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Behavior and Ethology | Biology


Kristina Timmerman


Hippopotamuses (Hippopotamus amphibius) are known to forage on land during the night and spend the daytime in shallow pools to thermoregulate and to protect their skin from UV radiation. Daily use of pools may lead to competition for space and facilitate aggressive interactions between hippopotamuses. In this study, we looked at the difference in occurrence of aggressive behavior in the morning and evening hours between hippopotamuses (hippos). Our hypothesis was that hippos will be more aggressive at different times of the day, and we predicted that the higher aggressive activity will be in the morning hours, as hippos our returning to the pool. Our data was collected at the Retima Hippo Pool, Orangi River, Serengeti National Park, Tanzania in May 2022. Aggressive behaviors were counted and recorded using transect methodology (six pairs of observers watched a transect across the pool and recorded at pre-set times). We defined aggressive behavior based on previous publications. Results showed that hippos were more aggressive during evening hours as compared to the morning (96 and 54, respectively). Based on these results, our hypothesis was not supported. A potential explanatory factor might be that the annual spring rains did not occur in 2022, so the pool level was extremely low. This may increase concentration of both hippos and fecal matter, and this may have altered when and how often aggressive behavior occurred. If we repeated this observational experiment, we would extend the study period to include more than one season.