Using goats to control the spread of invasive alien plants

ReStory narrator: Ken Coetzee; Conservation Management Services

Credit: Ken Coetzee

In the Unites States and in Australia domestic goats have been used to control the spread of invasive alien weeds, shrubs and trees. Goats will eat almost anything and have been found to be particularly successful in the control and eradication of very dense herbaceous and shrub alien invaders. They relish plants with thorns and will happily consume plants with the secondary plant compounds that usually deter browsers.

The use of goats must be carefully managed. Firstly, they must be adequately contained within the specific area to be controlled and, secondly, they can only feed on what they can reach. The most important advantage in the use of goats is that no harmful chemicals need to be used to control the alien plants.

Goats are most effective for controlling the expansion of plants invasions. The three distinct phases of control with goats are as follows:

a) Containment: Goat browsing prevents the plants from flowering and producing seeds for further infection. The seed reserve is thus eventually depleted under repeated goat browsing. Goats do not spread the seeds of alien plants in their dung. They chew them up effectively and their stomach juices completely break them down.

b) Suppression: Heavy goat browsing reduces the competitive ability of the alien plants and provides the indigenous vegetation with an opportunity to return to the site.

c) Eradication: Repeated defoliation by goats, in an effective browsing camp rotation system, will eventually lead to the death of most alien plants. Plants that can survive the repeated defoliation, or that do not get completely defoliated by the goats, can possibly be controlled mechanically or by means of biocontrol.

The goats must be contained, in the area to be controlled, by means of portable electric fencing. Electrified plastic or wire netting is effective but the fence must be sturdily constructed, even if temporary, because goats are renowned escape artists. A system of camps should be constructed in the control area so that a type of rotational grazing can be applied to achieve effective control of the alien plants. In the United States, a system of 1 acre (0.404ha) camps were used for 40 to 50 goats on rotation. The size of the camps, however, will depend on the type of vegetation in the camps and the number of goats used.

If a landowner wishes to use goats for alien plant control but does not farm with goats, consideration can be given to hiring a herd of goats for the task. Payment for hire can, for example, be the forage provided in the browsing camps plus the cost of transporting the goats to the site. If invasive alien plants are a particular problem on any particular farm, consideration should be given to permanently establishing a herd of goats to help control the spread of the alien plants.

In less well-funded rural South Africa the goats could possibly be herded and kept in the target areas by herders with dogs without the need for expensive and unobtainable fencing materials.

The most important advantage is that no chemicals are used to control the spread of the alien plants and that the locally indigenous vegetation will be able to recover in a rotational browsing system. For taller alien plants like trees and high-climbing creepers, the goats will need some assistance. They are extremely effective in what they do but only as far as they can reach. They are particularly good at consuming the coppicing regrowth of felled alien trees or the tangled branches of invasive creepers that have been pulled down to within their reach. In the Eastern Cape of South Africa goats have been used to control the spread of grey poplar (Populus canescens) regrowth from root suckers after the mature trees were felled. Poplar in South Africa are sterile so this is a very effective way of ensuring complete eradication of the poplar after mechanical felling. Poplars also only grow along streams and rivers, which are sensitive systems in which the use of chemical herbicides would be devastating.

In Australia goats are used to control massive invasions of European brambles (Rubus sp.). The creeping plants are pulled down out of trees by workers and the goats do the rest. In the United States goats have been successfully used to completely eradicate dense infestations of European gorse (Ulex europaeus). Other plants that have been known to be controlled by goats are: Chinese tamarisk (Tamarix chinensis), Scotch thistle (Cirsium vulgare), Kudzu vine (Pueraria lobate), English ivy (Hedera helix), Port Jackson willow (Acacia saligna), Black wattle (Acacia mearnsii)andGrey poplar (Populus canescens). But because goats do eat almost anything, this list of alien plants can be a great deal longer.

Using goats to control invasive alien plants could provide an economic opportunity for small livestock farmers in South Africa. Goat farmers can become entrepreneurs that run alien plant clearing goat herds and so become indispensable in the fight to control and eradicate invasive plants. There is also the great advantage of the goats being a lucrative source of meat and skins with a ready market. We have invasive alien plants in almost every part of South Africa and if properly managed, goats for aliens could become economically important in smaller rural communities.

If you know of the effective use of goats for clearing or controlling alien plants, I would like to hear from you. Please reach me by either phoning (cell no.: 0762275056) or emailing (consken@mweb.co.za).