An Evolutionary Game Theoretic Model of Rhino Horn Devaluation

Rhino populations are at a critical level due to the demand for rhino horn and the subsequent poaching. Wild life managers attempt to secure rhinos with approaches such as devaluing the horn. The most common strategy of devaluing horns is dehorning. Game theory has been used before to examine the interaction of poachers and wild life managers. A manager can either ‘dehorn’ their rhinos or leave the horn attached. Poachers may chose to to behave ‘selectively’ or ‘indiscriminately’. The approach described in this paper builds on this previous work and investigates the interactions between the poachers. Using evolutionary game theory, we determine which strategy is preferred by a poacher in various different populations of poachers. The purpose of this work is to discover whether conditions which encourage the poachers to behave selectively exist, that is, they only kill those rhinos with full horns. Notwithstanding, the analytical results prove that poachers will never adopt a selective strategy as long as there is gain from a partial horn. Additionally, poachers behaving indiscriminately is stable and robust. However, the model is adapted further to include a disincentive factor, which may represent factors such as harsher punishment, or lower demand for horn. With a disincentive, poachers can be encouraged to behave selectively, but only when there are few devalued rhinos. This paper aims to contribute to the necessary research needed for informed discussion about the lively debate on legalising rhino horn trade. 1 ar X iv :1 71 2. 07 64 0v 1 [ qbi o. PE ] 2 0 D ec 2 01 7