wes_von_papineäu
Our Roving Correspondent
NEW SCIENTIST (London, UK) 17 April 08 Roadkill is 93% amphibian (Michael Marshall)
Most people know that amphibians are in steep decline at the moment, thanks to a list of problems ranging from a deadly fungus to shrinking habitats. A new study suggests we should add another problem to the list: roadkill.
Three researchers from Purdue University, led by Andrew DeWoody, looked at the animals killed on four roads in Indiana over a 16-month period. They found that amphibians were by far the most common, making up 93% of the 10,515 total deaths. The most commonly-killed species were Bullfrogs, with 1,671 killed (the next highest figure was that for Virginia Opossums: just 79).
Most studies of roadkill have tended to look at large mammals like deer, so there's little information about its impact on other groups of animals, particularly small ones. This study tries to rectify that, but the researchers are at pains to point out that their figures are a huge underestimate. Due to "carcass degradation" (a technical term for "being flattened and going mouldy"), many of the animals were unidentifiable, while others had been eaten or otherwise removed.
I should point out that the high number of bullfrog deaths isn't itself a cause for concern. Bullfrogs are not endangered, and are actually a pest in many areas. It seems likely that so many were found because they are very common, and may indeed be out-competing the other frogs. The researchers say they "were the species we heard most often and observed near the survey routes. Bullfrogs are prolific breeders, often laying several thousand eggs per female."
Rather, the key point about the study is that it gives us an indication of how much roads can affect an amphibian population, if they're built in a key location. The roads surveyed were right next to a wetland: classic amphibian territory. As a result they cause sizeable losses, especially when the frogs make their yearly migration to their breeding grounds.
The researchers suggest a tentative figure, of "roughly 7.6 dead amphibians and reptiles per kilometre per day". In the case of a big population of rapid breeders like the bullfrogs, presumably that wouldn't matter. However, a population already weakened by fungus and habitat loss might not be able to cope. For such cases the researchers suggest various measures that could help, such as underpasses and barriers alongside roads.
The findings are published in Herpetological Conservation and Biology (vol 3, issue 1, p 77). (http://www.herpconbio.org/Volume_3/Issue_1/Glista_etal_2008.pdf).
http://www.newscientist.com/blog/en...P=ILC-hmts&nsref=specrt13_head_Frogs vs roads
LIVE SCIENCE (New York, New York) 17 April 08 Road Kill: Too Many Frogs Croak (Clara Moskowitz)
Ribbit, ribbit, ribbit, croak. Dozens of species of frogs and other amphibians end up as road kill all too frequently, a new study finds.
Many of these species are already endangered due to habitat loss, disease, climate change and other factors, and the added threat of whizzing cars on the highway may contribute to their decline, researchers speculate. About a third of worldwide amphibian species are threatened and hundreds have already gone extinct over the past two decades alone.
Over 17 months researchers drove along 11 miles of roads in Tippecanoe County, Ind. and documented the road kill they found. The scientists counted 10,500 dead animals, of which 95 percent were frogs and other amphibians.
"On hot summer nights when it rains, there are literally thousands of frogs out there," said Andrew DeWoody, a zoologist at Purdue University in Indiana who led the study.
Amphibians are often-slimy, four-legged creatures whose body-heat is regulated by their external environment (sometimes called cold-blooded). They play a vital role in many ecosystems, both as predators of insects and as food for larger animals.
The highway victims found by the researchers included 142 eastern tiger salamanders, a finding DeWoody said was troubling.
"The absolute number might not look that large, but most of these individuals were mature, up to 10 years old," DeWoody said. "Many of them were gravid, or females bearing eggs on an annual trip to breeding grounds where they often lay 500 to 1,000 eggs. This could make a potentially big difference for the population."
Along with the thousands of amphibians the highway-trolling researchers found, there were also 79 opossums, 43 raccoons, 36 chimney swifts, 35 garter snakes and 4 white-tailed deer.
DeWoody said his official tallies were probably underestimates, because many animals are scavenged, moved or degraded beyond recognition. He estimated about five times as many animals died on the roads than his team was able to count.
To help reduce the number of road kill victims, the researchers suggest building structures such as underpasses, viaducts and overpasses to allow wildlife safe passage, as well as special fences to keep animals off roads.
