Date: August 10, 2010
Title: Astronomy for Non-human Life Forms
Podcaster: Steve Nerlich & The Ordinary Guy
Description: Steve and the Ordinary Guy from the Brains Matter podcast discuss those other astronomers amongst us who were already hard at work long before Galileo came along
Bio: Cheap Astronomy offers an educational website where brains really do matter.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Cheap Astronomy, www.cheapastro.com . It’s more than you bargained for! OK, enjoy!
Hi, this isn’t the Ordinary Guy (OG) from the Brains Matter Podcast www.brainsmatter.com. And this isn’t Steve Nerlich from Cheap Astronomy www.cheapastro.com. But this is Astronomy for non-human life forms.
Steve: Isn’t it just sheer hubris to assume that us humans are the only ones who have ever looked up and searched the sky for meaning – and even tried to look beyond the visible spectrum for other hidden data that might help us understand the world we live in. So, this podcast is for all those four-footed, winged, finned, shelled, antennae-ed, pseudopodia-ed…
OG: OK Steve, I think they get it.
Steve: Oh, sorry… So, will we start with the birds?
OG: Let’s do that.
Steve: I wanted to tell you about some German researchers back in the 1950s who were doing things with birds in planetariums – and what they would do was release the birds with a particular night sky projected on the planetarium ceiling. What they found was if they – and remember these are northern hemisphere birds – if they presented those birds with an autumn night sky (and this is where Betelgeuse is in the east) if it was an autumn night sky the birds would fly south, so they’re flying south for the winter – but if it was a spring night sky, then the birds would fly north (and they’d know it was spring because Betelgeuse was in the west).
OG: Well, there are some sea birds called the Leach’s Storm Petrels, named after the wonderful William Elford Leach. The sworn enemy of the Petrel is the Slaty-Backed Gull (that sounds very Harry Potter I think).
In a paper by Yutaka Watanuki at Hokkaido University in 1986, he said that petrels reduced their activity in moonlight when predation rates by the Slaty-Backed Gulls was highest. It was found that petrel activity levels were inversely correlated with light intensities from our Moon, and the conclusion was that nocturnal activity and moonlight avoidance by the petrel colonies evolved as a defence mechanism.
Steve: So am I right in thinking they don’t fly when the Moon is up – because they are visible to their enemies?
OG: Pretty much. When they are going foraging post-dusk, they do realise when the Moon’s out they are more likely to become dinner.
Steve: All right. I was telling you about how the birds can navigate by the stars. They can also navigate by the Sun. There’s some researchers who’ve looked at swallows.
OG: Is that European or African swallows?
Steve: Well, even if an African swallow could carry a coconut – they’re not migratory. So these migratory swallows, which are European swallows, are often found perching on power lines and if you look carefully (at least these researchers allege) – in the morning they’re always facing east and in the evening, they’re always facing west. What they are doing is getting their bearings from sunrise and sunset – and the birds can pick up polarised light from sunlight, so as the Sun’s coming up in the morning it might not come up at due east, but the light that it’s transmitting always has the same orientation – and it would seem that the birds are able to pick up the light that’s being polarised in a particular plane. That’s telling them where due east is – so when they compare that to where the Sun actually is they a reasonably good sense of what latitude they’re at.
I can keep going – I’ll you more about pigeons. So birds have ways of navigating by night using the stars and by day using the Sun – but they also have an extra sense – this is magnetoreception – and this is of course a sense for the Earth’s magnetic field – which might help them get around when it’s cloudy and overcast. Pigeons seem to be particularly good at that – you can give them these little goggles so they can’t see very far in front of them and they can still home. So pigeons rather than being migratory just have a strong urge to fly back to their nest essentially. So their homing pigeons and their magnetic sense to home – so first to go out and them to come back again. OK, I’m finished.
OG: Now I’m going to talk about loggerhead sea turtles. These turtles have an amazing sense of navigation and orientation – though it’s not believed that they use visual cues such as the stars to navigate. As soon as the hatchlings are born, they go straight towards the open sea, and they can maintain their heading, well after you lose sight of land. So how do they manage these feats?
Let’s start at the beginning – experiments were done on hatchlings back in 1960 and 1968 to see if they could find water if they had their eyes covered. They found that once the hatchlings had their eyes covered, they couldn’t find their way to water. So it’s believed that the oceanic horizon at night is brighter than the landward horizon, given that water reflects more moonlight and starlight than the land. If you imagine yourself with coke bottle glasses in front of your eyes you might not see things clearly, but you can see where the light is.
