Nutria on a partially submerge grocery cart. Photo credit: Trevor Sheffels

Urban locales are not the typical place one thinks of when the word “nutria” is spoken. Yet this invasive species is living, nay thriving, in metropolitan Portland, Oregon.

Typically found in coastal and inland freshwater marshes, nutria are perhaps better known for their feeding and burrowing behaviors which are destroying coastal wetlands in Maryland and Louisiana, but they can currently be found in 15 states, coast-to-coast.  Nutria are large semi-aquatic rodents that resemble native beavers and muskrats. Native to South America, nutria were introduced into the United States for their fur in 1899, and although some populations have been eradicated, other populations exist as remnants or are thriving.

Normally this quest for survival takes place in the “wilderness,” not blocks from the local coffee shop.

But in Portland, feral nutria have made the metropolitan area their home. Nutria have inhabited the Pacific Northwest since the 1930s, and have frequented the Portland metro area since about 1936 or ‘37. Nutria can be found where there is slow-flowing water deep enough for them to swim in. These herbivores eat aquatic and terrestrial vegetation, feeding on the base of plant stems, and digging for roots in the winter. Their grazing habits can strip large patches of marsh and their digging overturns the marsh’s upper peat level and erodes streambanks.

Even though nutria have been in the Pacific Northwest for more than 80 years, there has not been a lot of research on them or their impacts on the ecosystem.

Until Trevor Sheffels that is. Sheffels, who studied the metropolitan nutria with the USGS for his doctoral dissertation, looked at habitat suitability, movement patterns and ways to offset the damage nutria cause. His study is the basis of this article.

Nutria live about two-to-three years, and they can have two-to-three litters a year with an average of five young in each litter. They are very active during the day, at levels higher than reported previously, providing more opportunities for nutria to be in close contact with humans.  People have been observed feeding nutria as if they were pigeons in Central Park, except in this case they are feeding an invasive species that is adaptable to human systems.  The nutria in this study stayed within the small urban habitat restoration wetlands instead of traveling long distances, which suggests these restoration sites are suitable for sustaining nutria populations.

To manage the species, plastic mesh tubes have been used to protect woody vegetation from nutria, while new multiple-capture live-traps have shown promise for use in urban areas because they virtually eliminated the capture of other species.

In the Pacific Northwest and nationally, the nutria problem is likely to worsen as a result of climate change.  Coupled with the fact that nutria are inhabiting urban areas, it is important to find ways to minimize habitat degradation, economic losses, and human safety concerns associated with this invasive species.

Current research shows that with climate change, nutria in Oregon and Washington may continue to expand eastward, while nationally there is the potential for the animals to move farther north if the temperature changes just a few degrees Celsius.

Nutria can be found in many non-marsh systems that have permanent bodies of water such as the ponds in golf courses, urban parks, constructed wetlands used to treat sewage, and drainage canals. In addition to the problems they cause in systems, these areas provide refuges from which their nutria can repopulate areas that have had their nutria populations eradicated or reduced.

Want to know more about Nutria? Please visit these resources:

• Nutria, Eating Louisiana’s Coast (PDF)
• Nonindigenous Aquatic Species Nutria Fact Sheet

Collage: USGS scientists handle a Burmese python in the Everglades; USGS scientists pull in a net full of mostly Bighead Carp ; two USGS scientists display a bighead Carp in the bottom left hand corner.

Over the last several decades, non-native species have continued to invade sensitive ecosystems in the United States.  Two high-profile species, Asian carp in the Midwest and Burmese pythons in the Everglades, are the focus of much attention by decision makers, the public and the media. USGS scientists will discuss issues related to invasive species and explain innovative methods used to help detect and control these invaders.

Time: Wednesday, July 11, 2012 • 7-8pm
Speakers: Sharon Gross, Robert Reed and Cynthia Kolar
Location: 12201 Sunrise Valley Drive Reston, VA 20192
Phone:  703-648-4748
Please Note: This event takes place at a Federal Facility — Photo Id is Required

FREE and Open to the Public
Follow this event live on Twitter @USGSLive

This announcement and directions can be found online.

Requests for accommodations (i.e. sign language interpreting) require notice at least two weeks before the event. Please email jcorley@usgs.gov or call 703-648-7770.

The USGS public lectures are held monthly in Reston, Virginia. These evening events are free to the public and intended to familiarize a general audience with science issues that are meaningful to their daily lives. USGS speakers are selected for their ability and enthusiasm to share their expertise with an audience that may be unfamiliar with the topic; speakers are encouraged to thoroughly explain the subject matter and to define any words or terms that may be unfamiliar.

