Common hippopotamus are known to live in herds of up to forty animals, and an adult hippo can weigh as much as 3600 kg (7936 lbs). Hippos can be found in the lakes, rivers and streams of central and sub-Saharan Africa. Hippos are amphibious and are excellent swimmers. In fact, calves are born in the water and must immediately go to the surface to breathe, and they even nurse underwater. 
Physical Characteristics: Common Hippos have a head and body length of 10.8-11.3 feet (3.3–-3.45 m). Males are normally larger and weigh more than females. 
Life Span: Common Hippos can live up to 45 years in the wild, up to 49 years in captivity. 
Common Hippopotamus Nutrition Guide
Diet in the Wild 
Hippopotamuses are herbivorous foregut fermenters, with the vast majority of the food eaten being grass, although some broad leaved plants are bound to be ingested incidentally as well (Eltringham, 1999). They have been termed ‘pseudo-ruminants’ because, despite having a four chambered stomach, they do not ruminate. There is no caecum. Hippopotamuses crop grass entirely by the use of their wide, strong lips, not with the front teeth, which play no part in feeding. They walk slowly, swinging their head in a regular pattern from side to side with the muzzle close to the ground. As the muzzle swings close to the ground, the lips close over a mouthful of grass and it is wrenched away (Kingdon, 1979). The grass is then passed to the back of the mouth by the tongue and chewed by the back teeth. Coarse, tussock forming grasses are not suitable as they slip through the lips and so creeping species are preferred (Eltringham, 1999). This grazing habit results in very short grass areas called “hippo lawns” which are then interspersed with areas of long grass. When Hippo density rises above a certain level, the longer grasses are exploited too and this can eventually lead to soil erosion (Eltringham, 1999).
Hippopotamuses will also sometimes eat aquatic plants, with observations being made of them nibbling on floating plants as well as various types of reeds (Eltringham, 1999) (Pers. obs, 2007). They will also occasionally eat the leaves, bark or fallen fruit of trees (Kingdon, 1979).
There have been many occurrences of Hippos being observed eating meat and even participating in cannibalism. Observations of scavenging are most common, with them often being seen consuming the meat of other animals that have been killed, particularly by crocodiles. The killing of other animals has often been witnessed and is not surprising considering the highly aggressive nature of Hippos (Eltringham, 1999). Hippos that have been injured during fights are especially likely to vent their aggression on another species. Reports of predation have been commonly made, however it is assumed that it is more likely a case of aggression, as predation implies killing an animal with the intention of eating it (Eltringham, 1999). Meat eating in Hippos should be regarded as either abnormal behaviour or more likely as a reaction to nutritional stress and the need to replace something missing from their natural diet (Eltringham, 1999).
Hippos are a nocturnal species and move out of the water during the night to feed. They can move anywhere between 5-10km away from water and spend up to 5 hours grazing during the night (Kingdon, 1979).
Captive Diet 
As a non-selective grazing species, captive Hippos are commonly fed a high fibre ration based on grass hays. They typically consume approximately 1.5% of their body weight daily (dry matter basis). Hippo diets should contain approximately 12-15 % protein and 38-44% neutral detergent fiber (the most common measure of fiber used for animal feed analysis). In captivity, due to their largely sedentary lifestyle and restricted movements where they would naturally walk anywhere up to 10km in a night to graze, care needs to be taken to avoid animals becoming overweight. Hippos can sometimes tend towards obesity, which can lead to problems with breeding and cause arthritis in later life. For this reason, care should be taken to avoid Lucerne hay. The Hippos at Taronga Western Plains Zoo are fed on meadow hay only.
It is important to know the weight of a Hippopotamus so as to determine the amount of hay to be fed out. The following is an example of a Hippo feed chart, taken from Taronga Western Plains Zoo.
Below is a Feeding chart for the Hippopotamus from Taronga Western Plains Zoo 
Hippo: “HAPPY” Offer 16 kg meadow hay (and 1 kg meadow hay left on the boat (at beach) for Zoofari at night). Does not have access to grass for grazing. Happy should be fed in the box daily. Some of his food can be fed out on the beach side of AFX11 as he can take too long in the box. He should be fed in the box first, before feeding on the exhibit. Happy MUST NOT have access to the raceway overnight.
Hippo: “MANA” Offer 17 kg meadow hay. Feed Mana only in the box from AFN66. Mana can be fed once during the day and again at 4pm when the girls come in.
Hippo: “RUMBIN” Offer 6.5 kg meadow hay. She has access to grass for grazing. Still requires more weight loss. Rumbin can be fed in the cement holding yard AFN 59. Don’t let her out until Mafuta has finished her ration.
Hippo: “MAFUTA” Offer 8 kg meadow hay. She has access to grass for grazing. Still require more weight loss. Mafuta can be fed in the cement holding yard AFN 60. Don’t feed her out on exhibit as she becomes reluctant to come into the holding yards. If Mafuta doesn’t come in, hold her food back and offer her 12 kg meadow hay the next day. Record on report if she doesn’t come in, and extra food given.
Hippo: “SUZIE” Offer 8 kg meadow hay each in PM. Does not have access to grass for grazing. Still require more weight loss. PM – Suzie being locked into AFN 64 or AFN65. Rotate between the two.
Hippo: “NILE” Offer 13 kg meadow hay in PM. Does not have access to grass for grazing. PM – Nile being locked into AFN 64 or AFN 65. Rotate between the two.
Hippo Beach AM – Offer 2kg meadow hay each, placed in two (2) separate piles for public feed. This feed is added to be a part of their total daily ration.
Ideally, a large grassy area should be provided for Hippopotamuses to graze on, which provides food, exhibits natural behaviours and provides exercise.
Hippos generally do not require any dietary supplements. However, if there are any cracks or problems with their nails and feet, veterinary assistance can be sought to prescribe a Biotin supplement such as Hoof Food which can be given to encourage healthy nail growth. These supplements can be purchased from most equine product suppliers.
Presentation of Food 
As Hippopotamuses generally spend a lot of time in the water, feeding is a great way to get them out of the water and in front of the public. Keeper talks are best given during a scheduled feed so the animals are clearly visible. Hay should be placed in an area where Hippos can easily eat and preferably can be cleaned easily, such as a concrete surface. If there is more than one individual at the feed, hay should be spread into several piles to avoid dominant animals consuming more.
As each animal is fed according to weight, it is ideal to separate Hippopotamuses for feeding, usually at night, which is when they would naturally be feeding.
Enrichment can be given in the form of fruit or vegetables such as apples, lettuce or pumpkin. A whole pumpkin is particularly good as it floats and so the hippos will swim around chasing them and then bite them open and have to find all the pieces. Pumpkin seems to be particularly appealing to them with regard to taste as well. These foods can also be used for training purposes; however, they will easily be conditioned with hay as well.
Hippopotamus Fascinating Facts 
- Hippos excrete a red liquid from their pores, which protects their skin from sun and infection!
- Hippos can open their mouths up to 150 degrees wide! Adult hippos have only two enemies in the world: other hippos and humans!