HIGH-RANKING FEMALES BIAS THEIR INVESTMENT IN FAVOR OF MALE CALVES INCAPTIVE AMMOTRAGUS-LERVIA

Calf suckling behaviour is a valid measure of maternal investment in t he Saharan arrui, Ammotragus lervia sahariensis, since this variable i s strongly correlated with the inter-birth interval. High-ranking fema les allocate their resources preferentially towards their sons, as the average suckling rate is significantly higher in male calves than in female calves during their Ist month of life, when maternal investment reaches the highest values of the whole lactation period. However, av erage suckling-bout duration shows no sex differences. Some maternal b ehaviours, such as sniffing and licking, are strongly correlated with suckling events. Only during the calves' Ist week is the mother respon sible for maintaining proximity; but from the following week on the ca lves are mainly responsible for maintaining it. In addition, when the calves are 1 month old, high-ranking females tend to maintain a strong er link with their male calves. Female calves spend more time with the ir mothers than male calves during their Ist month of life, if the mot her's rank is lower than 60 %; otherwise, the opposite occurs, male ca lves being close to their mothers for longer, even from their 1st week of life. Finally, the higher the maternal rank the higher the proport ion of male calves delivered.