Context . Daily movement responses could indicate food deficiencies threatening population persistence before consequences for population performance become manifested. Animals should respond to food deficiencies by spending less time in foraging areas and hence by moving more frequently between such areas between one day and the next.
Aim . To establish whether the day-to-day movements of a locally threatened ruminant (sable antelope) reflected anticipated seasonal and annual variation in food stress, in comparison with a non-ruminant grazer that was thriving despite being dependent on basically similar food resources (zebra).
Methods . Diel (24 h) displacement distances that were derived from geographic positioning systems (GPS) telemetry were used to make the following comparisons: (1) between benign and adverse seasons, (2) among years differing in rainfall, (3) between the remnant sable herd and herds of zebra in the same region, and (4) between this sable antelope herd and sable herds in a wetter region where food should be more abundant.
Key results . Sable herds generally moved further from day to day in the late dry season than in the wet or early dry season, especially in the years with less rainfall, and greater movement was shown by the sable herd in the drier region than for herds in the wetter region. Zebra herds generally moved further from day to day than the sable herd occupying the same region, but showed less change in their diel displacement distances during the late dry season.
Key conclusions. Findings were consistent with the expected effects of seasonal, annual and regional differences in food availability on the daily movement distances of sable antelope herds.
Implications. Daily movement distances could serve as an indicator of when and where food deficiencies are experienced by sable antelope and perhaps other large ungulates.