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Attack of the giant toads! Seven devastating invasive species


By Daniel Martins
Digital Reporter
@DFLCMartins
Sunday, September 8, 2013, 2:03 PM

Here at The Weather Network, our regular Endangered Species series showcases animals which are threatened, and what people are doing to keep them from extinction.

But unfortunately, there are some species which have thrived despite Man's best efforts - and which we really, really wish would just go way.

Here are seven of the most devastating invasive species.

The giant African land snail is eating everything

You wouldn’t think a slow-moving mollusk would be the cause of so much trouble, but achatina fulica, the giant African land snail, is such a pest that wildlife officials in the United States and other countries are prepared to fork out millions of dollars to eradicate the critters.

Image: Alexander R. Jenner, Wikimedia Commons

Image: Alexander R. Jenner, Wikimedia Commons

While there is a risk the snails can transmit a form of meningitis to humans, the real threat is the species’ razor-tongue, and bottomless appetite. On the menu: More than 500 different plant species, including important cash crops like beans, cabbage, cauliflower and pumpkins. 

They’ve even been known to take the occasional bite out of concrete or stucco, in search of the previous calcium they need to keep growing their shells.

In 1966, a Florida boy smuggled three of them into the country and his presumably grossed-out grandma tossed them into the garden. In seven years, there were 18,000 of them (they can lay up to 1,000 eggs a year), and eradication efforts cost more than $1 million at the time.

Had authorities done nothing, the mollusks might have eventually caused around $11 million in damages a year in 1969 dollars.

Another outbreak in Florida began in 2011. This time, the state has spent more than $6 million, and has turned up almost 130,000 of the creatures. 

Luckily, the snails’ enormous size – they can reach 20 cm in length – means they’re not hard to spot and report to authorities. Florida authorities have even trained dogs to sniff out the ones that get away, helping out around 50 officers whose one and only job is to track down the pests.

The Florida outbreak is actually considered more-or-less under control, but the giant African land snail remains on the list of animals prohibited from exotic pet stores in many countries.

Cane toads are a deadly meal for Australia’s predators

When researchers in 1935 introduced bufo marinus, the cane toad – originally native to south and central America – to Australia, we’re sure it must have seemed like a good idea at the time.

Image: Thomas Brown/Wikimedia Commons

Image: Thomas Brown/Wikimedia Commons

The toads had one job: Eliminate a species of beetle that was harming the country’s sugar cane production. Check out this short film about the beasties, produced in the 1980s:

Turns out their intended prey didn’t tickle their fancy, but the toads soon learned to thrive in their new home. They’re now found in a huge swath of the continent-nation, and can move up to 55 km every year, so their range is ever-expanding.

They can theoretically dine on basically any land animal smaller than itself (they’ve even been observed eating rats), but it’s their innate toxins that make them a real threat.

The toads are easy prey for all kinds of predators, like snakes and crocodiles, who just can’t handle the invaders’ natural poisons. Most of them die after making a meal out of the amphibians.

Image: Bill Waller/Wikimedia Commons

Image: Bill Waller/Wikimedia Commons

The Australian government hasn’t had much luck checking the toads’ advance, but there are regular public education campaigns to warn residents to alert the authorities in case they see a toad (check out this pamphlet on how to toad-proof your garden).

Every now and then, there’s good news in the fight. Some scientists suggest the way to defeat these awful creatures is with some of the other, even more awful creatures that, happily, are already native to Australia.

It turns out at least three species of poisonous spider prey on the toads without any ill effects (For the spiders, anyway), while some varieties of crow have learned how to avoid the spider’s poison glands when feasting.

New research suggests the toads’ own venom might be the key to finally eradicating them:

The Australians built a fence across the continent to keep the rabbits out

Australia tends to be VERY strict about importing non-native species, and with good reason.

One of the first invaders was the unassuming oryctolagus cuniculus, better known as the common rabbit – introduced by a Victorian gentleman in 1859 who wanted to keep up his rabbit-shooting hobby by having a couple dozen sent over from the U.K.

Image: National Archives of Australia/Wikimedia Commons

Image: National Archives of Australia/Wikimedia Commons

Almost a hundred years later, 600 million of the fertile critters had flooded the continent (Detail: Australia’s entire human population today is only around 22 million).

They are, of course, about as harmless as you’d expect rabbits to be, except they can bear dozens of young a year and the Australian ecosystem can’t handle large numbers of them.

The result: They devour grass and shrubs, robbing grazing livestock of food and causing widespread soil erosion.

Early Australians were desperate to rid themselves of the environmental catastrophe in the making, desperate enough to build an actual fence across the continent to keep them out of Western Australia.

Those of our readers who have ever had a warren in their backyard can guess how that turned out, and even satirists at the time thought the idea was foolish:

Image: Queensland Figaro and Punch/Wikimedia Commons

Image: Queensland Figaro and Punch/Wikimedia Commons

Still, it got built, and it’s mainly been successful at checking the spread of certain kinds of vegetation and livestock, so much so that you can see the effects from space:

Image: Reto Stöckl/NASA Goddard Space Flight Center

Image: Reto Stöckl/NASA Goddard Space Flight Center

As for the rabbits, authorities had to resort to biological warfare to check their numbers, releasing a virus that killed more than 99 per cent of them in the 1950s.

The survivors developed an immunity, and the population recovered, although not to the extent of the pre-plague infestation, and Australian scientists had to try again with a new disease in the mid 1990s. They’re still looking ahead to the next offensive, for when rabbit numbers start rising again.

Open season on Burmese Pythons

The Burmese Python, python bivittatus, is apparently perfectly adapted to life in the Florida Everglades. 

