Seasonal variation of body condition in feral horses at Tornquist Park, Southern Pampas, Argentina

Abstract

Body condition of feral horses is important for animal welfare considerations and to anticipate population densities that may cause negative effects on the ecosystem. Body condition scores (BCS) of adult males and females were monthly estimated in 2001 and 2002 for a dense population of feral horses in a grassland nature reserve in Argentina. Monthly mean BCS showed a seasonal pattern for both sexes. Female BCS was higher throughout 2001 with respect to 2002, while males only showed this pattern between wet seasons. BCS was higher for males than for females throughout the study, and also higher during the wet season for both sexes. Mean monthly BCS of males was correlated to precipitation of the previous month. The seasonal variation found tracks the known trend in grass productivity in the area. Lower BCS values for females can be explained by the additional energy expenditure associated with pregnancy and lactation. The appropriate time to monitor body condition in the area would be during the autumn rainfall peak or the winter minimum, and the estimates corresponding to females more precise considering their dependence to density and rainfall. The implementation of management measures guided by BCS could minimize the risk of reaching population levels close to carrying capacity, reducing the negative impacts on the environment and on the welfare of the horses themselves.