The biology and use of the cactus (Opuntia exaltata) as a game defense barrier

Abstract

Human-wildlife conflicts result as a competition for resources between man and wildlife. This thesis describes the use of traditional and conventional game barriers in managing wildlife populations and the use ofcholla cactus (Opuntia exaltata) as a live fence in two main areas of Kenya and the problems facing the suitable growth and establishment of this live fence. Traditional methods of deterring wildlife such as noise, lighting fires, constructing thorny barriers and extermination are widely used. Conventional barriers such as moats, stone walls, wire fences, high tensile fences and electric fences are expensive to construct, have high recurrent costs and are only marginally effective. The cholla cactus (Opuntia exaltata) was introduced from South America and provides a "hard edge" barrier with its thick spiny stand and is used by ranches and small scale farmers in controllingwildlife dep.r.edation. The cholla cactus (Opuntia exaltata) is . distributed in a total of seven di.stricts but its use is concentrated in Nakuru and Laikipia districts. The growth of Opuntia exaltata as a managed fence was more successful in Nakuru then Laikipia district. To be an effective wildlife barrier it has to attain a height of - at least 2-3 m and be 1-2 m wide. However in some cases gaps and uneven height resulted in poor growth leading to an unsuitable barrier. This poor growth was caused by the physical conditions present in the soil such as compaction, shallow soil depth and poor moisture retention. The levels of nutrients in the different areas of growth were not significantly different and did not affect the growth. The presence of partial shade from neighboring trees at a minimum level of 1500 ~ E m -2 S-l and the presence of leaf litter from the overhead canopy of the trees resulted in better growth of the Opuntia exaltata fences. The limiting physical factors can be removed by excavating a trench and filling it with loose soil and manure to create a suitable matrix for root development and moisture retention. In areas with poor physical soil conditions and low rainfall this method would be suitable for growing a cholla fence. The cholla cactus (Opuntia exaltatay can provide a cheap, cost effective barrier for reducing human wildlife conflicts and its xerophytic properties can allow it to be used in semi-arid and arid areas.