Foraging activity of Acomys cahirinus under different illumination levels: Comparing giving-up densities to direct behavioral observations

Giving up densities (GUDs) have become popular in studies of foraging ecology and community structure, but the relationship between GUDs and direct foraging behavior has not been studied. We studied foraging of Acomys cahirinus using GUDs and direct observations in a large room for a dark night and an illuminated night. At one end, we placed a shelter, and in the opposite corners, two seed trays. The path to one tray was exposed, while on the path to the other tray there were several stones that provided shade, but no cover. Illumination reduced total activity of mice and increased the proportion of time devoted to foraging by reducing other activities, suggesting an energy-optimizing behavioral decision. Number of visits to trays was reduced during illuminated nights, especially to the exposed tray, and GUDs in this tray were higher than in the other, where mice spent relatively more time. During illuminated nights, mice stopped more frequently near stones, suggesting their use for camouflage. GUDs were negatively correlated with time spent on trays, but not with total activity or number of visits to trays, suggesting two separate foraging phases. Behavioral observations were more sensitive to enhanced perception of predation risk. Combining GUDs with an estimate of activity level increases the reliability of this technique.