When the settlers arrived, some were given parcels of virgin bush to farm. The ecology of KwaZulu-Natal at that time must have been very different, with few exotic trees or animals.
Kwa-Zulu-Natal is home to many poisonous snakes, including Black Mambas, Green Mambas, many species of cobras, Night Adders, Puff Adders, Berg Adders, Vine snakes and Boomslangs.
We can only assume that there were far more of all these creatures back then, since there were fewer people around to kill them off.
If you want to know more about the reptiles your ancestors were dealing with, the KwaZulu-Natal Amphibian and Reptile Conservation has a fascinating Facebook page. The picture shown is from that page. It shows an angry Black Mamba. You can see that the inside of the mouth is black, that is where this snake gets it’s name, not from the colour of it’s skin.