The USGS lecture series provides the public an opportunity to interact with USGS scientists and ask questions about recent developments in Natural Hazards; Water; Energy Minerals and Environmental Health; Climate and Land Use Change; Ecosystems; and Core Science Systems. Ultimately, the goal is to create a better understanding of the importance and value of USGS science in action.

Back-lit photographs of wings of White-nose Syndrome (WNS)-positive little brown bats, one with subtle circular and irregular pale areas (arrows) indicating areas of fungal infection (A) and another bat (B) with areas of relatively normal tone and elasticity (black arrow), compared to a WNS affected area that looks like crumpled tissue paper with loss of elasticity, surface sheen and areas of irregular pigmentation (white arrow). (C) Microscopic section of wing membrane from a little brown bat showing extensive infection with the fungus (magenta structures), G. destructans.

The United States is under an economic and ecological siege by alien invaders — America’s Most Unwanted. More than 6,500 of these harmful non-native species cause more than 100 billion dollars in damage each year to the U.S. economy as the country battles to control the economic, ecological, and health threats these invaders pose. Increased global travel and trade are providing more pathways for both intentional and unintentional introductions of invasive species.

Invasive species affect just about everyone in every State in the country, in urban centers and wilderness areas. And their costs are borne by all of us — farmers, ranchers, businesses, and local, State, Tribal, and Federal governments.

The Cost of Invasives

Costly effects of invasives include crop decimation (cactus and gypsy moths), clogging of water facilities (quagga and zebra mussels) and waterways (hydrilla, giant salvinia), wildlife and human disease transmission (West Nile virus, monkeypox, and diseases in some ships’ ballast water), threats to commercial, native, and farmed fisheries (Asian carp, snakehead fish, sea lamprey, Asian swamp eel, whirling disease, and viral hemorrhagic septicemia), increased fire vulnerability (cheatgrass, brome, and buffelgrass) and adverse effects for ranchers and farmers (leafy spurge and cheatgrass).

Researchers with the USGS Invasive Species Program work on every one of those species mentioned; in fact, our researchers work collaboratively on all significant groups of invasive organisms in terrestrial and aquatic ecosystems in all regions of the United States. Across the Nation, our invasive species experts partner with States, other Federal agencies, businesses, agriculture, and natural resource managers to help solve the problems posed by these invaders.

Key components of invasive species activities include prevention, monitoring and forecasting threats, and control and management of established invaders.

During Invasive Species Awareness Week, we will feature some of America’s Most Unwanted each day to highlight the impacts of invasive species to the nation’s Ecosystems and economy.

The USGS National Wildlife Health Center conducts a bat autopsy as part of its efforts to study the fungus that causes white-nose syndrome in bats.

Invasive Wildlife Diseases: USGS scientists collaborate with public health and animal health agencies on notable invasive zoonotic diseases – invasive diseases that are transmissible between animals and people. Such diseases are a potential collateral result of exotic animal introductions. Specialized biological containment facilities at the USGS National Wildlife Health Center (NWHC) in Madison, Wisconsin, allow scientists to provide diagnostic surveillance and research, information needed by all levels of government to adequately respond to wildlife diseases. NWHC scientists used patterns of wild bird mortality from West Nile virus, a wildlife disease introduced to the United States in 1999, as an indicator of the spread and activity level of this emerging disease. This information allowed public health officials to estimate human population risk and enact control and prevention activities. USGS and USDA surveillance also indicated that monkeypox, an invasive disease introduced to the United States from Africa through the international pet trade, had not spread from pets or humans to free-living wildlife. Since 2006, USGS along with other agencies, has been conducting surveillance and monitoring of wild birds to detect highly pathogenic avian influenza, an important zoonotic and economic disease, if it invades the United States through migratory birds.

An Emerging Bat Disease: The sudden emergence of white-nose syndrome (WNS), a devastating disease of hibernating bats, demonstrates the importance of a national and international infrastructure to investigate and respond to emerging wildlife diseases and their ecological and societal threats. Since 2008, when scientists first began investigating this unknown disease in bats of the northeastern U.S., WNS has spread to 16 states and 4 Canadian provinces. WNS has caused precipitous declines of some bat species.  Not only are bats important ecologically, but a recent USGS and partner study showed their pest control services likely save the U.S. agricultural industry at least $3 billion a year.  Since the USGS first identified the WNS fungus, our ongoing research has provided critical information about the fungus and the disease, guiding state, federal, NGO and tribal disease-response activities. Land-management agencies rely on our research and disease investigations to support on-the-ground actions, to help develop the WNS National Plan, and to assist with other national disease-management plans.

