Pilot Investigation of Socio-Spatial Relationships in an Ex Situ White Rhino (Ceratotherium simum simum) Bachelor Group

Nonbreeding white rhino bulls are traditionally housed individually in zoos, but space limitations require the exploration of alternative techniques. There are no studies of group-housed bulls, and the feasibility of managing a bachelor group is unknown. Six bulls (two bulls each of 3-, 5-, and 8-yr-olds) in a 3.1 ha enclosure were observed for 30 min each 2×/wk for 20–31 wks. The 3-yr-olds were relocated after the first 20 weeks. Rhino location, nearest neighbor, aggressive behaviors, and dominance interactions were recorded. There was no evidence of habitat spatial segregation. The 3- and 5-yr-olds grouped together by age; 8-yr-olds did not associate as much as younger rhinos. Aggressive vocalizations and physical aggression were infrequent (range 0–1.5/h/bull and 0–1/h/bull, respectively). Eight-year-olds displayed and received aggressive vocalizations the most; three-year-olds displayed and received physical aggression the most. After the 3-yr-olds were removed, the habitat usage and social proximity of the remaining bulls did not change. Aggressive behaviors increased, but vocalizations (range 0.18–3.1/h/bull) remained more frequent than physical aggression (range 0.18–0.73/h/bull). The highest-ranking 8-yr-old engaged in physical altercations the least. The bulls shared space, and the use of vocalizations more than physical aggression deterred injury. These findings indicate that bachelor group management is feasible in a large enclosure with young bulls.