Monitoring of large carnivores in Botswana for conservation management

Abstract

Assessing the range, population size and trend of large carnivores are required for conservation management at global to local scales. Survey techniques should be precise with low bias, detect population trends and cover large areas efficiently. Track surveys may be used to monitor populations of lion (Panthera leo), leopard (Panthera pardus), spotted hyaena (Crocuta crocuta), brown hyaena (Parahyaena brunnea), cheetah (Acinonyx jubatus) and African wild dog (Lycaon pictus) in Botswana. Call up surveys is an alternative to survey lion and spotted hyaena. I recalibrated the published relationships between track density and true density. Linear regression through the origin was justified over linear regression with intercept for all models tested. Models through the origin fitted better and Akaike Information Criteria showed that these models were more robust. A review of the track survey method clarified ambiguous terminology and inappropriate analyses of data. This allows others to replicate track surveys in a way that improves inter-survey comparisons of results. I calculated species-specific calibrations to estimate confidence intervals of track densities from track incidence frequencies, and thus carnivore densities, for the entire southern African large carnivore guild. Calibration of carnivore response is required to estimate density from call up surveys. There correlation between the mean number of lions per calling station and reference density was significant (P < 0.05). Response probability did not differ by sex and age among surveys (call duration 90 minutes). Site-specific calibrations performed better than published calibrations. Call up surveys are unlikely to detect population trends in the Okavango Delta due to the high coefficient of variation (>200%). I collated data from various sources and conducted track surveys to assess brown hyaena distribution and density across land uses in Botswana. Density ranged from 0 brown hyaena / 100 km² in parts of northern Botswana, to 2.94 (2.16–3.71) brown hyaena / 100 km² in the southern Central Kalahari Game Reserve. The estimated brown hyaena population is 4642 (3133–5993). Agricultural land in Botswana is important to link populations in South Africa, Namibia and Zimbabwe. In 2005, Botswana implemented a minimum age threshold strategy to manage sustainable trophy hunting of male lions. I evaluated tooth: pulp width and area ratios to estimate age of trophy-hunted male lions in Botswana as a post hoc monitoring of compliance (2005 – 2007) to the 6-year minimum-age threshold. I used digital radiographs of the second premolar for measurements and cementum annuli analysis to calculate reference ages. The linear regression y = 0.990 x + 2.512 (r² = 0.647), between the tooth root area: root pulp cavity area ratio (R: RPA) and reference ages < 10 years (F1, 23 = 42.244, P < 0.001), was used to estimate age from R: RPA ratios. The 95% confidence intervals of age estimates from R: RPA ratios for the reference age classes 4 - 5 years and 6 - 7 years were mutually exclusive, showing the methods ability to distinguish between animals older and younger than the minimum age threshold. Wildlife tourism can provide economic incentives for conservation. I evaluated tourism potential in the Northern Conservation Zone of Botswana, using wildlife biomass and diversity estimates from aerial survey data as indicators of tourism potential. Areas used for High Paying Low Volume tourism had significantly higher mean wildlife biomass and wildlife diversity than the areas avoided for this type of tourism. Only 22% of the Northern Conservation Zone has intermediate to high tourism potential. Tourists will have significantly better wildlife sightings in areas with high tourism potential compared to low potential areas. Although the largest part of the Northern Conservation Zone has low tourism potential, it has a high conservation value. Alternative conservation strategies should be developed to complement the economic incentive provided by wildlife-based tourism in Botswana.