No abstract

Small mammals play important roles in many ecosystems, and understanding their response to disturbances such as cattle grazing is fundamental for developing sustainable land use strategies. However, how small mammals respond to cattle grazing remains controversial. A potential cause is that most of previous studies adopt rather simple experimental designs based solely on the presence/absence of grazing, and are thus unable to detect any complex relationships between diversity and grazing intensity. In this study, we conducted manipulated experiments in the Hulunber meadow steppe to survey small mammal community structures under four levels of grazing intensities. We found dramatic changes in species composition in native small mammal communities when grazing intensity reached intermediate levels (0.46 animal unit/ha). As grazing intensity increased, Spermophilus dauricus gradually became the single dominant species. Species richness and diversity of small mammals in ungrazed and lightly grazed (0.23 animal unit/ha) area were much higher than in intermediately and heavily grazed area. We did not detect a humped relationship between small mammal diversity and disturbance levels predicted by the intermediate disturbance hypothesis (IDH). Our study highlighted the necessity of conducting manipulated experiments under multiple grazing intensities.

Aim China is among the countries with highest mammal diversity in the world, but a considerable proportion of Chinese terrestrial mammal species is currently at risk of extinction. For effective conservation, it would be fundamental to answer the following questions: (1) Is extinction risk randomly distributed among families in Chinese terrestrial mammals? (2) If not, which families are more threatened than expected by chance? (3) What are the major ecological predictors of extinction vulnerability? (4) Does taxonomic difference exist in ecological correlates of extinction risk? (5) To what extent does anthropogenic disturbance contribute to variations in extinction risk? Location China. Methods We collected data on biological traits, environmental factors and anthropogenic disturbance for 453 Chinese terrestrial mammals. We used phylogenetically controlled regression models and model selection to identify predictors of extinction risk for the whole species set and for the three large taxonomic groups (Carnivora, Artiodactyla and Lagomorpha) separately. Results We found that extinction risk was not randomly distributed among families. Seven families (old world monkeys, gibbons, cats, civets and genets, musk deer, deer and bovids) contained significantly higher proportions of threatened species than expected by chance. Geographic range size was the only factor consistently supported in all the best models for the whole species set and for three large taxonomic groups. Although considered important in the global model for the whole species set, body weight was a poor predictor of extinction risk in taxon‐specific analyses. We also detected considerable differences in ecological correlates of extinction risk among Carnivora, Artiodactyla and Lagomorpha. After controlling for phylogeny, anthropogenic disturbance was not significantly correlated with extinction risk. Main conclusions For effective conservation, we should pay special attention to those highly threatened families and the species with limited range size. Our results also highlight the importance of performing taxon‐specific analyses for conservation practice.

Rodents often act as keystone species in communities and play important roles in shaping structures and functions of many ecosystems. Understanding the underlying mechanisms of population fluctuation in rodents is therefore of great interest. Using the data from a 25-year field survey carried out in Inner Mongolia, China, we explored the effects of density dependence, local climatic factors, and a large-scale climatic perturbation (El Niño–Southern Oscillation) on the population dynamics of the striped hamster (Cricetulus barabensis), a rodent widely distributed in northern China. We detected a strong negative density-dependent effect on the population dynamics of C. barabensis. Rainfall had a significant positive effect on population change with a 1-year lag. The pregnancy rate of C. barabensis was negatively affected by the annual mean temperature in the current year, but positively associated with the population density in the current year and the annual Southern Oscillation Index in the previous year. Moving-window analyses suggested that, with a window length of 12 years, there was a significant interaction between rainfall and density dependence, with increasing rainfall alleviating the negative effect of density dependence. As C. barabensis often causes agricultural damage and can transmit zoonotic diseases to human beings, our results also have implications for pest and disease control.