The isolation of feral goats of the Tankwa Karoo National Park in the Northern Cape – a unique goat population – date back to the early 1900s, but are at risk of extinction. Prof Antoinette Kotzé of the National Zoological Gardens in Pretoria, in collaboration with researchers from Northern Cape Agriculture and the University of the Free State, recently conducted a study on this population. As part of their research, they gathered genetic information to guide further investigation into the conservation and breeding of these animals to ensure their survival and effective utilisation.
Their results suggest a relatively high variability and detectable genetic differentiation from other breeds. And, because these animals are highly adapted to a harsh environment without human intervention such as artificial selection, the breed may offer possibilities of commercialisation. The goats at Tankwa have been free-roaming for more than 50 years, during which time the population size has varied between 100 and 300. Departmental officials have confirmed that the Tankwa feral goats are well adapted to harsh grazing conditions, are parasite-resistant, have good maternal abilities, and can survive high predation pressures.
An important aim of the study was to investigate their possible genetic uniqueness for a conservation framework. An analysis of the population structure suggests certain unique features in the population. Although these may reflect decades of random drift, they could also reflect adaptation to a harsh environment through natural selection.
Varying goat colours
The hair of the Tankwa goats has a high degree of variation in colour and appearance. Their coat tends to be longer than the typical South African Boer Goat and other indigenous types, with the primary colours being black, red, white and grey, mixed with spotted, dappled and tricolour variations. Several studies have been conducted to genetically characterise South African indigenous farm animal breeds, resulting in a rich variety of genetic resources.
These animals often include those with low production potential, but better adapted to South Africa’s different climatic regions than imported European breeds. There are a number of examples elsewhere in the world where domesticated animals have become wild and subsequently adapted to harsh climatic and environmental conditions. Examples include the wild horses of the Namib desert, and feral cattle on Chirikof Island, Alaska.
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When SANParks initiated the removal of these feral goats from the Tankwa Karoo National Park, the Northern Cape Department of Agriculture, Land Reform and Rural Development (NC-DALRRD), realised that they might be the source of unique genetic material. The department’s interest was the result of its commitment to the goat industry in the Northern Cape and the Commercialisation of Goats Programme. This spawned the Tankwa Goat conservation framework.
For the study, 66 feral goats from Tankwa Park as well as Tankwa goats kept on a private farm were genotyped using eight microsatellite markers. The data was compared with genotypical data of selected commercial breeds – Angora goats, Boer Goats and Saanen dairy goats. The diversity values of the Angora breed were the highest in all cases. However, the diversity values of the Tankwa population are based on individuals from relatively small and isolated populations.
The values of the other breeds, on the other hand, are representative of the breed as a whole, rather than individual populations. There is also an indication of a shared genetic background, or introgression, with the Boer Goat and Saanen breeds in a limited number of Tankwa animals. This could, however, be the result of an ancient shared ancestry, rather than recent events.
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Treated as separate groups, there seems to be considerable variation among the breeds, with 19,7% of variation attributed to differences between breeds, and 80,3% to within-breed diversity. Because almost 20% of overall variation in the goats is between breeds, there may be a reservoir of diversity for directed selection of goat breeds.
A significant proportion of the Tankwa goat’s uniqueness reflects simple drift, resulting from decades of isolation. However, there may be an adaptive component to the uniqueness, resulting from an extended period of natural selection by the specific environmental conditions. Since the Tankwa goat has not been studied for production, specific production advantages are currently not known.
Move to research station
The Tankwa Karoo National Park was originally declared in 1986 to protect the Succulent Karoo, now acknowledged as one of 25 biodiversity hotspots in the world. In 2007, the Northern Cape Department of Agriculture, Land Reform and Rural Development decided to move the goats from the park to the Carnarvon Research Station in the Northern Cape. According to the department, the move was necessary because these free-ranging domesticated goats pose a threat to the park’s rare endemic succulent species.
“International research papers have stressed the detrimental effect of the species on vegetation composition and structure, leading to ecosystem degradation and biodiversity loss,” says Conrad Strauss, manager of the Tankwa National Park. This was despite the fact that there were relatively few of them and they were using only 2 500ha of the total 140 000ha area.
Eventually, 87 were captured in jump traps, which proved difficult due to the steep slopes and the goats’ habit of foraging on high cliffs.
Unfortunately, 30 of the captured goats died in Carnarvon, mostly due to old-age and disease, but possibly also due to the effects of trying to adapt to their new environment. The aim now is to establish a viable Tankwa goat population at the station.
Some uncertainty exists about what to do with the goats remaining in the park. Keeping free-ranging farm animals in a national park is likely to clash with local and international biodiversity principles.
Email Prof Antoinette Kotzé at [email protected].