Would an electromagnetic pulse disrupt a carrier pigeon?
January 5, 2013 9:37 AM   Subscribe

Would an electromagnetic pulse disrupt a carrier pigeon?

I'm asking this due to some amusing but interesting questions in this g+ post on carrier pigeon national security.

"Last year, Mr. Decool became concerned that France could be outdone in carrier-pigeon expertise by China, which maintains a platoon of 50,000 birds with 1,100 trainers for communication in border and coastal areas, according to the Chinese Ministry of National Defense."

Related questions

Something else I have wondered about in the past is whether migratory patterns for organisms with magnetoreceptors would be disrupted during a geomagnetic flip. (or maybe they would be dying due to radiation?)

How important is magnetoreception to an animal that uses it for orienteering cues? Is it minor? Learning and other cues are probably more important?

How would an organism experience an EMP from an explosion?
posted by bleary to Science & Nature (5 answers total) 5 users marked this as a favorite
Best answer: Quick scattershot answer since I'm in a hurry:

Different organisms have different methods of magnetoreception -- an EMP might confuse those which actually have "compass-needle" type magnetoreception, but not those that rely on weird optical/quantum effects (I mentally file these under "magic" until such time as I actually need to understand them). There's a old paper entitled "Orientation of demagnetized bees" which shows that bees are not affected by fields which would demagnetize a compass needle, indicating that they'd be immune to EMPs. Not sure if it's been firmly established how they do sense magnetic fields.

Re non-magnetic cues in pigeon navigation: there was a study some time in the past few years which showed that homing pigeons make heavy use of landscape features for navigation, though that doesn't mean that they're not using magnetic fields as well. Sorry, don't have a reference but should be googlable.

Re geomagnetic flips, the magnetic field does not disappear completely, but can be vastly reduced in strength. If I recall correctly, there are vertebrates which do have "compass-needle" magnetoreceptors, and these magnetoreceptors are far larger than what would be necessary for the current magnetic field. One explanation is that they need to be that big to cope with the weak field during reversals.

A lot of this stuff is the subject of ongoing research and is not fully nailed down yet. If you want the nitty gritty, the biomagnetism publications of Joseph Kirschvink might be a good starting point.
posted by pont at 10:09 AM on January 5, 2013 [3 favorites]

Here's that study of pigeon navigation that indicates a strong usage of landmarks, although geomagnetic navigation hasn't been wholly ruled out.
posted by dhartung at 12:11 PM on January 5, 2013

EMPs have three components: E1, E2, and E3. E1 is the one most associated with damaging electronics, whereas E2 and E3 produce EM effects comparable to natural phenomena. Since E1 is by far the most powerful component, it would seem most likely of the three to cause effects in animals. However, it lasts for only a microsecond, which is about three orders of magnitude shorter than the time it takes a vertebrate to perceive a stimulus. Something that brief is not likely to be perceived at all unless it's strong enough to cause lasting activation of (or damage to) the sensory organ.

If animals can sense EMPs, I'd put my money on shallow-water sharks and rays, since their electroreceptor organs are presumably more designed for fine temporal and spatial resolution.
posted by dephlogisticated at 3:52 PM on January 5, 2013

Response by poster: pont: "
A lot of this stuff is the subject of ongoing research and is not fully nailed down yet. If you want the nitty gritty, the biomagnetism publications of Joseph Kirschvink might be a good starting point

A lot of them are too advanced for me, but I found one that is more approachable. Bats Use Magnetite to Detect the Earth's Magnetic Field.

This investigates whether bats use magnetite as a compass. They use a technique that has been applied to bacteria (‘Kalmijn-Blakemore’ re-magnetisation) to see if it would have an affect on the way-finding abilities of the bats. They've got a control group of bats, a group of bats that had magnetic pulses applied in parallel, and the group of bats that had the magnetic pulses applied anti-parallel (you'd expect these guys to be confused). Then they release the bats and see if they make it back home.

Figure 1 shows results! C is the antiparallel-pulsed group. Some of them go the opposite direction from the nesting site, but not all of them!

discussion bit
Not all bats exposed to an antiparallel pulse appeared to be affected, however. Indeed the behaviour of the group appears to be bimodally distributed between homeward and opposite headings and this is supported by significant orientation in the antiparallel group if it is treated as axial. If the magnetite was not free to rotate then the pulse may have caused this axial response. However as the bats used in this experiment were normally free-foraging, it is possible that some of them were familiar with the release site and simply flew home, ignoring conflicting compass information. This is consistent with previous results [8] showing that although big-brown bats are initially deflected in their homing direction by a magnetic treatment in a Helmholtz coil, many of them nevertheless found home during the release night. Alternatively we hypothesize that bats have, and use, additional directional information that they could switch to when they realised that the magnetic compass was faulty (for example an alternative compass mechanism), or that perhaps some bats weighed higher than others in a hierarchy. Previous experiments on birds have indicated that reliance on different compass mechanisms may change with age and experience [39]. It is also consistent with the results of cue conflict experiments in other animals in which different animals may use different strategies from the same release site [40]. It is unlikely that relative experience per se was responsible for the effect in the antiparallel group as this would have required the non random assortment of inexperienced individuals into this experimental group only. There was also no effect of sex on vanishing bearings and so the effect could not be explained in terms of a differential response between male and female bats. If the axial response in the antiparallel group is indeed due to an alternative compass mechanism or navigation strategy and not a response to the pulse per se then our results indicate that the magnetite in the magnetoreceptor cells is free to rotate, which would make an important distinction from birds [33] where the results do not support freely rotating magnetite.
posted by bleary at 9:54 AM on January 6, 2013

Response by poster: I don't know what alignment magnetic fields would have in an EMP. Definitely probably nothing nearly like the pulses applied in that experiment.
posted by bleary at 9:57 AM on January 6, 2013

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