ABSTRACT
Herbivores foraging on rangelands differ in their vulnerability to poisonous plants, and not all species of deleterious plants pose an equal risk. Animals foraging in familiar environments are less likely to be poisoned than animals foraging in unfamiliar settings. Some poisonous species are eaten repeatedly despite the consequences, whereas others are sampled and then largely avoided. Some mixes of plants prompt toxicity, whereas others are likely to diminish poisoning. Herbivores have receptor systems for detecting changes in both the external and internal milieu. Sight, smell, and taste enable animals to discern changes in plant attributes, and chemo-, osmo-, and mechano-receptors allow animals to detect changes within the body. Interactions among these receptor systems typically enable herbivores to circumvent toxicity. Herbivores are likely to eat plants containing toxins that do not stimulate the emetic system. Ruminants eat an array of plant species, varying in nutrients and toxins.
