Foxes Use Magnetic Compass for Hunting

In heavy snow, red foxes (Vulpes vulpes) hunt using a technique called “mousing.” The fox intently listens for the sounds made by a mouse or vole moving through tunnels under the snow (Figure 1). Once located, the fox erects it ears and cocks its head from side to side to better locate the source of the sounds. Then, the fox jumps high in the air and drives its muzzle deep into the snow to grab the unsuspecting vole in its teeth.

In a recent paper Cerveny and colleagues (2011) report that foxes orient their “mousing” attacks in a specific direction and may use the Earth’s
magnetic field to align their attacks.

Twenty-three experienced wildlife biologists observed “mousing” behavior in 84 wild foxes in the Czech Republic over a two year period. They recorded the foxes body orientation and the success of each of the 592 attacks.

redfox
Figure 1. A red fox (Vulpes vulpes) hunting for small mammals. (from Flickr/tiny_packages)

Surprisingly, the orientation directions were non-random. Instead, the majority of the time foxes prepared for a “mousing” attack by facing in a north-eastern direction. In addition, attacks oriented between 340
o and 40o were successful 73% of the time. Whereas attacks oriented in other directions rarely resulted in a meal for the fox.

mousing
Figure 2. Angular data of mousing foxes in high vegetation or snow cover. The direction of the arrow represents the mean vector of angular data. (b) all jumps and (c) known successful jumps. (From Cerveny et al. 2011)

The researchers ruled out explanations such as sun position, polarized light patterns, wind direction, and inter-observer bias. In the absence of other possible explanations, the researchers proposed that the alignment patterns were in response to geomagnetic fields. But why orient in one preferred direction? The answer may be that the geomagnetic field provides a horizontal distance to target. In other words, a range-finder to measure the distance from fox to prey when the prey are hidden beneath the snowpack. If true, this may explain the significantly higher success rate of foxes orienting their attacks in a northward direction.


References

Cerveny, J., Begall, S., Koubek, P., Novakova, P., and H. Burda. 2011. Directional preference may enhance hunting accuracy in foraging foxes.
Biology Letters, 1-3. doi: 10.1098/rsbl.2010.1145