Trophy quality trends outside a protected area (CAMPFIRE): Does soil fertility influence quality?
In Zimbabwe, all the trophies hunted are measured and evaluated by the Parks and Wildlife Management Authority. The data of evaluated trophies are collected and stored in the National Trophy Database of Zimbabwe in a standardized way. Data collected for this study on trophy quality were based on task/horn length and weight, all measured using the Safari Club International (SCI) system for elephant tusks and spiral-horned species, e.g., greater kudu. An existing database of trophies and their measurements from the Tsholotsho Rural District Council was used. Another database using the Safari Club International (SCI) system was obtained from Taxidermy Enterprises, Bulawayo, Zimbabwe. Taxidermy Enterprises had a certified SCI measurer who measured on behalf of the Tsholotsho RDC. Any missing data from the Tsholotsho Rural District database was confirmed from the Taxidermy Enterprise records, as often was the case. SCI measures the greatest length and weight of tusks and horns and adds the figures to come up with a total score. The records from 2009 to 2015 were matched to their respective areas using an already existing database. However, the period during which these data were collected had its own fair share of challenges in terms of climate, management and politics. With such challenges, the period under the analysis of this data is not homogeneous. The economic and political status of the country between the period 2009 and 2015 may have an influence on population dynamics and trophy size. For soil data, the National University of Science & Technology and Department of Research and Specialist Services (DR&SS) laboratories were used for preparing and testing soil properties (physical and chemical). Soil testing included an analysis of the soil chemical properties and an evaluation of the soil nutrient-supplying capacity at the time of sampling. The soil analysis process involved taking soil samples, analysis of soil samples, and interpreting the results of the sample analysis.
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We used data from annual hunts within the two management systems (protected and unprotected) where trophy hunting is carried out. Using the Safari Club International (SCI) standards, tusk size and horn length were measured along the external side of the tusk or horn, from the base of the tusk/ horn to the top. When both tusks and horns of an individual were measured, the average length/weight were retained. Tusk weight and horn length was considered as a proxy for trophy size. Both trophy measurements were expected to reliably indicate trophy size. An existing database of trophies from the National Parks and Tsholotsho Rural District Council was used, another measured trophy record database using the SCI system was obtained from Taxidermy Enterprises, Bulawayo, Zimbabwe. SCI measures the greatest length, width and weight of tusks and horns and adds the figures to come up with a score. The records from 2009 to 2015 were matched to their respective areas using these databases. Soil samples were collected from the surface (0 – 10 cm) and subsurface (10 – 20 cm) soil layers using a 6cm diameter stainless steel soil corer. At each selected site, soil cores were collected in four cardinal directions (N, E, S and W). Soil samples in each hunting zone (core and periphery) were bulked, mixed thoroughly, and a composite sample drawn. Field fresh soil samples were collected in the surface and subsurface soil layers in the core and periphery zones of the two hunting areas. Each composite sample was sieved through a 2 mm mesh screen and any visible roots and large fragments of organic debris were manually removed in order to avoid any marked immobilisation during storage. Each collected sample of 200 g of soil was sealed in polyethylene bags and transported to the laboratory to be analysed. Physical processing of the soil samples was done at the Forest Ecology Laboratory of the National University of Science and Technology in Bulawayo. For the determination of mineral N, soil samples were transported to the laboratory at the Department of Research and Specialist Services, Chemistry and Soil Research Institute, in Harare, Zimbabwe. The soil samples were analysed for organic N, P, K, Ca, Mg and Na as described in Chapter 3. Soil pH was measured in a 1:2 mixtures of soil and deionised water using a glass electrode. Trophy size differences and soil parameters were tested for significant differences among treatments using ANOVA. Differences between means were tested using Tukey HSD post hoc test with a level of significance of p < 0.05. Logistic regression was performed to ascertain the effects of land management (protected and unprotected land) and hunting zone (core and periphery) on the likelihood that a trophy will meet the SCI standard of quality. Two predictor variables were used to predict the probability of an event occurring based on a one-unit change in an independent variable when all other independent variables are kept constant.