The abundance and prevalence of parasitic infection often vary in different host sexes, and this phenomenon has been named sex-biased parasitism. Brandt's voles are the dominant rodent species in typical steppe habitat and are widely distributed in Inner Mongolia, China, but the prevalence of parasites in Brandt's voles are poorly reported. In this study, we investigated the prevalence of six intestinal parasites in Brandt's voles in May, June, July, and August 2022 around the Xilingol Grassland in Inner Mongolia, China. The results showed that Syphacia obvelata, Aspiculuris tetraptera, and Trichostrongylidae family were the dominant intestinal parasites in Brandt's voles that we captured in this study, and the infection rates of the three parasites were significantly higher in males than females, which showed obvious male-biased parasitism. Season and human activities such as grazing had no significant effect on the infection rates for different parasites, while the parasite reproduction level was higher when the ambient temperature was around 18 °C. Sexual size dimorphism was ubiquitous in Brandt's voles, and it was mainly manifested by the differences in body weight and length between males and females. Simple linear regression analysis showed a significant positive correlation between bodyweight and parasite infection rates, so the sex-biased parasitism in Brandt's voles could be explained by the body size hypothesis, as a larger body could provide more ecological niches for parasitic infection.
Keywords: Brandt’s voles; body size hypothesis; intestinal parasites; male-biased parasitism; sexual size dimorphism.