Among all animals, amphibians are in the worst shape; fully 30 percent are classified as threatened or endangered. Amphibians – including frogs, toads and salamanders — are under attack by a deadly fungus. They are losing habitat to farms and cities, and collected as food or pets. Amphibians are suffering from chemical pollution and the warming climate.

The present is harsh enough, but the future seems worse.

This week, Nature publishes the first global attempt to forecast the impact of three big threats to amphibians by 2080 – a year chosen to be one century after the study’s baseline data.

By comparing areas with plenty of amphibian species with projections of climate change, land use change and the chytridiomycosis fungus, the researchers forecast a grim future for these cold-blooded, four-legged vertebrates. “The bad news is that more than two-thirds of all high-richness regions will probably be affected, to a high intensity, by one of these three threats,” said lead author Christian Hof, who did the work as a Ph.D. student and post-doctoral fellow at the University of Copenhagen.

The geographic study of data on 5,527 amphibian species found little overlap between the cool, moist areas afflicted by fungal serial killer chytridiomycosis, and the places likely to suffer the worst effects of changes in climate and land use.

And the losers win!

In forecasting the future of amphibians, the study coined two technical terms: “losers” — species that are expected to suffer due to disease or changes in climate or land use, and the less numerous “winners,” which are expected to prosper by 2080.

The projection hinged on whether an expected change would make a habitat more or less suitable to the species, says Hof, who’s now at the Biodiversity and Climate Research Center in Frankfurt, Germany. “We ran a number of climate-change models and based on them, calculated a change in climate suitability for each region across the globe.”

Based on these changes in suitability due to climate, land use and disease, Hof adds, “We calculated the number of species that would probably decline due to a decline in habitat suitability. We classify the species as a loser in a particular region, but that does not mean it will decline across its whole range.”

Overall, the researchers found an increasingly dire future for amphibians. For example, 54 percent of frogs are likely to be “climate losers” in the average grid cell of their model. And heavy impacts are projected for about two-thirds of the regions with the highest species richness in frogs and salamanders.

In fact, the future could be even worse, since the study ignored a number of potentially damaging factors, including chemical pollution from cities, factories and agriculture.

Photo: Robert Fletcher, Ohlone Preserve Conservation Bank

Tougher times might await this prowling California tiger salamander, an endangered California native.

Going down!

It’s frustrating but understandable that the study could not predict rates of decline among amphibians. “For many species, we are not sure about the actual distribution, many have tiny ranges and we don’t know where they occur, so we can’t relate historic changes to, say, climate change. We were very careful not to predict extinctions, based on these uncertainties.”

Data are scarce in the study of amphibians, agrees Anna Pidgeon, an assistant professor of forest and wildlife ecology at University of Wisconsin-Madison. “It’s frustrating, amphibians are out at night, often in remote areas, they are small and many are cryptic, so it’s a huge challenge” to understand their populations and ecologies. “We work with the best data we have all the time … and try to make inferences from what we know about close relatives.”

Pidgeon, an expert on habitat needs of vertebrates, says predicting 70 years into the future is always dicey, but that the study’s analysis of multiple threats and global scope are major accomplishments. “They did a lot of things to make sure they were using consensus data, and that makes it a pretty solid approach.”

Although the study looked at overlapping threats, it did not actually look at interactions between those threats, Hof says. “What needs to be done, and we could not do that with our model, is to look at, for example, how climate change would affect susceptibility to the fungus. How would habitat fragmentation affect susceptibility to climate change?”

Although the study does not suggest practical changes that could sustain amphibians in the short run, “The general conclusion is that it’s very important, when thinking about the future for amphibians, to consider different threats together,” says Hof. “Just looking at one threat will not give us the whole picture.”

– David J. Tenenbaum

In Africa, elephants trample farms. Some traditional herders are prohibited from grazing their herds on land occupied by tourist-magnets like lions, leopards, giraffes and gazelles.

And buffalo, zebras and antelopes eat grass that could feed cattle.

