The Great Lakes are under threat from an Asian carp invasion that could wipe out fishing stocks, and with it, the lakes’ billion dollar fishery. On Friday, officials from the Army Corps of Engineers reported that genetic material from the carp had been found for the first time in a nearby river beyond an elaborate barrier system, which has cost millions of dollars and was meant to block their passage [The New York Times]. There is concern that if carp make it into Lake Michigan, they will gobble up the plankton that native fish feed on.
Officials also say that recreational boating may be affected–the carp can grow up to 4 feet long and weigh up to 100 pounds, and the massive fish will occasionally leap up and strike boaters. Since they were found to be moving up the Mississippi River in 2002, agencies have been trying everything they can think of to slow them down, including erecting the expensive electric barriers that cost around $9 million. The barriers work by sending low-voltage electric current through steel cables that are strung across the canal; this creates an electric field that’s uncomfortable for the fish and that’s supposed to prevent them from swimming across it.
In an ironic twist, the weaponry of the fire ants that have invaded the American South is also their potential downfall. Entomologists have found that the fire ants’ venom contains chemical compounds that attract their natural foes, the parasitic phorid flies that turn ants into zombies before decapitating them.
The invasive red fire ants first came from South America by boat, and from their original disembarkation point in Mobile, Alabama, they have spread across the South, from Texas to Maryland. Their painful stings and their habit of shorting out electrical equipment make them a serious pest to humans, and biologists have been attempting to control their numbers by importing and distributing the parasitic phorid flies. But until now, researchers didn’t know how the flies homed in on the ants. So researcher Henry Fadamiro hooked electrodes up to the antennae of flies to investigate which of several stimuli prompted nerves to fire. By exposing the antennae to extracts from different ant glands and body parts, the researchers determined that juice from the venom glands got antennae buzzing [Science News].
What’s worse than having one gigantic-but-relatively-docile python species invading Florida? Finding out that an extremely aggressive python species is moving in as well, and learning that the two species could theoretically interbreed to create a hybrid monster.
Florida wildlife officials have been concerned for some time about the 20-foot-long Burmese pythons that are thought to have been released by irresponsible pet owners and have established a thriving colony in Everglades National Park. But over the past year, four African rock pythons have also been sighted or captured in Miami-Dade county, giving biologists new cause for concern. Says herpetologist Kenneth Krysko: “They are just mean, vicious snakes…. You couldn’t get a worse python to become established. A Burmese python is just a docile snake. These things will lunge at you” [Miami Herald].
At some point in the first half of the 20th century, a couple of ants hitched a ride on a boat and ended up on Christmas Island, an Australian territory in the Indian Ocean. And so began the rampage of the “yellow crazy ants,” creatures that have been named one of the top 100 most invasive species in the world. On Christmas Island, scientists have now declared an “invasional meltdown” of the original ecosystem [Science News].
The latest evidence: The ants are so plentiful and bothersome that they’re preventing birds from feeding on berries, and the birds are therefore failing to disperse seeds around the island.
Researcher Dennis O’Dowd explains that the long-legged yellowish ants earned the named “crazy” because when they are disturbed they run around frenetically. O’Dowd says crazy ants form large super-colonies and cover ground and vegetation in densities of around 1000 ants per square metre. “These ants are three-dimensional foragers,” he says [ABC Science]. The ants can thickly cover the forest floor and swarm up vines and plants.
The burgeoning 150,000-snake python population in Florida’s Everglades National Park threatens crops, livestock, and native animals. And, as the July 1 story of the toddler killed by a pet python demonstrates, the snakes can also threaten human lives. The snake overpopulation began when python owners discarded their unwanted pets in the wild; now, lawmakers are pushing for legislation to combat this invasive species. Not surprisingly, there is disagreement over the best way to do it.
Florida Senator Bill Nelson, who filed a bill in February to ban the importation of Burmese pythons, told a Senate panel on Wednesday that the snakes are slithering their way into a wider geographical area. Then he explained in graphic detail how a pet python… strangled a toddler in her crib last week in a town northwest of Orlando. ”It’s just a matter of time before one of these snakes gets to a visitor in the Florida Everglades,” Nelson said [Miami Herald]. Nelson said he’s been pestering the U.S. Fish and Wildlife Service for three years to halt the growth of the snake population, but the agency has not yet taken action. In addition, an environmental scientist at the panel emphasized the need to majorly restructure the policies that regulate and control import of exotic species like the python.
The union between the native California tiger salamander and the non-native barred tiger salamander, which was brought in huge numbers from Texas beginning 60 years ago by California bait dealers [The New York Times], has produced an alarming hybrid offspring. A new study of the hybrid’s behavior in artificial ponds serves as a reminder that invasive species can alter ecosystems in unexpected ways: in this case, by getting too cozy with the natives of central California.
