As honeybee colonies in the United States and Europe continue to suffer from a mysterious syndrome called colony collapse disorder (CCD), scientists are scrambling for answers. Another answer arrived this week, with a publication¹ that implicates a widely used insecticide.

CCD endangers many crops, but none more than almonds, which are pollinated by bees in more than a million hives trucked to California during the flowering season. Trucking stresses the bees, and stress is one of several likely contributors to the collapse syndrome.

Indeed, CCD could be several conditions lumped under one name, but here’s the trademark: The bees die away from the hive, obscuring the cause or causes of the collapse.

In the new study, scientists in France glued radio frequency identification tags to bees. Half were fed non-lethal doses of thiamethoxam, a common insecticide, then all the bees were released 1 kilometer from the hive. At the hive, the scientists used a radio-frequency gizmo to count how many flew home.

The tags did not affect the results, says Mickaël Henry, a researcher at the French National Institute for Agricultural Research, in Avignon. “Previous studies have shown that they do not impair movement or behavior of bees, or their time budgets for foraging activity.”

In any case, the control bees also sported tags.

What’s wrong?

How did the insecticide reduce the return rate so significantly? Most likely by causing difficulties with orientation, or locomotor activity, or both, Henry says.

When the experiment was repeated over a distance of just 70 meters, 92 percent of exposed and 98 percent of control bees returned, so both sets of bees were able to fly. The major impairment of exposed bees on the unfamiliar, longer route suggests that the insecticide was most damaging to the ability to learn a new route.

The neonicotinoid insecticides, the category that includes thiamethoxam, trigger nicotinic acetylcholine receptors, which are normally excited by a signal from a neurotransmitter. According to the new study, “Effects of sublethal neonicotinoid exposures in honey bees may include abnormal foraging activity, reduced olfactory memory and learning performance, and possibly impaired orientation.”

These insecticides make bees stupid, in other words.

The experiment was designed to count how many bees failed to return rather than pinpoint the reasons for that failure, Henry stresses. “The next step is to go into deeper detail about the behavior, with time-activity budgets, and looking at their foraging.”

Not the whole story

“This is a nice study, and it does clarify something that a lot of people have pointed to in the disappearance of bees,” says Phil Pellitteri, a faculty associate in entomology at the University of Wisconsin-Madison. “Insecticides have been known to cause bees to get lost, that’s one symptom of collapse. But colony collapse is a complex thing, and you can’t hang it all on one factor.”

Honeybees have long been attacked by viruses, protozoans and mites, Pellitteri says, and pesticides may decrease immunity, thus increasing susceptibility to pathogens. These, combined with the stress of long-distance travel and the scarcity of natural foraging grounds “are the general direction a lot of CCD research is pointing to. It’s a number of things, and their interactions.”

Henry and colleagues fed their data on return rates into a mathematical model, which predicted a perilous slide in colony populations. “The disappearances we observed may cause the colony to reach a population size low enough to be sensitive to other stressors,” he says. “Most bees are exposed to pesticides, and this confirms that exposure can put the colony at risk of collapse; this is the take-home message.”

Should an artificial waterway in Chicago be closed to block two highly destructive fish from entering Lake Michigan and then the other four Great Lakes?

On Feb. 27, the Supreme Court said ‘no’ when it declined to revisit an appeal by the State of Michigan, which wanted to compel closure of the Chicago Ship and Sanitary Canal. The canal, created to drain stormwater and wastewater from Chicago, could allow silver and bighead carp from the nearby Des Plaines River to enter Lake Michigan.

Since the two carp, native to Asia, escaped from fish ponds in the South in the 1970s, they have occupied much of the Mississippi River system, and have become extremely abundant in rivers near the Canal. Biologists, state agencies and the Great Lakes Commission warn that once the fish reach Lake Michigan, they will likely spread through the five lakes, then into the St. Lawrence River.

The Great Lakes hold almost 20 percent of the world’s fresh water and border eight states and two Canadian Provinces. Given the silver carp’s fearful jumping habits, and the potential for both species to steal food from the mouths of sport fish, the invasion could threaten recreational boating and commercial, sport and tribal fishing that gross $16.4 billion per year.¹

Although the Great Lakes already house at least 180 invasive species, ecologists warn about irreparable harm from Asian carp. They say prevention is cheaper and easier than eradication — which may be a practical impossibility.