In the East African savannas, the interactions between wildlife and the people whose livelihood depends on cows and goats, are complicated, critical and contentious.

Grazing is about the only way to make a living in this hot, dry land, but livestock and many wild herbivores eat similar vegetation.

And so the competition is obvious: How can a cow eat forage that a zebra ate first?

The question answers itself, and so nobody studied the issue.

Not so obvious after all

But in other realms, ecologists have found that organisms that seem to compete may actually aid each other. “We are just beginning to understand that the relationship between species is highly contextual,” says Truman Young, a professor of plant sciences at the University of California at Davis, “and this interaction includes competition and facilitation. Once, people thought if two species were similar, they always competed, but years ago, it became clear that facilitation exists in certain situations.”

Young is senior author of new study showing that in Kenya’s highland savannas, competition is partly offset by facilitation; although during the dry season wildlife steal food from the mouths of cattle, so to speak, the situation is reversed during the wet season.

When the rains come, wild ungulates (mammals with hooves), particularly zebras, seem to benefit cattle by eating fibrous, woody grasses and revealing the more delectable, higher-protein grasses beneath.

This gives cattle access to forage with more protein, and their wet-season weight gains nearly counterbalance the dry-season losses inflicted by wildlife.

Well done

The study was performed during 2007 and 2008, on nine fenced plots, or “exclosures,” each 4 hectares in size. The researchers placed four young, unbred females of an African breed called Boran on each plot for 16-week periods, and measured their eating habits and weight gain in three conditions:

First author Wilfred Odadi, a postdoctoral researcher at Princeton University and the African Wildlife Foundation, wrote us to explain that facilitation nearly equaled competition. “Wildlife-driven depression of cattle weight gain in the dry season is 35 to 40 percent. In the wet season, cattle put on weight faster by about the same percentage when they forage with wildlife.” The real-world situation, he added, would “depend on the lengths and frequencies of dry and wet seasons.”

This was the first experimental evidence that wildlife and livestock are engaged in facilitation and competition, Young says. “There is a basic-science excitement here. With this large-vertebrate system, we have shown that you can actually sometimes have competition and sometimes facilitation.”

It’s possible that the 15-year history of experiments on the site has changed the vegetation enough to weaken the results. But the continuous grazing of cattle kept the site’s vegetation similar to the surrounding savanna, Young says. “If we had excluded all large herbivores, the rangeland would become very different, and our inferences would be skewed. But because cattle are the dominant herbivores … the plots were not that different. My belief is if we had started the exclosures last year, we would have gotten the same result.”

What are the practical implications?

Killing wildlife, except for rogue animals, is illegal in Kenya, but it still happens, Odadi told us. “Because in Kenya wildlife belongs to the state, and not to the land owner, some livestock keepers still show a negative attitude towards wildlife because of perceived ‘detrimental’ effects on livestock including competition, livestock depredation and disease transmission. Some people react by fencing off their properties to keep wildlife away. There are also situations where water sources are fenced off by pastoralists to make them inaccessible to wildlife. In extreme cases, wild animals are actually killed, albeit illegally.”

And so in a region with unreliable rainfall and few resources, it’s good news for advocates of biodiversity conservation that the competition between domestic and wild ungulates, at least on savannas, may be more apparent than real.

Good news for conservation

Indeed, large mammal ecologist Johan du Toit of Utah State University, wrote in Science that the new information should eventually “provide managers with opportunities to capitalize on facilitative interactions, intervene against competitive ones, and enhance animal production overall.”

Rangeland managers often mix native and non-native plants, du Toit added. And after “bold experimentation and a break from orthodoxy,” a similar approach with animals could boost production while conserving biodiversity.

Odadi says better knowledge of cattle-wildlife interactions could support short-term changes, such as slaughtering or marketing livestock “at the end of the wet season, when they have recovered from competition in the preceding dry season, and also to minimize competitive effects (by reducing densities) in the next dry season.”

