I did answer you on that Fred by here is a quick difference between the antelopes you can confuse it with. Basically there are 4 that people confuse the antelopes with
1. Grey Rhebok
2. Mountain Reedbuck
3. Southern Reedbuck
4. Oribi.Oribi(with your picture shows, and can be seen by the black tip on the tail
Oribi grow to around 92–110 cm (36 to 43 inches) in length, with a shoulder height of 50–66 cm (20 to 26 inches) and weigh an average of 12–22 kg (26 to 49 lb). They can run at speeds of up to 40–50 km/h (25–31 mph). In captivity they have a lifespan of up to 14 years.
The back and upper chest is yellow to orange-brown. The chin, throat, chest, belly and rump are white. The tail is short and bushy, the upper side black or dark brown
The thick coat is soft and wooly. The upperparts are greyish brown. The underparts, ring around eyes and white patches on chin & muzzle. A dark, narrow stripe runs down the front of the legs. The tail has a white tip
. Grey Rhebok are fast runners, reaching speeds of up to 60km/h.
Horns:Only rams carry horns. they are straight, long, thin & pointed. The horns are partially ridged at the base, with smooth tips. Length: 15-29cm.Mountain Reedbuck
A medium-sized, graceful and shy antelope. Rams attain a mass of about 32 Kg and measures 750mm at shoulder. Ewes are smaller at 30 Kg. Fur is predominantly grey, but the head and shoulders are a reddish-brown. It has a fluffy white tail and striking white underparts.
Forward curved horns are only found on rams. This species has long narrow ears. Southern(common) Reedbuck
The Southern Reedbuck, or Common Reedbuck (Redunca arundinum) is an antelope, found in Angola, Botswana, Zimbabwe, Zambia, Mozambique and northern South Africa.
Southern Reedbucks average 85 cm at the shoulder, and weigh around 70 kg. They have grey-brown coats with a white underbelly and black forelegs. Males have ridged horns of around 35 cm, which grow backwards and then curve forwards.
Southern Reedbucks live in valley and upland areas, where they eat grasses and reeds. Old Southern Reedbuck males are territorial, living with a single female, which they follow at all times to prevent it having contact with rival males. Females and young males are usually solitary, except in the dry season, when they sometimes form herds of up to twenty individuals out of necessity. They are diurnal, but inactive during the heat of the day.
That was just n Quick description of them all. You can search each by name on Google and just ad image and you will find lot of photos of each. Hope this help you to confirm its Oribi