Plant Taste Affects Diet Selection by Plateau Zokors (Eospalax baileyi)

ABSTRACT Diet selection can be influenced by many factors and is crucial for survival. In this study, we measured the diet selection (Ei index) of plateau zokors (Eospalax baileyi) by comparing the composition of plant species present in overwinter caches and inside nearby quadrats of zokor burrow systems on the Qinghai-Tibet Plateau. Based on human volunteer taste-testing, or assignment using the Chinese Materia Medica Monographs, we divided the collected plant species into four different taste groups (sweet, bitter, other-taste, and tasteless) and then compared Ei values to determine whether plant taste can affect zokor diet selection. A total of 124 burrow systems were analyzed and 103 plants were used in the analyses. Kruskal-Wallis tests revealed statistically significant deviations (from the mean) in Ei values among the four taste groups (χ2 = 199.033, df =3, p = 0.000). Pairwise Mann-Whitney U tests showed that, at the p = 0.05 or higher significance level, the Ei values of the four taste groups could be ranked as: sweet > bitter = other-taste > tasteless. Using bootstrapping analyses, we detected ten sweet and five bitter plants that were positively selected by zokors (p < 0.05). Taken together, these findings indicate that plant taste plays an important role in the dietary choices of plateau zokors. Moreover, our results suggest that there were obvious trade-offs between choosing to gain nutrients and avoiding disadvantageous secondary plant metabolites.