Seasonality of breeding in wild tuco-tucos Ctenomys talarum in relation to climate and food availability

The present work describes the association between environmental variables and reproductive seasonality in wild femaleCtenomys talarum Thomas, 1898. We assessed monthly variation in external reproductive features and vaginal smears of free-living females over a year-long period. We examined the relationship between frequency of lactating and pregnant females and temperature, plant biomass, plant water content, and rainfall (same month and 1 month prior) using path analysis. About 80% of the variance in the occurrence of pregnancy was explained by the model that included all of the above mentioned variables. Temperature had a direct negative effect on pregnancy. However, temperature had a positive effect on pregnancy through plant-water content and thus, positively influenced frequency of pregnancy. Although plant biomass was correlated with plant-water content, plant biomass had no significant effect on frequency of pregnancy. There were no effects (direct or indirect) of rainfall on pregnancy. The combination of vaginal smears and external features from free-living and autopsied females showed that reproductive activities occurred when new plant tissues were more abundant. Thus, enhanced energetic demands during gestation and lactation were assured. Moreover, births occurred when ambient temperatures provided a favorable thermal environment for pups that demonstrated poor thermoregulatory abilities during their initial phase of development.