Vetnews | September 2025 26 « BACK TO CONTENTS herds [32, 34, 51]. Solitary mature bachelor elephants often linger near herds, waiting for mating opportunities with herd cows [34]. These lone bachelors showed a noticeable preference for reservoirs at certain times of the year and day (Table 2), roughly coinciding with the times that herds visited reservoirs [32, 34]. Although reservoirs were visited mostly at night, test results indicated no preference for a particular waterhole type at night (Table 2). Concrete pans were preferred in the morning, while earth dams were favoured at midday and in the afternoon. The results of the generalised linear models (GLMs) to determine the effects of Season, Daily Period, Waterhole Size, Waterhole Type, and social Group Type visiting waterholes on frequency of elephant visits to the waterholes revealed significant effects for various of these factors (Table 5). The main waterhole types selected at the study site were reservoirs and concrete pans. Waterholes were used most during the wet season, with a preference for medium-sized waterholes. Breeding herds were the most frequently observed group visiting waterholes, favouring mediumsized reservoirs and their troughs (Table 1). Adult and sub-adult animals that could reach water in reservoirs used these, while juvenile animals used troughs. Bachelor groups were commonly observed at waterholes during morning and afternoon periods. Overall, waterholes were most visited during midday, with reservoirs and concrete pans being the most frequented. Medium-sized waterholes were preferred across all daily periods, with large waterholes being used during midday and afternoon. Breeding herds, consisting of females and their young, may prioritise safety and the availability of clean water sources, leading to a consistent preference for reservoirs. Bachelor groups, composed of young males, may select waterhole types based on factors such as opportunities for interaction with breeding herds or their own social dynamics. Black rhinos displayed different patterns in their waterhole visits compared to elephants. They visited waterholes across all daily periods, with specific peaks during the dry and wet seasons. Dry season peaks were between 02:00 and 03:00, at 06:00, between 13:00 and 15:00, and again at 21:00 (Fig 4B). Wet season peaks were at 10:00, 13:00, and again at 18:00 (Fig 4B). These results align with the findings of Du Toit [33], who found that black rhinos drink throughout the day and night depending on environmental conditions and water availability, though further research is needed to clarify potential seasonal variations in this behaviour. They also align with previous studies conducted in different arid and semi-arid areas [52, 53]. In arid areas, black rhinos drink when it is cooler, often in the evenings or during the day on overcast days [52, 53]. Kasiringua, Kopij, & Procheş [52] reported that for the arid Waterberg National Park in Namibia, black rhinos drink at night during the dry season, where these authors classified them as evening and night drinkers. Seidel et al. [53] found that for the semiarid Etosha National Park in Botswana, black rhinos visited waterholes after dusk and before dawn. OWNR is not classified as an arid environment with extreme daily temperatures, resulting in the black rhino on the reserve visiting waterholes throughout the day and night, but with peaks as listed above. Findings for this study indicate that black rhinos exhibited a preference for earth dams throughout the year (Fig 5B). Du Toit [33] reported a preference for artificial waterhole types, although the specific types were not detailed. Earth dams were favoured at night, midday, and in the afternoon, while concrete pans were preferred in the morning (Fig 6B and Table 3). Bachelor black rhinos showed a preference for earth dams in the dry season and no preference for any waterhole type in the wet season (Fig 5B). They preferred this waterhole type during the midday period, with no preference during other daily periods. Even though black rhino bachelor groups visited concrete pans in the wet season during the afternoon period, binomial test results (Table 3) did not indicate a preference for this waterhole type. There were no recorded visits to any of the waterhole types for the dry season, leading us to believe that bachelor groups visited alternative water sources that did not have camera traps monitoring them. Solitary black rhino cows preferred earth dams in the wet season and concrete pans in the dry season. There was a preference for earth dams during the midday period, and although they visited concrete pans in the morning and afternoon, binomial test results did not indicate a preference for this waterhole type (Table 3). Black rhino cow groups favoured earth dams in the wet season, with no visits recorded for the dry season. As for black rhino bachelor groups, we speculate that black rhino cow groups visited alternative water sources that did not have camera traps monitoring them. While there were visits to earth dams during the midday and afternoon periods, and results were significant, lower confidence intervals were below the 25% chance threshold. There were no recorded visits to waterholes by cow groups during the night and morning periods. The “unknown adult black rhino” category preferred earth dams across both the wet and dry seasons (Fig 5B). Earth dams were favoured at night, midday and in the afternoon, with concrete pans preferred in the morning (Fig 6B). Black rhino bull and cow groups preferred earth dams across both the wet and dry seasons and across all daily periods. We speculate that bachelor black rhino groups at the study site, often consisting of sub-adult bulls, used concrete pans to avoid confrontation with aggressive territorial bulls who were often with cows at earth dams. GLM results (Table 5) suggest that unknown black rhino adults preferred large (P = 0.04) earth dams (P < 0.00) in both the wet and dry seasons (P = 0.01) for three of the daily periods, midday, afternoon and night (P < 0.00). White rhinos displayed specific patterns in their waterhole visits, with peaks during certain daily periods and variations between the wet and dry seasons. White rhino visits during the dry season peaked at 08:00 and between 16:00 and 18:00 (Fig 4C). Sutherland, Ndlovu, & Pe´rez-Rodrguez [48] recorded peaks in the dry season from 00:00 to 01:00, from 11:00 to 12:00 and a spike in visits between 17:00 and 22:00. Wet season waterhole visits for our study peaked at 09:00, 18:00 and again at 21:00. Wet season visits for the Sutherland, Ndlovu, & Pe´rez-Rodrguez [48] study showed a peak at 17:00 and from 20:00 to 22:00. Du Toit [33] states that white rhinos visit waterholes in the morning, at midday and in the afternoon. Kasiringua, Kopij, & Procheş [52], for the arid Waterberg National Park in Namibia, classified white rhino as evening and night drinkers. In general, our study has similar results to that of Sutherland, Ndlovu, & Pe´rezRodrguez [49] for the wet season, in that there are three peaks (Fig 4C) and differs from Du Toit [33] in that we recorded night visits (Fig 6C). Our results also differ from those of Kasiringua, Kopij, & Procheş [52] in that we recorded morning visits (Fig 6C). The sample size for the white rhino in this study was restricted due to a lack of suitable habitat at the study site, compared to the elusive black rhino, which prefers dense thickets. Although white rhinos visited troughs during both the wet and the dry seasons (Fig 5C), binomial test results only indicate a preference for this waterhole type during the wet season (Table 4). Du Toit [33] found that white rhinos had no preference for a particular waterhole type, whereas we found a preference for troughs and earth dams. Earth dams were preferred during the afternoon, and even though troughs were frequented at night, in the morning and at midday, results did not indicate a preference for troughs during these periods (Table 4). Bachelor white rhinos preferred troughs across both the wet and dry seasons, and although troughs were visited across all daily periods, binomial test results did not indicate a preference for them, or any other waterhole type (Table 4). Bachelor white rhino groups visited earth dams and concrete pans during the dry season, with no visits recorded for the wet season. Test results showed no seasonal or daily period preferences for any waterhole types by bachelor groups (Table 4). Cows visited only the earth dams across the wet and dry seasons (Fig 5C). Earth dams were visited by cows during the night, morning and afternoon periods, with no recorded Research Article
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