A test of the predator satiation hypothesis, acorn predator size, and acorn preference

Abstract

Mast seeding is hypothesized to satiate seed predators with heavy production and reduce populations with crop failure, thereby increasing seed survival. Preference for red or white oak acorns could influence recruitment among oak species. We tested the predator satiation hypothesis, acorn preference, and predator size by concurrently measuring acorn production, mouse abundance, and white versus red oak acorn removal rates in exclosures allowing access by mice (HW), squirrels and smaller-sized vertebrates (WW), or all-sized vertebrates (C) for 12 years. Annual removal rate varied, but virtually all acorns were eventually removed from all exclosure types all years except one. Acorns were removed more slowly from HW than from WW or C exclosures, indicating that large vertebrates were not major acorn consumers, locally. Red and white oak acorn removal rates were similar except in two years, when red oak acorns were removed more rapidly. Removal slowed with increasing acorn crops, suggesting that heavy crops can “swamp” predators. Removal rate was negatively correlated with crop size the previous fall. A positive trend between mouse abundance and crop size the previous fall was evident; abundance decreased sharply the year following crop failures but not after moderate or heavy crops, suggesting that poor crops can dampen acorn predation the following year.