Australian scientists fight cane toad invasion with cat food and laced sausages

Scientists from the University of Sydney are getting creative with their efforts to combat destructive cane toad populations in Australia and to protect native species from the pests. Cane toads were introduced to Australia in 1935. Cane toads, which were introduced to Australia in 1935 from Hawaii in an attempt to eradicate cane beetles, have caused a decline in other native species populations, such as snakes, lizards and quolls. Scientists have been trying to control the spread of cane toads for years; recent experiments have shown progress. For example, Georgia Ward-Fear and colleagues used open cans of cat food to lure native meat ants to the shores of ponds inhabited by baby cane toads. Once there, the meat ants turned to the baby toads for a food source. Since the toads’ natural defense mechanism is to freeze and secrete a poison from glands in their backs, the effort is no match for the impervious meat ant. Rick Shine, who heads the lab where both studies were conducted, describes the interaction in a Reuters article: All we’re doing is encouraging the ants to flourish somewhere where they already flourish, letting them know there’s particularly good food around so we get more of them down there on a very short-term basis. Baby toads are incredibly stupid and their reaction to being attacked is to freeze. I think they’re trying to advertise the fact they’re poisonous and let the predator get a taste of that, but it doesn’t work for the ant because it isn’t affected. The results, published in February edition of the Journal of Applied Ecology, are impressive: the meat ants attacked 98% of the toads within the first few minutes. In addition, over 50% of the attacks were immediately fatal and 88% of escapee toads died within 24 hours. Native animals, like this Tiger quoll, are threatened by the rise in cane toad populations. In other research, Stephanie O’Donnell and colleagues are training quolls, one of the predators affected  by the toads, to avoid eating the poisonous amphibians. Quolls, most of which are listed as threatened, are carnivorous marsupials related to the Tasmanian devil. They rely mostly on insects, birds, rodents and amphibians as a food source. However, since the cane toad is non-native, quolls are not predisposed to avoid them. Shine explains in a press release: Quolls have largely disappeared from the areas where cane toads occur. We know from Stephanie’s work that if you don’t train quolls to leave toads alone they’re very likely to eat the first toad they encounter and die as a result. The researchers are attempting to train the quolls to associate the...

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EPA releases action plan to clean up the Great Lakes

In a follow-up to last year’s approval of $475 million for the cleanup of the Great Lakes ecosystem by the Obama Administration, the Environmental Protection Agency (EPA) has announced an action plan to do just that. Lake Michigan from Milwaukee, WI Yesterday EPA Administrator Lisa Jackson met with governors of Great Lakes states to discuss the goals for cleaning up Superior, Michigan, Huron, Erie and Ontario from 2010 through 2014.  The plan focuses on five specific efforts: pollution prevention and cleanup, prevention of invasive species invasions, reduction of urban, suburban and agricultural runoff into the watershed, habitat and wildlife protection and restoration, and education, public outreach and strategic partnerships. According to the plan, these efforts include “the first-ever comprehensive assessment of the entire 530,000 acres of Great Lakes coastal wetlands for the purpose of strategically targeting restoration and protection efforts in a science-based manner.” It also requires the collection or prevention of 45 million pounds of electronic waste, 45 million unwanted pills and 4.5 million pounds of household hazardous waste in the Great Lakes basin by 2014. In addition, it calls for the reduction of harmful algal blooms, which have polluted drinking water, and for the cleanup of 9.4 million cubic yards of toxic sediment. The plan also calls for a “zero tolerance” policy regarding invasive species and requires a 40% decline in such species by 2014. This is particularly targeted at Asian carp, a non-native species known for its voracious appetite. According to a Reuters article, around $60 million of the funds will go directly to combating Asian carp populations. An Asian carp was reportedly found in the ship canal connecting the Mississippi River to Lake Michigan late last year. As a result, several states asked the U.S. Supreme Court to force Chicago to shut down its shipping locks in an attempt to keep the Asian carp from infiltrating Lake Michigan. The Supreme Court sided with Illinois and declined to close the locks over concerns of endangering the $7-billion fishing industry. Last month, however, DNA evidence suggested the presence of Asian carp in Lake Michigan. The Associated Press reports that wildlife officials are currently searching for carp in the Chicago area and will continue to for the next two to three weeks. Read the full action plan at http://greatlakesrestoration.us. http://www.flickr.com/photos/indykethdy/ / CC BY-SA...

