 The impala is a medium @-@ sized , slender antelope similar to the kob or Grant 's gazelle in build . The head @-@ and @-@ body length is around 130 centimetres ( 51 in ) . Males reach approximately 75 – 92 centimetres ( 30 – 36 in ) at the shoulder , while females are 70 – 85 centimetres ( 28 – 33 in ) tall . Males typically weigh 53 – 76 kilograms ( 117 – 168 lb ) and females 40 – 53 kilograms ( 88 – 117 lb ) . Sexually dimorphic , females are hornless and notably smaller than males . Males grow slender , lyre @-@ shaped horns 45 – 92 centimetres ( 18 – 36 in ) long . The horns , strongly ridged and divergent , are circular in section and hollow at the base . Their arch @-@ like structure allows interlocking of horns , which helps a male throw off his opponent during fights ; horns also protect the skull from damage . 
