The Long-term Impacts of Hunting on Population Viability of Wild Ungulates in Tarangire, Northern Tanzania
Authors:   , Rija Alfan Abeid 
Published: November 2021

<p>Hunting through illegal and legal means is increasingly recognised as a threat to the sustainability of wildlife populations in reserves throughout Africa. Despite this, in Tanzania, legal hunting has persisted and serves as a source of revenue for conserving these species. Poaching remains a major threat to wildlife populations in many parks and reserves of Tanzania and wildlife habitats are diminishing due to human activities. I examined the impacts of hunting on the long-term persistence of four wild ungulates; impala (Aepyceros melampus Matschie), Thomson's gazelle (Gazella thomsonii Gunther), wildebeest (Connochaetes taurinus Thomas) and zebra (Equus burchellii Matschie) around Tarangire National Park, in northern Tanzania. I investigated the population sizes of these species using Distance sampling method and determined there were 4534 plus or minus 1393 impala 1398 plus or minus 491 Thomson's gazelle, 5199 plus or minus 2670 wildebeest, and 11223 plus or minus 4216 zebra, in the study area. I obtained an estimate of the legal offtake over a five year period from data provided by hunting companies and districts offices in charge of hunting in the area to establish an average size of annual legal offtake of the area. I estimated the poaching levels for each species using random response method by interviewing 298 household respondents within communities living around the area. This established that illegal kill were 2-3 times higher than legal offtake for all four animal species except zebra. The total annual harvests were 6.6% for impala, 18.2% for Thomson's gazelle, 5.2% for wildebeest and 2% for zebra, of population sizes. Using literature review I obtained vital life-history parameters for each species either from within Tarangire, or elsewhere in East Africa. The long-term viability of the four species was then examined under a computer program-VORTEX by constructing a series of models to test the effects of different hunting regimes. The models integrated mortality and fecundity rates, species population sizes and harvest (legal and illegal) rates. Of the four species, impala and Thomson's gazelle fared badly under all simulations, with up to 76% and 68% respectively of the modelled populations going extinct within 100 years under present 3 hunting levels. Wildebeest and zebra were more resilient to hunting. Zebra populations remained robust under current hunting rates. However, its population will slowly decline towards extinction when the hunting exceeds the current rate of 2%. The population of wildebeest will decline towards extinction if the current offtake of 5% persists. The impacts of illegal hunting are severe. This study is the first attempt to characterise the dynamics of the harvested ungulate populations in Tarangire, Tanzania. Poor understanding of this ecosystem especially on the demographic variables of these species, limit firm conclusions. Nevertheless, the findings presented here suggest that VORTEX modelling may be a useful tool for managing hunting at Tarangire and for highlighting research priorities.</p>