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Modelling the effect of human-caused mortality on a lion sub-population using spreadsheets

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dc.contributor.advisor Milton SJ, Prof en
dc.contributor.advisor Van Vuuren JH, Prof en
dc.contributor.advisor Funston PJ, Dr en
dc.contributor.author Herrmann E en
dc.date.accessioned 2016-09-22T08:34:37Z
dc.date.available 2016-09-22T08:34:37Z
dc.date.submitted 2004 en
dc.identifier.uri http://hdl.handle.net/20.500.11892/31169
dc.description.abstract Free-ranging lions ("Panthera leo") in the Kgalagadi Transfrontier Park (KTP) have been subject to persecution by farmers following livestock depredation in adjacent grazing areas. In recent years at least one adult female was killed annually from a sub-population of five boundary prides that have home ranges adjoining these livestock grazing areas. While no long-term records of human-caused mortality are available, the impact of current rates of human-caused mortality is uncertain. Female-based, age-structured models were thus used to estimate the long-term viability of the KTP lion sub-population subjected to human-caused mortality under deterministic and stochastic environmental conditions. Population parameters incorporated in the models included age-class specific natural mortality, female fecundity and birth sex ratio. In so doing sustainable threshold rates of persecution were established, so that effective conservation measures can be taken, if required, to ensure the continued survival of boundary prides in the park. Sensitivity analyses of natural survival rates indicated that adult female survivorship is the most important population parameter with respect to maintaining population viability, compared to younger female age-classes, fecundity or birth sex ratio. Hence adults were also the most sensitive age-class with respect to human-caused mortality, as adult survival repeatedly acts upon individuals with the highest reproductive value. In the deterministic model, with the most optimistic survival parameter values, fecundity and birth sex ratio (female-biased) estimates, the sub-population is only able to sustain an annual persecution of three adult females, before the sub-population exhibits a sustained decline. In the worst-case scenario, where fecundity and sex ratio estimates are at their lower extremes, the maximum sustainable age-class specific persecution rate is zero, for all age-classes. Whilst these hypothetical scenarios are unrealistic, they do highlight the extreme thresholds of potentially sustainable persecution rates. Under the most optimistic scenario using the stochastic model, the highest achievable survival probability of the sub-population, when subjected to a persecution rate of one adult annually, was 78 percent. Although increased fecundity and birth sex ratio biased towards females may increase the survival probability, these parameters are generally at their mean values in the long-term, and may thus not necessarily prevent a sustained population decline. The models therefore suggest that the current persecution rate of one adult annually (or 4 percent of the adult sub-population), appears unsustainable in the long-term. To ensure the survival of existing boundary prides and to maintain a viable subpopulation, adult lionesses should, as far as possible, be afforded protection from persecution. en
dc.language English en
dc.subject Forest science en
dc.title Modelling the effect of human-caused mortality on a lion sub-population using spreadsheets en
dc.type Masters degree en
dc.description.degree MSc en

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