Seasonal movements and site utilisation by Asian water buffalo (Bubalus bubalis) in tropical savannas and floodplains of northern Australia

Abstract

Abstract ContextThe Asian water buffalo (Bubalus bubalis) is an introduced herbivore of the savannas and floodplains of northern Australia. Despite the significant environmental damage caused by water buffalo, important cultural and commercial stakeholders request this species is managed rather than eradicated. However, gaps in knowledge of buffalo ecology limit effective policy and planning. AimsTo better understand how buffalo, at current population densities, respond to seasonally changing resources in the two key habitat types that they occupy in northern Australian – upland eucalypt savanna and seasonally inundated floodplain. MethodsSatellite telemetry was used to record the location of a single female buffalo from each of 11 independent clans every hour over a 12-month period. Generalised linear mixed modelling was used to assess the extent to which buffalo movements, activity-space and site revisitation correlated with forage quality (inferred from the normalised difference vegetation index – NDVI) and localised buffalo density. Key resultsAs the dry season progressed, forage quantity and quality within the activity-space of buffalo clans decreased. In response, buffalo inhabiting floodplain exhibited increased rates of movement and enlarged the size of their activity-space. This resulted in low repeated visitation of foraging areas in the late dry season and NDVI remained relatively high within these areas. In comparison, buffalo in upland savanna maintained similar rates of activity and occupied the same activity-space size throughout the year. This resulted in frequent revisitation of the same areas in the late dry season and NDVI reached as low as zero in these foraging areas. Clan size and localised buffalo density had no significant effect on measured movement parameters. ConclusionsBuffalo exhibited a behavioural strategy in upland savanna that resulted in acute removal of green herbaceous vegetation within a few kilometres of the clan’s permanent water source. Buffalo inhabiting the floodplain used multiple wallows that reduced grazing impacts, but likely resulted in hoof-derived impacts over a broad area. ImplicationsCurrent buffalo densities in Kakadu National Park appear to be well below carrying capacity but localised environmental degradation around permanent water sources remains severe in upland savanna.