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).
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.
The study site was located in South Africa's Addo Elephant National Park (AENP) in the Main Camp (Addo) and Nyathi sections.
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).
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).
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.
Santymire R; Meyer J; Freeman EW. Characterizing sleep behavior of the wild black rhinoceros (Diceros bicornis bicornis). SLEEP 2012;35(11):1569-1574.