In the part of South Africa where I live we also have the American Grey Squirrel, introduced to this country by an arrogant, unpleasant English colonialist whose name is equivalent to a four letter word amongst the majority of the population. These squirrels have adapted fairly well to the urban environment where they are a pest in many towns of the Western Cape. In particular they are responsible for killing many young birds while still in their nests, a loss we can ill-afford. But fortunately they have not succeeded in adapting to the natural environment so their impact is limited.
But we have another alien here which makes your grey squirrel problem look like a Sunday School picnic in comparison. This is the Himalayan Tahr, a large mountain goat. Indigenous to the mountainous areas of India, a few were brought into the country late in the 1800’s by the same said gentlemen and placed in the Cape Town Zoo situated at that time on the lower eastern slopes of Table Mountain. In the 1930’s a pair escaped from the zoo and headed up the mountain. They had no natural predators. They were too large for the small members of the cat family and even for baboons, which will pull down small buck given the chance. They are incredibly skilful climbers and spend much of their time on precipitous rock faces and ledges. They rapidly multiplied. They competed for the same territory as a small indigenous buck known as the klipspringer (literal translation ‘rock jumper’) and are extremely intolerant of co-existing with other species. Soon the numbers of klipspringers started to decline alarmingly and they were in danger of being eliminated from the Table Mountain chain.
The Tahrs grazing habits are also completely unsuitable to the endemic fynbos vegetation in the Western Cape. They tend to completely strip a plant causing it to become unviable. As their numbers grew areas becoming denuded of vegetation increased with a loss of biodiversity and erosion during heavy winter rains.
All this presented the Environmental Agencies with a problem. Should they do nothing and allow ‘nature’ to take its course with the inevitable elimination of the klipspringer and many of the fynbos species? Or should they intervene and take active steps to remove these alien Tahrs from the area.
The dilemma was compounded by the fact that capturing and relocating the Tahrs was impossible due to their habitat of living on the rock faces of the mountain. The only way to deal with them was to hunt and shoot them.
Would be interested to hear views on what your recommendations would be if you were charged with the responsibility of making the final decision.