The “island effect” is a term that basically describes the evolution of animals that live on islands. Mammals, birds, reptiles and some amphibians that live there have been shown to develop in completely different ways than their species. Land or continent.
New research published in Journal of Science (Science) On March 9, a study conducted on 1,500 species of animals that lived for more than 23 million years examined why animals living on islands develop differently from those living on the mainland, a phenomenon known as the “island effect.” island effect).
And the “island effect,” according to the new study, is a law that basically describes how animals living on islands change.
This includes the tendency for large-bodied species to shrink in size due to food restrictions on islands, while smaller-bodied species swell due to the absence of predators there. Some animals are becoming extinct due to overfishing and habitat destruction.
What happens on the islands?
In the new study, researchers focused on island-dwelling mammals, examining 1,231 pre-existing species, in addition to 350 species that became extinct in the past 23 million years.
They found that island mammal species are either larger or smaller than their continental counterparts at risk of extinction or are already extinct.
Another study published in Journal of Natural Sciences, conducted in 2021, the extent of zoonotic dwarfism or giantism depends on the size of the island and its isolation. Smaller, more remote islands led to more pronounced changes in species sizes.
The study also found that factors such as limited resources and space are a major reason for the decline of animals adapting to smaller habitats. On the other hand, lack of competition and lack of predators frees small-sized species from constraints, making them larger than normal.
Examples of “island effect” animals
mentioned Science Journal website (Science Daily), rodents can grow up to 100 times their terrestrial mass, whereas the “extinct” mammoth’s weight shrank from 9072 kilograms to 907 kilograms.
According to Euronews website (EuroNews) About 10,000 years ago, islands in the Mediterranean Sea were covered with pygmy hippos and elephants. Large mammals face certain constraints, such as having fewer areas to forage for plants or less prey, which limits their growth and ultimate size.
The Philippine island of Mindoro also has a small buffalo that is 21% the size of its closest species elsewhere. Some islands have spotted deer, which make up 26% of the deer population on the mainland.
In contrast, the dodo, the giant flightless pigeon of Mauritius, the huge and endangered Komodo dragon, and the giant rat are twice the size of small mammals.
They face fewer predators overall and don’t have as many reasons to hide or flee, resulting in gigantic versions compared to terrestrial species.
Risk of human predation
The study also found that the influx of people to the islands increased extinction rates more than 10-fold. Humans have played a major role by hunting, destroying habitats and introducing diseases and invasive predators, disrupting pristine island ecosystems.
“We see all kinds of exotic species on the islands that you can’t find on the mainland,” said Kate Lyons, a paleontologist at the University of Nebraska and co-author of the study.
He said these animals are naive to dealing with new predators and humans coming to the islands because they are easy to hunt and kill, and because the islands are isolated, these animals can change easily. perished.
From what we know from recorded history, he says, when sailors visited many islands, they hunted and ate animals easily and without problems.
Why are animals becoming extinct on islands?
Specifies the siteABC News(ABC News), islands are hotspots of biodiversity, and although they make up less than 7% of the land area, they contain up to 20% of terrestrial species.
“Because of the island effect, all kinds of weird and wonderful animals can be found on islands, many of which are already extinct,” says Lyons. “These islands are home to a large percentage of the planet’s diverse species, but around 50% of them are at risk of extinction, which is very disappointing.” “.
The islands’ fauna includes species such as hippos, buffaloes and wolves, and they face the threat of extinction, making them some of the most unique species on Earth.
According toScience Journal website (Science Daily), island animals face the most existential risk of extinction. About 75% of the documented extinctions in the last 500 years occurred on land areas covered by water. Half of the animal species now listed as endangered by the International Union for Conservation of Nature live on islands.
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