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Pet snakes could be next big eco-menace

Scientists at USGS released a 300-page report today detailing the vulnerability of U.S. lands to invasion by large snakes from other continents. The report finds that Burmese pythons, northern and southern African pythons, boa constrictors and yellow anacondas are a high-risk animal for invasion. The report echoes the unfortunate situation on the America territory of Guam, where introduced brown tree snakes have extirpated most forest vertebrates, including some birds endemic to the island. Released from natural predation pressure, these snakes altered the island’s natural ecology so much that it affected human habitats and business. The USGS report mentions that the five snake species that could pose a threat are common in the pet trade. These species have been spotted in the wild but have yet to establish detectable reproductive populations.  Which begs the question: Does the presence of one or two neglected pets in the wild thus necessitate the production of a 300 page report? Absolutely. The reason the brown tree snake story is such a sad one is simply lack of initiative before it became too late.  The report points to animals which, because of their habits, preferred habitats and likely predators and prey items, have the greatest potential to become invasive.  Now is the critical time to circulate this information, so that a hapless Burmese python owner thinks twice about letting his now-unwieldy pet loose in his backyard. Read the full report (and its abstract)...

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Invasive tree disease disrupts pine/bird mutualism

Many trees with large seeds rely on vertebrate seed predators to disperse their seeds. The whitebark pine, a key subalpine species, has coevolved with the Clark’s nutcracker into a tight mutualism.  In their paper in the April Ecological Applications, Shawn McKinney, a post-doc at the University of Montana, and his colleagues studied a natural disruption to this mutualism: an invasive tree fungus. Clark’s nutcrackers feed on whitebark seeds throughout the summer. Beginning in late summer, the nutcrackers extract ripe whitebark pine seeds from pinecones and bury them in the ground for use as food during the winter and spring. Although the nutcrackers harvest and cache seeds of other pines, whitebark pines depend nearly exclusively on nutcrackers for seed dispersal. White pine blister rust, a disease caused by a tree pathogen that kills cone-bearing branches, has been spreading through the subalpine forests and now occurs in almost all whitebark pine populations. According to the researchers, mortality from blister rust reaches 90 percent or higher in some populations in the northern Rocky Mountains. For the trees, this disease can spell disaster: When whitebark pine seeds are scarce, the nutcrackers often leave subalpine forests in search of food at lower altitudes. Decimated by disease and left without dispersers to spread what few seeds they produce, whietbark pines can dwindle rapidly. McKinney and his colleagues quantified forest conditions and ecological interactions between nutcrackers and whitebark pines in three Rocky Mountain ecosystems that differed in levels of rust infection and mortality. They estimated that within each hectare, a threshold level of 1000 pinecones, or more than a 5-meter square area of trees, is needed for a high likelihood of seed dispersal by nutcrackers. The researchers say that their estimates can be used by forest managers to assess when and where to plant new stands of whitebark pines to encourage nutcrackers to stick around. They say the estimates will be especially useful in Montana, where pinecone production and tree density fell below threshold levels. McKinney, S., Fiedler, C., & Tomback, D. (2009). Invasive pathogen threatens bird–pine mutualism: implications for sustaining a high-elevation ecosystem Ecological Applications, 19 (3), 597-607 DOI:...

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Asian oyster idea nixed for Chesapeake

The state governments of Maryland and Virginia, along with the Army Corps of Engineers, announced yesterday that Asian oysters will not be allowed in the Chesapeake bay. The decision capped a five-year study on the nonnative oyster to assess its potential to replace the rapidly diminishing native Eastern oyster, Crassostrea virginica. The decision ultimately came down to the Army Corps of engineers, since Virginia officials supported the introduction and Maryland officials opposed it. For now, at least, the states and federal government will put their money on resuscitating populations of native oysters, which have dwindled to as little as 1 percent of their peak populations because of disease and overfishing.  So far these attempts have had limited success, and future efforts could cost as much as $50 million per year, ten times more than was invested in years past. The presence of oysters in the bay has more far-reaching importance than just the fisheries industry: the bay needs a core filter-feeder to clean its increasingly polluted waters. The five-year study was inconclusive about whether the Asian oyster could invade and wreak havoc on the system — much like freshwater zebra mussels have in the Great Lakes  — instead of settling into the native oysters’ niche and providing the much-needed ecosystem service.  The decision, then, was not to risk it. ESA issued a press release and urged ecologists to speak up about this experiment last October. You can read more about the history of native oyster restoration at the NOAA Chesapeake Bay web...

