Illegal Offtake

Illegal hunting could affect the survival of reedbuck, waterbuck, lechwe and puku in all of the floodplain habitats. It could also prejudice the success of the introductions recommended above. Martin used a population model to explore the maximum illegal harvest which wetland grazer populations could sustain. It is assumed that mortality would affect both sexes and all ages equally. The 'doubling time' is the number of years it would take for the population to double its numbers at the given rate of illegal harvest.

Without any illegal hunting the population grows at slightly more than 10% per annum and it can sustain a maximum offtake of about 9%. The higher the offtake, the lower is the growth rate of the population and the effects become severe above a 5% illegal harvest.

Within State Protected Areas a major effort is being made at present to contain illegal hunting, control fires and, in general, to implement park plans. The present MET staff numbers, equipment and infrastructure are insufficient to meet the challenges (PW 1998) but improvements are taking place in all these aspects. The annual operating expenses required to protect all the State Protected Areas in the Caprivi has been estimated at about US$1 million (Martin 2002b, 2003). However, the total area of floodplain habitats in the State Protected Areas is only about 500km2 and, even with existing resources, this is not an overwhelming area to police effectively.

The larger issue is the conservation of the other five-sixths of the floodplain habitats outside the protected areas. This protection is unlikely to be achieved through conventional law enforcement. And illegal hunting is only a part of the problem - the clearance of new lands for agriculture and habitat degradation through cattle grazing are the other two. These provide a strong reason for seeking new institutions involving partnerships with local communities.

Sport Hunting

Martin used a population model to explore the effects of hunting quotas on reedbuck, waterbuck, lechwe and puku populations.

Findings: Sport hunting quotas for reedbuck, waterbuck, lechwe and puku populations should never exceed 3%. (Figure 23)

Hunting selectivity is centred on the 6-7 year old males, with 40% of trophies coming from this age group, but the rest are spread fairly evenly over the range of age classes. The available quota of trophy animals is taken from the various age classes in the proportions set by the selectivity profile ((i.e. if the quota was 100 animals it would take 5 animals from the 3 year old age-class, 10 animals from the 4 year-old age class, 15 animals from the 5 year-old age class ... and so on). However, if there are insufficient animals in any age class to meet the quota demand, the animals are then sought in the age class immediately below it as would happen in practice. The percentage quotas apply to the total population and it is assumed that males under 5 years old would not be hunted.

As the quota is increases from zero, little change takes place up to a quota of 1.5%. The sex ratio alters slightly from 1.7:1 to 2:1 but none of older male age classes disappear from the population (Figure 23). The older age classes begin to disappear at a quota of 2% when all of the animals older than 8 years are removed from the population. A quota of 3% results in all animals older than 6 years being removed, a 4% quota removes all animals aged 5 years and older and, at 5%, only 3 year-old males are left to breed. This would suggest that sport hunting quotas for reedbuck, waterbuck, lechwe and puku should not exceed 3%. At a 3% quota there are still some 6 year old males left in the population as prime breeding animals. Above a 3% quota, the sex ratio begins to shift dramatically in favour of females.

It is not necessary to know the numbers of animals in the population in order to set sustainable quotas. Much more robust adaptive methods for quota setting can be used instead.