Little brown bat with fungus on muzzle.

Viral Hemorrhagic Septicemia Virus:

Viral hemorrhagic septicemia virus (VHSV) is among the most important viral pathogens of finfish, causing losses in both freshwater and marine species. In 2005-2006, VHSV emerged in the Great Lakes Basin, resulting in a series of fish kills. As of June 2011, the virus has been found in 31 fish species from Lakes Erie, Superior, Huron, Michigan, Ontario, St. Clair, as well as the Niagara and St. Lawrence rivers, and inland lakes in Michigan, New York, Ohio, and Wisconsin. Significant VHSV outbreaks have affected many species of fish, such as muskellunge, freshwater drum, goby, burbot, yellow perch, gizzard shad, and smallmouth bass. Research by USGS scientists, in collaboration with state, federal, and Canadian partners, focuses on using molecular genetic tools to identify and track strains of the virus, developing improved diagnostic methods, determining methods for disinfection of eggs, and testing for virus transmission pathways. A three-year project funded by the Great Lakes Fishery Trust to the USGS’s Western Fisheries Research Center and colleagues at Cornell University and Michigan State University has allowed USGS scientists to compare the genetic sequences of VHSV strains obtained from fish at 37 locations in the Great Lakes Basin with those representing strains from other regions of the world. The very low level of genetic diversity within the Great Lakes is consistent with a recent, single introduction of VHSV to a native population of fish. To date, the route of introduction has not been determined.

Viral hemorrhagic septicemia has recently emerged in the Great Lakes and caused severe epidemics in many fish species.

For more information on USGS research on invasive diseases:

USGS Viral Hemorrhagic Septicemia Virus Page

National Wildlife Health Center

National Wildlife Health Center Avian Influenza Research

National Wildlife Health Center White-nose syndrome research

USGS Monkeypox fact sheet

Vaccination and Flea Control to Assess Invasion of Plague into the Conata Basin, South Dakota

Development of a White-nose Syndrome Disease Tracking System

Fort Collins Science Center: White-nose syndrome

Evaluation of the Efficacy of Iodophor Disinfection of Walleye and Northern Pike Eggs to Eliminate Viral Hemorrhagic Septicemia Virus

Bighead carp are a large and troublesome invasive species from Asia found in the great rivers of the central United States.

Under Siege! America’s Most Unwanted Invasive Species

The United States is under an economic and ecological siege by alien invaders — America’s Most Unwanted. More than 6,500 of these harmful non-native species cause more than 100 billion dollars in damage each year to the U.S. economy as the country battles to control the economic, ecological, and health threats these invaders pose. Increased global travel and trade are providing more pathways for both intentional and unintentional introductions of invasive species.

Invasive species affect just about everyone in every State in the country, in urban centers and wilderness areas. And their costs are borne by all of us — farmers, ranchers, businesses, and local, State, Tribal, and Federal governments.

The Cost of Invasives

Costly effects of invasives include crop decimation (cactus and gypsy moths), clogging of water facilities (quagga and zebra mussels) and waterways (hydrilla, giant salvinia), wildlife and human disease transmission (West Nile virus, monkeypox, and diseases in some ships’ ballast water), threats to commercial, native, and farmed fisheries (Asian carp, snakehead fish, sea lamprey, Asian swamp eel, whirling disease, and viral hemorrhagic septicemia), increased fire vulnerability (cheatgrass, brome, and buffelgrass) and adverse effects for ranchers and farmers (leafy spurge and cheatgrass).

Researchers with the USGS Invasive Species Program work on every one of those species mentioned; in fact, our researchers work collaboratively on all significant groups of invasive organisms in terrestrial and aquatic ecosystems in all regions of the United States. Across the Nation, our invasive species experts partner with States, other Federal agencies, businesses, agriculture, and natural resource managers to help solve the problems posed by these invaders.

Key components of invasive species activities include prevention, monitoring and forecasting threats, and control and management of established invaders.

During Invasive Species Awareness Week, we will feature some of America’s Most Unwanted each day to highlight the impacts of invasive species to the nation’s Ecosystems and economy.

