Evolution: dwarf islands, giant islands

Giant growth in the middle of the ocean

However, a completely different phenomenon appeared on several islands. Here the newcomer does not shrink, but, on the contrary, grows to an unusual size. Most of the time, “giant islands” can be found on small islands that are inaccessible to land mammals. Hundreds or even thousands of kilometers from the next continent often overtake species that are very good at flying, swimming, or very hardy – for example, small animals that survive several weeks of accidental sea voyages on rafts.

If you land on the edge of a deserted island, you enter a world full of new possibilities. In the course of evolution, they have repeatedly occupied ecological niches that mammals often claim elsewhere. On Phillip Island in the South Pacific, for example, scientists recently discovered the centipedes occupying the top spot in the food chain. With their venom, the arthropods, some of which are more than 30 cm long, kill the chicks of domesticated birds.

But birds can also play the role of apex predators. With a wingspan of three meters, the giant Haastadler, for example, has no more natural enemies in its native New Zealand. There is also a shortage of ungulates for grazing in grasslands and savannas. “So birds like to adapt to these unused resources,” explains ecologist Manuel Steinbauer of the University of Bayreuth. And because there are no foxes, otters or other predators there, they can also live without flight, which is associated with high energy costs. Instead, evolution plays all the advantages of scale. Some species evolved into giants that could reach the leaves on the top floor of trees on foot or swallow fruit that didn’t fit the beak of a nipple or the world’s best-desired blackbird. “In the forests of New Zealand, the moa chickens with their necks stretched out like a giraffe on two legs up to 3.60 meters tall graze on the leaves of forest trees,” said paleontologist Paul Schofield of the Canterbury Museum in Christchurch, New Zealand. The three-meter-tall elephant bird in Madagascar and the similar large thunderbird in Australia, belonging to the geese, developed in a similar way.

NS sane people Monsters are fat prey

“After the first Maori ships landed in New Zealand about 800 years ago, the moa disappeared in less than 100 years,” explains Paul Schofield. After all, these giant birds weren’t adapted to intelligent theropods who could only cut the tendons in their legs and spoil the entire clan. “For the same reason, giant tortoises have always been at the mercy of humans,” said Uwe Fritz, reptile researcher from the Zoological Museum at the Senckenberg Natural History Collections in Dresden. For millions of years they have relied on their recipe for success: Hold your head and stay in the tank until the danger is over. Nothing prepared them against the sailors who had gathered them, and carried them on their backs, and in this predicament, from which they could not free themselves, they dragged them onto their ships as provisions for life.

Even if it seems to be found only on islands today, giant tortoises are not the case for giants on the island, as discoveries suggest that they have also been found on land. The animals were mostly large lawn mowers, like many ungulates, that graze on meadows, Fritz said. Even the most powerful predatory teeth are difficult to break the shell. “There were giant tortoises even in Central Europe, and they were found in southern Spain even two million years ago,” Fritz said.

So researchers at Senckenberg suspect that giant tortoises didn’t first evolve on the islands, but actually arrived as giants. This is also demonstrated by the giant shell turtle, which became extinct only in 1840 and once lived on the Mascarene Islands in Reunion, Mauritius and Rodrigues in the Indian Ocean. Since there were no dangerous predators with strong teeth, their thick armor became unnecessary and ended up being just thin. Because of their economy, giant tortoises have been able to survive long voyages to distant islands quite well, and can sometimes live without food for years. Obviously, a long time in salt water doesn’t bother them too much; This is evidenced by the giant tortoise Aldabra that stomped the beach on December 14, 2004 on the East African coast of Tanzania. Some of the barnacles had grown on their legs and shell, which must have settled there in the saltwater. Therefore, the animal must be immersed in salt water for several months. It is assumed that the giant tortoise of the Aldabra Atoll was swept by ocean currents at least 740 km without food and fresh water to the coast of Africa. Obviously, the reptiles survived this long journey quite well. “He was thin, but he looked healthy,” explains Uwe Fritz.

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