About the "little incident" of bringing a herd of rabbits to Australia in 1859

Produced by: Science Popularization China

Author: Su Chengyu

Producer: China Science Expo

It all started 160 years ago, in 1859.

In 1859, a wealthy man named Thomas Austin moved to Australia from England. He was remembered by history not for his academic achievements, but for bringing a group of cute little animals with him.

Thomas Austin

(Image source: Wikipedia)

As a member of the Victorian Acclimation Society, Thomas Austin brought many species from England, such as thrushes, partridges and blackbirds, and of course our protagonist, the burrowing rabbit (Oryctolagus cuniculus).

Rabbit

(Image source: Wikipedia)

There were 24 wild rabbits in total, which were breeding rabbits raised on his own farm. The reason why he brought the rabbits was simple: he wanted to hunt rabbits for fun.

Although there were only 24 rabbits, due to their strong reproductive and adaptability, as well as the lack of natural enemies, these invasive European rabbits took only about 50 years to spread across the entire Australian continent.

Rabbits all over the plains

(Image source: Wikipedia)

Because the living conditions required by the rabbit are very simple, as long as there is soil suitable for digging holes and enough short grass for food. These conditions are almost readily available in Australia, as Australia is almost all wide plains.

In addition, rabbits are famous for their strong reproductive capacity. They can start breeding at a very young age and can mate all year round without any time limit. Each year, these rabbits can produce more than four litters of pups, with an average of two to five pups per litter.

Australian rabbit

(Image source: CSIRO)

The rampant rabbits have had a devastating impact on Australia's ecosystem. They consume a large amount of local pasture, shrubs and trees. In many places, not a single blade of grass is left. The shrubs have become bare branches and the bark of the trees has been gnawed away. One of the consequences is that the original ecosystem has been completely disrupted, and many native species have disappeared. The second consequence is that the rampant rabbits have fed more foxes and cats and other predatory invasive species. These creatures will prey on native species while killing rabbits, causing the extinction of a large number of native species. The third consequence is that the land without vegetation coverage faces serious erosion problems, and these lands may not recover for hundreds of years. At present, these rampant rabbits still pose a serious threat to Australia's ecology.

Rabbit infestation causes severe erosion in a South Australian ditch

(Image source: Wikipedia)

You may ask, why do we slander Austin? Is there any evidence that the rabbits that are now rampant are the descendants of the rabbits he brought?

There is evidence. In 2022, a study published in the Proceedings of the National Academy of Sciences (PNAS) confirmed that Australia's wild rabbit population is entirely descended from the 24 rabbits introduced by Austin, combining genomic and historical data.

Australian rabbits have a lot of similarities to British rabbits, and have little to do with French rabbits.

(Image source: Document 1)

In order to deal with these rabbits, the Australian government tried every possible way. The first method was to build fences. In order to prevent rabbits from spreading to areas where there were no rabbits, people built rabbit-proof fences across Australia. The effect of this fence was not very good. Many times, people found that there were already rabbits living on both sides of the fence while building the fence. Other methods include destroying rabbit holes, placing poison, hunting rabbits, etc., but because rabbits reproduce too quickly, the final effect of these methods is very limited.

Rabbits hunted in Australia in the early 20th century

(Photo credit: PAUL C. NOMCHONG/NATIONAL MUSEUM OF AUSTRALIA)

Because all these methods did not produce good results, scientists proposed the idea of ​​biological control. In 1950, a virus called myxoma virus (MYXV) was released in Australia.

Electron micrograph of myxoma virus

(Image source: Wikipedia)

Myxoma virus is a poxvirus that was first discovered in South America. Its natural host is rabbits in South and Central America, such as the American cottontail rabbit (Sylvilagus spp.). Myxoma virus only causes mild diseases in them, such as benign skin tumors. But when Europeans brought the virus to Europe, the virus quickly led to a large number of deaths in rabbits. These infected rabbits will have tumor-like swellings under the skin, eyelids, genitals, etc., and most rabbits will die within 5 to 12 days.