Part 2

Asian Carp

In areas where Asian carp are abundant, they have interfered with commercial and recreational fishing, caused reductions in zooplankton (animal plankton, an important food for many aquatic species), and harmed native fish communities. Bighead and silver carp have moved up the Illinois River and are now poised to enter the Great Lakes. Resource managers fear that Asian carp would have ecological impacts and negatively affect the $7 billion-a-year fishery in the Great Lakes. Early USGS research focused on understanding the distribution, abundance, and habitat use of these fish, along with collecting information on their biology and life history from around the globe. USGS researchers are currently examining aspects of risk to the Great Lakes from Asian carp in the Chicago Area Waterways System, as well as conducting studies to develop and test ways to reduce the abundance and distribution of Asian carp.

Bighead carp are a large and troublesome invasive species from Asia found in the great rivers of the central United States.

Q: What are Asian carp?

There are many carp native to Asia, but in North America, “Asian carp” usually refers to bighead, black, grass, and silver carp — all of which are nuisance species in inland waterways. The Asian carp that have garnered the most attention are bighead and silver carp (together, the bigheaded carp), large fish that filter plankton from the water column. Grass carp primarily feed on aquatic vegetation, and black carp feed almost exclusively on mussels, clams, and snails. Grass carp (often sterilized to prevent reproduction) are sometimes stocked to control nuisance aquatic vegetation in lakes and ponds but can be considered a nuisance when they enter waters they were not intended to colonize or when they become established. Bighead, black, and grass carp are still sometimes used in aquaculture in North America.

Q: Why were they brought here?

Bighead and silver carp were imported to the United States in the early 1970s as a method of biological control of nuisance algal blooms in wastewater treatment plants and aquaculture ponds as well as for human food.

Q. How big do they get and what do they eat?

Both bighead and silver carp become fairly large; records of both species approach 100 pounds, but silver carp over 20 pounds and bighead carp over 30 pounds are uncommon. The North American record for bighead carp is a 106-pound fish from Missouri. Both bighead and silver carp feed on plankton, algae, bacteria, and detritus (various small, organic debris) — items that form the base of aquatic food webs.

Silver carp are a large a troublesome invasive species from Asia found in the great rivers of the central United States. Silver carp have been observed to jump in response to rocks thrown in the water, passing trains, geese taking off from the water, or just when they unexpectedly find themselves in a tight place. However, a speeding boat seems to especially frighten them and often dozens of the fish will be airborne at once, sometimes reaching heights of ten feet in the air.

Q: Where are they in the United States?

Asian carp are found in the great rivers of the central United States, especially in the Missouri, Illinois, and Mississippi Rivers. Bighead and silver carp are not known to be established outside the greater Mississippi and Mobile River basins, though individuals have been captured in many locations. However, experts are quite concerned about the risk of invasion by this species to other waterways in the United States, including the Great Lakes.

Q: How abundant are Asian carp in U.S. waters?

An exponential increase in the population numbers of bighead and silver carp began in the mid-90s and continued through the mid-2000s in parts of the Mississippi and Illinois rivers. The Illinois Natural History Survey has estimated that a population of more than 4,000 silver carp (almost 10 tons) per mile  exists between two Illinois River dams that limit their movement. USGS scientists hope to use genetic methods to determine the number of spawning Asian carp in different river reaches that are not bounded by dams.

Q: Do Asian carp affect native species?

Many studies show that bighead and silver carp substantially change ecosystems where they have been introduced. Studies around the world, including a USGS study in the Missouri River, found that zooplankton populations are dramatically reduced when Asian carp are abundant.  In the presence of high densities of silver carp, large phytoplankton (plant plankton) species decline, but very small phytoplankton species, too small to be fed on by silver carp, usually become more abundant. The end result is water that appears very green but has little zooplankton. Native fish that eat zooplankton may be negatively affected by Asian carp if food resources are limited. Furthermore, since nearly all fish feed on zooplankton when they are very young, most species have the potential to be affected. There is also evidence of native planktivores being out-competed by Asian carp for food resources in the U.S. as well as around the world.

Q: I’ve seen video footage of Asian carp jumping out of the water. Do people get hurt?

Silver carp have been observed to leap into the air simultaneously as an apparent fright reaction to rocks thrown in the water, passing trains, geese taking off from the water, or when they unexpectedly find themselves in a tight place. Speeding boats seem to especially frighten them, and often dozens of the fish will be airborne at once, sometimes reaching heights of 10 feet off the water. When they collide with boaters or property, injury and damage can result.

Q: Is it possible to eradicate Asian carp once they are in an area?

