The impact of dehorning on the white rhinoceros (Ceratotherium simum) and the evaluation of novel anti-poaching tactics

Abstract

The white rhinoceros (Ceratotherium simum) is experiencing unsustainable poaching losses fuelled by an increased demand for horn. In an attempt to reduce poaching pressure and faced with rising security costs, increasingly, private and state reserves are dehorning their rhino populations as a management approach. Despite the procedure’s wide-scale practice, significant knowledge gaps exist on how dehorning may affect the behaviour or physiology of white rhinos. Given that rhinos require continued protection after dehorning, there is also a need to develop effective, low-cost techniques to aid on-the-ground conservation efforts. This research employed a combination of field studies and laboratory experiments to address this.

To determine whether dehorning affected the social behaviour of white rhinos, behavioural observations were conducted on free-ranging horned and dehorned populations in South Africa. Dehorned individuals exhibited similar agonistic and cohesive social behaviours to horned individuals. However, a rise in the rate of agonistic interactions was detected after a repeat dehorning procedure. The results also provide the first evidence of a non-territorial dominance hierarchy among free-ranging white rhinos, with the lowest ranked individuals shifting in social position after dehorning.

To investigate whether white rhinos exhibited a long-term physiological response to horn removal, changes in adrenal and gonadal steroid levels were monitored in faecal samples. Long-term hormone profiles were not influenced by the number of times a rhino had been dehorned. Furthermore, there was no detectable difference in corticoid concentrations between a dehorned and horned population. Dehorning did not appear to act as a chronic stressor and thus compares favourably to other conservation techniques, such as translocation.

Horn use in a non-social context was examined by camera trapping and behavioural observations. Dehorning did not have a detectable impact on resource access, with no change in digging behaviours observed during geophagy and wallowing, nor on the frequency of horn rubbing behaviours, suggesting limited impact of the procedure on this aspect of the species ecology.

Date of Award	Nov 2019
Original language	English
Awarding Institution	University of Brighton
Supervisor	Angelo Pernetta (Supervisor), Rachel White (Supervisor) & Dawn Scott (Supervisor)