However, some experiments done in 1992 found that slope might be a driver, as well as the amount of light. And slope makes sense as land tends to slope towards the water in coastal areas.
So going on a bit from there. Lohmann and Lohmann in 1993 also discovered that magnetic orientation played a part in directional preference for loggerhead turtles. The turtles oriented set to north in a geomagnetic field. They tested this by placing control conditions and observing where the turtles oriented themselves. Curiously, once the magnetic fields were reversed, so were the orientations of the turtles.
So the best way to view the way loggerheads oriented themselves is through the following. From when they’re hatchlings going from the shore to the ocean – it’s a combination of visual clues, and the slope of the land. And once they’re in the water close to land they do it by wave orientation, because as waves come closer to the shore there’s a certain periodicity as it comes closer to the shore – as opposed to out in open water. In the open sea where there’s a lack of visual cues and a lack of periodicity, they go via magnetic orientation. And that exactly what the turtles are doing.
Steve: Did you know that the basis of a lot of magnetoreception is a compound called magnetite – which is a particular sort of iron ore where the electrons of a collection of iron atoms are all oriented in a particular way so that you have a magnet – so magnetite is just a natural magnetised material. But it would seem a lot of animals, everywhere from bacteria up to complex animals like birds, absorb that magnetite from the environment. And at least in the bacteria and insects we know they further modify that material to essentially build crystals within their bodies – and at least in the smaller animals we can tell they are essentially just lining those crystals up so that you have a compass needle within that animal. And I can only refer to the small animals – it becomes quite difficult to isolate the magnetite in larger animals because they’re that much larger. It’s hard to dig into their brains to find exactly where this magnetite is.
So I’m telling you all this because we also know humans have magnetite in their brains. It’s unclear whether that’s just the result of us just absorbing some natural magnetite from the environment, or whether it’s a sort of evolutionary hangover from an ancestor that actually used it for magnetoreception or whether it does have some effect on our sense of the world.
Some research has suggested their might be a few individuals within large groups who seem to be better at finding their way around with no visual cues than others, but it does seem to be a very weak sense if there is one at all. So I wonder if anyone feels they have magnetoreception at any level – I don’t think I do.
OG: I don’t think I do either – but if you do, please contact us.
Steve: Yes, send emails.
OG: And you mentioned the magnetite just then and I’m glad you did because I want to talk a little bit about bees. Bees are colour blind in dim light – or so it’s thought anyway. They are primarily active during the day and as we know have compound eyes. Willam Kerfoot wrote a paper in Animal Behaviour in October 1967, that the nocturnal bee, Sphecodogastra texana – which was observed in some experiments 1962, 1964 and 1965, that the foraging of texana was based on the lunar cycle and he classified in two parts – the crepuscular period and the moonlight period.
The crepuscular period is from between sunset and the end of twilight (so not a huge amount of time), and the moonlight period occurred from the day after the new moon until three days after the full moon – and during this time, foraging continued to happen as long as the moon was up. So Kerfoot wore that the lunar activity was an extension of the twilight foraging.
A paper called “Biogenic magnetite as a basis for magnetic field detection in animals” mentions that there are a large number (10^8) superparamagnetic magnetite crystals in honey bees. And that’s what I’ve got to say about bees.
So what we’ve discovered today is that there’s a huge influence that astronomy has on all these creatures. So we’ve talked about visual cues, magnetic cues – the effect of the Earth’s magnetic field, the Sun, the Moon, the stars – on the way these creatures live and I don’t know if many people would normally think about creatures being influenced by astronomy.
Steve: Well, I’m worried we’ve been talking for nearly ten minutes and we haven’t mentioned sex. I think this is an important issue here…
OG: But we’ve already talked about the birds and the bees, I must point that out.
Steve: That’s true – you’re right. But was going to mention coral reefs, we find this around Australia particularly, coral reefs are made of individual coral organisms – which are animals. And they need to reproduce and they’re sort of stuck in hard calcium shell-like structures – they can’t really get out and get to know each other. So what they is to coordinate the release of eggs and sperm – and they do this by seemingly tracking the lunar cycle, so that there’s a particular night when all the coral will spawn at the same time – and that’s how they manage to reproduce.
OG: Well, I’ve certainly learnt a lot today.
Steve: Yes, me too. Alright, shall we do our wrap up?
Thanks for listening. This is Steve Nerlich from Cheap Astronomy, www.cheapastro.com and this is the ordinary guy from the Brains Matter podcast, www.brainsmatter.com. Cheap Astronomy offers an educational website where brains really do matter. No ads, no profit, just good science. Bye.
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365 Days of Astronomy
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