Should I shoot or should I go? Simple rules for prey selection in multi‐species hunting systems

Abstract

Across the tropics, unregulated hunting targeting many different species presents a major conservation challenge. Prioritizing resources for monitoring and enforcement is difficult when multiple prey species are exploited. However, identifying which prey species are subject to hunting pressure can be achieved with diet choice models. We evaluate hunter diet sets using data from Southwest China and compare two diet choice models: optimal foraging theory and a relatively new diet model originating from economic optimal stopping problems. The optimal stopping diet choice model required fewer field parameters than optimal foraging models and more accurately reflected hunter catch in Southwest China. The optimal stopping model also indicated that hunters should be less selective when they experience a larger opportunity cost for their time. Finally, we illustrate a new method to evaluate harvest impact from single sites with limited data using dietary thresholds. This technique could be used to evaluate whether or not the community of exploited wildlife has shifted in its trait distribution, providing a means to anticipate trait‐biased defaunation from minimal data.

Multiple co‐occurring bioeconomic drivers of overexploitation can accelerate rare species extinction risk

“…Previous attempts to model overexploitation to extinction have treated the AAE and opportunistic harvest as independent mechanisms, reducing harvester behaviour to a single aspect (Damania et al, 2005; Holden & McDonald‐Madden, 2017; Rowcliffe et al, 2003). However, this assumption is likely too narrow given that many species are exploited in multi‐species harvest systems (Bi et al, 2017; Chang & Drohan, 2018). Focusing on the harvest and sale of ground pangolins as a case study, we show that, when considered in tandem, AAE and opportunistic harvest lead to increased and accelerated extinction risk compared to either mechanism alone.…”

“…Moreover, our model follows previous approaches in portraying opportunistic harvest as a ‘two‐species system’, where the harvest of a single common species subsidizes the opportunistic harvest of a rare species. In reality, however, harvesters can hunt and sell substantially more than two species (Chang & Drohan, 2018; Damania et al, 2005; Rowcliffe et al, 2003). While we addressed this uncertainty by exploring dynamics where the common species followed one of two life‐history types, our model structure is most well suited to situations where harvest dynamics are known to be closely tied to two species, such as the opportunistic snaring of babirusa during wild pig hunts in Sulawesi (Clayton et al, 1997).…”

“…Wildlife trade threatens terrestrial vertebrate species with extinction, primarily via overexploitation (Maxwell et al, 2016). In the case of commercial trade, extinction risk often depends on whether harvest remains profitable as populations are depleted, since labour and opportunity costs associated with locating scarce prey impose financial burdens on harvesters preventing harvest to extinction (Branch et al, 2013; Chang & Drohan, 2018; Fa et al, 2002). When species have high enough market value, however, a plausible pathway to extinction via overexploitation is the anthropogenic Allee effect (AAE), which is a positive feedback loop whereby there is financial incentive to harvest a species as it becomes increasingly rare (i.e.…”

Prey preferences of modern human hunter-gatherers

“…Modern human hunter-gatherer groups tend to have a set of behaviors and motives that direct what or when to hunt, and how to hunt safely. These behaviors, which are passed from generation to generation, are often shaped by needs within each group and likely follow the tenets of the optimal foraging theory (Chacon, 2012;Chang & Drohan, 2018).…”