In Ecology News: Python vs the Everglades

Are exotic pythons devastating Florida’s Everglades National Park? By Liza Lester, ESA communications officer Sometimes the snake wins. The exotic Burmese python is a new and deadly predator allegedly squeezing the wildlife of Florida’s already environmentally pressured Everglades. Large snakes have been observed swallowing American alligators and 80-pound deer, but more common prey are small mammals like raccoons, rabbits, and ‘possums, which have been disappearing. Credit, Lori Oberhofer, National Park Service. ________ A WAXING population of Burmese pythons has suspiciously paralleled waning sightings of native critters in Florida’s Everglades, says a paper out this week in the Proceedings of the National Academy of Sciences. Following on the tail of an announcement two weeks ago (Jan 17th) that the U.S. will ban imports and interstate sales of the exotic python and three other large constrictor snakes (yellow anacondas and northern and southern African pythons), the story has been attracting plenty of media attention. The case against the python is not a slam dunk, but the authors amass circumstantial evidence of its guilt in connection to the missing native fauna, and legislators are buying it. [See: EcoTone, 21 Sep 2011, “Deregulation of protections against invasive species can have dire long-term economic consequences.”] Burmese pythons (Python molurus bivittatus) are native to the warm latitudes of Southeast Asia, and arrived in Florida as pets. The python has an eclectic appetite, dining on more than forty varieties of evergladian mammal, bird and reptile, including other carnivores, endangered species, and the occasional alligator. Visitors and rangers have sighted pythons in the park for thirty years, but the park only began to view them as a resident population in 2000. A short decade later, the python had risen to the disreputable distinction of “conditional reptile,” and was officially blacklisted. Hopes that the cold winter of 2010 would kill off the pythons have been disappointed, as Terence explains in Tuesday’s EcoTone post. In July 2010, Florida Fish and Wildlife forbade acquisition of new pythons, required grandfathered owners to microchip their pets and obtain a license, and instituted a permitting system for civilian python hunting in the public parks. The US has imported 112,000 Burmese Pythons since 1990, according to the US Fish and Wildlife Service. Owners have been known to release their sinuous darlings after the snakes, which can reach almost 20 feet, grow too large to cohabitate comfortably in the house. But park managers speculate that the 1992 category 5 storm Hurricane Andrew may be the primary source of the python population explosion. An internal Fish and Wildlife study found little genetic variation in the python population—a sign of a small, closely related foundling group. “At...

Read More

Scientists detect aquatic ecosystem warning signal

Scientists have found what appears to be the stress signals of a lake ecosystem that is on its way to collapse. Stephen Carpenter of the University of Wisconsin, Madison and colleagues carefully monitored the food web in a Wisconsin lake as they gradually introduced largemouth bass into the ecosystem. The researchers noticed a shift in the algae populations that were directly related to the altered feeding behavior of smaller lake fish after the addition of the larger predators. “Because the smaller fish shifted to shallow waters where bass threaten them less, [Carpenter] explains, the algae that inhabit the more open waters of the lake were free of their predators and their populations fluctuate more,” wrote Jennifer Carpenter in a Science Now article. “Carpenter and his colleagues report online today in Science that these fluctuations were a warning that the lake’s food web is changing.” As explained in a National Science Foundation press release, the researchers “detected what they say is an unmistakable warning—a death knell—of the impending collapse of the lake’s aquatic ecosystem.” “We start adding these big ferocious fish and almost immediately this instills fear in the other fish,” Carpenter said in the release. “The small fish begin to sense there is trouble and they stop going into the open water and instead hang around the shore and structures, things like sunken logs. They become risk-averse.” A big indicator, according to Carpenter, was a boom in water flea populations. Carpenter and colleagues explained in the release that these signals are universal and could be incorporated into work on “rangelands, forests and marine ecosystems.” Photo Credit: Eric Engbretson,...

Read More

Birth control for Bremen’s cats

As spring days are punctuated with the chirps and trills of bird song, a recent article in the Guardian seems especially timely.  The northern German city of Bremen plans to take action to curtail its burgeoning population of free–roaming cats, estimated to be at least 1,000 strong. Whether feral or domestic—cats take a significant toll on birds and many other small wild animals.  A U.S. Fish & Wildlife fact sheet on bird mortality puts the figure at several 100 million a year in the United States. The German city of Bremen is concerned about both its local songbirds, such as the Sedge warbler (Acrocephalus schoenobaenus) as well as the spread of disease.  Under the proposed new law, all stray cats would be neutered and any pet owner found to have their cat roaming out of doors would be required to pay neutering fees.  Supporters hope that if the law passes in Bremen it will spark similar laws across Germany.  Public official Undine Kurth said in the Guardian article: “It would help a lot if the federal ministry of agriculture would initiate a debate on the wretched situation.” Recent population estimates in the United States put cat ownership in this country at 93.6 million.  Domestic cats (Felis catus) are not native to North America; European colonists brought them here several centuries ago.  Yet unlike our view of dogs, which must be leashed and cleaned up after, many Americans continue to feel that their cats should be allowed to roam free.  And while cat owners may feed their felines gourmet cat food, this does not curb cats’ natural instinct to hunt and kill small prey. Multiple states, veterinary organizations, and bird conservation groups all encourage voluntary steps by cat owners to keep their cats leashed or indoors.  State Departments of Natural Resources offer information on the impact of cats on native wildlife, the American Veterinary Medical Association encourages owners of domestic cats in urban and suburban areas to keep them indoors, and the American Bird Conservancy has a handy brochure of tips to keep an indoor cat happy.   Many of these organizations point out that in addition to helping native wildlife, cat owners who keep their pets indoors also protect them from disease, cars, and predators such as coyotes. Meanwhile, back in Germany, according to the Guardian article, a few other German towns, such as that of Paderborn, introduced castration of stray cats several years ago.  All residents are required to tattoo or implant their cats with a microchip.  And those who give their cats the boot get socked with a steep fine. Photo: http://www.flickr.com/photos/7955467@N03/3488673676          ...

