Abstract
In response to the increasing number of observational studies on an apparent south-north orientation in non-homing, non-migrating terrestrial mammals, we experimentally tested the alignment hypothesis using strong neodymium magnets on the resting orientation of individual cattle in Portugal. Contrary to the hypothesis, the 34 cows in the experiment showed no directional preference, neither with, nor without a strong neodymium magnet fixed to their collar. The concurrently performed 2,428 daytime observations—excluding the hottest part of the day—of 659 resting individual cattle did not show a south-north alignment when at rest either. The preferred compass orientation of these cows was on average 130 degrees from the magnetic north (i.e., south east). Cow compass orientation correlated significantly with sun direction, but not with wind direction. In as far as we can determine, this is the first experimental test on magnetic orientation in larger, non-homing, non-migrating mammals. These experimental and observational findings do not support previously published suggestions on the magnetic south-north alignment in these mammals.
Highlights
We have been unable to find an experimental study for large mammals, which, at the time of observation, are neither homing nor migrating
In a study using high resolution Google Earth images and snow prints [33], it was suggested that large mammals, i.e., cattle and deer, respond to the Earth’s magnetic field
There was no obvious correlation between compass orientation of cows with or without a magnet
Summary
The ability of animals to sense the Earth’s magnetic field has been demonstrated by field observations for several animal taxa, including insects, e.g. ([1], [2], [3]), fishes, e.g. ([4], [5], [6], [7], [8]), amphibians and reptiles, e.g.([9], [10], [11], [12], [13]), birds, e.g. ([14], [15], [16], [17], [18], [19], [20]), small mammals e.g. ([21], [22], [23], [24], [25], [26], [27], [28]) and larger mammals like dogs [29], foxes [30] and wild pigs [31], but not horses [32]. While the majority of these studies are based on behavioural and tracking observations in the field, strong experimental evidence for sensing the Earth’s magnetic field is provided for relatively small animals in studies for homing, e.g. We have been unable to find an experimental study for large mammals, which, at the time of observation, are neither homing nor migrating. In a study using high resolution Google Earth images and snow prints [33], it was suggested that large mammals, i.e., cattle and deer, respond to the Earth’s magnetic field. They would preferentially align their bodies in a south-north direction when at rest [33].
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