Can Plants Practice Mimicry to Avoid Grazing by Mammalian Herbivores?

Mimicry has been suggested as a grazing avoidance mechanism for plants. This study examined the ability of a mammalian herbivore to generalize conditioned flavor aversions (CFAs) to determine if the conditions for plant mimicry exist. Nine sheep (treatment group) were averted to cinnamon on ground rice while an additional 9 sheep (control group) received cinnamon on rice with no negative post-ingestive consequences. When offered a choice between wheat and cinnamon-flavored wheat the control group ingested more (P < 0.05) cinnamon-flavored wheat (45 ± 6%) than did the treatment group (3 ± 1%) in four test periods. This implies that herbivores generalize CFAs and thus non-poisonous plants could mimic the flavor of poisonous plants to avoid grazing. Next, the animals were given a choice between soybean meal (SBM) in a food box which smelled of cinnamon and SBM in a food box with no added odor. The treatment group ate less (P < 0.05) SBM with cinnamon odor than did the control group in the first test period (13 ± 10% vs 58 ± 11%). However, the following three periods revealed no intake differences between control and treatment animals. This suggests that odor alone is not persistently effective in preventing herbivory by sheep, but that both taste and odor must be similar for one plant to successfully mimic another.