Resource selection of free-ranging goats and potential behavioral mechanisms

Abstract Background: Herbivores rarely move and forage randomly in rangelands. They tend to move in ways that balance energy acquisition from food intake and energy expenditure to find food, which are generally influenced by biotic and abiotic factors respectively. However, few studies have explored the relative importance of energy acquisition and expenditure in the foraging behavior of livestock or wild angulates in the absence of predation and human disturbance. There is also limited understanding of the trade-offs between forage quality and quantity and its implications to foraging behaviors of livestock. Methods: Satellite remote sensing, vegetation surveys, and GPS-tracking of 181 free-ranging Zhongwei goats over five years (2013-2017) were used to assess how biotic and abiotic factors affect the spatiotemporal distribution of free-ranging goats when foraging in the semiarid grassland of Loess Plateau. Results: The goats tended to use gentler slopes throughout the year which likely reduced energy expenditure. The spatial distributions of goats, however, primarily responded to the spatiotemporal variation of biotic factors rather than abiotic factors of elevation, slope and solar radiation. They preferentially used areas with higher forage quantity in the spring, areas of higher forage quality and quantity in summer, areas of higher quality in terms of abundance of palatable species in autumn, and areas of higher forage quantity in the winter. Conclusions: Our results suggest that, energy acquisition is of priority to energy expenditure in the foraging process for the Zhongwei goats. The preferences of the goats for forage quality or quantity vary with forage availability, selecting for higher forage quality when the forage is plentiful and for higher forage quantity otherwise. Better understanding of the patterns and drivers of spatiotemporal distribution of the goats can improve our ability to predict foraging behavior of livestock in heterogeneous environment and lead to better management practices and policy for sustainability of these arid landscapes and associated ecosystem services.