Evolution of grazers and browsers into the savannah

A HERD of zebra drinking water


LAST week we saw how antelopes such as topi and wildebeest are using different chemical to give names to their calves, we also saw that antelopes migrated from Europe to Asia and African savannah about three million years ago when the grassland was expanding due to weather changes in the world.

Some scientific researches indicate that antelopes evolved between 2,588,000 to 11,700 years ago while fossils records indicate that gazelles started to roam in Africa more than 2,588,000 years ago.

This was the time when finally the modern continents were essentially at their present positions, it was the time when weather on the Earth was characterized by continuation of El Nino with trade winds affecting big water bodies of the world such as Pacific ocean and Indian ocean which influenced types of weather in the prehistoric days of East Africa.

It is estimated that due to this and other factors 30 percent of the world was covered by heavy and wide blanket of ice, scientists say the current fast melting glaciers of Mount Kilimanjaro, Mount Kenya and the Ruwenzori Range in east and central Africa were between 1,500 to 3,000 meters larger.

Scientists say during that period the Earth passed through severe climatic changes which sent level of the ice sheet to fluctuate from time to time and affected life of different plants and animals which were present on the ancient world.

This caused a large part of the world to become totally depopulated because most of ancient plants and animals retreated southward in front of the advancing glacier as a result of tremendous stress.

Different researches indicate that mostly severe stress resulted from drastic climatic changes which reduced living space, and affected both hunting and grazing grounds for big mammals which dominated the world those days.

These changes affected the northern hemisphere very bad and sent a big number of species of plant and animals into extinction, to escape that most antelope decided to migrate southward to Asia and Africa where they dominate animal sanctuaries such as Ruaha, Serengeti, Katavi and others in Tanzania.

On the other hand scientists define antelopes as members of a number of even toed ungulate species indigenous to various regions in Africa within the family of bovines which dwell in savannah in groups called herd.

Antelopes are found in 91 species which are found in about 30 genera, they are described as members of bovine’s family which do not include sheep, cattle, or goats but it includes impala.

Historians say the ancestors of modern impala were smaller and evolved in Ethiopia between 5.333 million to 2.58 million years ago when the world continued to cool and caused the disappearance of forests and the spread of grasslands and Savannah’s.

These and other factors forced the impala to migrate into Kenya, Tanzania, Zimbabwe, South Africa, Botswana, Namibia and other countries which are located south of Sahara where national parks such as Ruaha, Serengeti, Mikumi, Mkomazi, Lake Manyara, Arusha and Tarangire are known for harboring a big population of these beautiful antelopes.

Different geological factors indicate for the past three million years ago at different time the savannah grassland of East Africa has contracted and expanded between two to three time and enabled Tanzania, Kenya, Uganda and Ethiopia to have one of the largest population antelopes in the world.

Scientists believe that during those days different pockets of animal’s sanctuaries were created and protected by natural forces through isolation which enabled antelopes to thrive in the greater Serengeti ecosystem which covers more than 30,000 square kilometers.

The greater Serengeti ecosystem is said to have one of the largest population of antelopes in world because between January and March everyday more than 40,000 calves are bony by wildebeests.

This is natural phenomenal which strengthen the great annual migration which involves 1.7 million wildebeest, 470,000 gazelles, 260,000 zebra and other antelopes such as topi from Serengeti national park.

This most popular park in East Africa covers 14,750 square kilometers and located in Mara and Simiyu regions of Tanzania is known for the biggest population of Thomson’s gazelle in the world.

Depending on the location where the annual migration rest, at a certain time of the year Serengeti national park may be a home of more than 550,000 individuals which are grazing along wildebeests and zebra.

The zebra is an African member of horse family which its ancestors evolved more than 54 million years, that was the time when the world was passed through a period called Eocene which was marked low amount of carbon in the atmosphere.

It is believed that this situation made the warm temperatures during the early Eocene to cause an increase of methane production into the atmosphere which would in turn warm the troposphere, cool the stratosphere, and produce water vapor and carbon dioxide through oxidation.

The breakdown of methane in an oxygen atmosphere produces carbon monoxide, water vapor and infrared radiation which affected the weather of the world during those days while affecting life of ancient creatures including ancestors of zebra.

Scientists say ancestors of modern zebra were fox sized animals with three toes on the hind feet, and four on the front feet, also they were herbivorous browsers on rela tively soft plants, and already adapted for running.

It is possible that at that time when the continent of Africa and Indian subcontinent were still connected the ancestors of zebra could run at top speed of 64 kilometers per hour from Serengeti to greet other horse family members in the savannah of the today’s Uttar Pradesh province of India.

Zebras are members of horse family which is made by more than seven different species including wild horse and the beautiful stripped mammal of the African savannah. Scientists believes that before coming to Africa, the horse family originated in America about 5.6 million years ago when zebra like mammal evolved with a donkey like head shape.

Major changes happened in the horse family four million years ago when zebras dropped out from the group and migrated to Africa where they stay until today. In Africa, zebras are divided into three main species which are grévy’s zebra, mountain zebra and plains zebra.

Unlike their relative of the horse family such as horse and the domesticated African donkey it’s the Zebra who are decorated with black and white stripes. Some earliest researches showed that because of a white underbelly, at the beginning of time zebras were white animals and black stripes came later as result of evolution processes.

Today scientists say that embryological evidence show that at the beginning zebras were black but due to a combination of evolutional factors white stripes were added later for different functions.

The stripes lay vertically on head, neck, forequarter and the main bodies of the animal while rear side, tail and on the legs the lines elegantly spin vertically. Scientists say the vertical stripping help the zebra to hide in the middle of savannah grassland, through a camouflaging style called disruptive coloration the stripes break up the outlines of the animal just like military uniforms in a battle grounds.

It is believed that when these animals stand or walking slowly together in a large group they create another camouflaging tactic called motion dazzle. This tactic enable zebras to disguise themselves with a very large body which confuse their enemies such lions with a conspicuous pattern, which makes the object visible but harder to locate.

This is an important strategy which helps the zebra to reduce or avoid attacks from big cats such as lions which are colour blind.

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