Experimental evidence for sex-based palatability variation in fourwing saltbush

Abstract

Two small-plot grazing trials were conducted in the spring of 1996 and the winter of 1997 to determine whether sheep would differentially graze fourwing saltbush [Atriplex canescens (Pursh) Nutt.] on the basis of shrub sex in a uniform garden. Consumption was determined using an Australian method of leaf tagging in conjunction with the Adelaide Technique of biomass estimation. The results confirmed anecdotal field observations that herbivores prefer to graze the male shrub during late spring. No sex based preference was apparent during winter. We suggest that differences in physiological vigor and/or chemistry may influence relative palatability of the sexes through time. Results of these experiments contrast with those for an Australian member of the genus (A. vesicaria Hew. ex Benth.), for which it was found that the female was the preferred phenotype throughout the year.