Results. Bearings and mean directions of the initial orientation (a), orientation at the inner circle (b) and orientation at the wall of the arena (c); in the figure the radius of the circle corresponds to a mean vector length (r) equal to one. Graphs in the upper row show the results obtained under natural conditions, graphs in the lower row (highlighted) those obtained with the reversed magnetic field (n = 29 in all cases). Dashed lines indicate the 95% confidence intervals in cases of significant orientation (P < 0.05). Under natural conditions the magnetic North (mN) coincided with the true north direction (nN), whereas in the reversed field mN was opposite to nN. Coloured arrows indicate the direction to the pond (P), the direction from the hibernation area to the pond (HA) and the mean direction along the drift fence (D). In the case of the reversed field, corresponding arrows are placed on the opposite side, in paler colours, to illustrate the directions when following only the magnetic field.