Characterizing sleep behavior of the wild black rhinoceros (Diceros bicornis bicornis)

Abstract

Study Objectives: The objectives of this study were to characterize sleep patterns and determine factors, including sex, age, season, and environmental pressures, that influence sleep in the endangered black rhinoceros (rhino; Diceros bicornis bicornis). Design: To noninvasively observe sleep behavior of wild rhinos, digital infrared cameras were erected on poles at two bedding sites from September 2009 to March 2010. Setting: The study site was located in South Africa's Addo Elephant National Park (AENP) in the Main Camp (Addo) and Nyathi sections. Participants: A total of 2,417 photos captured rhino sleep behavior on eight individual rhinos during 40 separate sleeping bouts (Addo, n = 15; Nyathi, n = 25). Inventions: N/A. Results: Results demonstrated that age and season did not affect rhino sleep behavior (P > 0.05); however, sex did influence the length of sleep bouts with males (n = 27; mean, 105.6 ± 11.3 min; range, 14.0-202.0 min) sleeping longer (F1,48 = 6.93, P = 0.01) than females (n = 13; mean, 58.6 ± 10.4 min; range, 11.0-132.0 min). Park section did not influence the length of sleep episodes, but did affect (rw40 = 0.88; P < 0.025) the time at which rhinos slept (Addo, 20:00-24:00; Nyathi, 20:00-04:00). Conclusions: This is the first study to characterize sleep behavior in wild black rhinos. This study resulted in a greater understanding of the biologic factors that affect sleep in wild rhinos and can provide information to assist their management and conservation.