Image: Tim Vickers/Wikimedia Commons

Image: Tim Vickers/Wikimedia Commons

That’s a huge problem for the local wildlife, because it’s not supposed to be there, and once it reaches a certain size, it has no natural predators. A typical length is around 1.8 metres, but the largest can be more than five metres long.

They usually prefer to eat small mammals and birds, but they’ll take pretty much anything they can get their coils around, even the occasional (and, we presume, very surprised) alligator.

Image: Lori Oberhofer, National Park Service

Image: Lori Oberhofer, National Park Service

There’s been a breeding population of the snakes since possibly the 1980s, likely the result of owners releasing them into the wild (they are popular as exotic pets, although the United States banned the import and interstate transportation of Burmese pythons in 2012). 

This source suggests some may even be descended from escapees from a breeding facility destroyed during Hurricane Andrew.

Florida runs regular public awareness campaigns, and has specially trained specialists on hand to trap and remove any snakes reported to local hotlines.

The Floridian government actually declares open season on the snakes from time to time. The 2013 contest attracted more than 1,500 people from across the United States (including at least one participant from Canada).

They’re going to have the step it up a bit. That horde of hunters only bagged 68 pythons, barely making a dent in an estimated population that could be as high 150,000.

Africanized honey bees are cranky and will chase you for a mile

Like Australia’s cane toads, we can file the Africanized honey bee, apis mellifera scutellata, under “it seemed like a good idea at the time.”

Wikimedia Commons

Wikimedia Commons

When several African bees were imported to a research station in Brazil in 1957, they were supposed to be used in attempts to cross-breed a new kind of bee more suited to the climate than European honeybees – until several queens and workers were accidentally released into the wild.

The Africanized bees are HUGELY aggressive. They’ll swarm much easier than “regular bees,” chasing perceived intruders up to a mile (1.6 km) before letting them go.

Their stings are no more poisonous than regular bees' but their sheer aggression has earned them the reputation of being "killer bees" (this source says the interlopers kill two to three people per year in the U.S.), and they can be very dangerous to children, livestock, the elderly, and others who have trouble escaping their stings.

Which is why this pest control worker in Texas is VERY careful when he goes about his work:

The bees also breed more often, but they’re lousier at pollination, put less effort into storing honey, and abandon nests more frequently.

Local bees just can’t compete against their Africanized cousins. The aggressive newcomers have spread across south and central America, and are now expanding into the southern U.S. from Texas to California, as well as Florida.

Many researchers consider them a very real threat to the country’s $140 million honeybee industry and the less efficient pollination they bring could cause billions of dollars in indirect losses to regular farmers.

But some countries in Latin America have embraced the Africanized breed, either breeding out the aggressive trains or learning to manage the drastic behavioral differences, with some apparent success.

As well, this source claims U.S. farmers were prepared for the bees’ arrival, and have minimized their impact in Florida, where they make up around 70 per cent of wild colonies.

The Asian long-horned beetle snacks on whole forests

When this invasive little bug showed up in North America a couple of decades ago, wildlife officials knew what was at stake.

Kyle T. Ramirez/Wikimedia Commons

Kyle T. Ramirez/Wikimedia Commons

In China, where anopolphora glabripennis is actually in its home environment, some 40 per cent of the country’s poplar plantations have been damaged by the beetle’s larvae, amounting to 1.2 million hectares. 50 million trees had to be cut down in Ningxia province alone in an early 1990s effort to keep the insect at bay.

In North America, where the beetle probably arrived in wood packing material from the Far East, up to 35 per cent of urban trees in the eastern U.S. are at risk, a potential loss worth $670 million, not to mention the damage the beetle could wreak on lumber and maple syrup industries.

At least three U.S. states have quarantines in place, and most of the other 47 are at risk, with public awareness campaigns in full swing.

In Canada, border services have intercepted the beetle since around 1982, and in 2003, a major infestation was discovered in the cities of Vaughan and Toronto, Ontario.

Authorities ended up having to remove more than 30,000 trees that were either infested, or at risk of infestation, in a 150 square kilometer quarantine zone.

It seems to have worked. The last confirmed sighting was in 2007, and the beetle was listed as eradicated from Canada in 2013.

Authorities are still vigilant, but they’ve had less success with another unwanted insect invader: The emerald ash borer.

Image: Howard Russell/Michigan State University

Image: Howard Russell/Michigan State University

Since its detection in North America in 2002, the borer has killed tens of millions of trees and threatens billions more in the continental United States.

In Canada, Quarantine zones are widespread throughout Ontario and Quebec, but this government website still announces new detections every few months.

The enormous Nile Perch ate 200 species almost to extinction

We’d like you to take in this picture of a specimen of lates niloticus, the Nile perch:

Wikimedia Commons

Wikimedia Commons

This invasive species can grow up to 200 kg and two metres in length, and has been a complete disaster for more than 200 other fish species in Africa’s Lake Victoria since its introduction in 1954.

It’s a predatory species that, in Lake Victoria at least, is pretty much at the top of the food chain, so it either devoured many of the native species, or out-competed them for food.

The population has declined somewhat in recent years (presumably because there’s now a smaller prey ecosystem to sustain them, but the perch is now so dominant, the Invasive Species Specialist Group says it’s not actually possible to eradicate them.

In fact, it may not even be desirable. Fishermen around the lake have adapted to the invasion by harvesting the invaders … such that production and export values are three times what they were in the 1970s, after the perch population exploded.

In fact, the United Nations’ Food and Agriculture Organization recommended in the 1980s that the Nile perch be exploited “for the maximum economic benefit of the  lakeshore communities,” while at the same time noting the rapid expansion of the industry has led to deepened income and social inequalities.

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