CONICET | Buscador de Institutos y Recursos Humanos

The activity budget and diet of primates are influenced by climatic seasonality and day length. Here, we examined the effect of seasonality on the activity budget, food availability, and diet of black and gold howler monkeys (Alouatta caraya) living close to the southern limit of their geographic distribution in a subtropical environment near the transition to a warm temperate climate. The habitat is characterized by seasonal fluctuations in temperature and day length. In winter, days are colder and about three hours shorter than in summer. Autumn and spring are intermediate in terms of temperatures and day length. There was a marked seasonality in resource availability, mainly in seasonal foods: new leaves, flowers, and fruits. Non-seasonal foods, mostly mature leaves, were less variable and more abundant throughout the year. The activity budget and diet composition differed between seasons. The time spent resting was maximum in summer and minimum in spring. The time spent moving and that engaged in social activities were maximum in spring, the season with the highest availability of seasonal foods. Temperature had no influence on the activity budget. There was a negative relation between abundance of non-seasonal foods and time spent feeding, as well as between the abundance of seasonal foods and time spent resting. The abundance of seasonal foods correlated positively with time spent moving and time spent in social activities. During spring, the diet was dominated by new leaves. In summer and early autumn, the diet consisted mainly of mature leaves and fruits. Our results indicate that seasonality influences the activity budget and diet of Alouatta caraya living close to the southern limit of distribution. The periods of time with low availability or absence of seasonal foods may be the key variable to determine the limits for primates in the geographic distribution toward southern latitudes.