Originally, the watersheds of the Great Lakes and Mississippi River were separate. The two were united by the Chicago Sanitary and Ship Canal, which drains stormwater and treated wastewater into the Mississippi River system.

Don’t fence me out!

Although three electric “fences” across the canal have apparently managed to block the fish from entering Lake Michigan, many scientists view the barriers as stopgaps at best, and Asian carp DNA has been found several times beyond the fences.

While that DNA suggests that the carp are already in Lake Michigan, the fish have not been found there. Still, ecologists, accustomed to studying the disastrous aftermath of invasives on land and in water, would love to protect the Great Lakes from the carp by closing the canal. That would also protect the Mississippi River from invasion from the Lakes.

“The Asian carp situation is analogous to medicine, where an ounce of prevention is worth a pound of cure,” says Jake Vander Zanden, a professor of zoology at University of Wisconsin-Madison, and an expert on freshwater invasive species. “It makes so much more sense to keep them out, rather that let them in and deal with the consequences forever.”

The shipping industry, reliant on these waterways, wants to keep the Chicago waterways open, said Mark Biel, chairman of UnLock Our Jobs by email. “Nobody wants to see the Asian carp get into the Great Lakes… This is, however, a manageable issue that requires a long-term, comprehensive plan, and separation is simply not a solution. Given the size, scope and complexity of separating the two bodies of water, it’s clear that the costs would be enormous and the timeline — if it’s possible at all — would do nothing to address the immediate threat of Asian carp.”

Invasions can be expensive. The Environmental Protection Agency figured that just the invasives delivered in ballast water cut commercial fish landings by 13 percent to 33 percent in the U.S. Great Lakes, at an annual cost of $200 million. The estimate did not cover Canada’s part of the lakes, or species that arrived by other means.

What’s the problem with carp? What can be done to prevent their entry into the Great Lakes and beyond? Are invasive species always so damaging to ecosystems?

What’s the beef about carp?

Asian carp are heavy-bodied fish native to Asia that have occupied large parts of the Mississippi River watershed, where their rapid reproduction, voracious feeding (up to two or three times their body weight in plant and animal plankton per day), and made-for-home-video jumps are making life miserable for native fish and fishing people alike. The two carp considered most threatening to the Great Lakes — silver and bighead — originated in Southern fish ponds, where they were placed as natural vacuum cleaners to suck plankton from dirty ponds.

Since at least 1980, when the escape of the silver and bighead was detected, that voracious appetite was transformed from selling point to sticking point.

You might observe — correctly — that species have been moving since life began. It’s true that invasions are an old story, but it’s only half the story: the process has been force-fed by commerce and technology. “This is a natural process; it was once a trickle, but the rate at which it happens now is so devastating,” says Vander Zanden. “With globalization, trade, travel, things are moving so fast, it’s a fundamentally different process, and the implications are huge.”

It’s impossible to predict exactly how well Asian carp would fare in the Great Lakes; their abundance will depend on temperature, food supply, the emergence of diseases and predators, and factors that we can’t predict. But the lakes have a wide variety of habitats, and inevitably some would be conducive to the invaders.

The fundamental reason why invasive species reach nuisance levels resides in the predators, diseases or competitors they leave behind in their homeland. In the new habitat, the traveling species often gets an unfair advantage, enabling it to grow to astonishing abundance and crowd out native species.

Asian carp provide a perfect example of the process. They were deliberately imported to work on Southern fish ponds, and their ability to outcompete native fish for food and habitat “has led to the widespread establishment of Asian carp in the Mississippi River, impacting the natural balance of the aquatic ecosystem,”².

Can we keep carp from the greatest lakes?

On January 31, 2012, the Great Lakes Commission, an international body charged with maintaining the environmental and economic vitality of Earth’s largest lakes, issued a report describing three options for physically separating the two giant drainages to block invasions in both directions. The report was greeted by a number of officials from the region, including Michigan Senator Debbie Stabenow and Chicago mayor Rahm Emanuel.

The Obama Administration opposes closure of the Chicago canal, and in February it proposed to spend $51.5 million on Asian carp research. The money will buy more trapping and netting, to assess whether the fish have reached Lake Michigan, research on fish trapping with chemical attractants, and noisemakers to scare carp from entrances to the lake.

