Foraging Behavior Development of Foals in Natural Grassland

Abstract

Early relationships between young mammalian herbivores and social models (e.g., mothers or peers) have been proposed as playing a major role in the process of diet learning. Diet selection is an important factor influencing animal development and ecology, especially in natural and seminatural grasslands, with a large diversity of plant species. To explore the learning process of foraging behavior and diet selection choices by foals, six free-ranging Criollo foals and their respective mares were monitored through continuous bite monitoring from birth to 130 d old, in the Pampas Grasslands of southern Brazil. Cumulative suckling time decreased exponentially from birth to 130 d old, while dry matter intake, foraging time, and bite mass of foals increased continuously. It was possible to identify three marked periods in the foal’s foraging behavior development: 1) an exploratory phase (from 0 to 40 d old) marked by limited forage intake from a large diversity of plants; 2) a specialization phase (from 40 to 110 d old) with a marked increase in forage intake and a specialization around the same plants as the ones selected by the mares; and 3) a stabilization phase (after 110 d old) in which forage intake still increases but diet composition of foals stabilized similarly to the one of the respective mares. The higher diversity at young ages could be explained by exploratory hypothesis, where foals test different forages to discover their environment, given that their nutritional needs are fulfilled by milk consumption, not by forage intake. As requirements shift toward solid items, bite mass and foraging time increase and diet choices become similar to that of the mares. Our results detail how young foals develop their foraging behavior and suggest, without testing it and under the circumstances of this study, that they learn their diet through social transmission from their mothers.