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The ecology within

The concept of biological control is no new idea in ecology – people have been transporting living things to control other living things since the late 18th century. The most famous examples seem to be the big failures, where biocontrols become invasive themselves – such as mongooses introduced to Hawaii to control rats but that instead decimated populations of native birds. Geneticists at the University of Queensland have now successfully applied the biocontrol concept to the ecology of a disease – dengue fever, to be precise. The researchers have cultured a strain of the Wolbachia bacteria that cuts the lifespan of mosquitoes in half — enough time to prevent the dengue virus within them to mature. The result is that even when infected young mosquitoes bite onto human flesh, the human gets away dengue-free. The bacteria don’t prevent the mosquitoes from breeding, so introducing the Wolbachia into wild mosquito populations won’t wipe them out. Because only the longest-living insects harbor the mature, virulent dengue, the researchers also think that the bacteria is “safe”: the disease probably won’t be able to evolve a shorter life cycle itself. But, of course, this remains to be seen in the wild. Just goes to remind us that ecology is as important in the guts of some of the smallest animals on the planet as it is across continents. Read more about Scott O’Neill and his colleagues’ work in last week’s Science (full text by subscription only) and in this great article on...

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When scientific fiction replaces good science

Good science writers – as with all reporters – should verify the validity of their stories before publishing, making sure to cite the peer-reviewed research detailing a new discovery. But as in the case of the purported cane toad-eating frog, an exciting enough fact with weak empirical support can sometimes take off like….well, an invasive species. In 2005 and 2006, several media sources (including the Australian Broadcasting Corporation, the BBC, and ESA’s journal Frontiers in Ecology and the Environment) reported that the native Australian Dahl’s frog could survive after eating cane toad metamorphs, which are normally toxic to predators.  The report was exciting because the invasive cane toads have wreaked havoc on Australia’s ecosystems since their introduction in the 1930s, and this provided the first supposed evidence of a possible biocontrol to thwart the toads’ spread. The finding, however, was reported by a community watch organizer who had fed metamorphs to five Dahl’s frogs in a terrarium at his home. As Rick Shine and colleagues point out in a Dec. 10 e-view paper in Frontiers, titled “The myth of the toad-eating frog,” this finding was based on anecdotal evidence and lacked an appropriate sample size, control groups and replicated groups. The finding was not reviewed by scientists; indeed, even when reported in the media, no other scientists were contacted to comment on the story.  In a bizarre twist, Shine also reported in his paper that at least one prominent ecologist retold the story, believing it was supported by scientific evidence. When Shine and his colleagues tested the frog in a controlled setting with replication, randomization and appropriate sample sizes, they found that Dahl’s frog is just as susceptible to cane toad toxin as other native species. More than half of frogs that ate the toad metamorphs in captivity died. Further, the frogs that tried to eat cane toad tadpoles spit them out and learned to avoid them in subsequent trials. So, who’s responsible here? With today’s ease of self-publishing, the lines between expert and self-proclaimed pundit blur, making it ever more important for journalists to validate the reliability of their sources. But scientists are not guiltless – although this paper cries foul, it does so more than three years after the initial report.  If good ecological science is to inform public policy decisions, it’s up to scientists to ensure that the facts reported are...

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Invasive? Or just disturbed

Invasive species often succeed in new environments because they can outcompete native species within an area for some resource, such as food, mates or habitat. What’s less clear is exactly what gives them this edge over local species that should be experts at living in their home territory. A study by Joshua King and Walter Tschinkel published online in the Proceedings of the National Academy of Sciences investigates just what gives a common southern pest, the invasive fire ant, the ability to muscle out local ants seemingly everywhere there’s a human disturbance. Notorious for their huge nests (as many as 100,000 ants per colony on average), aggressive swarming behavior and painful stings, these red ants have become a major menace in the U.S., Australia, the Philippines, China and Taiwan. Because the ants are usually found in highly disturbed areas, such as roadsides, parking lots, strip malls and subdivisions, the authors wondered if the ants’ success depends on their environment.  The authors compared the success of native ant populations in areas that were recently disturbed by humans to natural areas where fire ants were introduced. Somewhat surprisingly, the fire ants by themselves had less of a negative effect on native ant populations than simple plowing.  The ecologists suggest that fire ants may not be so much an invasive species but a “disturbance specialist,” with the ability to capitalize on an open niche when they see one – a description that might fit other invasive species as...

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