The focus on Chicago is misleading, according to Biel, who notes that the Great Lakes and Mississippi River Interbasin Study, from the Army Corps of Engineers, found “18 aquatic pathways throughout the region (not just Chicago alone) by which the Asian carp could get into the Great Lakes. The existence of these other pathways, which cannot simply be closed, demonstrates the importance of a regional solution to control Asian carp populations. That’s why we have to expand our sights beyond Chicago to determine a comprehensive control plan that implements measures in all of the pathways… .”

Philip Moy is a senior scientist at the Aquatic Sciences Center at UW-Madison who previously worked on the issue for the Corps of Engineers. “Electric barriers buy us time, and we need to do two things,” Moy says. “We should look into additional barrier technologies that can be added to augment the electrical approach… . We need to look pretty hard at the Great Lake Commission report suggesting that the lake and river can be re-separated. It would cost a lot of money, a century of infrastructure has built up there, but what’s the logic of waiting another 10 years to get started on a project that can take a generation to complete?”

The “mid-system separation alternative” proposed by the Great Lakes Commission was estimated to cost $3.26 to $4.27 billion. The latest federal appropriation for monitoring and research related to Asian carp will bring the three-year cost for controlling Asian carp in the area to $156.5 million.

Separation, Biel wrote, “would effectively end waterborne commerce through the Chicago Area Waterway System. The Great Lakes Commission report mischaracterizes how vessels could move containers around the Chicago rail gridlock, giving the impression that there would be a way to facilitate both separation and continued cargo movement.”

Muscling in on the mussels

There are good reasons why zebra and quagga mussels are often mentioned in discussions about invasives in the Great Lakes. Since the zebra entered the lakes in ballast water used to stabilize ships a couple of decades ago, it has clogged water intakes at power plants and water utilities.

Along with a later arrival, the quagga mussel, the zebra has eaten enough plankton to change the ecology of the lakes, and the zebra is now spreading to smaller lakes and rivers.

To prevent further hitchhikers in ballast water, ships now must replace their ballast water in the ocean with salt water, which carries organisms that are unlikely to survive in the freshwater lakes. “Every ship coming in is inspected by the Coast Guard before it reaches the Great Lakes,” Moy says, “and we haven’t discovered another ballast-related species since 2006. In the lakes, there is a growing spirit of cooperation between the companies that operate ships and the states.”

p. 74, “Aquatic invasive species in the Rio Bravo/Laguna Madre Ecological Region”

Salt-water invaders are carried in ballast water and through the pet and fishery trades.

Species invasions also plague smaller lakes, which explains the growing push to prevent the movement of invasive fish, mollusks and plants, by requiring boaters to clean and dry their boats and trailers as they leave a lake.

In Wisconsin, at least, that effort seems to be succeeding, even though not every boater complies, Moy says. “Some people say, ‘If this guy didn’t do it, it’s not the end of the world if I don’t also,’ but it usually takes multiple introductions over time to establish a population. If we reduce the number of introductions per year, we reduce the potential for establishment. Every person makes a difference.”

Buying time, but could time be on our side?

As ecologists pursue the science of invasives, what to do about the carp now knocking on the door of the Great Lakes? Biel, of the shipping industry, says, “Despite the uptick in hysteria on this issue, Asian carp populations in Illinois haven’t actually moved up river in six years. That said, we fully support funding the existing electric control barriers because their effectiveness has been demonstrated over and over again.”

Despite “substantial strides” in controlling Asian carp in Illinois and Indiana, including a third electric barrier and physical barriers along the Des Plaines River and the Illinois and Michigan Canal, “there’s simply not enough being done by other Great Lakes states,” Biel says. “Continued calls for lock closure remain a higher priority for our neighbors and other like-minded groups than actually implementing tactics for prevention.”

During the years it would take to seal the Chicago waterways, control technology may improve, says Moy, who points to fresh ideas from the U.S. Geological Survey. Instead of using the pesticide rotenone as a “big hammer” to kill all fish, he says, the Survey is testing a coating for rotenone that would make a deadly fish feed. Once sprinkled in the water, carp and other filter feeders would eat the feed, but only Asian carp have the enzyme that can dissolve the coating to release the rotenone. “It’s much more specific; an elegant application that takes advantage of the fish’s feeding behavior and internal physiology, using an existing, certified” chemical agent, Moy says.

There are benefits to working several angles at once, Moy adds. “These invasions are not inevitable. We can reduce the rate of invasions and the number of introductions per year, and that reduces the likelihood of establishment, and each year we delay introduction to a lake gives research time to come up with a solution.”

