Pretoria is known as the Jacaranda City, and Stellenbosch as the Eikestad. The South American Jacaranda and the European Oak line their respective streets. These trees are under control, and in the case of the oaks have to be carefully looked after. Other exotic trees, such as two from Australia, have their uses. The Port Jackson stabilizes dunes. The Wattle provides bark for tanning, among other uses. Neither are easy to control and have become pests – the wattle invades water courses. Pine trees are useful, not only for shade and as wind-breaks, but on a large scale as timber trees. They have the virtue that they can be grown in neat rows, leaving access for harvesting in the course of time. For pines are easy to manage. Usually.
Various pine species have been tried in plantations in Southern Africa. They propagate easily and mature rapidly. The quality of the wood, such as infrequency of knots, and other factors, made them plantation favourites. So it came about that Monterey Pine, Pinus radiata, was a candidate, and a promising one.
There was one problem with the Monterey pine. Unlike other pines it readily propagated itself. There was a solution. Exotic species often fared well in their new home precisely because they left some of their restrictions at home. The Monterey pine left the Emperor Moth, Imbrasia cytherea. A pest thought to be specific to it.
There was one problem with this emperor moth. Its caterpillars did their work too well. Other pine species were acceptable substitutes for the Monterey pine. There was a solution. Pigs located the pupae easily. They relished them. Various pig races were released in the plantations, and they controlled the Emperor Moths.
There were still problems. While the pig races were found to be efficient against Emperor Moths, they readily became feral, and some progeny began to show atavistic tendencies. Such as strong, sharp tusks, and a readiness to use these. Walking through some kloofs in the Western Cape could be made memorable by a feral pig, particularly a sow with a litter. But, after all, before shooting of every largish animal in the region, people would have experienced the same sort of fear.
People reported the disappearance of grazing sheep, goats, and the occasional calf, and of dogs, small and large. One of the people involved in the original decision to import the Monterey pine first saw a pug print in the mud by a stream in a kloof. And the print was still filling with water. He looked around him, and realized how difficult it would be to see amongst the sun-dappled vegetation an object with spots. Even one about the size of a man.
The report that pug prints were seen very close to the town was probably apocryphal, but the passage from pine, to pupa, to pig, to Panthera pardus was not.