Acorns were good until tannins were found: Factors affecting seed-selection in the hazel dormouse (Muscardinus avellanarius)

Seed selection by forest rodents is based on several factors such as seed palatability, manipulation time and caloric content. The final result of this decision-making process has critical consequences on seed predation and dispersal, and thus on tree demography.Previous studies on seed selection have mainly focused on non-hibernating terrestrial rodents. Arboreal rodents may be less adapted to cope with seed defences, usually being more frugivorous. Furthermore, hibernating species need to accumulate fat reserves in autumn, which is when acorns are available and may be the only available resource. We selected the hazel dormouse (Muscardinus avellanarius, an arboreal hibernating rodent) as model species for our study and focused on three seeds which are an important constituent of the hazel dormouse diet and which are characterized by different defensive strategies.We here report the results of a series of experiments targeted towards understanding the effects of manipulation time, energy intake and tannin content on seed selection by the hazel dormouse and the effects of such selection on individuals’ body condition. Each of these factors was treated separately through a series of coupled food trials. Our results showed a clear order of consumption with first choice biased towards seeds with lower tannin content (Q. pubescens vs Q. cerris) and/or more caloric seeds (C. avellana vs Q. pubescens) despite the higher degree of mechanical protection of the former. Seeds with high levels of tannins led to weight decrease, despite the large amounts of seed mass ingested by dormice. Our results suggest that seed selection by the hazel dormouse is targeted towards maximizing fat storage, which is pursued despite the cost of higher manipulation time.