Eradication of any established population of Asian carp would be extremely difficult and expensive, if possible at all. Effective management of established invasive species that cannot be eradicated usually employs integrated pest management. This approach involves integrating as many feasible methods of control available for a given species into one management and control plan, each focused at the appropriate life stage and each applied most appropriately in time and space to achieve the desired level of control while minimizing economic costs and environmental risk. Generally, possible control methods include the use of fish poisons, physical barriers, physical removal, habitat alteration, or biological controls such as the addition of predators, parasites, or pathogens. Much research to potentially control the distribution or population size of Asian carp is ongoing as part of the Asian Carp Control Strategy Framework.

Q: How might I accidentally spread Asian carp?

The capture and movement of wild-caught baitfish is of special concern for spreading Asian carp. Young Asian carp could easily be transferred, as baitfish, from one body of water to another. In particular, juvenile silver carp sometimes school with gizzard shad and are similar in size, shape, and color. If you catch your own bait, in addition to being familiar with the bait regulations of your State, it is safest to use the bait only where it was caught and not to transport it to new waters, especially above dams.

Bighead carp are a large and troublesome invasive species from Asia found in the great rivers of the central United States.

Q. Can I eat Asian carp?

Asian carp of all types have white, firm, mild flesh, which is excellent table fare, but all Asian carp also have intramuscular bones in the filets that many people find undesirable. Asian carp feed low on the food web, are fast growing, are low in fat in the filets, and are not usually bottom feeders — all properties of fish that are lower in contaminants. Like any fish taken from inland waters, however, be aware of restrictions on consuming fish from any particular water way. For instructions on how to deal with the bones in Asian carp filets, see Flying Fish, Great Dish.

Carpé Carp!

Developmental rate and behavior of early life stages of bighead carp and silver carp

Asian carp recipe

UMESC Asian Carp Page

This large Burmese python, weighing 162 pounds and more than 15 feet long at the time of its capture in 2009, was caught alive in the Everglades and was found to have eaten an American alligator that measured about 6 feet in length. University of Florida researchers in the photo: Michael Rochford is holding the python's head, and Alex Wolf and Therese Walters are holding the python's body.

Under Siege! America’s Most Unwanted Invasive Species

The United States is under an economic and ecological siege by alien invaders — America’s Most Unwanted. More than 6,500 of these harmful non-native species cause more than 100 billion dollars in damage each year to the U.S. economy as the country battles to control the economic, ecological, and health threats these invaders pose. Increased global travel and trade are providing more pathways for both intentional and unintentional introductions of invasive species.

Invasive species affect just about everyone in every State in the country, in urban centers and wilderness areas. And their costs are borne by all of us — farmers, ranchers, businesses, and local, State, Tribal, and Federal governments.

The Cost of Invasives

Costly effects of invasives include crop decimation (cactus and gypsy moths), clogging of water facilities (quagga and zebra mussels) and waterways (hydrilla, giant salvinia), wildlife and human disease transmission (West Nile virus, monkeypox, and diseases in some ships’ ballast water), threats to commercial, native, and farmed fisheries (Asian carp, snakehead fish, sea lamprey, Asian swamp eel, whirling disease, and viral hemorrhagic septicemia), increased fire vulnerability (cheatgrass, brome, and buffelgrass) and adverse effects for ranchers and farmers (leafy spurge and cheatgrass).

Researchers with the USGS Invasive Species Program work on every one of those species mentioned; in fact, our researchers work collaboratively on all significant groups of invasive organisms in terrestrial and aquatic ecosystems in all regions of the United States. Across the Nation, our invasive species experts partner with States, other Federal agencies, businesses, agriculture, and natural resource managers to help solve the problems posed by these invaders.

Key components of invasive species activities include prevention, monitoring and forecasting threats, and control and management of established invaders.

During Invasive Species Awareness Week, we will feature some of America’s Most Unwanted each day to highlight the impacts of invasive species to the nation’s Ecosystems and economy.

Burmese pythons are now found across more than a thousand square miles of southern Florida, including all of Everglades National Park and areas to the north such as Big Cypress National Preserve. This snake threatens both the native animals and ecosystems in South Florida because they eat a wide variety of prey (mammals, birds, and alligators), and pose a risk to the ecosystems and the animals that live in them, including many including threatened and endangered species. Scientists do not know exactly how many Burmese pythons are living in Everglades National Park, but they believe at least tens of thousands are there.

