What Is Megafauna?
The megafauna comprises the large or giant animals of an area, habitat, or geological period in terrestrial zoology. Megafauna simply means big animals. As are giraffes, whales, cows, deer, tigers, and even humans, the elephants are megafauna.
These are found in all the terrestrial regions of the world. The average weighting threshold for megafauna is over 40 kgs or over a tonne. However, in practice, land animals larger than a human and are not domesticated constitutes megafauna. It is used for the largest extant and extinct terrestrial wild animals. For eg., Giraffes, elephants, rhinoceros, hippopotamus, etc. In academic and popular writing, the most common usage encountered describes land mammals roughly larger than a human that are not (solely) domesticated.
Charismatic Megafauna
With the widespread popular appeal due to their attractive appearance the huge plant and animal species are known as charismatic megafauna. They can be identified easily. The giant panda, lion, humpback whale, grey wolf, bald eagle, etc. some of the charismatic megafauna in the world.
These animals are generally used by environmental activists in conservation campaigns because they can attract the public. Most of the organizations use these animals as their logos. For example the World Wildlife Fund uses Panda in their logo.
Extinct Megafauna
There are a large number of extinct megafauna. When there were no human settlements in an era the animals freely evolved. The extinction of the megafauna is being led to human interference. Early humans would have hunted these large animals to feed their families which led to the reduction in their number. Also, the large predators would have been killed to protect themselves from attack. The changing climate and atmosphere was another reason which led to their extinction over the years. There were sharks 50 feet long, wild otters as huge as wolves, and many more.
Following are the examples of some prominent megafauna that existed millions of years ago:
1. Glyptodon: These mammals became extinct 10,000 years ago. The glyptodons were the size of a VW beetle and were a well-armoured body with sharp spikes to protect themselves from predators. But they could not pull their head inside the hard turtle-like shell and depended upon their armoured body for defence.
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2. Argentavis: These were known to be the largest flying birds. It could grow to 24 feet which is twice the size of the largest bird, Andean condor, today. Their heavy body would have made it difficult to take off while flying, and so they are believed to have built their homes in the mountains. The bird was a scavenger and fed on the dead and decaying matter.
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3. Paraceratherium: It is one of the largest known mammals that have lived on the earth to date. It existed 25 million years ago and is believed to be 20 feet tall. They are believed to have fed on grass. Because of fewer fossil records available to the archaeological department, its appearance is not clear.
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4. Megalania: These were 23 feet long and weighed 4000 pounds. In Southern Australia it has lived during the Pleistocene era and is believed to be the largest venomous creature at that time. They fed on other large animals.
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Pleistocene Megafauna
These megafaunas appeared during the Pleistocene epoch. The giant birds, mammals, and reptiles in the late Pleistocene age got extinct in the Quaternary Extinction Event. Various factors such as altered habitat condition, climate change, disease, and the breakdown of food webs are considered responsible for the extinction of megafauna in this era.
The recent researches have come up with the overkill hypothesis responsible for the extinction. According to this hypothesis, human colonization was the main reason for the extinction of these animals in the Pleistocene age. Humans started hunting animals for food and to protect themselves from any harm. Slowly the animals became extinct.
Fun Facts
1. The term is most used for the Pleistocene megafauna – the large land animals of the last ice age, such as mammoths. For the largest living wild land animals, especially elephants, giraffes, hippopotamus, rhinoceros, elk, condors, etc, it's also being used.
2. Most of the large land animals which were alive 12,000 years ago are now extinct, and there is much discussion as to what has caused this. The two main theories are hunting by humans, and climate change. These reasons together are enough to explain why these previously successful animals are now extinct.
3. Elephant birds on Madagascar were certainly hunted to extinction, as were the Moas in New Zealand. Archaeological sites With evidence of moa hunting there are archaeological sites in all over New Zealand. About five hundred years ago the moas became extinct. The moas had survived being hunted by Haast's Eagle, but they did not survive being hunted for food by the Maoris.
FAQs on Megafauna
1. What exactly defines an animal as ‘megafauna’?
An animal is generally classified as megafauna if it is large, typically with a body mass over 45 kilograms (100 pounds). The term isn't a strict taxonomic classification but rather a way to group large animals. This includes a wide range of species, from modern-day elephants and whales to extinct creatures like the woolly mammoth and the sabre-toothed cat. It encompasses mammals, birds, reptiles, and fish that meet the size criteria.
2. What are some key examples of living and extinct megafauna?
Megafauna can be found in both present-day ecosystems and the fossil record. Here are some prominent examples:
- Living Megafauna: African Elephant, Blue Whale, Giraffe, White Rhinoceros, Tiger, and Polar Bear.
- Extinct Megafauna: Woolly Mammoth, Sabre-toothed Cat (Smilodon), Giant Ground Sloth (Megatherium), the Irish Elk, and the giant Australian marsupial Diprotodon.
3. Why did most of the world's giant prehistoric megafauna go extinct?
The widespread extinction of megafauna during the late Pleistocene, known as the Quaternary extinction event, is believed to be caused by a combination of two major factors. First, significant climate change at the end of the last Ice Age altered habitats faster than these large, slow-breeding animals could adapt. Second, the increasing sophistication and expansion of early human populations led to hunting pressure, often called the 'overkill hypothesis'. Most scientists agree that both of these pressures working together were responsible for their decline.
4. Are humans considered megafauna, and what is our ecological role?
Yes, by the standard weight definition, humans (Homo sapiens) are considered megafauna. However, our ecological role is unique. While other megafauna often act as keystone species or ecosystem engineers through grazing or predation, humans have become a global force of environmental change. Our activities, from agriculture to industrialisation, fundamentally alter landscapes, ecosystems, and even the climate, making our impact far greater than that of any other megafaunal species in Earth's history.
5. How did the disappearance of megafauna impact global ecosystems?
The extinction of megafauna had significant cascading effects on ecosystems. The loss of giant herbivores, like mammoths, led to major changes in vegetation; for example, vast grasslands (often called 'mammoth steppes') transitioned into scrubland and forests. This also impacted nutrient cycling, as these large animals were crucial for transporting minerals across landscapes. Furthermore, many plant species that co-evolved with megafauna for seed dispersal faced challenges in propagation after their animal partners disappeared.
6. What was the main difference between the megafauna of Australia and North America?
The primary difference was in their evolutionary lineage, showcasing the concept of adaptive radiation on separate continents. North American megafauna were dominated by placental mammals, such as mammoths, mastodons, giant beavers, and sabre-toothed cats. In contrast, Australian megafauna consisted mainly of giant marsupials and reptiles. Examples include Diprotodon (a wombat-like creature the size of a rhino), Procoptodon (a giant short-faced kangaroo), and Megalania (a giant goanna lizard).
