Global patterns and gaps in the study of terrestrial birds and mammals’ use of freshwater sources: A mapping review

Water availability strongly influences the ecology of terrestrial birds and mammals. It will likely play an increasing role as a limiting factor as climate change and human demand make water availability scarcer. However, we lack a knowledge synthesis describing our current understanding of the use of water sources, particularly for wildlife hydration. To provide a comprehensive overview of the available research regarding the utilization of water bodies as hydration sources by terrestrial birds and mammals, we conducted a mapping review based on an extensive search of papers in the Web of Science and Scopus databases published up to 2022. We compiled 181 papers that met our inclusion criteria. Earlier papers date back to 1965, but a stable production was not reached until 2005, and significant growth since 2015. The USA, Mexico, and Zimbabwe had the most published papers. Studies were concentrated in areas with a mean annual precipitation lower than 1000 mm, predominantly deserts and xeric shrublands, as well as tropical and subtropical grasslands, savannas, and shrublands. Studies heavily focused on mammals and less frequently included birds and mammals, with an overrepresentation of least concern species for both groups. Very few studies focused on water sources in the canopy, and even fewer compared surface vs. arboreal water sources. Cameras and direct observations were the main methods to document wildlife’s water use. Attention to water use by birds and mammals shows an increasing trend; however, given the globalized reduction of water availability and quality, it is urgent to widen the scope of studies to include a greater variety of habitat types, water sources, and animal species. Such an increase in scope is necessary to unravel the magnitude of the impacts reductions in water availability can have in the short and long term for wildlife viability.