Hippos spend most of their days in or near the water in groups called pods. In the evenings, pods break up and the hippos leave the water, either singly or as females with their calves. They wander as much as three miles from the water in search of food. Hippos spend most of the night eating grass.
They use their wide mouth like a lawnmower, grazing the grass down to a few inches from the ground over a large area. A hippo can eat up to 90 pounds of grass in one night! Hippos are so aquatic that females even give birth in the water!
The babies, weighing 50 to pounds, surface right after birth to take their first breath. For the first year of their life, the youngsters nurse -- either under water or on land, depending on where mom is when they get hungry. After they're weaned, calves remain with their mothers until fully grown, at about eight years of age. Female hippos and their calves gather into groups during the day.
But when they leave the water at night, groups breaks apart and each female goes off with her own calves to graze. Most males hang out in bachelor groups. Each territorial bull defends his own stretch of land along the water's edge. Along with the real estate come exclusive mating rights to all females who live in his domain. The territorial male will allow bachelor males to wander into his territory, providing they know who's boss and behave submissively.
If a bachelor male challenges the territory holder, a bloody battle can break out. Dagger-sharp canines, up to 20 inches long, can seriously injure -- or even kill -- an opponent.
Hippos may not know it, but they help other animals that live in their habitat. As they walk from the water to their grazing grounds, hippos create well-worn paths. Other animals use these paths, too. And when hippos "mow" grass, they create hippo lawns. Other animals, like gazelles, benefit from the new green shoots that grow there. When hippos return to the river, they help the fish who swim there.
Why process and store oolichan grease? Because not only was it available — it was unique! Unlike the oil from seal, whale, and salmon, oolichan fat is very low in polyunsaturates both omega-3 and omega-6 [12]. Its primary fatty acids are mono-unsaturated, much like olive oil. So why might this be? Why wait around for a school of little fish when harpooning a single whale or a few sea lions gives you the same amount of fat?
The answer is found in lipid chemistry — the more double bonds you have in a given amount of fat, the sooner it goes rancid. Rancidity occurs when oxygen molecules are added to the fat, changing the taste and destroying its nutritional value. The human nose identifies rancid fat as offensive. And seal, whale, and most fish oils go rancid within a few weeks unless refrigerated or stored in airtight containers, whereas oolichan grease like olive oil can be stored for a year or more without going rancid.
Again, this can be explained in part by simple chemistry. The human body stores fat for reserve energy to sustain itself if there is nothing else to eat, and our bodies seem to favor the storage of monounsaturates over other classes of fatty acids. Monounsaturates, along with saturates, appear to be what our cells want to burn when they are adapted to burning mostly fat.
Oolichan grease is rich in monounsaturates, and thus is more like human fat than anything else in the region. Thus oolichan grease appears to have an ideal fat composition for humans who consume a diet appropriately rich in fat. Somehow, without the benefit of modern chemistry or nutritionists to tell them what to do, a diverse collection of people's inhabiting miles of the Pacific coastline of North America discovered this, and built their cultures and a regional trade economy around this one source of fat.
Schweinfurth I then became curious about the composition of hippopotamus fat. Stephen Phinney and Dr. A hippo can open its mouth to almost degree without tearing any muscles apart.
When you see a hippo opening wide its mouth like it is "yawning", it's not a sign of fatigue, but a threat showing that it's angry and ready to attack. Contrary to many people's impression, the semi-aquatic animal does not excel at swimming. If you have seen a hippo in water, it "walks" than "swims. They have to come up to the surface for air every few minutes.
A hippo sleeping underwater can rise and breathe without waking up. There are only two species of hippos: The common hippo and the pigmy hippo, both endemic to Africa. The common hippo is the third largest land mammal, coming after the elephant and the white rhino. Despite their bulky and heavy appearance, hippos' subcutaneous fat layers are quite thin. The 2,kilogram giant is mostly made up of muscles, and 6-centimeter thick skin.
The hippo's skin can secrete an oily red substance that is neither blood nor sweat, but a natural sunscreen which also inhibits the growth of disease-causing bacteria. However, this natural sunscreen cannot prevent the animal's skin from cracking if it stays out of water for too long. Everybody knows what a hippo looks like. This gives us the illusion that the animal is very common.
0コメント