SELECTIVE HERBIVORY BY THE DESERT WOODRAT (NEOTOMA LEPIDA) ON JOSHUA TREES (YUCCA BREVIFOLIA)

We studied herbivory by the desert woodrat (Neotoma lepida) on Joshua trees (Yucca brevifolia) in the Mojave Desert to determine whether N. lepida fled selectively based on leaf nitrogen content. We measured leaf nitrogen content and the location and amount of herbivory by woodrats on Y brevifolia trees in southwestern Utah, USA. Neotoma lepida removed the outer tips of leaves (1/3 to 2/3 of total leaf length) but left leaf bases, which had lower nitrogen content, uneaten. Herbivory by N. lepida also was concentrated on rosettes that were oriented south, and these had significantly higher nitrogen content than rosettes that were oriented north. Finally, X lepida led more on trees that had higher mean leaf nitrogen contents. Thus, M lepida selectively foraged among leaf parts, among rosettes of leaves, and among trees of Y. brevifolia, and disproportionate foraging was correlated with nitrogen content of leaves.