Conservationists in East Africa and elsewhere are seeking “to manage land for ecosystem biodiversity and short-term extractive value,” says Young, “but it’s pretty hard to find good examples, other than assertions about the profitability of ecotourism. We were able to show that wildlife and cattle have a complex interaction; that wildlife is not uniformly bad for cattle, and that allows us to be a little more lenient toward wildlife.”

– David J. Tenenbaum

Humans and cats go way back. The relationship sprouted around 2000 BC in Egypt, where humans first domesticated felines. Today, more than 90 million cats in the United States alone enjoy the companionship of humans, while another estimated 90 million are stray or feral.

As in most relationships, there are still secrets between humans and their feline friends. But a recent study published in the Journal of Wildlife Management shed light on one secret that may have been nagging cat owners: what do outdoor cats, otherwise known as “free-roaming,” do all day?

Since there are several cat enthusiasts at The Why Files, we, too, wondered about the answer to that question. And the answer belies a few thorny predicaments peculiar to the cat-human relationship.

A day in the life of a free-roaming cat

Decked with radio collars that tracked their every move, 42 free-roaming cats (18 of them pets, 24 of them owner-less) were the stars of the two-year University of Illinois study. The researchers’ goals were to compare what owned versus un-owned cats did all day, where and how far they wandered, and how likely they were to survive in the often risky outdoors.

Certainly, to no cat owner’s surprise, the felines spent much of their time lounging or sleeping, just like their strictly-indoor counterparts. However, the amount of time pet cats versus owner-less cats spent snoozing differed significantly. Pet cats lazed about for 80 percent of their days, while un-owned cats loafed for “only” 62 percent of the time.

“That alone is very interesting. It could be associated with their requirements. It’s possible that the cats without owners have to spend more time looking for resources to take care of themselves,” speculated Nohra Mateus-Pinilla, study co-author and wildlife veterinary epidemiologist at the Illinois Natural History Survey.

Another important finding, according to Mateus-Pinilla, were the differences in the cats’ ranges. While, not surprisingly, un-owned cats roamed further afield than owned cats, Mateus-Pinilla and her co-authors were surprised by how far the stray cats strayed and by the diversity of habitats they skulked in, as compared to pet cats. While most of the pet cats stuck close to home, the most itinerant stray cat wandered around a 547-hectare (1,351-acre) area.

From original map by Jeff Horn

Despite range differences, un-owned and owned cats’ territories can overlap. The red outline shows the largest range tracked for an un-owned cat in the study, and the yellow dot indicates one pet cat’s range.

“Because of the large home range sizes in the evidence of both cats without ownership and cats that are owned, their home ranges are overlapping. And because of the mortality evidence, these animals could be facing a certain amount of risks that we are unable to measure,” said Mateus-Pinilla.

Indeed, the risks of being a free-range cat are much higher than those of indoor cats, and if the cat has no owner, its fate is almost always bleak. In their study, six stray cats died, while only one owned cat died.

Mateus-Pinilla said their study raises many new questions. To The Why Files, however, it seems that living in the company of humans has its advantages for cats. But keeping this relationship indoors may have advantages for wildlife and people too—-implications that drive the otherwise curious research on free-roaming cats.

Too many kitties on the range

While the indoor-outdoor debate lives on in the cat owner community, and regardless of whether or not cats enjoy the out-of-doors, their secret lives outside entail some dirty secrets that are alarming scientists and laypeople alike.

The sheer number of free-range cats, owned or not, has become a conservation and health concern, some scientists say. Like any species, too many can spell trouble.

Cats, by nature, are superb predators. A cat stalking a bird or squirrel is simply doing what cats do. However, their prowess as hunters, combined with their overpopulation, has wildlife biologists and enthusiasts biting their nails over the potential endangerment or extinction of some prey species.

“There are a growing number of landscapes in which free-ranging cats are not only the most abundant mid-sized mammalian predator, but they can outnumber all of the native mammalian mid-sized predators combined. So they really do become the dominant mid-sized predator in many landscapes,” said Stanley Temple, an emeritus professor of forest and wildlife ecology at the University of Wisconsin-Madison, who was among the first to study the ecological impacts of free-roaming cats.

