Mother–offspring conflict in captive plains zebra (Equus burchellii): Suckling bout duration

Recently, a lack of any significant relationship between suckling bout duration and milk or energy intake has been revealed in several mammal species. However, a short suckling bout duration could be taken as an indicator of shortage of milk and lack of maternal care, and could therefore be used to test the parent–offspring conflict hypothesis. We examined suckling bout duration of 20 plains zebra (Equus burchellii) foals, at the Dvůr Králové Zoo, and collected data on suckling events during 19 months of observation. In total, we recorded 3252 suckling bouts during 831 h of observation. As expected, suckling bout duration decreased with increasing age of the foal. The suckling bouts differed in duration when terminated by the foal, mother or any other adult mare (foal > mother > herdmate). Thus, bouts terminated by the mother should indicate that demands of the foal were not satisfied. The shortest bouts were those terminated by a herdmate; however, herdmates terminated few suckling bouts. Moreover, since the foal was able to resume suckling after interruption, the effect of a herdmate on suckling behaviour was very limited. Finally, we found that suckling bout duration was shorter in pregnant mothers than in non-pregnant ones, suggesting higher mother–offspring conflict when the mother was pregnant. In conclusion, this study demonstrates the importance of the termination of suckling bouts and the mother's pregnancy when interpreting suckling bout duration of equids, which has received little attention in previous studies. Our study showed that environmental condition can affect the suckling behaviour of captive equids.