Individual behavioural differences in the captive Southern ground hornbill Bucorvus leadbeateri

Abstract

Southern ground hornbills (ground hornbill) Bucorvus leadbeateri are among Africa’s most recognisable birds. The ground hornbill is formally listed as ‘Vulnerable to Extinction’ on the IUCN Red List and is endangered in both South Africa and Namibia. The ground hornbill is a nationally protected species in South Africa, yet the population numbers are still declining. The species is thus a conservation priority, and studies of captive individuals are needed to assess the suitability of individuals for breeding and potential future release. I investigated the behaviour of five captive populations of ground hornbills in Gauteng Province, and one population in the Western Cape Province, South Africa with the aim of investigating individual behavioural variation in these captive ground hornbills. Firstly, I described nine broad behavioural categories in the captive ground hornbills, and used these behaviours as a basis for further analysis. Secondly, I studied the activity patterns of the captive ground hornbills and found that the ground hornbills in my study did not conform to the bimodal pattern of their free-living counterparts, but rather their activity, at least for the three common behaviours (perching, locomotion, object interaction) remained fairly constant throughout the sampling time. The captive ground hornbills spent the largest proportion of their time perching, followed by locomotion and probing with their beaks. The three behaviours that were displayed the least were thermoregulation, vocalising and feeding. Behaviours varied by location on the overall behaviour but no sex effect. Thirdly, I recorded transactional (behavioural) interaction and found that aggression was rare and occurred in just one population. In contrast amicability was common and occurred more often than chance in three populations. Fourthly, I also found differences in the space use of individuals within populations, where space use was greater in some individuals in each institution. Individuals in each population commonly used less than 50% of their cage, frequently at the same time, linked to feeding, cage composition and their natural patrolling tendencies. Fifthly, I investigated the risk-taking behaviour and found that individuals in each institution varied their behavioural responses inconsistently in a startle test but with some showing consistent responses in novel object tests, indicating personality in ground hornbills. There were also population differences in the responses to a novel object. Finally, correlations among the behaviours indicated that ground hornbills display a behavioural syndrome (i.e. consistent behaviour responses across contexts). These findings allow for a greater understanding of the individual differences in captive ground hornbills, which are important when considering iv how individuals are managed and respond to interactions with conspecifics in captivity and for the inclusion in future release programmes. KEYWORDS: Activity patterns; Animal behaviour; Behavioural syndrome; Risk-taking behaviour; Space use; Southern Ground Hornbill; Transactional behavioural interaction.