leads to bigger ideas about the natural world and how it all fits together. Join a naturalist, a science educator, and a conservation biologist for friendly, science-based nature chat. Wild Ideas … the Podcast won’t keep you indoors! Take the wild ideas outside to enrich your personal observation and play – it’s good for you, good for your kids, and good for nature. Wild Ideas … the Podcast is produced by The Wilderness Center, a nonprofit nature center, land conservancy, and ecopreneurial organization.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by John Sandlin because a little astronomy illuminates the darkest nights.

Additional sponsorship for this episode of 365 Days of Astronomy has been provided by Kylie Sturgess and the Token Skeptic podcast, a weekly show about superstition, science and why we believe – at www.tokenskeptic.org.

Transcript:

Wild Ideas…the Podcast for 365 Days of Astronomy

Intro music

Gordon Maupin, Naturalist
I’m Gordon Maupin, a naturalist with Wild Ideas…the Podcast and with me today is science educator Joann Ballbach

Joann Ballbach, Science Educator
Hi!

Gordon
And conservation biologist Gary Popotnik

Gary Popotnik. Conservation Biologist
Hi, everyone!

Gordon
We’d like to share many of the connections between astronomy and animal species in the natural world and one of the things that comes up often is lunar cycles and how they affect wildlife and people. Or not.

Joann
Well, Gordon, there’s a saying about how the moon affects people.

Gordon
Well, OK. I’m going to read a list here. The homicide rate, traffic accidents, crisis calls to police or fire stations, birth of babies, suicide, major disasters, casino payout rates, assassinations, kidnappings, aggression by professional hockey players, violence in prison, psychiatric admissions, assaults, gunshot wounds, stabbings, emergency room admissions, lycanthropy (that means werewolves), vampirism, alcoholism, sleepwalking, epilepsy, and human fertility.

Joann
That’s the list of weirdness blamed on the moon!

Gordon
And it’s all claptrap and confirmation bias. So just…

Joann
Not true.

Gordon
It’s just not true. All this stuff has been examined statistically and when you look at the numbers, they have no relation to lunar cycles. But people have great confirmation bias. It’s a big error people can make so easily. By having it put into the folklore that something might be associated with a full moon, then, when there’s a full moon and they notice something weird, they go “Oh!” and that’s just pure confirmation bias. When you look at it through a statistical lens where you actually keep careful track of it, all these effects disappear.

Gary
Well, the one that really surprised me were vampires. I mean, I know werewolves are around the full moon, but you know Bela Lugosi sucked blood no matter what.

Joann
Oh, come on, you guys! Get back to the science. I went and looked up some scientific studies, well controlled, not confirmation bias, about predator and prey in the moonlight and how moonlight affects them. I found a lot of information about owls.

Some owls are auditory hunters and rely almost solely on their hearing. Moonlight doesn’t really affect them. But some owls also hunt partially visually and moonlight does affect them. There was a study by Woods and Brigham, published in the Wilson Journal of Ornithology, about Poorwills. Now, they‘re not owls, but they are preyed upon by owls. They’re a little bird. They call. Woods and Brigham showed that the Poorwills call more in response to an owl call during times of full moon than they do during times of new moon.

They think that’s because the light of the moon lets them see better, so they forage more efficiently so they have extra time on their hands after they foraged, they don’t have to look for food as much. It’s easier for them to move around, so the males can move and defend their territories, and it’s easier for them to detect the predators. They can see those owls coming.

Gordon
And you have to see an owl because they are absolutely silent.

Joann
They really are. They’re completely silent.

So, Woods and Brigham quoted other studies that showed that small nocturnal birds that have acute vision that are preyed upon by owls are often more active during full moon times.

They also cited some other studies that I thought were interesting. So some animals that are eaten by owls are actually more active during the full moon, but some animals that are eaten by owls are less active during the full moon and the example they quote are gerbils and desert rodents. They can’t see the owls coming as well. They adjust their foraging patterns. The owls prey on them so, during full moon, they’re less active.

There were also follow-up studies by some of the people in this study, that showed that brown tree snakes and Short-eared Owls have basically the same habits. They prey more, they’re more successful in their predation, during the time of a full moon, probably because of the light.

Gary
You know, brown tree snakes, that’s

Joann
Brown tree snakes

Gary
That’s pretty cool because most of the time we think of reptiles, and snakes in particular, as a diurnal animal and not with nocturnal hunting skills.

