▁occurs ▁between ▁May ▁and ▁July , ▁and ▁bir thing ▁usually ▁takes ▁place ▁between ▁January ▁and ▁March , ▁at ▁the ▁start ▁of ▁the ▁wet ▁season . ▁Wil de be est ▁females ▁bre ed ▁season ally ▁and ▁ov ulate ▁sp ont ane ously . ▁ ▁The ▁est r ous ▁cycle ▁is ▁about ▁ 2 3 ▁days ▁and ▁the ▁gest ation ▁period ▁last s ▁ 2 5 0 ▁to ▁ 2 6 0 ▁days . ▁The ▁cal ves ▁we igh ▁about ▁ ▁at ▁birth ▁and ▁sc ram ble ▁to ▁their ▁feet ▁within ▁minutes , ▁being ▁able ▁to ▁move ▁with ▁the ▁her d ▁soon ▁afterwards , ▁a ▁fact ▁on ▁which ▁their ▁surv ival ▁re lies . ▁The ▁main ▁pred ator ▁of ▁the ▁cal ves ▁is ▁the ▁sp otted ▁hy ena . ▁The ▁cal ving ▁peak ▁period ▁last s ▁for ▁ 2 – 3 ▁weeks , ▁and ▁in ▁small ▁sub pop ulations ▁and ▁isolated ▁groups , ▁mort ality ▁of ▁cal ves ▁may ▁be ▁as ▁high ▁as ▁ 5 0 %. ▁However , ▁in ▁larger ▁aggreg ations , ▁or ▁small ▁groups ▁living ▁near ▁large ▁her ds , ▁surv ival ▁rates ▁may ▁be ▁over ▁ 8 0 %. ▁ ▁Gr oups ▁of ▁w ilde be est ▁females ▁and ▁young ▁live ▁in ▁the ▁small ▁areas ▁established ▁by ▁the ▁male . ▁When ▁groups ▁of ▁w ilde be est ▁join ▁together , ▁the ▁female ▁to ▁male ▁ratio ▁is ▁higher ▁because ▁the ▁females ▁choose ▁to ▁move ▁to ▁the ▁areas ▁held ▁by ▁a ▁smaller ▁number ▁of ▁males . ▁This ▁female - domin ated ▁sex ▁ratio