How Energetic Demands and Habitat Utilisation Can Make or Break Giraffes

ABSTRACT

Understanding how large herbivores balance energy intake and expenditure is critical for effective rangeland management and conservation. Giraffes (Giraffa camelopardalis), as selective browsers, depend on high-quality forage resources that vary seasonally, influencing their movement patterns, home range and habitat selection. However, the extent to which nutritional constraints drive giraffe spatial ecology in arid savanna ecosystems remains poorly understood. This study aims to examine the relationship between giraffe movement patterns, habitat selection and the nutritional properties of preferred vegetation communities within the Rooipoort Nature Reserve, South Africa. We fitted seven male and eleven female giraffes with GPS collars to track their spatial movements over 12 months. Habitat selection was analysed using ArcGIS to identify high-use areas and preferred vegetation types. Nutritional analyses of dominant forage species, including Senegalia erioloba, Ziziphus mucronata and Vachellia tortilis, were integrated with movement data. Statistical analyses included t-tests for sex-based movement differences, linear regression for home range overlap vs. rainfall, and ANOVA for seasonal habitat use. Males exhibited significantly larger home ranges (utilising ~63% of the study area) and travelled greater distances than females (p = 0.005), primarily due to reproductive roaming strategies. Habitat selection varied seasonally, with dry-season nutritional stress leading both sexes to expand their ranging. High-protein browse species (approximately 10%–20% crude protein) were preferentially selected, indicating that nutritional constraints shape spatial distributions. Giraffes rely on specific high-energy forage species and concentrated resource areas, making them vulnerable to habitat degradation and seasonal resource shortages. Conservation management should prioritise the protection of Senegalia erioloba woodlands and Ziziphus mucronata shrublands—critical dry-season refuges of high-quality forage—to support sustainable giraffe populations.