Seasonal performance of foraging goats in sarcocaulescent scrubland

Traditional goat husbandry in arid rangelands copes with pronounced seasonal variability in forage availability. Therefore, we quantified how sarcocaulescent scrubland dynamics relate to mobility and performance of a free-ranging goat herd in the Baja California peninsula, Mexico, during 2023. We combined six unmanned aerial vehicle campaigns across nine plots to estimate normalized difference vegetation index (NDVI) and vegetation cover, Global Positioning System collar data from a representative lactating doe to estimate walking distance and distribution on rangeland, and concurrent herd measures of milk yield and body weight (BW) by physiological stage. NDVI and vegetation cover showed marked seasonality, with the lowest values from mid-spring to mid-summer (May-August). Goat movement behaviors were likewise seasonal: daily distance traveled was greatest in May and lowest in August, while weekly home range was largest in August-September, suggesting broader space use when resources were patchy. Vegetation cover was positively associated with milk yield, and lactating-doe BW correlated positively with daily walking distance. The poorest vegetation in the dry summer had stage-specific effects on goats' performance: maintenance adults kept BW; doelings ceased gaining weight; pregnant does reduced BW gain; and lactating does reduced their BW and milk yield. Additionally, the number of goats decreased during the dry summer, and their distribution across physiological stages changed, which might buffer the negative effect of reduced vegetation on goats' performance. These results support adaptive management in traditional systems, including the timing and type of supplementation and the alignment of foraging allocation with remotely sensed forage availability.