Because of their impacts on both native predators and prey, conservation scientists consider free-roaming cats invasive species. While not the greatest threat to wildlife, they add to the increasingly complex web of existing threats.

Species most at risk of death-by-kitty are birds that spend a lot of time on the ground, small mammals and reptiles, according to Temple. In fact, cats are second to habitat destruction as the cause of bird extinction. Thirty-three bird species have met their fate to the paws of cats since the 1600s.

The world’s ever-shrinking “islands” of wildlife habitat are hotspots of conservation concern over free-roaming cat populations, since the native species in these areas are the hardest hit by invading cats. For example, birds that live in America’s dwindling grasslands or on the increasingly crowded seashore are finding themselves in a precarious situation.

Open and fragmented landscapes, which also include forest outskirts and farmland, are the territories of choice for cats. And, except in subtropical locales, they tend to stick close to humans. Even if un-owned, most cats are still dependent on people for either food or shelter, or both.

“They are remarkably resourceful at taking advantages of the opportunities that we present,” said Temple, who clarified that free-roaming cats are only truly “feral” if they are completely independent of humans.

Their dependency on humans highlights another dilemma: free-range cats can easily spread diseases and parasites that can jump from cat to cat, cat to wildlife, and even cat to human. The list of contagions includes feline leukemia, feline immunodeficiency virus, worms, rabies and toxoplasmosis, a parasite-caused disease that can damage the developing brains of unborn human babies, if their mothers are infected.

Free-roaming cats’ close proximity to both humans and other animals thus creates a potentially strong reservoir for these diseases. While vaccinating both owned and un-owned cats can help reduce the spread of disease, vaccines are not 100 percent effective and the logistics of vaccinating every single cat may be impossible, especially since many vaccinations are annual.

Photo: Rodrigo Basaure

These street cats certainly benefit from a human handout, but do humans benefit from the cats’ potential disease threat?

It’s complicated

Indeed, solutions to these predicaments aren’t easy. While the science may seem to imply that rounding up every cat on the range may be the best solution, the ubiquity of free-roaming cats and the emotions wrapped up in some people’s relationship with felines complicate the matter.

Studies suggest that many free-range cats are people’s beloved pets that are allowed outside, said Temple. But, while keeping every pet cat indoors would significantly and immediately cut the number of free-range cats, not every cat owner agrees that indoor life is best for kitty.

To further complicate things, one of the often promoted “humane” methods of attempting to reduce un-owned cat populations — trap, treat, neuter, release — repeatedly fails. Not only are there always the cats that get away, but releasing the cats back into the “wild” still does not eliminate the risks to wildlife.

Temple believes that for a cat-control method to work, three criteria must be met: the strategy must actually control cat numbers over large areas, it can’t harm any other part of the ecosystem, and it is socially acceptable. The last criteria can be the trickiest to meet and often creates tension between humans.

Photo: Flickr

Is this outdoor kitty taunting his indoor pal? But who has the better life?

“The divide over how to deal with cat overpopulation, in one way, can be simplified as the group of people who are really concerned about ecological impacts of cats versus those that are really concerned about the welfare of individual animals,” said Temple, based on his years of experience conducting public outreach on the issue. He clarified that he likes cats and is actually the owner of a 21-year-old feline.

Temple believes solutions that meet both factions on common ground do exist. Keeping pet cats inside and trapping, treating, neutering and confining un-owned, free-roaming cats are two strategies that meet his criteria. Though, for some people, it will take some convincing.

Mateus-Pinilla was careful to emphasize that their study did not seek to evaluate management options. They were focused on adding to the science and remaining neutral in the debate about solutions to the issue of free-roaming cats.

– Jenny Seifert

Hoping to avert a biological infestation that could eventually stretch across a band of southern states, the U.S. Fish and Wildlife Service has proposed to ban the import and interstate transport of nine giant constrictor snakes. After the comment period expires May 11, the agency will review its options and consider whether to push forward with regulations.

