Sunlight-

Hippos are endothermic, but since most hippos mainly live in Africa, they need to be submerged in water for most of the day because their skin is vulnerable to overheating and dehydration.  They have adapted to this by spending most of the day with their body underwater and only part of their head and nostrils above water in order to breathe.  

Hippos don’t have sweat or sebaceous glands but they do produce a liquid that turns red a few minutes after being in the sun. This protects the hippopotamus’ skin from sunlight.

Anatomical Positioning-

Their eyes, ears, and nostrils are positioned on their top of their head so they can be submerged as much as possible and still be able to hear above water noises, and breathe.

 

Disease-

Most of the rivers that hippos live in are murky and filled with bacteria and microbes.  To protect themselves from disease and infections, they same liquid their skin produces for sunlight protection is used. The fluid becomes brown and works as an antiseptic.  This antiseptic is extremely acidic and is “hundreds of times more powerful than vinegar” (Hippo Sweat par. 4) 

Hearing and Communication-

Hippos can produce and hear sounds above water and below water. They also have adapted to be able to hear and produce both above water and below water sounds at the same time, called simultaneous amphibious sounds or SASs.  These noises are made at the amphibious position, with ears, eyes and nostrils above water, but the mouth and throat positioned below the surface.  Their exceedingly large lower jaw is especially adapted to make these calls and conduct sound waves. The calls are made in times of danger and a hippo on the surface will make an SAS sound, which causes hippos underwater to surface (Barklow 1128).  To warn other hippos of upcoming danger, these calls can be passed up and down rivers to different herds.