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Written by | Shen Mengxi
Over the years, we have seen or heard about the ecological disasters caused by more and more invasive species, which, due to their rapid growth rate, strong reproductive capacity and wide adaptability, will spread rapidly when they are intentionally or unintentionally introduced by humans, squeezing the living space of indigenous species and even leading to mass extinction of indigenous species.
And this phenomenon of species invasion does not only occur in one place, but almost all over the world. Taking China as an example, a simple combing of our tables can see many far-reaching invasive species: African snails, bullfrogs, proto-shrimp, tilapia and so on.
Figure/flicker
Photo/pixabay
From top to bottom, they are bullfrogs, crayfish (original shrimp of Kleurizi), tilapia, although they are now regular customers at our table, and they are very tasty regular customers, but due to poor management of aquaculture, they have escaped to the wild environment across the country, causing a devastating blow to the local original ecosystem.
Compared with China, Australia is a country where invasive species have begun to roll in. Because Australia itself is surrounded by oceans and has been isolated for millions of years, the evolutionary pressure on organisms is relatively small; moreover, because of Australia's own drought and natural conditions of poor soil, which have led to monotonous and fragile ecosystems, it has little ability to fight back from the invasion of foreign species.
Australia is separated by the sea, for a long time was an isolated and isolated continent, relatively speaking, Eurasia is a vast area, and there are passages with other continents, and there are human habitations, so it is more "rolled" than the flora and fauna of Australia Figure/pixabay
Since the first arrival of exiles from England in 1788, the area has faced serious ecological disasters. First of course, cattle and sheep, then a variety of vegetation carefully planted to breed cattle and sheep, followed by the famous rabbit, which is said to have been introduced only for hunting, but because of Australia's unique environment, it quickly multiplied to 10 billion; and then there is the popular cat owner, which has multiplied to 6 million in Australia, killing 800 million native animals every year, and scientists believe that cats have made Australia 74 mammals, 40 species of birds, 21 species of reptiles and 4 species of amphibians are in a state of extinction.
In order to control the rabbit population, Australians use various methods such as fire, flooding, power grids, chemical weapons, biological weapons, etc., but the effect is still limited. In terms of the definition of invasive species, in fact, all species in Australia's current economic pillar - pastoralism are deeply harmful invasive species Figure/flicker
Everyone's beloved cat owner is also a powerful invasive species in Australia Photo/pxfuel
These are just some of Australia's most famous invasive species, and there are many more less prominent creatures under the prestige of these invasive species, but also caused great ecological trauma, one of which has even evolved a serious cannibalism tendency because of the too roll, which is the sugar cane toad.
Sugar cane toad, considering the level of acceptance, I have tried to find a good picture /wikipedia
In 1935, Australian farmers suffering from sugarcane beetles introduced 100 sugarcane toads (also known as sea toads, scientific name: Bufo marinus) to their sugar cane plantations in Australia. This large toad, native to South America, is very foodous, and in South America it can eat small rodents, reptiles, other amphibians, birds, plants, dog food and even garbage in South America. Preyed upon by a variety of predators in South America and competing with organisms of the same ecological niche, they did a good job of suppressing sugarcane beetles.
The large sugar cane fields in Queensland, Australia, to put it mildly, are also considered invasive species in Australia./wikipedia
When the sugarcane toad arrived in Australia, due to their own huge size (adult average body length of 10-15 cm, the largest body size up to 2.65 kg, 38 cm), and the extracorporeal poisonous glands for other animals, resulting in them having no natural enemies in Australia, and there is no other competitive kind, so they quickly became a new powerful invasive species in Australia in addition to curbing the sugarcane beetle disaster to some extent.
In 2007, a website reported on a giant sea toad found in Australia photo/news.mongabay.com
It is estimated that in the 86 years since their introduction, their numbers have quickly increased to 200 million in exponential form, and their population density in a suitable coastal environment may exceed 1000 per 100 m, which is about 50-100 times that of their South American origin. It is precisely because of this huge population density that they may have quickly fallen into the point of no rolling – their juvenile manifestation already has the behavior of cannibalism.
Scientists have found that sugarcane toads can lay 8,000-25,000 eggs each time, the length of the egg band can reach 20 meters, and once some of these eggs hatch tadpoles, these tadpoles will quickly begin to swim to their siblings who have not yet hatched, and as long as a small group of tadpoles hatch, they can eat 99% of the eggs. During the subsequent wandering of these tadpoles, once they again feel that there are other sugarcane toad eggs around them, they will also flock to them and eat them up – not only that, but the large tadpoles will also have a high probability of eating the small tadpoles when they see them.
The eggs of the sugarcane toad, each sugarcane toad lays thousands of eggs each time Figure/wikipedia
In order to verify whether this behavior is a common habit of sugarcane toads or a habit peculiar to Australian sugarcane toads, scientists have conducted a series of experiments. The first was the collection of sugar cane toads from Australia and South America, and the reproduction, breeding the newly hatched small tadpoles and the more mature large tadpoles, and then placing the large tadpoles with the small tadpoles, it turned out that the Australian sugarcane toad tadpoles were 2.6 times more likely to eat the small tadpoles than their South American relatives. In further experiments, the scientists used two identical containers, one containing eggs and the other empty. Australian tadpoles are 30 times more likely to actively swim to eggs than they are to swim to empty containers; the Probability of South American SugarCane Toad Tadpoles swimming to both is equal. The final study found that the eggs of the Australian sugarcane toad developed much shorter than those of their South American relatives — hatching early to become hunters rather than prey.
These findings suggest that the Tadpoles of the Australian Sugarcane Toad have evolved a distinct cannibalism habit. This unusual habit has appeared in 86 years, and this rate of evolution of sugarcane toads has been very fast throughout the evolution of organisms, and perhaps we can see fierce fighting between adults in these toads in the near future.
Don't be schadenfreude, and don't be indifferent to yourself, because they are already close to us. This invasive toad has been found in our province of Taiwan.
The distribution of sugarcane toads, red is the invaded area figure/wikipedia
Without human help, they would never be able to cross the ocean, so from this point of view, the biggest and most dangerous invasive species should be us humans, right?
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Cover source: pixabay
Reference: https://docs.qq.com/doc/DQlRFR0d0dUVlbkVk
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