The proposal was not popular with snake enthusiasts and the pet trade, but these giant constrictors are big, fearsome predators that can even kill alligators and panthers.

In short, these snakes (including the boa constrictor, four pythons and four anacondas) seem more suited to Tarzan movies than Florida travel brochures.

The major existing threat comes from thousands of Burmese pythons living in and around Everglades National Park, where the 2006 discovery of a nest confirmed that the python is breeding. It’s uncertain far north the snake is established, but Art Roybal, a Fish and Wildlife Service biologist in Florida, says they are “most likely” breeding in the Myakka River drainage in Sarasota County, but “Future events will determine whether that likely population can persist, spread, or extend to additional animals.” (Here’s a map of Burmese python sightings in Florida).

Although Burmese pythons seldom attack humans, some have killed their owners in captivity.
Fish and Wildlife is also proposing to ban the import and interstate transport of eight other giant constrictors, including the boa constrictor, which has been established for decades west of Miami, and the northern African python, which may be reproducing in South Florida. The agency hopes to designate the snakes as “injurious wildlife” under the Lacey Act.

Over the last 10 years, more than 1.8 million live constrictor snakes, including 12 species, were imported into the United States. Most, however, are ball pythons, which are not included in the Lacey-act proposal.

The snake problem arises almost entirely from pet owners, says the wildlife agency. Some of the invaders (or their ancestors) are escaped pets. Others came from pets that grew big and were dumped into the wild by owners who did not know, or did not care, that these animals could start to play house in the hospitable southern clime.

Although snake dealers generally disdain these proposed restrictions, Gordon Rodda, a U.S. Geological Survey invasive snake expert, says “there already are tens of thousands of these snakes in captivity in the United States, and no-one is proposing any restrictions on that. Private possession of pets is a state responsibility. These proposed rules would affect only the import of new stock and transport across state lines, not the keeping of existing stock or their progeny.”

The art of the invader

Invasive species, whether plants, mammals, insects or reptiles, have inherent advantages over natives: they often lack diseases or predators, and native wildlife and vegetation cannot counter their competitive tactics. “We are talking about non-native predators that our native species have not evolved to cope with,” says Roybal. “They get so large, up to 200 pounds and up to 20 to 23 feet long. They are a sit-and-wait predator. The native species are not used to animals of that sort, and haven’t developed behaviors to avoid them.”

The large constrictors are especially dangerous to threatened and endangered species, says Roybal. “The thing that really opened our eyes was the consumption of three key largo woodrats [by the python] in the Florida keys. This is a very imperiled species, there probably are only 200 to 300 left in the wild. If a large constrictor got established in the keys, it could mean severe impacts and possibly extinction.”

The Burmese python could occupy all of Florida, experts say, and even spread far beyond, according to a U.S. Geological Survey study of the snake’s climate requirements.

Roybal adds that the boa constrictor, and possibly the reticulated and Burmese pythons, recently started breeding in the forests of Puerto Rico, where officials has already removed more than 100 boas. “This is not just a Florida problem,” he says.

Photo: Guam DOA

The last wild Guam flycatcher was seen in 1985; the bird is extinct due to the brown tree snake.

Unimpressed with the threat of invasive snakes? Then check out Guam, where the brown tree snake has eliminated 10 native birds since arriving in about 1950. As many as 13,000 brown tree snakes occupy a square mile on the island.

This venomous snake does not shy away from housing, so it also poses a safety threat.

Brown tree snakes have since hitchhiked from Guam to several Pacific islands, yet there are finally signs of progress in controlling the repellent reptile, says Gordon Rodda, brown tree snake guru for the U.S. Geological Survey. To halt further invasions, Rodda says, “The first and most intense effort was getting them away from the port and airport; that’s been very successful.”

