The Interactions between Taiwan Vole (Microtus kikuchii) and Alpine Meadow Herbs at the Ho-huan Area: Effects of Nutrition and Abundance of Dominant Herbs

Ecological mechanisms explaining how animals and plants interact are fascinating topics in ecology and evolutionary biology. Particularly, selective foraging by herbivores could alter plant species composition and diversity in various ecosystems. Previous studies have suggested that selective foraging by small mammalian herbivores is affected by the differential abundance and palatability of plants. The palatability is in turn influenced by chemical characteristics, like nutrition, secondary compound, and toxin contents, in plants. Under the growing threats of global warming, it is urgent to understand the ecological mechanisms in alpine meadow. In alpine meadow ecosystem vegetation is easily modified by the selective herbivory because of the low growth rates of plants. The endemic Taiwan vole (Microtus kikuchii), a glacial relic species, is the dominant small mammal herbivore in the Yushan cane (Yushania niitakayamensis) grassland in Taiwan. To understand the selective foraging and the involving mechanism, I proposed to test the following hypotheses: (1) Taiwan voles forage selectively (not an opportunist): different plants have different palatability to voles; (2) chemical characteristics, like nutrition, secondary compound, and toxin contents, in plants could account for the differential palatability: palatable plants have higher protein, lower fiber and lower protein-binding phenolics than less palatable ones; (3) food selection by Taiwan voles is a two-step process: the factors accounting for unpalatability and the degrees of palatability are different; (4) Taiwan voles prefer dominant plants: palatable plants have greater cover area than less palatable ones; (5) the distribution of Taiwan voles is influenced by the distribution of food resource: the distribution of voles is positively correlated with that of highly palatable plant species, negatively with less palatable ones. I surveyed the population of small mammals and the plant community in the Yushan cane (Yushania niitakayamensis) grassland in the Ho-huan Mountains to determine the distribution and abundance of different species. I assessed the palatability and chemical characteristics content of dominant plants by feeding trials and chemical analysis in the laboratory. The results showed that different plants had different palatability to voles, and the two-step forage selection process was not supported because no toxin in plants was found. Taiwan voles consumed greater amount of plants with greater cover areas and more hemicellulose contents. Such traits allowed adult voles find food and gain energy quickly. The selective foraging may prevent dominant plant species from over-dominating. The distribution of Taiwan voles also seemed to be affected by the distribution of food.