The new hybrid “superpredator” grows larger than either of its parent species, and its bigger mouth enables it to suck up a wide variety of amphibian prey, said lead study author Maureen Ryan…. Mostly on the menu are smaller pond species, such as the Pacific chorus frog and the California newt—both of which were “dramatically reduced” in population by the hybrid in the experiments [National Geographic News].
More than 220 years since a ship wrecked on the rocks surrounding a remote Aleutian island, biologists believe they may have finally cleaned up the resulting mess. Rats have ruled the island since 1780, when they jumped off a sinking Japanese ship and terrorized all but the largest birds on the island [Reuters]. The voracious rodents feed on bird eggs and even chicks and small adult birds, and they so dominated the tiny island that it was given the name Rat Island. Biologists embarked on an ambitious effort to wipe out the rats last year, and now say they may have accomplished their task–but the campaign may have resulted in some avian casualties.
Nine months after scattering poisoned pellets across the island, biologists say they haven’t spotted any remaining rats, but they have found the carcasses of 186 glaucous-winged gulls and 41 bald eagles. U.S. Fish and Wildlife spokesman Bruce Woods said it’s unlikely carnivorous eagles ate the Rodenticide grain pellets, but they may have devoured some dead rats that had consumed them. “Eagles are scavengers of opportunity,” he said. “Rats don’t make up a big part of their diet naturally, but if meat is available, they’re going to take it” [Anchorage Daily News].
Scientists may finally be on their way to controlling the pesky fire ants that have invaded the American South: They’re releasing swarms of parasitic flies that first turn the ants into zombies and then decapitate them. The non-native ants are at the top of scientists’ hit lists because they cause an estimated $1 billion in damage in Texas each year. The insects swarm on circuit breakers and other electrical equipment, damaging them severely. Swarms of the stinging insects can also severely injure humans and can kill smaller animals, such as calves and pets, that stumble across nests [Los Angeles Times].
Over the past ten years, Texas agricultural researchers have begun releasing several species of phorid flies, imported for this task from the South America. The flies “dive-bomb” the fire ants and lay eggs. The maggot that hatches inside the ant eats away at the brain, and the ant starts exhibiting what some might say is zombie-like behavior…. “There is no brain left in the ant, and the ant just starts wandering aimlessly. This wandering stage goes on for about two weeks” [Fort Worth Star-Telegram], says researcher Rob Plowes. Eventually the ant’s head falls off and the mature fly emerges, ready to lay its own eggs in a new round of ants.
Researchers in Australia think they have found a solution to the country’s toxic cane toad problem: make Australian meat ants eat them. Cane toads—which can grow up to 8 inches (20 centimeters) in length—were imported from South America to Queensland [in northeast Australia] in 1935 in a failed attempt to control beetles on sugarcane plantations. Trouble was, the toads couldn’t jump high enough to eat the beetles, which live on top of cane stalks [AP]. Since their introduction… cane toads have spread through most of tropical Australia, eating and poisoning native animals [New Scientist]. No one has been able to get their population growth under control, and past suggestions to do so by introducing exotic diseases have only raised concerns about causing as much harm as the toads have themselves.
But a research team led by ecologist Rick Shine found that cane toads are more vulnerable to being eaten by Australia’s predatory meat ants than are native frogs, which may allow the ants to be used as a “safe” biocontrol agent that would not interfere with native frog species. Shine said the team plans to try ways of encouraging meat ants to build colonies near toad breeding ponds. One way would be to plant trees the ants favour [The Australian]. He is hopeful the strategy will work because unlike native frogs, cane toads are active during the day, when meat ants roam about scavenging for food. Toads also tend to breed in ponds that are out in the open sun, which results in their young emerging onto bare, baked mud areas, a habitat where meat ants like to forage [Sydney Morning Herald]. The toad is also more vulnerable because it lays its eggs in the dry season when water is low and there’s little protective vegetation at the pond’s edge [The Australian].
The cats ate the birds until the humans killed the cats, but now the rabbits are out of control.
That’s the sad state of affairs on Macquarie Island, an island near Antarctica that was declared a world heritage site in 1997 due to its status as the sole breeding ground for the royal penguin. For decades researchers have attempted to get rid of the invasive species that have altered the island’s ecological balance, but a new study notes that the latest effort, an all-out push to eradicate feral cats, has had the unintended consequence of allowing a boom in the rabbit population. Those rabbits have quickly denuded the landscape of its vegetation, researchers say.
Things began to go wrong on Macquarie Island … soon after it was discovered in 1810. The island’s fur seals, elephant seals and penguins were killed for fur and blubber, but it was the rats and mice that jumped from the sealing ships that started the problem. Cats were quickly introduced to keep the rodents from precious food stores. Rabbits followed some 60 years later, as part of a tradition to leave the animals on islands to give shipwrecked sailors something to eat [The Guardian]. The invasive species all thrived to the detriment of local species, and by the 1970s biologists were concerned enough to introduce a rabbit-killing disease called myxomatosis, which thinned the rabbit herds considerably. However, that left the cats with less available prey and caused them to begin hunting the island’s native burrowing birds.