The next step, Rodda adds, is to “expand the defensive perimeter and clear the whole island” with poison bait. Because Guam has no native snakes, “We can put out bait and only the brown tree snake will eat it. In Florida, they have a large number of native snakes and … you can’t go and poison them willy nilly.”

Photo: U.S. Geological Museum

After the brown tree snake invaded the Pacific island of Guam, 10 of 12 native birds disappeared.

If the brown tree snake can be eradicated, it would be logical to restore native birds from other islands, but Rodda says most of Guam’s suitable habitat is owned by the U.S. military, which is unreceptive to the idea.

Controlling giant constrictors

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CAPT The art of camouflage. A python basks near a canal in the Everglades. Pythons are hard to see, and most of the Everglades is inaccessible to people, so even removing pythons from roads and levees will barely dent the population.
ATTRIB Photo by R.N. Reed/USGS
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Why not just trap these invading snakes?

When it comes to invasive species, and especially snakes, experts agree that prevention trumps eradication. The Burmese python is extremely difficult to find, as it “lives in the middle of the Everglades, the largest wilderness east of the Mississippi River, and in national wildlife refuges,” says Frank Mazzotti, an associate professor wildlife ecology at the University of Florida.

“People don’t really appreciate how hard it is to catch a Burmese python,” says Mazzotti, an expert on snakes in South Florida. In studies of other snakes, he adds, “when people knew the snake population and had well-developed methods for finding and catching them, if they catch 10 percent of them, they feel extremely lucky. It’s not unusual to catch more than 50 percent of a mammal population.”

In an effort to contain the invasion in Florida, federal agents have already trapped a Burmese python on Key Largo, the first major link in the chain of fragile islands called the Florida Keys.

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CAPT A biologist removes a trapped Burmese python on Key Largo. How many evaded the traps?
ATTRIB Photo by R. Rozar, USGS.
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Snakes in general are camouflage experts, says Art Roybal of the Fish and Wildlife Service. “We are told by scientists that for every one snake that you do see, there are 1,000 that you don’t see. … Large constrictor snakes are notoriously cryptic and often hidden and immobile and are therefore difficult to detect.”

“You have to understand the difficulty of finding an animal that looks like a vine that is spread over 10,000 square kilometers of woody swamps,” adds Gordon Rodda of the U.S. Geological Survey. “There is no track record of success in controlling invasive reptiles and snakes. There are reasons to be pessimistic that the Florida population [of Burmese pythons] will ever be controlled.”

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CAPT To slow the invasions, agencies in South Florida are imploring pet owners to find a responsible way to get rid of their pets. Florida now stages periodic “amnesty days” where owners can safely dispose of unwanted snakes.
ATTRIB Army Corps of Engineers
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Along with many other biologists, Rodda, who heads the USGS response to the brown tree snake on Guam, says, “Prevention is way better than fighting the crisis once it’s occurred. Once the snake is established, your chances of eradication are virtually gone.”

Meager options for control and eradication

When the USGS looked at predators and diseases for controlling snakes, it saw no good options. Predators are futile against snakes that can fight back against the big teeth: Burmese python can eat leopards and panthers, and Mazzotti says a captured 16-foot Burmese python threw up a 6-foot, 30-pound alligator. “‘Wow!’ doesn’t even do it justice. It was amazing!”

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TITLE World Wildlife Wrestling FOLLOW WITH A TRADEMARK SYMBOL?
CAPT An American alligator wrestles for keeps with a Burmese python in Everglades National Park. Although the gator seems to have the upper hand (upper fang?), pythons are powerful enough to eat gators.
ATTRIB USGS
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In these struggles, “Probably more often than not, the alligator win, but that doesn’t mean their numbers will be significantly be depressed by alligators,” says Rodda. The death-tangle between a giant snake and a big toothy gator may be eye candy for TV, “but if a small alligator gets pulled from the water at night and swallowed, you are never going to see that. If the alligator was sufficient to control the Burmese python, the snake would not have spread.”

