Partial acorn consumption by small rodents: implication for regeneration of white oak, Quercus mongolica

Abstract

Partial consumption of acorns by rodents, birds, and insects has been widely reported in various oak species. However, to what extent these partially eaten acorns contribute to the regeneration of oak trees is poorly understood. To date, there is limited knowledge of the effects of seed availability on partial consumption of acorns. Herein, we released tagged Quercus mongolica acorns in two consecutive years with different seed crops, to explore the probability of partial acorn consumption. We also placed simulated partially consumed acorns in the field to investigate their contribution to regeneration of white oak. Our results showed that more acorns were partially eaten in a good crop year than in poor crop year, reflecting an effect of predator satiation on acorn partial consumption by rodents at the population level. Partially eaten acorns were more likely to be damaged at the basal end, suggesting consistent consumption preferences of small rodents. Although, partially consumed acorns were less likely to be scatter-hoarded by small rodents, they germinated more rapidly than the intact acorns in the field, offsetting the negative effects of the non-buried deposition. Despite lower germination rates, lightly damaged acorns exhibited greater growth of roots and shoots, suggesting a compensatory response to partial acorn consumption. Partial consumption may spread predation pressure on acorns and thus appears to be much better for the plant than total consumption by seed-eating animals. Therefore, partially consumed acorns as dispersal leftovers may play a potential role in natural regeneration of Quercus mongolica, especially in mast years. However, this role and the underlying mechanisms of partial acorn consumption by rodents, birds, and herbivore insects need further investigation.