Iraq resents American drones that monitor outside the U.S. embassy in Baghdad. Iran is delighted to capture a high-tech U.S. drone. And the United States plans more drone purchases even amid slowing growth of the military budget.

As remote-control airplanes get cheaper and better, drones seem to be everywhere:

And it turns out that drones are ideal for watching wildlife: rabbits, sea lions, gulls and a range of elusive or inaccessible species.

Counting the mini-bunnies

Researchers in Idaho have used drones to track the pygmy rabbit, a hand-size mammal that eats sagebrush. The rabbit, a “species of concern” in Idaho, is already extinct in neighboring Washington State.

Pygmy rabbits are reclusive, spending much of their time inside burrows, says Jennifer Forbey, an assistant professor of biology at Boise State University. Forbey, along with Janet Rachlow at the University of Idaho, the U.S. Geological Survey, and Washington State University, is using used military drones called Ravens to explore how habitat factors like cover, forage quality and temperature affect rabbit populations.

The Ravens are small, and able to carry only one of these instruments at a time:

The drone can cover the entire two-kilometer square site in about three hours, but its gadgetry sees neither rabbits nor their burrows. Because the drone noise would scare the rabbits back into their burrows, the plane does not work when the bunnies are likely to be active.

To find the animals, Forbey says, “We have to walk for days and days, to identify where the rabbits are. We hike around, looking for fresh fecal pellets, fresh digging, fresh clipping on plants.”

But the data on forage quality, combined with tried-and true shoe-leather counting, shows that the rabbits are discriminating eaters. “They are specialized to sagebrush, but not all [sagebrush] plants are created equal, some types are more palatable, and also provide better cover for them,” Forbey says.

It’s possible that in winter drones could get a better picture of rabbit activity by looking for tracks in the snow.

To actually see rabbits from the air without frightening them, Forbey suggests a back-to-the-future approach — perhaps lighter than air craft.

“We are trying to develop some other platforms, maybe blimps, that could stay static over burrows to get infra-red video of rabbits without making noise.”

Although airborne surveys have begun, they are a help but not a panacea, says Forbey. “Not much is known about pygmy rabbits. They are cryptic. You have to spend the time walking the habitat.”

Gulls in Spain

Black-headed gulls nest in large colonies, and like many colonial birds, monitoring from the ground is difficult, and viewing from conventional aircraft can be expensive and confusing.

Pick up a battery-powered, radio-controlled model airplane, and the picture changes, says Francesc Sarda, at the Center for Forestry Technology of Catalunya, in Spain. When the drone flies over at an altitude of 30 to 40 meters, “The gulls hear it, but they don’t identify it as predator, don’t know what kind of element it is, and so they do not care about it.”

In a 2010 study,¹ Sarda equipped the plane with a still camera, pointing straight down. A video camera in the “cockpit” broadcast a live feed to a laptop on the ground, where the “pilot” operated controls.

The plane is “easy to fly, many people do it for hobby,” says Sarda, and it’s affordable — at just 1,400 Euros for the plane and the equipment. Depending on wind, the plane can stay aloft for 15 to 20 minutes, but batteries are cheap, and easily replaced before the next flight.

Water birds often nest in dense colonies, and can be difficult to study. Those that nest on cliffs can be observed from the side. On flat land, wildlife biologists may have to walk through the colony, but “If there are thousands of birds, it’s very difficult to count,” Sarda says.

Encounters with human counters can also annoy the birds, he adds. “In our case, they will fly away, even if there are chicks or eggs on the nest. You have to be very careful.”

The drone sidesteps this problem, he says. “You can do your count, and repeat your sampling” after a week or a month, to assess changes.

Laws about low-level flight are much less stringent in Spain than in the United States, Sarda says, and the system is “very cheap, compared with manned aircraft. You can use it yourself, whenever you want.”

See the sea lion

Sea lions and the fishing industry are squaring off in the Gulf of Alaska, where a rapid population decline of Stellar sea lions has been blamed on a scarcity of the fish they eat. But studying these fearsome and elusive creatures is difficult and data are sketchy, says Greg Walker, who manages the unmanned aircraft program at the University of Alaska. “The sea lion is an endangered species, and it’s affecting the fishery, but the science behind it is pretty spotty. The sea lions that have been monitored are healthy, not starving.”

