Activity and Pool Use in Relation to Temperature and Water Changes in Zoo Hippopotamuses (Hippopotamus amphibious)

SIMPLE SUMMARY: The following study examined the behaviors and water vs. land use of an outdoor exhibit by three zoo hippos. Behavioral observations were correlated with water temperatures at the exhibit, and compared to the number of days (0, 1, or 2 days) since the water within the outdoor pool had been dumped and refilled. The water changing of the pools had little effect on either the behaviors or pool use itself by the hippos. Water temperatures affected both the behaviors and pool use by the hippos, with warmer water temperatures being directly correlated with greater activity and overall pool use. The results suggest that temperature, rather than water change, was the more important factor in increasing overall pool use and general activity for the exhibited hippos. ABSTRACT: In the wild, hippopotamuses spend much of their daily activity in the water. In zoos, it is less clear the extent to which hippos spend time in the water. We examined how much time Woodland Park Zoo’s three hippos spent in their outdoor pool, based on: (a) temperature of the pool water, and (b) when the pool water was changed (approximately three times a week). Several digital temperature data loggers collected water and air temperature readings once every hour for six months. We correlated the water temperature readings with several behaviors the hippos could engage in, where the hippos were on exhibit (pool vs. land), and how many days it had been since a dump (0, 1, or 2 days). The results indicated that water changes had little effect on pool usage, while increasing water temperatures resulted in both increased activity and pool use. The results are discussed in terms of how these findings relate to wild hippo activity, current knowledge of zoo-housed hippo welfare, and future directions for zoo-housed hippo welfare and research.