The tradeoff between parental effort and mating effort in male animals may be mediated by testosterone (T). The pattern of association between T and paternal care in birds is consistent with this hypothesis, while it is poorly studied and not universal for mammals. We used the correlation approach to test two predictions of T-mediated tradeoff hypothesis for a biparental vole, Microtus mandarinus: (1) that T levels in males decrease from before pair formation to after birth of the first litter and (2) that paternal responsiveness of males negatively correlates with their T levels. T сoncentrations were measured in fecal samples collected before pairing and then immediately before behavioral testing on day 5 after birth of the first litter. Both nonpaternal and low paternal males had high initial T that decreased after birth of pups, though the decrease was only significant in low paternal males. In highly paternal males, the initial T was low and did not change after birth. Our results support the predictions