The population cycles of small rodents have puzzled biologists for centuries. There is a growing recognition of the cascading effects of climate change on the population dynamics of rodents. However, the ultimate cause for the bottom-up effects of precipitation is poorly understood, from a microbial perspective. Here, we conducted a precipitation manipulation experiment in the field, and three feeding trials with controlled diets in the laboratory. We found precipitation supplementation facilitated the recovery of a perennial rhizomatous grass (Leymus chinensis) species, which altered the diet composition and increase the intake of fructose and fructooligosaccharides for Brandt's vole. Lab results showed that this nutrient shift was accompanied by the modulation of gut microbiota composition and functional pathways (especially for the degradation or biosynthesis of L-histidine). Particularly, the relative abundance of Eubacterium hallii was consistently increased after feeding voles with more L. chinensis, fructose or fructooligosaccharide. These modulations ultimately increased the production of short chain fatty acids (SCFAs) and boosted the growth of vole. This study provides evidence that the precipitation pulses cascades through the plant community to affect rodent gut microbiome. Our results highlight the importance of considering host-microbiota interaction when investigating rodent population responses to climate change.

The collapse of large wild herbivores with replacement of livestock is causing global plant community and diversity shifts, resulting in altered food availability and diet composition of other sympatric small herbivores in grasslands. How diet shifts affect the gut microbiota of small mammals and whether these changes may translate into complex interactions among coexisting herbivores remain largely unknown. We conducted both a field experiment and a laboratory diet manipulation experiment to test whether sheep grazing induces a diet shift and thus alters the gut microbiota of a small rodent species living in grassland. We found that enclosures subjected to grazing were mostly dominated by Stipa krylovii (accounting for 53.6% of the total biomass) and that voles consumed significantly more S. krylovii and less Cleistogenes squarrosa in grazed enclosures. Voles in grazing enclosures exhibited significantly lower abundances of Firmicutes, higher abundances of Bacteroidetes and significantly lower measurements of alpha diversity. The microbiota from voles in the grazed enclosures had a smaller and more simplified co‐occurrence network with relatively higher percentage of positive interactions. Analysis based on dietary clusters indicated that grazing‐induced changes in diet composition contributed to the distinct gut microbial community of voles in enclosures. We verified our findings using laboratory experiments, in which voles were exclusively fed C. squarrosa (high carbohydrate, high fibre and high in secondary compounds), S. krylovii (low carbohydrate, low fibre and low in secondary compounds) or Leymus chinensis (nutritionally intermediate). We observed that the gut microbiota of voles changed with the three different diets, supporting the idea that the effects of sheep grazing on the gut microbiota of Brandt's voles may be related to grazing‐induced diet shifts. Our results highlighted the negative effects of livestock grazing on small mammals in grassland via changes in plant community and gut microbiota of small mammals and help to better understand the cascading consequences of realistic scenarios of world‐wide decline in large wild herbivores.

Livestock grazing has shaped grassland ecosystems around the world. Previous studies indicated grazing showed various impacts on small rodents; however, most studies were conducted over 1-2 years without controlling for confounding factors such as immigration/emigration and predation in rodents. Brandt's voles (Lasiopodomys brandtii) are generally recognized as pests because of food overlap with domestic herbivores, but are also important for biodiversity conservation because they provide nests or food to many birds. Fully understanding the ecological relationship between domestic herbivores and small mammals is essential to making ecosystem management decisions. To address these needs, we carried out a field experiment during the period 2010-2013 to assess the effects of sheep grazing on vegetation and the population density of Brandt's voles along a gradient of three grazing intensities by using 12 large-scale enclosures. Responses of Brandt's voles to livestock grazing varied with grazing intensity and year. As compared to the control group, sheep grazing had no effect on vole abundance in the first year but an overall negative effect on vole abundance in the following 3 years. Successive grazing caused decreases in survival and male body mass of voles, but had no significant effect on fecundity. Negative effects of grazing were associated with a grazing-induced deterioration in both food quantity (reflected by biomass and cover of less-preferred plants), and food quality (measured by tannin and total phenol content). Our findings highlight the urgent need for more flexible management of yearly rotational grazing to optimize livestock production while maintaining species diversity and ecosystem health.

Predator odors are non-intrusive natural stressors of high ethological relevance. Animals are daily challenged with stressors of varying intensity and it is essential for their survival to respond to a wide range of threats. Behavioral and hormonal responses and changes in the level of medial hypothalamic c-fos mRNA were examined in Brandt's voles (Lasiopodomys brandtii) exposed to the feces of a domestic cat (Felis catus) stored for different periods. One hundred voles were tested in the defensive withdrawal apparatus. The voles showed an aversion to freshly collected cat feces, indicated by high levels of flight-related behaviors, increased freezing behavior, and more vigilant rearing compared to old feces. The serum levels of adrenocorticotropic hormone and corticosterone significantly increased when the voles were exposed to fresh cat feces. The level of c-fos mRNA in the medial hypothalamic region was highest in the individuals exposed to fresh cat feces. All of these behavioral, endocrine and c-fos-mRNA responses were lower when voles were subjected to older cat feces. We conclude that these responses depend on volatile chemical constituents of cat feces rather than their physical characteristics and that this accounts for the lower responses to feces stored for longer periods.