Joann
Well, the brown tree snake is a nocturnal predator and it hunts in the forest canopy and on the ground. It uses both visual and chemical cues so it’s that visual component that the moonlight is helping.

Gary
Wow.

Gordon
Confirmation bias can be really powerful. I remember one time driving across northern Missouri at night, a full moon, and it seemed like every billboard along the highway had a Great Horned Owl perched on it. And I was thinking “Wow! Full moon. These owls are really active.” And only later did it dawn on me (no pun intended) that it was the breeding season and they were showing off. But the light enabled me to see owls that I would drive by totally oblivious to them on any other occasion.

Joann
I wonder also if it had affected their behavior. There was another study by Abbruzzese and Ritchison that said that Eastern Screech Owls are another of these owl species that hunt partially by vision, and so they actually perch higher during full moon, because they can see farther, than they do during new moon. So maybe your Great Horned Owls were perching higher, too.

Gordon
Well, in the breeding season they certainly want to be seen.
A lot of stuff involves the oceans and the lunar cycles. One of the more dramatic ones that has only recently been discovered is they got into submarine warfare and trying to figure out how to hide submarines

Joann
Now you’re not going to tell me submarines come out with the full moon, are you?

Gordon
Well, they do come out with the full moon. And they also come out any other time of the month as well.

But there’s a layer in the ocean. It’s called the deep scattering layer. Living things move up and down in the water column in response to the amount of light and so the deep scattering layer, composed of everything from microscopic plankton, copapods, and that sort of thing, to the little tiny fish that eat them, to the bigger fish and the bigger fish that eat them are in a layer that moves up and down. Down in the daytime and deeper during the full moons so that these species can escape visual hunters like sea lions and sharks and that sort of thing and then, in the dark of the moon and at night time, the deep scattering layer moves higher. So this is a real effect on wildlife of the lunar cycle.

Joann
But of course, what I think of when I think of the lunar cycle and its effects on earth are the tides. The tides have so much effect on ocean creatures.

Gary
It really does. And this can be seen in horseshoe crabs.

Gordon
They look like a horseshoe with a tail.

Gary
They do look like a horseshoe

Joann
They do!

Gary
These guys also depend on the moon, but not with the brightness of the moon. It actually has to do with where the tides are at their greatest extent, either very low tides or very high tides.

Now, during the spring, usually in April and May, out in the Atlantic Ocean, we get this great influx of horseshoe crabs.

Joann
What does it have to do with the tides?

Gary
They choose the highest tide to deposit their eggs. Now what’s also timed in behind this is the migration of shorebirds. Good gosh, Dunlins and Red Knots and all the plovers and all the stilts, variety of species that are coming up the east coast and it’s timed almost perfectly with the deposition of eggs from horseshoe crabs and they’ll just start consuming eggs. In fact, it makes up 90-95% of their diet during migratory periods of time.

Gordon
So you have a cascade effect. The moon makes the tides, the tides create the right conditions for the horseshoe crabs to lay their eggs, and then the shorebirds arrive.

Gary
And then the shorebirds arrive.

Joann
And eat the eggs.

Gordon
Another effect with the moon and sea life in particular is that the full moon can act as a trigger for synchronicity in wildlife and this was done with corals. They have no eyes, but they have light-sensitive cells and they can detect a full moon and corals will synchronize the release of egg and sperm. They release egg and sperm into the ocean at large and it’s very important for these creatures to synchronize that because if you put

]oann
So that they meet!

Gordon
So the egg and sperm happen to be out there at the same time and that’s the way corals reproduce and the full moon is a trigger for that.

Joann
So it’s a little surprising, even though there aren’t any werewolves, Gordon, how much effect the moon; its light, its tides has on the earth and some creatures.

Gary
Well, I’m going to have to remove all that garlic I have over my doorway and around my windows.

music

Gordon
Wild Ideas…the Podcast is on the same page in iTunes under Natural Sciences as 365 Days of Astronomy. Thanks for having us! You can find The Wilderness Center and Wild Ideas…the Podcast on the web at wildernesscenter.org.

music

End of podcast:

365 Days of Astronomy
=====================
The 365 Days of Astronomy Podcast is produced by the Astrosphere New Media Association. Audio post-production by Preston Gibson. Bandwidth donated by libsyn.com and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. Until tomorrow…goodbye.