Effect of Temperature on Activity Patterns in a Small Andean Rodent: Behavioral Plasticity and Intraspecific Variation

The activity rhythm of a species is ruled by internal signals as well as external factors. Among them, ambient temperature strongly influences the amount, duration, and distribution of an organism's activities throughout the day. The result is a pattern of activity that, between certain limits, can be flexible to deal with seasonal and spatial thermal heterogeneity. The range of behavioral plasticity increases with environmental variability and could be beneficial for a species' persistence under novel conditions. Thus, the goal of this study was to experimentally explore the behavioral plasticity in Phyllotis xanthopygus, a rodent species inhabiting an altitudinal gradient in the Central Andes Mountains of Argentina. In the laboratory, we assessed activity rate and pattern under different temperatures by comparing groups of individuals collected at different altitudes. All animals were acclimated to subsequent thermal treatments in a paired design. As expected, P. xanthophygus showed changes in activity under different temperatures, and animals from diverse altitudes were differently affected. In particular, animals from mid‐altitudes and high altitudes reduced their activity under high temperatures. Intraspecific differences across the altitudinal gradient suggest that animals from mid‐altitudes and high altitudes are less heat tolerant than those from lower sites, in spite of acclimation to equal conditions. We propose that climate ranges experienced in the field possibly promote this different response. Our results are discussed in light of recent forecasts of temperature rises in the region, which could constrain P. xanthophygus activity in space and time.