Rabbits infected with myxoma virus in the UK

(Image source: Wikipedia)

The virus spread rapidly in Europe, causing the number of wild rabbits to drop by 99% in the UK, 90-95% in France, and 95% in Spain. The decline of wild rabbits in these places has led to the extinction of Iberian lynx and Spanish eagles that feed on them, and has also had a major impact on the domestic rabbit farming industry in these places. However, in Australia, rabbits have no natural enemies and are also invaders of the local ecosystem, so people directly introduced the virus in the hope of eliminating rabbits in Australia.

When the virus was first released, it quickly spread across Australia, and scientists estimated that the mortality rate of rabbits infected with the virus was close to 99.8%. It was once an effective means. However, soon, on the one hand, the virus was replaced by a less toxic strain, and on the other hand, the rabbits also developed resistance to it. It took less than ten years for the number of rabbits to return to the level before the virus was released, and they continued to flood.

To understand how rabbits overcome myxoma virus, scientists studied rabbit specimens collected in museums in the UK, France and Australia before the virus spread.

Scientists sampled rabbits at different locations

(Image source: Document 1)

The scientists then sequenced all the genes that could affect immune defense and compared them with the genomes of rabbits from the same locations today.

This rabbit specimen was sampled by Darwin

(Photo credit: THE NATURAL HISTORY MUSEUM)

It turned out that a change in one of the alleles affected the rabbits' production of interferon, a specialized protein released by immune cells that sounds the alarm when a virus attacks and helps trigger an immune response.

Scientists have found that compared to rabbits before infection, the interferon produced by rabbits now responds better to controlling the virus. Of course, in the past 70 years, it is not only rabbits that are evolving herd immunity, but the myxoma virus is also constantly mutating. According to scientists' research, in the 1970s, the virus developed a stronger ability to suppress the rabbit's immune response. The mutation of the virus has caused the number of rabbits in Australia to decline again.

This evolutionary arms race between viruses and rabbits continues, and although myxoma virus is still highly prevalent in Australia, it is clear that rabbits are superior - of course, what is more obvious is that we humans have once again lost the "war" with rabbits.

In fact, it's not just rabbits, people in Australia are also fighting other invasive species. As an isolated island, Australia has been invaded by hundreds of other creatures since humans settled there, including mammals, arthropods, freshwater fish, birds, plants, mollusks, fungi, etc.

Some of these species were introduced accidentally, while others were introduced intentionally. Some of them were originally introduced to control other invasive species, such as the cane toad, which was originally introduced to Australia as a natural enemy of the gray-backed beetle (which can cause great harm to sugarcane). However, after arriving in Australia, it no longer eats gray-backed beetles, but instead feeds on some local creatures. The cane toad is highly toxic, which has led to the death of a large number of local creatures due to predation on the cane toad.

Cane Toad

(Image source: Wikipedia)

We humans have adopted various methods such as poisoning, trapping, hunting, and biological control to deal with these creatures, but the results are not very good. Many seemingly cute "alien species" can easily change into a different appearance when they invade a new environment, causing fatal damage to the local ecology and other species.

When facing invasive species, "prevention" is better than "cure". Compared with racking one's brains and spending a lot of money to deal with species that have already invaded, preventing the invasion of alien species is obviously a better option.

Today, we must learn from history and avoid doing things like "taking a group of rabbits to Australia" when traveling abroad or shopping overseas. We should not release creatures that do not belong to the local ecology at will and destroy the local ecological balance.

References:

[1]https://www.science.org/doi/10.1126/science.aau7285

[2]https://en.wikipedia.org/wiki/Thomas_Austin_(pastoralist)

[3]https://en.wikipedia.org/wiki/Rabbit_hemorrhagic_disease

[4]https://education.nationalgeographic.org/resource/how-european-rabbits-took-over-australia

Editor: Guo Yaxin

(Note: Latin text should be italicized.)