Fig. 1.

Using magnetometer data to distinguish between different meerkat postures. The Earth’s magnetic field ${\overrightarrow{B}}_E$ (green arrows) inclined at a dip angle of δ with respect to the horizontal plane (salmon-pink disk) subtends components (blue arrows) equal in magnitude and opposite in sign along the collar sensor’s (in red) roll axis during (a) vigilance, and (b) curled-up resting, demonstrated in the simplified case when the roll axis is perfectly aligned with the local vertical direction. When the roll axis lies in the horizontal plane, as shown in (c), the measured component of ${\overrightarrow{B}}_E$ is further affected by the possibly arbitrary azimuthal angle α