The role of the male flower spike as a cue for selective grazing in bladder saltbush

Abstract

Abstract. This paper reports the results of three cafeteria trials used to study palatability variation between the sex phenotypes of bladder saltbush (Atriplex vesicaria Heward ex Benth.). The results of the first trial show that Merino sheep preferentially grazed female samples compared to male ones, which supported earlier paddock-scale grazing trials and observations. In the second trial, the removal of male flower spikes led to increased consumption of male samples, suggesting that male flower spikes contain a grazing deterrent. The third trial showed that sheep were able to detect male material with or without spikes even when it was completely hidden within female plant material. In combination with observations made during the trials, these results suggest that there is a grazing deterrent present in male plants and that sheep use the male flower spike primarily as a visual cue when making grazing decisions.

Evidence for palatability variation between the sex phenotypes of bladder saltbush from small-plot grazing trials

“…Instead, these trials lend support to the alternative hypothesis (Graetz 1978) that sheep avoid the male flower spikes. Later research using cafeteria trials confirms indeed that sheep use the male flower spike as a visual cue to an underlying chemical deterrent in male shrubs (Maywald 1998;Walsh et al 2005).…”