Assessing the dual impact of market feedbacks and harvest strategy on the overexploitation of a declining pangolin species

Background/Question/Methods

Commercial wildlife harvest may drive thousands of terrestrial vertebrate species extinct in the coming decades, primarily via overexploitation. One principle pathway to extinction via overexploitation is the Anthropogenic Allee Effect (hereafter AAE), which is a positive feedback loop whereby there is financial incentive to harvest a species as it becomes increasingly rare. However, rare species are seldom harvesters’ exclusive target, especially when labor and opportunity costs associated with locating scarce prey impose financial burdens on harvesters. Instead, flexibility and adaptability in species targeted can allow harvesters to ensure a steady source of income, often only including a rare species as opportunity arises. This opportunistic harvest of rare wildlife can itself serve as mechanism of overexploitation to extinction, and likely affects a wider array of species than the AAE. We consider these two bioeconomic mechanisms of overexploitation (AAE and opportunistic harvest) into a single model that accounts for the ability of harvesters to employ both single and multi-species hunting strategies. As a pertinent case study, we model the harvest of ground pangolins (Smutsia temminckii) and assess how including multiple harvest strategies with market-based feedbacks alters expectations of extinction risk.

Results/Conclusions

Our analyses show that estimates of extinction risk that incorporate the possibility of multiple harvest strategies are fundamentally different from estimates that assume only a single harvest strategy. Single-species harvest strategies insufficiently captured pangolins' extinction risk, as opportunistic harvest allowed harvesters to exploit pangolins to extinction in the absence of an AAE. Importantly, pangolins' short term extinction risk increased when harvesters used a combination of single and multi-species harvest strategies while also responding to increased rarity value. Our results suggest that risk assessments based only on a single pathway to extinction (e.g. AAE or opportunistic exploitation) may be insufficient to protect many species threatened by the commercial wildlife trade.