When experts examined 57 potential predators to control the brown tree snake on Guam, none were deemed acceptable. Indeed, introduced predators are not much good for controlling invasive animals, according to the USGS:

BLOCK QUOTE
“The record of successes is small, and the number of catastrophic failures (non-target species decimated or even driven extinct by the predator) is large. As a result, it is against U.S. Fish and Wildlife Service policy to introduce predator-based biocontrol agents for vertebrates (there is also a question as to which higher order predator would qualify for preying on giant constrictors!), and we will not entertain that notion further.”
END BLOCK QUOTE

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CAPT Researchers implant a radio transmitter in a 16-foot, 155-pound female Burmese python at Everglades National Park. Radio-tracking shows the snake’s movement, helping guide control efforts.
ATTRIB USGS
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Could bugs or bounties work?

Pathogens – viruses, bacteria or fungi – could theoretically be used if they were specific enough to target the invasive snakes, but Rodda says that the knowledge of snake diseases “is all about snakes in captivity. Nothing is known about transmission of disease in the wild.”

Considerable time and money would be needed to research pathogen control against the giant constrictors, according to the USGS.

The vertebrate immune system can adapt to many new pathogens, and viruses sometimes evolve to become less lethal. When Australian authorities tried to eliminate a massive outbreak of introduced rabbits with a virus, the virus worked at first, and then the rabbits returned to running rampant.

Bounties were used to eradicate wolves from most of the lower 48 states, but bounties can boomerang if hunters breed the target animals in captivity or distribute them to new habitat. On the Caribbean island of St. Lucia, for example, bounty hunters began breeding the fer-de-lance, a deadly invasive snake from Africa, that was targeted for elimination. “Once you start assigning a value to invasive animals, there is an impetus to some people to keep them out there,” says Robert Reed, a USGS invasive species scientist and herpetologist, “And there is no funding that would allow us to hire people to catch snakes.”

The trapping option

Several projects have tested whether Burmese pythons in Florida can be trapped without harming native snakes and wildlife. Traps can either attract snakes with bait, or be located along a fence that intercepts the snakes and ushers them into a trap.

Reed says both types of traps have caught Burmese pythons in South Florida, but trapping experiments are at an early stage, and the ideal trap probably depends on the context. For example, some former farmland on Florida’s mainland has so many rats that “attractants may not work well because the snakes don’t have to hunt around for food.”

Although it’s too early to know how much trapping will cost, they are not a magic bullet. “Traps alone will not be sufficient to eradicate the Burmese python from the Everglades,” Reed says. “It might be a great option if we are trying to locally control snakes around an area with high ecological value, such as a wood stork rookery,” where reducing the snakes without eliminating them might allow the birds to survive.

GRNAME Rozar 2009 KL trap round flap MEDIUM SIZE
CAPT This trap for Burmese pythons, in use at Key Largo, is about 2 meters long and has entrance funnels at each end; the live rat that serves as bait is protected by a smaller cage from the snake.
ATTRIB Photo by R. Rozar, USGS
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A changing ecosystem?

As Burmese pythons spread through South Florida, it’s too early to say for sure how they are changing the Everglades, an ecosystem that has already sustained massive invasions from other animals and plants, not to mention numerous disturbances to natural water flow.

Some rare species have already been found inside snakes, but biologists are also noticing that some common species are becoming scarce. “In the 1970s, ’80s and ’90s, when I used drive the main [Everglades National] park road, I would see marsh rabbits maybe every 50 meters,” says Mazzotti. “Now I don’t see them anymore, zero; and we are finding fewer in the stomachs of pythons. We find lots of marsh rabbits in areas without pythons. That’s a correlation that does not imply cause and effect, but these are the kind of impacts you would expect.”

As the spotlight turns to the nine giant constrictors, Reed says invasive reptiles are always tough to control. A recent scientific review, he notes, “saw no evidence that an introduced reptile population had every been intentionally eradicated. These are cryptic animals and by the time you notice them, the odds are pretty decent that they are already established.”

Into constrictor control? Meet the strict constrictionists in our bibliography.