Fishing restrictions are costly to the industry, and Walker observes that boats are catching more fish in the same amount of time, which suggests no scarcity of prey. “Their technology is no better than it was five years ago, and if they are catching more fish, maybe there are more fish” in the Gulf, he says.

Currently, sea lions are counted by looking at “haulouts,” rocky locations along the shore where these mammals mate and give birth, but the Aleutian Islands are hardly an ideal place to fly, Walker says. Airports can be hundreds of miles apart, and weather predictions cannot accurately say if clouds will block the view, wasting time and money.

Last June, Walker and his colleagues launched a drone from a fishing boat standing offshore. After a 12-mile flight, the drone flew over the colony, without causing obvious disturbance, and obtained video and photos clearly showing the sea lions.

Ironically, the same restrictions on fishing that were enacted to protect the sea lion have made fishing boats scarce. “We started working with a fishing cooperative; would fly off their boat while they were fishing, since they were going to be in the area anyway,” says Walker. “But closing the fishery has meant fewer fishing boats in the area,” and the lack of convenient launch pads could raise the price of drone-based monitoring.

If cost can be contained, larger surveys are possible, Walker says. “We will try to survey more of the island coastline, not just the historic haulouts. We want to know, is this a real population decline, or are they just in another part of the habitat? If you are always looking at the same street address, when someone moves down the street,” you may think they are dead, he notes. “Maybe a more consistent survey would find more of the sea lions.”

Eventually, if he can round up a bigger drone, Walker would like to use synthetic aperture radar, which can see through clouds, and could sidestep, finally, the cloud problem. But he also hopes the drones can fly at 500 feet, beneath many clouds. Flying that low is dangerous for manned aircraft, but that concern does not apply to disposable drones.

Having proved the concept of drone-powered surveillance of the sea lions, Walker and associates are planning to begin a three-week campaign in March.

Stop us from droning on!

Drones have a broad range of advantages compared to other ways of studying the environment. We’ve already mentioned how they can get access to awkward locations without bugging the animals.

Flying low and slow, drones can also identify and measure invasive weeds or many other types of ecological dislocation.

H. Franklin Percival, program leader for unmanned airplane research at the University of Florida, says safety is a critical motivation for using drones. “Low-level manned aircraft is the leading cause of workplace mortality for wildlife biologists. Wildlife biologists do this kind of thing all the time, studying salmon nesting, alligators in Florida, seals in Alaska, there’s a lot of low-level stuff.”

In 2010, a pilot and two biologists died in a helicopter crash while studying salmon nesting on the Selway River in Idaho. “That drives the interest [in drones] now,” says Percival. Before nesting, salmon fan away sand and gravel on the river bottom, “and we can see these from the air.”

FAA blues

In the United States, a major limitation on scientific use of drones comes from the Federal Aviation Administration, which is, rightly, worried about collisions between piloted planes and drones. Currently, the FAA requires that the pilot or a spotter be a licensed pilot, and limits a drone’s range and altitude to avoid danger. Those restrictions raise both the cost and bureaucratic rigmarole, and ecologists and the unmanned airplane industry are hoping for a change.

On Feb. 6, the Senate sent legislation to the President requiring FAA action on the issue within three years, USA Today reports.

If the concern is safety, new, more relaxed standards seem most appropriate to drones that fly short distances at low altitude.

If the FAA redrafts regulations to maintain safety while allowing more civilian use of drones, Forbey of Boise State expects ecologists to be lining up for unmanned aircraft. “This integration of technology with ecology and conservation is really exciting. I think what these planes provide is a spatial level that you can’t get from satellite, and can’t get from being on the ground. Both in terms of the area they can cover, and the type of data they offer, they fill a gap.”

Let a thousand drones bloom

Robot planes and the associated technology of cameras, communications and GPS-based recording of location are moving ahead even as the FAA promulgates regulations. At the University of Florida, Percival, who has directed the development of five generations of a robot plane called Nova, says drones should be designed according to the scientific goal. “What are the data required? Can it deliver that kind of data, and can you do the appropriate statistics to give reliable information? The airplane should be built around your question.”

As drones with ever more sophisticated sensors return a growing quantity of data, Percival favors automating data-processing to spit out reliable data that can be manipulated statistically. “To estimate the number of nesting birds in a pelican colony, we want to differentiate the components in the imagery with a computer as opposed to some guy’s eyeballs.”

