Spicing up restoration: can chili peppers improve restoration seeding by reducing seed predation?

Abstract

Seed predation by rodents presents a significant barrier to native plant recruitment and can impede restoration seeding efforts. In nature, some plants contain secondary defense compounds that deter seed predators. If these natural defense compounds can be applied to unprotected seeds to inhibit rodent granivores, this approach could improve restoration seeding. Capsaicin is the active ingredient in chili pepper (Capsicum spp.) seeds that creates the burning sensation associated with human consumption of hot peppers. This compound has a similar effect on other mammals and is believed to have evolved as a deterrent to rodent seed predators. We used seed‐coating techniques to attach powder ground from Bhut Jolokia (Capsicum chinense) peppers to native plant seeds and evaluated the efficacy of these seed coatings for deterring rodent seed predation and enhancing native plant recruitment using laboratory and field experiments. Laboratory feeding trials demonstrated that native deer mice (Peromyscus maniculatus) consumed far fewer pepper‐coated seeds compared to untreated control seeds. Field seed‐addition experiments consistently demonstrated that rodent seed predation reduced native plant recruitment over the 4‐year study. Coating techniques used in the first 3 years were not persistent enough to reduce rodent seed predation effects on plant recruitment. However, a more persistent coating applied in conjunction with late‐winter sowing negated rodent seed predation effects on recruitment in year 4. Our results demonstrate that coating seeds with natural plant defense compounds may provide an effective, economical way to improve the efficacy of plant restoration by deterring seed predation by ubiquitous rodent granivores.