Offspring grazing and suckling rates in a sexually dimorphic ungulate with biased maternal investment (Ammotragus lervia)

Abstract

An analysis of resource gain is provided forAmmotragus calves during their Ærst year of age. Both grazing and suckling rates are analysed and potential e ects caused by age, sex, mother's rank and weaning period studied. During their Ærst day of life, calves devote their time mainly to suckling, grazing starting at the second week of age and exceeding suckling rate from the fourth week onwards. When suckling rate reaches a signiÆcant decrease (at 2 mo), male calves show a signiÆcantly higher grazing rate than female calves, suggesting a higher energetic demand for males at this age. When calves are 1 mo old, sons of high-ranking mothers devote less time grazing than those of low-ranking ones, which is in accordance with the higher maternal investment they receive. Grazing rate shows distinctive values for the di erent weaning periods distinguished in this species, but the resumption of mothers' sexual activity, when a mother±o spring conØict occurs, does not a ect grazing behaviour. These results are consistent with the biased maternal investment recently found in the same study population but focusing on another aspect, i.e. grazing behaviour, which is determined by calves' own decisions.