Influence of Stock Density and Rate and Temporal Patterns of Forage Allocation on the Diet Mixing Behavior of Sheep Grazing Sagebrush Steppe

Document Type

Article

Journal/Book Title/Conference

Applied Animal Behaviour Science

Volume

100

Issue

3-4

Publisher

Elsevier

Publication Date

2006

First Page

207

Last Page

218

Abstract

An animal's ability to select a diet depends on forage availability, the density of herbivores, and the allocation of forage resources. We hypothesized that the temporal and spatial availability of forages in sagebrush steppe vegetation both influence food selection and may encourage lambs to learn to use sagebrush, a shrub that contains high levels of terpenes that limit food intake. We conducted a field study with three treatments of 20 lambs each. Forage resources were manipulated by restricting grazing areas. Lambs in treatment H grazed at a high stock density, whereas lambs in treatment L grazed at a low stock density; both groups were moved to fresh pasture daily. Lambs in treatment H3 had three times the area of treatment H, but they were moved every 3 days, making the total area grazed by H and H3 equal, but with a different temporal allocation of forage. Scan sampling was used to record the incidence of consumption among sagebrush and understory herbs. During 24 days of conditioning, stock density and temporal patterns of forage allocation both influenced the behavior of lambs. Lambs in H spent more time foraging on sagebrush (25%) than lambs in H3 (16%), and lambs in both H and H3 spent more time foraging on sagebrush than lambs in L (1%) (P < 0.05). For lambs in H3, foraging on sagebrush was cyclic and depended on the daily availability of herbs. Use of sagebrush, expressed as a percentage of total foraging time, wasH3 > L (P < 0.005). Thus, the availability of alternative foods, manipulated through animal density and the temporal allocation of those resources, both affected how readily lambs learned to use sagebrush.

Comments

Originally published by Elsevier. Publisher's PDF and HTML fulltext available through remote link.

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