The present status of knowledge on the global use of rhinoceros dehorning: A systematic review

Poaching remains a major threat to rhinoceros (hereafter rhino) species, particularly in southern Africa. In response, the use of dehorning (removing the horns of live rhinos) is increasing. We systematically reviewed 120 publications (44 % peer-reviewed) published prior to June 2024 to assess the present knowledge regarding rhino dehorning. The use of dehorning has increased across southern Africa, with no records of its use in eastern black rhinos or Asian rhino species, while the cost of dehorning per rhino and mortality rates associated with the dehorning procedure have decreased. The discussion of legal trade in relation to dehorning was the most common theme (56 %, n = 67), followed by biological/ecological impacts (24 %, n = 29) and anti-poaching effectiveness (23 %, n = 27). However, only 45 % and 37 % of the latter two themes were peer-reviewed, respectively, most of which only focused on one site and so were not generalisable to other areas. Publications discussing potential legal trade supplied through dehorning presented mixed views, with questions surrounding the potential conservation benefits of trade and the difficulty in predicting market responses. We found little evidence of any dehorning impacts on rhino reproduction, although there was some indication of changes to social structure and ranging behaviour, which warrant further investigation. The present peer- and non-peer-reviewed literature suggests dehorning is effective in reducing poaching on a site-specific scale. However, large-scale, peer-reviewed studies with robust counterfactual analyses, including on possible poaching displacement from dehorned to horned sites, are needed to inform global rhino conservation.