Tuesday, August 26, 2008

Magnetic cows? Well, maybe not.

Science journalists love a kooky headline.

The latest is magnetic cows. It seems rather blown out of proportion.

Google earth photos indicate a tendency for cows (and some other grazers) to line up north-south. But supposedly you can't tell if they are facing north or facing south or any mixture of the two.

So, here's a conjecture*:
In the morning, cold cows stand side on to the sun (which is in the east), thus exposing a greater area to the sun.
In the late afternoon, cold cows stand side on to the sun (which is in the west).
In both cases, they will face either north or south (and probably won't prefer one much over the other).
In the middle of the day, warm cows in a paddock with little shade might even stand backside toward the sun (thus reducing sun exposure when they're hot)... and thus tending to face either north or south, depending on the hemisphere.
Consequently, there would be some tendency for cows to line up north-south, purely as a way of managing sun exposure in order to be more comfortable.

[*Yes, yes, I know it says in the BBC article Their study ruled out the possibility that the Sun position or wind direction were major influences on the orientation of the cattle. Dr Begall said: "In Africa and South America, the cattle (were) shifted slightly to a more north-eastern-south-western direction."
"But it is known that the Earth's magnetic field is much weaker there," she explained.
How does that establish anything? If sun and wind hypotheses have been ruled out, why not explain how? The bit about Africa and South America really doesn't help that much, so if that's what they've got, it's damn weak.]

Edit: Well, reading the physorg link more closely, it looks like they used "shadows" to discount the effect of the sun. It's not clear what precisely they did -- there are a variety of possible conjectures that might involve the sun. I'll have to try to get the PNAS paper. I just went looking for it, but in spite of the fact that the library supposedly has electronic access, the article is not showing up, either in the most recently available issue there, nor in the articles that have immediate access.

Indeed, I can think of several other perfectly simple explanations that I'd want to eliminate before I start hypothesizing magnetic cows.

Does that mean that I assert cows don't have a magnetic sense like some birds?
Not at all. Such a thing would be particularly useful for some migrating animals, say, caribou or wildebeest, so it's certainly not completely out of the realm of possibility. But you have to at least show that it's not some rather obvious and simple thing like sun exposure before you take it at all seriously. And you need a lot more than "they looked at shadows" or "the cattle were at a slightly different angle in Africa" before concluding that you've eliminated alternative explanations.

That cows tend to align north-south is interesting. But magnetic cows is a bit overblown on that basis alone. At best its a plausible conjecture.

Well, I guess we wait and see. If anyone does see the paper, I'd be curious to know just how strong the arguments for the elimination of alternative explanations actually was.


NotZed said...

Thought the same thing. Of course it is easy to test - place them in a disoriented magnetic field and see what happens.

Which of course is the sort of basic science that should be done BEFORE this sort of nonsense hits the airwaves.

Blake Stacey said...

Here's the paper.

Efrique said...

Thanks Blake.

I'll be able to access the full article as soon as I'm on campus again, but even the abstract sounds much more sensible, presenting the observations as a puzzle to be explained. I note also the abstract is almost entirely about deer, but the news items focused much more on the cows...