Sunday, October 9, 2011

Elephant Bird (Aepyornis)

 
 
 
 

Elephant birds were among the heaviest birds that have ever existed. Following the extinction of the last dinosaurs 65 million years ago, the mighty reptiles that had dominated the earth for more than 160 million years, the long overshadowed birds and mammals evolved into a great variety of new species, some of which gave rise to giants like the elephant bird.

In their general appearance, elephant birds were similar to the fiightless birds called “ratites” with which we are familiar today, such as the emu ( Dromaius novaehollandiae ), ostrich ( Struthio camelus ), rhea ( Rhea  sp.), cassowary ( Casuarius  sp.), and kiwi ( Apteryx  sp.); however, the biggest elephant bird,  Aepyornis maxiumus,  was enormous. It was about 3 m tall and probably weighed about 450 kg (the giant moa of New Zealand was actually taller but was way behind the elephant bird in terms of bulkmoa are discussed later in this chapter). On the island of Madagascar, there were few large predators, and the ancestors of the elephant birds had no need to fiy; therefore this ability was gradually lost. Grounded, these birds went on to become animals that were bound to the land. Their skeletons show that they had very powerful legs and that they plodded around Madagascar on their big feet. The wings were reduced to tiny structures and were probably not visible beneath the bird’s plumage. These birds had become so well adapted to a life without fiight that the large and specially modified chest bone (keellike sternum) found in most birds, which serves as an attachment for the wing muscles, had all but disappeared.

We don’t know exactly what the elephant birds ate, but we can assume from the shape of their bill that they were not carnivorous. Some people have suggested that certain Madagascan plants that are very rare today depended on the elephant birds for the dispersal of their seeds. The digestive system of these large birds was ideally suited to breaking down the tough outer skins of these seeds. Some were digested, but others passed through the bird intact and in a state of readiness for germination.

The remains of the elephant bird that have been found to date allow us to build up a picture of how this extinct animal lived. The most intriguing remains are the bird’s eggs. Some have been found intact, and they are gigantic—the largest single cells that have ever existed. They are about three times bigger than the largest dinosaur eggs, with a circumference of about 1 m and a length of more than 30 cm. One of these eggs contained about the same amount of yolk and white as 200 chicken’s eggs. These huge shelled reminders of the elephant bird are occasionally unearthed in the fields of Madagascan farmers, and one is even known to contain a fossilized embryo.

The number of elephant bird species that once inhabited Madagascar is a bone of contention among experts, but it is possible that Madagascar supported several species of these large birds. On their island, surrounded by abundant food and few animals to fear, especially when fully grown, the elephant birds were a successful group of animals. Then, around 2000 years ago, their easy existence was overturned as humans from Africa, Indonesia, and the islands around Australia reached this isolated land of unique natural treasures. Humans by themselves are one thing, but thousands of years ago, humans did not travel alone—they took their domestic animals with them. The elephant birds, in their 60 million years of evolution, never saw a human, and they wouldn’t have recognized them as dangerous. The humans, on the other hand, saw the elephant birds as a bounteous supply of food. Hunting had a disastrous eff  ect on the populations of these giant birds. They had evolved in the absence of predation and, as a result, probably reproduced very slowly. To add insult to injury, the animals the humans brought with them—pigs, dogs, rats, and so on—made short work of the elephant bird’s eggs. Other introduced animals, such as chickens, may have harbored diseases to which these giant birds had never been exposed. With no natural immunity to these pathogens, epidemics may have ravaged the populations of elephant birds, which were already under pressure from hunting and egg predation. Changes in climate may have led to the drying out of Madagascar, and this, too, could have aff  ected the populations of these impressive birds. The actual extinction timeline for the elephant birds is sketchy, but many experts suppose that the last of these great birds died out before 1600. The means at our disposal for the aging of ancient material are constantly improving, and some recent estimates move the disappearance of these birds into the nineteenth century. It is possible that some stragglers managed to survive until recent times, but we can be certain that no elephant birds survive today. 

Source: Wikipedia

1 comments:

i want to discover true colours of Extinct Animals of the Past for that i am researching on it. This article helped me a lot

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