Social isolation interaction with the feeding regime differentially affects survival and results in a hump-shaped pattern in movement activity

Eusocial insects depend on their colonies, and it is therefore clear why isolation triggers many negative effects on isolated individuals. Here, we examined the effect of social isolation on the desert ant Cataglyphis niger, asking whether isolation, either with access to food or under starvation, impairs survival, and whether isolation modifies movement activity and digging to bypass an obstacle. Social isolation led to shorter survival but only when food was provided. This effect might be due to food not being digested correctly under isolation. Although isolated ant workers were more active immediately post isolation than 2−24 hours later, their movement moderately increased two days post isolation. We suggest that the changes in movement activity are adaptive: first, the worker increases activity intended to reunite it with the lost colony. Then, when the colony is not found, it reduces activity to conserve energy. It later increases activity as a final attempt to detect the colony. We expected isolated workers to dig faster to bypass an obstacle, but we did not detect any effect on digging behavior. We demonstrate here the complex effects of isolation on survival and movement activity, in interaction with additional factors – feeding and isolation duration.