Extreme precipitation variability,forage quality and large herbivore diet selection in arid environments |
| |
| Authors: | James W Cain Jay V Gedir Jason P Marshal Paul R Krausman Jamison D Allen Glenn C Duff Brian D Jansen John R Morgart? |
| |
| Institution: | 1. http://orcid.org/0000‐0003‐4743‐516X;2. US Geological Survey, New Mexico Cooperative Fish and Wildlife Research Unit, New Mexico State Univ., Las Cruces, NM, USA;3. Dept of Fish, Wildlife and Conservation Ecology, New Mexico State Univ., Las Cruces, NM, USA;4. Centre for African Ecology, School of Animal, Plant and Environmental Sciences, Univ. of the Witwatersrand, Wits, South Africa;5. School of Natural Resources and the Environment, Univ. of Arizona, Tucson, AZ, USA;6. Dept of Animal Sciences, Univ. of Arizona, Tucson, AZ, USA;7. School of Agricultural Sciences, Northwest Missouri State Univ., Maryville, MO, USA;8. Dept of Animal and Range Sciences, New Mexico State Univ., Las Cruces, NM, USA;9. Arizona Game and Fish Dept, Yuma, AZ, USA;10. US Fish and Wildlife Service, Cabeza Prieta National Wildlife Refuge, Ajo, AZ, USA |
| |
| Abstract: | Nutritional ecology forms the interface between environmental variability and large herbivore behaviour, life history characteristics, and population dynamics. Forage conditions in arid and semi‐arid regions are driven by unpredictable spatial and temporal patterns in rainfall. Diet selection by herbivores should be directed towards overcoming the most pressing nutritional limitation (i.e. energy, protein nitrogen, N], moisture) within the constraints imposed by temporal and spatial variability in forage conditions. We investigated the influence of precipitation‐induced shifts in forage nutritional quality and subsequent large herbivore responses across widely varying precipitation conditions in an arid environment. Specifically, we assessed seasonal changes in diet breadth and forage selection of adult female desert bighorn sheep Ovis canadensis mexicana in relation to potential nutritional limitations in forage N, moisture and energy content (as proxied by dry matter digestibility, DMD). Succulents were consistently high in moisture but low in N and grasses were low in N and moisture until the wet period. Nitrogen and moisture content of shrubs and forbs varied among seasons and climatic periods, whereas trees had consistently high N and moderate moisture levels. Shrubs, trees and succulents composed most of the seasonal sheep diets but had little variation in DMD. Across all seasons during drought and during summer with average precipitation, forages selected by sheep were higher in N and moisture than that of available forage. Differences in DMD between sheep diets and available forage were minor. Diet breadth was lowest during drought and increased with precipitation, reflecting a reliance on few key forage species during drought. Overall, forage selection was more strongly associated with N and moisture content than energy content. Our study demonstrates that unlike north‐temperate ungulates which are generally reported to be energy‐limited, N and moisture may be more nutritionally limiting for desert ungulates than digestible energy. |
| |
| Keywords: | |
|
|