Photos show a lot, but they do not automatically reflect reality, Percival says. “Just because we can see well does not mean the numbers are as precise, as accurate, as we’d like.”

The seas’ most sought-after fish are swimming between a rock and a hard place: the fisherman’s net and an encroaching mass of suffocating water.

A recent study has uncovered a new dose of bad news for ocean fish and the fishing industry. Areas of the deep ocean with little dissolved oxygen, called dead zones, are expanding and, thus, shrinking many fishes’ watery homes.

One driving force behind the predicament is none other than that pesky climate problem.

“Climate change is actually working in tandem with overexploitation of the animals to push these populations into a real dangerous place in terms of population collapse,” said Eric Prince, a fisheries biologist with the National Oceanic and Atmospheric Administration’s Southeast Fisheries Science Center and co-author of the study.

For example, Prince and his colleagues calculated that the Atlantic blue marlin, an economically valuable fish that was a focus of their study, has lost about 15 percent of its habitat from expanding dead zones since 1960. Dwindling habitat threatens not only the lives of fishes, but also the sustainability of the already ailing fishing industry.

Breathing room

Like their above-water brethren, fish need oxygen, which is dissolved in the water. Big, predatory fish, such as the blue marlin, need more dissolved oxygen than most, because they require lots of energy to grow and survive. Without sufficient oxygen, they’ll suffocate.

The level of oxygen in the water thus partly delineates fish habitat boundaries. Dead zones often draw these borders.

As climate change causes open ocean dead zones to balloon, fish habitat deflates.

Diagram modified from one originally published in Deep Sea Research Part I: Oceanographic Research Papers, Vol 57, Issue 4, Lothar Stramma, Sunke Schmidtko, Lisa A. Levin, & Gregory C. Johnson. Ocean oxygen minima expansions and their biological impacts, 587-595, Copyright Elsevier (2010).

Technically known as oxygen minimum zones, dead zones are actually a natural occurrence. Found at depths of between 200 and 1000 meters, they are caused partly by seawater circulation and partly by the decomposition of organic matter, namely deceased sea critters that sink from surface waters.

As aerobic bacteria nosh on the organic matter, they use up the oxygen in the water. Eventually, hypoxia happens—the water becomes so depleted of oxygen that many creatures can’t survive.

Since deep-sea dead zones are insulated from the ocean’s surface, where the water borrows oxygen from the atmosphere, they can only reload with oxygen if currents make a long-distance delivery, according to Sunke Schmidtko, an oceanographer at the University of East Anglia, the other co-author of the study.

Deep-sea dead zones are different from their coastal cousins like the one in the Gulf of Mexico. Coastal dead zones form due to a buildup of agricultural fertilizer that rivers, such as the Mississippi, collect and then flush out to sea, causing abnormal blooms of plant life.

De-fizzing the ocean

But climate change is turning what Mother Nature does normally into a big problem. As the air is getting hotter, so is the water, and warmer water can hold less oxygen than colder water.

This is similar to what happens to a soft drink on a hot day. After sitting in the heat and sun, the fizz fizzles, and you are left with a flat, carbon dioxide-depleted beverage.

Also, warmer surface waters are less likely to sink to the ocean’s lower layers, because warm water is lighter than the colder water below, Schmidtko explained. In other words, as the oxygen-rich surface layers heat up, they could have a harder time delivering oxygen to the deeper ocean.

Schmidtko clarified that oceanographers are still trying to determine how exactly climate change is affecting the ocean, but with their knowledge of how water works, these represent their current speculations.

The rock below

With less oxygen to go around, oxygen minimum zones are swelling and intruding on many fishes’ living zones.

For example, marlins often dive deep to feed, sometimes as far down as 800 meters. However, in the eastern Atlantic’s growing dead zone, which is already one of the largest in the world, Prince found that marlins can’t dive as deep as their west-side counterparts.

“They need to go where the food is and where they can breathe,” he said.

With less breathing room below, the floor of their habitat rises, and they are pinned to the surface layers. With nowhere to go but up, marlins become squished into tighter, testier quarters with other predatory fish and their prey. They also find it harder to dodge a waiting fishing hook or net.

“Concentrating them makes it much easier for overexploitation by [humans],” said Prince.

The increasing concentration of animals at the top could also lead to a boost in the amount of sinking organic matter, which would further worsen the oxygen shortage below.

