The faunal diversity parallels its plant diversity. There are fifty six reptile species, twenty three being endemic to South Africa and three found only in the Baviaanskloof. The valley is also home to seventeen amphibian and fifteen fish species.
It was also once home to forty six medium-to-large mammal species but over the centuries, fourteen species, including lion, elephant and black rhinoceros became locally extinct. Cape Mountain zebra, black rhinoceros, red hartebeest, buffalo and eland have since been re-introduced in addition to existing bush pig, klipspringer, grysbok, grey rhebok, bushbuck, mountain reedbuck and duiker.
As the area encompassed within the reserve expands so more re-introductions will be possible.
The low-lying valley slopes and bottoms are a haven for bush loving species like kudu, bush buck, common duiker and Cape grysbok. Buffalo tend to lie up in thick ravine bush during the day and move up into the densely vegetated slopes at night to feed.
The high-lying grassy plateaus and fynbos covered mountains are home to the red hartbeest,
Cape mountain zebra, mountain reed buck, grey rhebuck and klipspringer. The eland are the great wanderers, moving over vast distances and utilizing a variety of habitats.
Caracal and leopard are the main predators in the area.
Although caracal may occasionally be seen, the sighting of a leopard is still a very rare and noteworthy event (recent evidence suggests that their numbers are increasing).
Cape clawless otter, bushpig, aardwolf, aardvark and a host of other smaller mammals are still reasonably common despite being seldom seen.
The most ubiquitous species must certainly be Chacma baboons. They seem to have been just as plentiful, if not more so, in earlier times. The Dutch word for baboon, "baviaan", gave the area its name.
The animals were so plentiful that the establishment of a small baboon-hide processing factory was initiated in the 1920's within the Baviaanskloof. Shoes, aprons, braces, rucksacks, and handbags were all made from the skins. Shoes were the most prized of all these items as baboon was well known as being the softest of all the leathers and, furthermore, wore particularly well. Baboons have a high level of internal fat which was used by the inhabitants to make soap. To-day the baboons are protected. You are asked to help authorities by refraining from feeding them as this leads to problem animals having to be shot.
Mature male baboons weigh up to 40 kg, more than double the mass of the females which average only 17 kg. There is also quite a wide spectrum in hair coloration. This relates to age, sex and also to which area the animals live in.
Baboons are reported to live for about 45 years. They are quite vocal animals as they roam around in search of food and “bark” alarms when they see a potential threat.