Reports of the Academy of Sciences. General Biology . 2010, vol. 431, no. 6, s. 836840. The Russian hen is a rare semi-aquatic mammal endemic to the territory of the former USSR, many aspects of the biology of which still remain poorly studied. In particular, there is no reliable quantitative data on the locomotion of the excrement. This report describes swimming movements and for the first time provides key parameters characterizing the kinematics of the swim of the excrete. The ejector in the active part of the rowing cycle strongly diverts the hindlaps away from the axis of the body . Moreover, as the analysis of animal maneuvering in the water shows, the moments of hydrodynamic forces with such frontal strokes can be large enough to provide a sharp turn of the animal in just one rowing cycle. However, there was no distinct yaw during straight-line navigation. This suggests the presence of forces that compensate for the rotational effect of frontal rowing movements. It is possible that such constant active compensation can be provided by transverse hydrodynamic forces that occur during tail undulation.