The study, funded by the Joint Transportation Research Program, a partnership of the Indiana Department of Transportation and Purdue, was published online in the latest issue of the journal Herpetological Conservation and Biology.
http://www.livescience.com/animals/080417-road-kill.html
Most people know that amphibians are in steep decline at the moment, thanks to a list of problems ranging from a deadly fungus to shrinking habitats. A new study suggests we should add another problem to the list: roadkill.
Three researchers from Purdue University, led by Andrew DeWoody, looked at the animals killed on four roads in Indiana over a 16-month period. They found that amphibians were by far the most common, making up 93% of the 10,515 total deaths. The most commonly-killed species were Bullfrogs, with 1,671 killed (the next highest figure was that for Virginia Opossums: just 79).
Most studies of roadkill have tended to look at large mammals like deer, so there's little information about its impact on other groups of animals, particularly small ones. This study tries to rectify that, but the researchers are at pains to point out that their figures are a huge underestimate. Due to "carcass degradation" (a technical term for "being flattened and going mouldy"), many of the animals were unidentifiable, while others had been eaten or otherwise removed.
I should point out that the high number of bullfrog deaths isn't itself a cause for concern. Bullfrogs are not endangered, and are actually a pest in many areas. It seems likely that so many were found because they are very common, and may indeed be out-competing the other frogs. The researchers say they "were the species we heard most often and observed near the survey routes. Bullfrogs are prolific breeders, often laying several thousand eggs per female."
Rather, the key point about the study is that it gives us an indication of how much roads can affect an amphibian population, if they're built in a key location. The roads surveyed were right next to a wetland: classic amphibian territory. As a result they cause sizeable losses, especially when the frogs make their yearly migration to their breeding grounds.
The researchers suggest a tentative figure, of "roughly 7.6 dead amphibians and reptiles per kilometre per day". In the case of a big population of rapid breeders like the bullfrogs, presumably that wouldn't matter. However, a population already weakened by fungus and habitat loss might not be able to cope. For such cases the researchers suggest various measures that could help, such as underpasses and barriers alongside roads.
The findings are published in Herpetological Conservation and Biology (vol 3, issue 1, p 77). (http://www.herpconbio.org/Volume_3/Issue_1/Glista_etal_2008.pdf).
http://www.newscientist.com/blog/en...P=ILC-hmts&nsref=specrt13_head_Frogs vs roads
LIVE SCIENCE (New York, New York) 17 April 08 Road Kill: Too Many Frogs Croak (Clara Moskowitz)
Ribbit, ribbit, ribbit, croak. Dozens of species of frogs and other amphibians end up as road kill all too frequently, a new study finds.
Many of these species are already endangered due to habitat loss, disease, climate change and other factors, and the added threat of whizzing cars on the highway may contribute to their decline, researchers speculate. About a third of worldwide amphibian species are threatened and hundreds have already gone extinct over the past two decades alone.
Over 17 months researchers drove along 11 miles of roads in Tippecanoe County, Ind. and documented the road kill they found. The scientists counted 10,500 dead animals, of which 95 percent were frogs and other amphibians.
"On hot summer nights when it rains, there are literally thousands of frogs out there," said Andrew DeWoody, a zoologist at Purdue University in Indiana who led the study.
Amphibians are often-slimy, four-legged creatures whose body-heat is regulated by their external environment (sometimes called cold-blooded). They play a vital role in many ecosystems, both as predators of insects and as food for larger animals.
The highway victims found by the researchers included 142 eastern tiger salamanders, a finding DeWoody said was troubling.
"The absolute number might not look that large, but most of these individuals were mature, up to 10 years old," DeWoody said. "Many of them were gravid, or females bearing eggs on an annual trip to breeding grounds where they often lay 500 to 1,000 eggs. This could make a potentially big difference for the population."
Along with the thousands of amphibians the highway-trolling researchers found, there were also 79 opossums, 43 raccoons, 36 chimney swifts, 35 garter snakes and 4 white-tailed deer.
DeWoody said his official tallies were probably underestimates, because many animals are scavenged, moved or degraded beyond recognition. He estimated about five times as many animals died on the roads than his team was able to count.
To help reduce the number of road kill victims, the researchers suggest building structures such as underpasses, viaducts and overpasses to allow wildlife safe passage, as well as special fences to keep animals off roads.
The study, funded by the Joint Transportation Research Program, a partnership of the Indiana Department of Transportation and Purdue, was published online in the latest issue of the journal Herpetological Conservation and Biology.
http://www.livescience.com/animals/080417-road-kill.html