50.0 MB (5.0 MB compressed)
7480 x 2336 pixels
63.2 x 19.8 cm ⏐ 24.9 x 7.8 in (300dpi)
MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Hippopotamus (Hippopotamus amphibius), on River Mara. A herd of hippo wallow in the shallows and sunbathe on the bank at the end of the dry season - early March. The hippo regulates its temperature by thermoregulation. Its thin epidermis has no sweat glands but can lose water at a higher rate than other mammals which can lead to dehydration and overheating. To avoid this they usually remain in or near water during the day, moving in and out to maintain a balanced temperature and have ticks removed by the oxpecker birds. Mud is a secondary means of cooling in hot dry weather. Two unstable acidic compounds, red, hipposudoric acid, and orange, norhipposudoric acid, are secreted and combine with mucus to form an effective sunscreen that sometimes colours the entire body. They rarely eat aquatic plants but graze on grasses and other plants at night to avoid overheating.
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