OPTIMIZING THE OFFTAKE OF LARGE HERBIVORES FROM A MULTISPECIES COMMUNITY

The Natal Parks Board annually sells hunting licences for the Controll ed Hunting Area (CHA) adjacent to the Mkuzi Game Reserve. A management objective is to maximise the revenue obtained from these hunting acti vities while ensuring that the population of each species is kept abov e some minimum level. This management problem is formulated as a linea r programming problem and solved for the fourteen different species in the CHA. The LP problem is formulated in such a way as to utilise the same data that is the basis for present management decision-making. T he objective function takes into account that animals are hunted for b oth meat and trophies. Only a fraction of each population is suitable for trophy hunting and higher prices an usual for such animals. The mo del considers fourteen species divided according to their food prefere nces into four groups. There is a carrying capacity constraint which l imits the weighted sum of the populations in each of these groups. Fur ther constraints relate to the specific growth rates of each species. The optimal equilibrium population levels were calculated to serve as goals or targets. However, droughts and other natural phenomena which affect population numbers are frequently encountered at Mkuze. A numbe r of experiments were therefore performed where the populations were s et to reduced levels. The optimal control problem which steers the pop ulations towards the target levels in an optimal way was formulated. S ome illustrative solutions are presented.