90: Full Moon Killers

Speaker 0 00:03 Welcome to brain junk. I'm Amy Barton and I'm Tracy Kerr. And today we've got a brainstorm about owls. This all starts with a September, 2019 article published in nature called differential fitness effects of Moonlight on plumage color morphs in barn owls. I think I kept up with that, but I look forward to you. Well, let's make it a little less sciency. So this is by a huge crew of people. Uh, the lead author is Louis M San Jose. What that title means is barn owls come in, two colors are reddish Brown all over, and then ones that are white, bellied or white all over. And when I say barn owls, those are the ones with the really round faces in a little tiny beak. Now I want you to think about the night world and the cycles of the moon. Okay? Because owls are nocturnal. That means they do all their hunting at night and on days near or on the full moon. Speaker 0 01:03 It's super bright. You know, I've been camping like the summer we went camping and there was a full moon. We were by the ocean. So there's not a lot of ambient light around. And I could read a book outside. It was that bright. Okay. Now if you are trying to hunt and it's really bright, scientists have always thought that these owls that are lighter colored, well they're going to reflect a lot more light and so they wouldn't be able to catch as many mice. And so they've wondered for a long time, why do they even come and white? You know, why hasn't that selected out? Yeah. Because usually nocturnal predators, nighttime predators are darker or stripey to hide them from view. They thought there has to be some reason for barn owls to come and white and there has to be a reason why more males come in white than females. Speaker 0 01:52 What did they find out? Well, they've been studying a Swiss population of barn owls for about 20 years and it's a long study that is a long study, except that families with white owl dads didn't seem to be having as much of a problem, you know? So during next season, if you're having a full moon cycle under Fred, chicks don't grow as much and they're less healthy. So you know, they're looking at those chicks to try to determine how well they're eating. And those nests have chicks with white colored dads were doing better than they expected. Oh, well. So here's a funny thing. Voles and mice, when they see a predator will freeze. Okay. When you have the bright white Moonlight shining on a white owl, the voles and mice froze longer. So it was easier for the white owl to catch mice. Wow. While a Brown owl on a full moon might catch less than the average, like maybe two or three on a bright full moon night, a white owl stands to catch four to six mice or voles, which does a big difference. Speaker 0 02:58 That's a huge difference. This is what explains why there are more white bellied males than females because you need a Brown female on the nest because then they're harder to see. Right. Detecting the babies. But you'd want a male that's this brighter color. Because if he's hunting, he's more likely to bring home more mice. That's very interesting. Isn't that fascinating? And I'm back on the how there, cause I can imagine not really knowing what's going on and why. And so as scientists are watching the voles and the mice frees up for longer, I always wonder about the objectivity of scientists if they're like, Speaker 1 03:38 yeah, Speaker 0 03:43 they, they, they studied it in the lab. What they did is they simulated that moonlit light condition and then they had voles that were loose eyes. The bowls. Well, but they didn't use owls. They use like a mockup that was either white or Brown that could reflect light and then, you know, they're like cruise it over and the voles, they could then directly see how long they were freezing. Okay. So while you eating, if you ran that Brown one through a freeze for a few seconds, the white one going through more reflective light, it was, you know, six or seven seconds on spared the scientists watching lots of little creatures get eaten. Well, I imagine that the, the people, yeah, the people on the study definitely saw a lot of of animals. Well, I mean maybe, maybe you wouldn't because I mean you, how do you follow an owl, uh, in the dark at night? Speaker 0 04:37 So you're watching nest. Yeah. You're watching the nest and you could count like, okay, here he comes and poop. He's got two mice or one my, you know, yeah, they see the product, but not the moment. What I love about this kind of science is where your hypothesis is, I don't understand how this could work. Logic says this thing is brighter. It shouldn't be benefiting from this. And yet there has to be a reason and then you find out. Well it is and that's why it works. I don't, I don't have that creative mind to wonder about some of those things until they bring it up. And then I'm like, huh, Oh, you're right. It's is going on there. That's fascinating. Well, that is my brainstorm about owls. I hope you enjoyed it as much as I did. Go watch some footage of barn owls flying. Oh, bands. They are big. I've had one fly past me and I didn't hear a thing. You know, normally when a bird flaps past you, you hear there was nothing. It flew by and it just, it kind of, you know, creepy. Yeah. And it was really close and it spooked the dog. It was funny cause we were out, you know, playing ball quite late at night and she yelped Oh, because it came out of nowhere. Awesome. Speaker 0 05:51 We're on Facebook and Instagram as brain junk podcast and you can find us on Twitter as at brain junk Speaker 2 05:58 trace. And I will catch you next time when we share more of everything you never knew. You wanted to know. And I guarantee you will not be bored.