Coping with transition: offspring risk and maternal behavioural changes at the end of the hiding phase

Hiding is a cooperative mother-infant behavioural strategy used by many ungulate species to mitigate infant predation risk. During the late stages of the hiding phase, infants begin a transition out of hiding and show behavioural changes that increase their exposure to predators. Mothers in many hider species are known to show potentially costly changes in habitat use, gregariousness and vigilance behaviour at the onset of the hiding phase. However, the effects of infant transitional behaviour on maternal behavioural patterns are understudied. In this study, we compare the behavioural patterns of Thomson's gazelle, Eudorcas thomsonii, females with young and transitioning fawns to determine the effect of fawn behavioural changes on maternal behaviour. We found that, although transitioning fawns were at greater risk than younger fawns while hidden, mothers of transitioning fawns were less vigilant than mothers of younger fawns during hiding periods. Mothers and fawns relied on group membership rather than heightened maternal vigilance to mitigate fawn risk during the transition. Group membership is apparently made possible by the shorter hiding bouts of transitioning fawns relative to younger fawns: more frequent activity bouts probably enable mothers to relocate their fawns more frequently, which helps the mother and fawn to keep up with group movements.