The Relevance of Burial to Evade Acorn Predation in an Oak Forest Affected by Habitat Loss and Land Use Changes

Abstract

Abstract:Seed burial has been proposed as an effective mechanism to evade predation in continuous forests. However, its relevance may be compromised in fragmented forests because: (1) predators are usually concentrated within forests patches, which elevates consumer pressure on seeds; and (2) fragmentation reduces seed production in remnant trees, decreasing food availability for seed consumers. Thus, predators might be forced to consume buried seeds after seeds on the soil surface are depleted. Indeed, they may explore the surrounding matrix in search of food when seeds within patches become scarce. This study assesses these issues in a fragmented oak forest where human activities have generated four habitat types: forest patches, patch edges, matrix habitat surrounding patches, and an abandoned agricultural fi eld in the neighborhoods of the fragmented forest. In this landscape, we assessed what animals consume acorn and compared removal rates between buried acorns and acorns exposed on the soil surface across these habitat types. Mice of the genus Peromyscus and birds of the genus Aphelocoma were the main responsible of removing acorns in all habitats types, but mice were only recorded during night and birds were only recorded during day. Buried acorns were less removed (12-35%) than exposed ones (42-68%) in the matrix habitat and the abandoned fi eld. Nevertheless, within forest patches and their edges, buried (78-81%) and exposed acorns (91%) showed no differences in removal rates. These results suggest that burial may be an effective mechanism to evade acorn predation in habitats strongly affected by human activities, while it would have little relevance within forest patches. Keywords: birds, fragmentation, Mexico, mice, seed predation.Resumen: El enterramiento de semillas es considerado un mecanismo efectivo para evadir la depredación en bosques continuos. Sin embargo, su importancia puede verse comprometida en bosques fragmentados debido a que: (1) los depredadores suelen concentrarse en los parches de bosque, lo que eleva la presión de consumo sobre las semillas; y (2) la fragmentación reduce la producción de semillas en los árboles remanentes, lo que disminuye la disponibilidad de alimentos para sus consumidores. Así, los depredadores podrían verse obligados a consumir semillas enterradas después de agotar las semillas en la superfi cie del suelo. De hecho, podrían incluso explorar el hábitat circundante en busca de comida cuando las semillas dentro de los parches escaseen. Este estudio se enfoca en estos temas en un encinar fragmentado, donde las actividades humanas generaron cuatro tipos de hábi-tats: el interior de los parches de bosque, sus bordes, la matriz de hábitat que rodea los parches, y un campo agrícola abandonado colindante al bosque fragmentado. En este paisaje se evaluó cuáles animales contribuyen a movilizar las bellotas, y se compararon las tasas de sustracción entre bellotas enterradas y expuestas en la superfi cie del suelo a través de esos tipos de hábitat. Ratones del género Perom...