Softening the hard place above

As a prized catch, Atlantic blue marlins are already victims of overharvesting. In fact, their populations have dropped 60-64 percent over the past three fish generations (14-18 years).

But the growing dead zones can actually fool scientists and fishermen into thinking fish populations are doing just fine, since more fish are squeezed into a smaller area. Thus, to ensure the dead zone-fishing vise does not become their demise, Prince said scientists must more carefully monitor fish populations, as well as the expansion of the dead zones.

While fish stock assessments are starting to incorporate this information, Prince warned the pace needs to quicken.

And if the Earth is to continue warming, as most scientists predict, Schmidtko added that humans should chill out on fishing.

After all, we will never be capable of “ventilating the ocean,” he said.

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

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

For controlling agricultural insects, bats are worth at least $3 billion a year to U.S. agriculture, according to a 2011 study from Boston University. “People often ask why we should care about bats,” said study co-author Paul Cryan, a research scientist with the U.S. Geological Survey in Fort Collins, Colo. “This analysis suggests that bats are saving us big bucks by gobbling up insects that eat or damage our crops. It is obviously beneficial that insectivorous bats are patrolling the skies at night above our fields and forests—these bats deserve help.”

As conservation officials scramble to respond to white nose, they are enacting quarantines to prevent people – cavers, bat-lovers and scientists alike – from transporting the fungus between caves. Last year, for example, the National Wildlife Refuge System halted public access to all caves and mines on its refuges, and set protocols to prevent scientists from spreading the infection.

In May, 2011, the Fish and Wildlife Service rolled out a national plan for confronting and controlling white nose syndrome.

But bats can do plenty of transportation on their own. Even non-migratory bats may fly 200 miles between their hibernation site and their summer range, says David Blehert, a microbiologist at the U.S. Geological Survey National Wildlife Health Center in Madison, Wis., and a leader of white nose studies. “They can move large distances, across state lines, so there is potential for significant disease spread based on bat-to-bat interactions.”

What is the white nose syndrome situation now? Why is it so deadly? What bright ideas are afoot to preserve insect-eating bats, and what is the likely end game?

Why deadly?

In the short time since white nose syndrome appeared in 2006, scientists have pinpointed a fungus called G. destructans as the killer. But how does G. destructans do its work? One clue comes from the fact that it only kills during hibernation, when bats live in mines and caves at a rather chilly 7°C. “The fungus only grows in the cold, and when insectivorous bats hibernate in a temperate region, they drop their core body temperature to the ambient level,” says Blehert.

(The fungus is not likely to attack fruit-eating bats, says Blehert, because they do not have long periods of “torpor,” the slow-metabolism hibernation state that is conducive to the white-nose fungus.)

A low body temperature allows the bats to survive winter without eating, but it could also curtail the immune system, Blehert says. “Studies of bat immunology are in their infancy, but based on what is known about the physiology of other hibernating mammals, especially the 13-lined ground squirrel it’s likely that the immune system becomes suppressed, and that leaves them particularly vulnerable” to the fungus.

How does the fungus kill? It apparently does not enter systemic circulation, as internal organs are not damaged. All mammals awaken from hibernation occasionally, but Craig Willis of the University of Manitoba has speculated that infected bats have more waking hours, causing them to run out of energy during a period when they neither eat nor drink.

Blehert and his colleagues favor a second explanation: dehydration. Despite the “white nose” name, Blehert says, the most significant infection occurs on the wings. “The wings of a bat have eight times as much skin as the trunk; it’s a massive, very delicate and exposed membrane” with a single layer of epidermis surrounding a thin layer of connective tissue and some muscles and glands. “The fungus selectively invades the wing skin, and destroys everything in its path,” Blehert says.

Beyond their role in flight, bat wings are also needed to regulate temperature, fluids and electrolytes. “The wings may be the Achilles heel that exposes them to such significant infection,” Blehert says.

Indeed, an emerging disease that is devastating amphibians, the chytrid fungus, also affects the skin, and is thought to kill by causing an electrolyte imbalance. “The amphibian’s skin is very important for the balance of water and electrolytes, which has been the basis for our hypothesis about why white nose syndrome is so deadly. There was a paper¹ in 2009 that demonstrated that a superficial chytrid infection causes an ion imbalance in frogs, causing a disruption of the potassium gradient that causes the heart to stop. A superficial fungal infection causes a cardiac arrest! This is a very different concept than getting athlete’s foot and having an itchy foot.”

