Abstract
Reliably predicting sustainable exploitation levels for many tropical species subject to hunting remains a difficult task, largely because of the inherent uncertainty associated with estimating parameters related to both population dynamics and hunting pressure. Here, we investigate a modelling approach to support decisions in bushmeat management which explicitly considers parameter uncertainty. We apply the approach to duiker Cephalophus spp., assuming either a constant quota-based, or a constant proportional harvesting, strategy. Within each strategy, we evaluate different hunting levels in terms of both average yield and survival probability, over different time horizons. Under quota-based harvesting, considering uncertainty revealed a trade-off between yield and extinction probability that was not evident when ignoring uncertainty. The highest yield was returned by a quota that implied a 40% extinction risk, whereas limiting extinction risk to 10% reduced yield by 50%-70%. By contrast, under proportional harvesting, there was no trade-off between yield and extinction probability. The maximum proportion returned a yield comparable with the maximum possible under quota-based harvesting, but with extinction risk below 10%. However, proportional harvesting can be harder to implement in practice because it depends on an estimate of population size. In both harvesting approaches, predicted yields were highly right-skewed with median yields differing from mean yields, implying that decision outcomes depend on attitude to risk. The analysis shows how an explicit consideration of all available information, including uncertainty, can, as part of a wider process involving multiple stakeholders, help inform harvesting policies.
Highlights
Many studies raise alarm over the present rate of wild meat harvesting as a major cause of population decline and extinction risk for many species [1,2,3]
With wild meat providing a major source of protein and household income to some of the world’s poorest people [4,5,6], both subsistence and commercial hunting in West and Central Africa are on the rise [1, 6, 7]
The studies were concentrated in five main research areas: the Ituri Forest (Democratic Republic of Congo); Makokou; Bioko and Rio Muno (Cameroon); Dzanga-Sangha and Dzanga-Ndoki National Parks (Central African Republic), and Arabuko Sokoke (Kenya)
Summary
Many studies raise alarm over the present rate of wild meat harvesting as a major cause of population decline and extinction risk for many species [1,2,3]. With wild meat providing a major source of protein and household income to some of the world’s poorest people [4,5,6], both subsistence and commercial hunting in West and Central Africa are on the rise [1, 6, 7]. Bushmeat yield versus survival trade-offs in heavily-hunted duiker Cephalophus spp
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