Some Ecological Effects of Feral Sheep on Santa Cruz Island, California, USA
Van Vuren D and Coblentz BE. 1987. Some Ecological Effects of Feral Sheep on Santa Cruz Island, California, USA. Biological Conservation. 41(4):253-268
Long-term overgrazing by feral sheep has resulted in moderate to severe ecological impacts to about one-half of Santa Cruz Island. Feral sheep were generalist herbivores, consuming a variety of plants according to availability and phenology. Insular endemic species in particular were preferred, and sheep reared on their hind legs to reach leaves of endemic shrubs. Effects of sheep on a grassland community included reduced herbaceous cover, increased bare ground, altered community structure, decreased litter, and increased erosion. Sheep browsing impacted shrubs by altering growth form and preventing regeneration, and by completely defoliating lower-growing shrubs. Trailing by sheep denuded 7% of some areas. Sheep-caused modifications of one plant community were associated with a dramatic decrease in density, species richness, and diversity of birds, including several insular endemic taxa. These results, along with those of other recent studies, demonstrate that feral sheep cause serious and unacceptable damage to sensitive insular ecosystems.
- Type
- Journal Article
- Authors
- Van Vuren, Dirk; Coblentz, Bruce
- Units
- CHIS
- Keywords
- Animal Studies, Feral Animals, Grazing, Impacts, Plant Studies, Santa Cruz Island Channel Islands National Park CA, Sheep (Domestic), Vegetation