Abstract
Both as consumers and dispersers of seeds, scatter-hoarding rodents often play an important role in the reproductive ecology of many plant species. However, the seeds of many plant species contain tannins, which are a diverse group of water-soluble phenolic compounds that have a high affinity for proteins. The amount of tannins in seeds is expected to affect rodent foraging preferences because of their major impact on rodent physiology and survival. However, variable results have been obtained in studies that evaluated the effects of tannin on rodent foraging behavior. Hence, in this study, we aimed to explain these inconsistent results and proposed that a combination of seed traits might be important in rodent foraging behavior, because it is difficult to distinguish between the effects of individual traits on rodent foraging behavior and the interactions among them. By using a novel artificial seed system, we manipulated seed tannin and fat/protein levels to examine directly the univariate effects of each component on the seed preferences of free-ranging forest rats (Apodemus latronum and Apodemus chevrieri) during the behavioral process of scatter hoarding. Our results showed that both tannin and fat/protein had significant effects on rodent foraging behavior. Although only a few interactive effects of tannin and fat/protein were recorded, higher concentrations of both fat and protein could attenuate the exclusion of seeds with higher tannin concentrations by rodents, thus influencing seed fate. Furthermore, aside from the concentrations of tannin, fat, and protein, numerous other traits of plant seeds may also influence rodent foraging behavior. We suggest that by clarifying rodent foraging preferences, a better understanding of the evolution of plant seed traits may be obtained because of their strong potential for selective pressure.
Highlights
Scatter-hoarding rodents often play an important role in the dispersal of seeds for some plant species because of their high relative abundance and ubiquity [1]
Only a few interactive effects of fat/protein and tannin were recorded in our study (Table 1, 2), higher concentrations of both fat and protein attenuated the exclusion of seeds with higher tannin concentrations by rodents, especially increasing rodent harvest velocity, i.e., reduction in the time to seed harvest (Fig. 2, 3)
It has been confirmed that dietary tannins can reduce digestion and inhibit assimilation in rodents [11,20]; it is logical that rodents preferentially select high fat/protein diets to compensate for the negative effects of tannin
Summary
Scatter-hoarding rodents often play an important role in the dispersal of seeds for some plant species because of their high relative abundance and ubiquity [1]. Acting as both consumers and dispersers of seeds, rodents play an important role on seedling regeneration, colonization ability, spatial distribution, and the reproductive ecology of trees [1,2]. The potential future value of seeds may influence current foraging decisions by rodents. Seed traits have been considered as one of the most essential factors that influence foraging preferences by scatterhoarding rodents, which in turn regulate seed fate [2,3,4,5,6,7]
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