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, 13 (4), e0187848
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An Experimental Approach in Revisiting the Magnetic Orientation of Cattle

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An Experimental Approach in Revisiting the Magnetic Orientation of Cattle

Debby Weijers et al. PLoS One.

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.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Rose diagram (full data set): Orientation of cows wearing and not wearing a magnet.
Rose diagrams: (A) the full data set of cow orientations with a magnet in the experiment (n = 97 measurements from 34 individual cows), (B) the full data set of cow orientations without a neodymium magnet in the experiment (n = 177 measurements from 34 cows).
Fig 2
Fig 2. Rose diagram (bootstrap data set): Orientation of cows wearing and not wearing a magnet.
Rose diagrams, each representing one realisation of a bootstrap data set of (A) and (B) 659 cows observed in the field, (C) and (E) 34 cows with a magnet in the experiment, and (D) and (F) 34 cows without a magnet in the experiment.
Fig 3
Fig 3. Rose diagram: the full data set of cow orientations in the field.
n = 2428 observations on 659 individual cows from 6 different farms in southwest Portugal.
Fig 4
Fig 4. Deviation of the compass needle from the magnetic north.
Deviation of the compass needle from the magnetic north (top of Fig) when exposed to one of the neodymium magnets used in the experiment (black dot). The dotted circle represents an area with a radius of 45 cm in which a clear deviation from the compass needle is visible.

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Grant support

The authors received no specific funding for this work.
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