Diet switching by mammalian herbivores in response to exotic grass invasion.

摘要: Invasion by exotic grasses is a severe threat to the integrity of grassland ecosystems all over world. Because grasslands are typically grazed livestock and wildlife, invasion community process modulated herbivory. We hypothesized that native South American Eragrostis plana Nees, an tussock-forming grass from Africa, could be deterred grazing if grazers switched dietary preferences included invasive as large proportion their diets. Bos taurus (heifers) Ovis aries (ewes) plots with varying degrees E. in replicated manipulative experiment. Animal positions species were observed every minute 45-min session. Proportion bites steps out tussocks measured used calculate several indices selectivity. Both heifers ewes exhibited increasing probability area covered increased, but they behaved differently. In agreement expectations based on allometry morphology, consumed low plana, except areas had more than 90% cover. Heifers proportionally ewes. Contrary our hypothesis, herbivores did not exhibit switching towards grass. Moreover, avoidance preference for short-statured species, both which should tend enhance invasion. Unless plants highly palatable livestock, effect deter limited, due inherent main ecosystem, particularly sheep.