Cues cattle use to avoid stepping on crested wheatgrass tussocks

Abstract

This paper tests 2 hypotheses regarding the cues cattle use to avoid stepping on crested wheatgrass (Agropyron cristatum (L.) Gaertner) tussocks. The first hypothesis is that cattle are attentive to shade and avoid tussocks by stepping on light areas (soil interstices) and avoiding dark areas (tussocks). In an experiment with 90 Angus heifers placed in a short-duration grazing paddock of 8.5 ha, the animals stepped with equal relative frequency on 28 patches of bare ground, 37 disks painted the shade and color of bare ground, and 37 disks painted to match vegetation over a 24-h period. We therefore reject the shade-cue hypothesis. The second hypothesis is that cattle are attentive to the vegetation itself in their avoidance behavior, and that as they crop the vegetation the frequency of trampling increases. In experiments similar to the first, cattle stepped on 85 intact tussocks 9 times, on 85 clipped (3 to 4 cm above litter) tussocks 28 times, on 85 vegetation-free tussock mounds 107 times and on 35 patches of bare ground 130 times. These differences are statistically significant. The data are consistent with the vegetation-cue hypothesis, except that the cattle also were attentive to the elevated substrate upon which the tussock grew. We conclude that, under the test conditions, hoof action does not have an important impact on crested wheatgrass pastures used for short-duration grazing. The impact could approach importance, however, if the pasture was grazed more heavily and if the vegetation was dry and dusty.