Forest fragmentation and predation on artificial nests in the Usambara Mountains, Tanzania

In the Usambara Mountains of Tanzania we compared nest predation rates in relation to forest fragment size and proximity to edge. To identify the most appropriate egg type to bait artificial nests, we first examined rates of nest predation among artificial nests baited with chicken, clay or a combination of chicken and clay eggs. Nests containing only chicken eggs experienced no predation events, while similar predation rates were recorded for the chicken/clay and clay-only treatments. Using nests baited with two clay eggs, we found no significant variation in predation rates related to fragment size or proximity to edge. Small-mouthed mammals comprised 87.7% of all predator types identified from tooth imprints left on clay eggs, and rodents were the most common small-mouthed mammals in our study area. An examination of museum specimens revealed that only one local small-mouthed mammal had an incisor gape greater than the width of a small chicken egg. Total rodent abundance did not vary significantly in relation to fragment size or proximity to edge. We believe the lack of an area or edge effect on patterns of nest predation is a result of the ubiquitous distribution of rodents in our study area.