Stopping the wave of death

As dead bats pile up in caves, what can be done to stop the spread of G. destructans? The first step, trying to slow dispersal, is already under way in affected states, with restrictions on cave entry, and new protocols for disinfecting equipment and people who have a legitimate reason to visit hibernation spots.

The fungus does respond to common anti-fungal agents, according to a 2011 study, which found, unexpectedly, that the meds worked at the low cave temperatures that the fungus prefers. “The challenge is, how could you use pharmaceuticals to manage a disease in free-ranging wildlife?” says Blehert. “They don’t go to the doctor, and they inhabit environments that are likely contaminated with fungus. Say you could treat bats and cure them of the infection. If you can’t remediate their hibernation sites, they will become reinfected when they re-enter the cave.”

The authors of the anti-fungal study did raise the possibility of using meds to decontaminate caves, but this process is not being done, Blehert says. “Going into a cave with a general fungicide would be like dropping a nuclear bomb on a city. Caves are full of bacteria, fungi, invertebrates and vertebrates that may only exist in that unique ecosystem, and getting rid of such an important group of organisms [fungi] could risk significant unintended consequences.”

Willis has proposed using little heaters, since bats seem to fare better in warmer regions of caves, perhaps because that sustains immune function. Small heaters are being tested as bat refuges in some New York State caves, says Lisa Warnecke, a post-doctoral fellow at Manitoba.

Lessons from Europe

G. destructans is an “emerging exotic disease,” and to investigate such diseases, scientists always want to know how the pathogen interacts with hosts in its land of origin, which seems to be Europe:

In 2009, the fungus was found in a greater mouse-eared bat in France²;

ENLARGE

Photo: Gabrielle Graeter, NCWRC

Is this bat unhappy about the tufts of fungus on its muzzle — or the researcher’s big hands?

During the winter of 2009-2010, infected bats were found in 76 of 98 sites in the Czech Republic; and

A 2010 study³ in Europe found a white nose pathogen in 21 of 23 suspected bats that was “100% identical” to the U.S. pathogen.

Although the fungus been found in at least five bat species in Europe, die-offs have not been seen there, suggesting that something is different about how the pathogen, host and environment interact. Pathogens and hosts co-evolve through time in a complex dance:

The pathogen may become milder, improving its own survival (and that of its host);

hosts may evolve immune resistance; and

hosts can change their behavior to reduce exposure to the disease.

In the lab in Manitoba, Willis and Warnecke are studying how long little brown bats are awake during hibernation, whether the fungus is a necessary and sufficient cause of death, and if the North American or European strains of fungus have different effects on the bats. “If both isolates show the same severity for North American bats, that may mean that bats in Europe have co-evolved with the fungus and are resistant to it,” says Warnecke. “On the other hand, if the European isolate does not cause trouble for North American bats, then the fungus in North America is a mutant that has gotten really aggressive.”

Other factors could explain the lack of disease in Europe, says Blehert. “European bats are larger, which may provide them with more of a buffer against a physical insult like a fungal infection.” The little brown bat, the preeminent victim of white nose, weighs about 6 grams – about the weight of two pennies, Blehert says.

European bats also tend to hibernate in small groups. “They don’t have those 100,000-plus hibernacula like we see in the United States. With fewer animals, the disease transmission dynamic is likely to be reduced, with less amplification of the fungus, and lower rates of bat-to-bat transmission.”

In the long run, Blehert says, American bats may evolve some resistance. “In general, the population decline in caves and mines comes to about 78 percent, but the bats have not disappeared. We would expect something that gets into population to cause high mortality and a steep drop-off in population. Then, with fewer animals around, disease transmission could moderate.”

Although the regional extinction of the brown bat has been predicted to occur 16 years from now, “our bats may ultimately develop population dynamics more like Europe, with fewer animals and moderated disease transmission and progression,” Blehert says.

Evolution, in other words, could select for animals that, for behavioral or immune reasons, are less susceptible to white-nose.

But letting the situation play out without trying to help the bats, Blehert says, amounts to a high-stakes gamble with one of the wonders of the night sky.

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

GRNAME IMG_0572.JPG
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.

GRNAME Rozar 2009 Goetz MEDIUM-BIG
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.”

GRNAME billboard
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!”

GRNAME gator_python
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
ALTTX

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.