Read More

The tiny, diligent gardeners of the Amazon

The gardeners described here are not concerned with trimmed topiaries or manicured lawns—though, like designers of landscape gardens, these workers are exceptionally picky. And they have to be if they are going to survive. That is, ants such as Myrmelachista schumanni and Camponotus femoratus of South America depend on certain plants for shelter, and in return, they offer these plants nutrients and protection from predators. As a result, they have developed a mutualistic relationship that has led to an incredible resilience for both species. For example, the ant M. schumanni has kept the plant Duroia hirsute alive in one area of the Amazon, known as a devil’s garden to locals, for more than 800 years. This particular type of ant-plant dependency is plentiful in the Amazon and it creates eerie patches of monoculture gardens amidst the rest of the lush, diverse rainforest. As biologist and photographer Alex Wild described in a recent Myrmecos blog post (complete with photos): I had been following an army ant raid for half an hour through dense tropical forest when the trees unexpectedly parted to reveal a small clearing. Sun broke through the canopy and fell on a low tangle of furry plants. It was a monoculture, looking as though planted by a reclusive sort of gardener. I had stumbled into a Devil’s Garden. Local lore holds that malevolent forest spirits create these unnatural crop circles, but the truth is just as weird. Devil’s Gardens are [cultivated] by ants. The plant species that compose these gardens—mostly in the genera Tococa, Clidemia, and Duroia—sport swollen structures filled by the nests of tiny Myrmelachista ants no more than 3 millimeters long. The ants are meticulous about caring for their hosts, removing [pesky] herbivores and injecting formic acid into the saplings of competing plants. Another ant species, C. femoratus, gathers the seeds of particular plants to cultivate in its nests, called ant gardens, and made of a mixture of animal feces, digested plants and other organic material. These nests are attached to vines, the sides of trees and even high up in the tree canopy. As Elsa Youngsteadt explained in the podcast Curiouser and Curiouser, ants followed chemical signals given off by seeds of certain plants, collected the seeds, carried them back and embedded them in the walls of the nests. The plants benefitted from the fertilizer mixed in the nest, and in turn, the roots helped to add structure to the ant garden. In addition, the leaves protected it from heavy rains that would otherwise have caused the material to disintegrate. “There are about ten plant species that are in ant gardens regularly that you don’t...

Read More

Scientists closely examine causes of frog abnormalities

urrently, research on the possible causes of limb deformities in amphibians is expansive, with evidence supporting parasite infection, chemical contaminants, UVB radiation and amputation as possible factors. However, as Mari Reeves from the U.S. Fish and Wildlife Service and colleagues explained in an article in the August issue of Ecological Monographs, the most likely cause of amphibian abnormalities is a combination of several stressors.

Read More

Iron-plated Snail

This post contributed by Nadine Lymn, ESA Director of Public Affairs  Another example of the ingenuity of nature: researchers are finding inspiration in the extraordinarily strong exoskeleton of a deep-sea snail, Crysomallon squamiferum.  The mollusk’s iron-plated shell is giving researchers insights that could lead to stronger materials for airplane hulls, cars, and military equipment. Researchers at the National Science Foundation (NSF)-supported Materials Research Science and Engineering Center at the Massachusetts Institute of Technology (MIT) write about the snail’s iron-plated protection in the January 19 issue of the Proceedings of the National Academy of Sciences. Also called the “scaly-foot gastropod”, Crysomallon squamiferum was discovered back in 1999, over two miles below the central Indian Ocean, deep within hydrothermal vent fields.  Fluids in these vents are high in sulfides and metals, which the snail incorporates into its shell.  The gastropod’s shell has three layers: a highly calcified inner layer, a thick organic middle layer, and an outer layer that is fused with granular iron sulfide.  It is unlike any other known natural or synthetically engineered armor. MIT project leader Christine Ortiz and her colleagues have been testing the shell’s properties, simulating predatory attacks with computer models as well as with “indentation testing”—striking the top of shells with a sharp probe to measure the hardness and stiffness of the shell. In a NSF press release Ortiz says: Our study suggests that the scaly-foot gastropod undergoes very different deformation and protection mechanisms compared to other gastropods.  It is very efficient in protection, more so than the typical mollusk. Potential predators that are found in the same regions as C. squamiferum include the cone snail, which penetrates its prey with a harpoon-like tooth before paralyzing it with venom, and sea-faring crabs, which use their claws to squeeze for days until the mollusk’s shell gives way.  The researchers write in the PNAS report that C. squamiferum’s impressive exoskeleton is: …..advantageous for penetration resistance, energy dissipation, mitigation of fracture and crack arrest, reduction of back deflections, and resistance to bending and tensile loads. Another vivid example of the evolutionary race between prey and predator which in this case also holds promise for better protective materials for humans. Photo credit: Dr. Anders Warén, Swedish Museum of Natural History, Stockholm, Sweden. Yao, H., Dao, M., Imholt, T., Huang, J., Wheeler, K., Bonilla, A., Suresh, S., & Ortiz, C. (2010). Protection mechanisms of the iron-plated armor of a deep-sea hydrothermal vent gastropod Proceedings of the National Academy of Sciences, 107 (3), 987-992 DOI: 10.1073/pnas.0912988107...

Read More