USGS Research on Burmese Pythons

Recent USGS research provides initial evidence that pythons may be able to survive in marine and estuarine environments such as bays, inlets and open seas. This study showed that in the lab, hatchling Burmese pythons were able to withstand exposure to saltwater long enough to indicate that the species could potentially expand its range through ocean and estuarine environments. These results raise concerns that the constrictor may invade nearby islands, such as the Florida Keys.

Other recent USGS and partner research has demonstrated that some mammal species have declined  in areas where Burmese pythons are established in Everglades National Park. For example the most severe declines, including a nearly complete disappearance of raccoons, rabbits, and opossums, have occurred in the remote southernmost regions of the park, where pythons have been established the longest. In this area, observations of raccoons dropped 99.3 percent, opossums 98.9 percent, and bobcats 87.5 percent. Marsh and cottontail rabbits, as well as foxes, were not seen at all. These mammal species were common in the park before pythons attained high densities, but research shows that their numbers have dropped dramatically over the same time that the pythons were becoming more abundant.

Fishing guide Camp Walker, Catalyst Charters, of Islamorada, Fla., took this photo of a Burmese python swimming in Florida Bay from the end of Twisty Channel toward End Key on Nov. 16, 2011.

Ongoing research may provide new tools that could limit python population numbers and help prevent further spread. In the meantime, agencies such as the USGS, National Park Service, Florida Fish and Wildlife Conservation Commission, and others are actively testing and applying control and eradication techniques, including trap development, refinement of visual searching methods, and testing detector dogs for locating pythons.

Brown Treesnakes

The invasive brown treesnake on the Pacific island of Guam is the poster child of the ecological and economic havoc an invasive species can cause. There, since the snake first invaded the island sometime right after World War II, mass extinctions of most of the island’s native birds, mammals, and lizards have occurred, which, in turn, have caused cascading and irreversible ecosystem changes.

For example, the loss of these native vertebrates means they are not available to disperse the seeds that pollinate trees and flowers. Consequently, some of the island’s native trees have greatly declined in abundance and may disappear. Similarly, as fish-eating birds have been lost from Guam by being eaten by the snakes, the natural nitrogen transport from aquatic and marine systems to bird rookeries has been lost as well, adversely affecting the growth of nitrogen-dependent plants on the island.

The Role of an Invasive

“Many invasive species take over the role previously occupied by a native species,” said USGS invasive snake expert Gordon Rodda, a scientist with the USGS Fort Collins Science Center. “While the non-native species might displace that native species, it doesn’t necessarily disrupt ecosystem processes. But when the brown treesnake came to Guam, it occupied a new role as a novel, arboreal night-time predator on birds, lizards, and mammals, a role to which these animals were not adapted.”

The result, said Rodda, is that with the extinction of most of the island’s vertebrates, the original ecosystem is simply not recoverable. It’s a cautionary tale for Florida where Burmese python populations are exploding.

Since Guam is overrun with brown treesnakes — as many as 13,000 per square mile in some places — current efforts focus on preventing them from invading the U.S. mainland or other snake-free islands such as the Northern Mariana Islands, Micronesia, and the Hawaiian Islands. This is challenging because shipping and air traffic from Guam to these other islands is a daily affair and because these snakes are masters at hiding in confined places where they can live a long time without food or water.

Prevention in Paramount

“Prevention of spread is paramount,” said Rodda. “It is much cheaper than intervention once a snake population establishes. With prey species that are unused to being hunted by snakes, invading brown treesnakes can remain well-fed with little effort while they continue to multiply. So it is crucial to keep alien species from sensitive environments.”

Without rigorous prevention, said Rodda, it is extremely difficult to control, let alone remove, an introduced reptile species. In the case of the brown treesnake, prevention efforts include working to detect stowaway snakes before they leave the island, as well as extreme vigilance on islands where the snakes are most likely to invade.

A multi-agency Rapid Response Team led by the USGS assists in detecting and capturing brown treesnakes that are found as stowaways or on other Pacific islands after being accidentally transported from Guam. This response team uses USGS research to help them improve their chances of finding snakes, as well as predicting the movements of snakes that could have accidentally made it to another island.

“If the brown treesnake gets to any of these other snake-free islands, it will find a veritable banquet of prey animals — and the same thing could happen there as happened on Guam,” Rodda noted. “It’s essential to get ahead of the curve and implement prevention efforts at the get-go, before an alien species becomes a problem.”

Of Parasites and Brown Treesnakes

As a consequence of being introduced to Guam in the late 1940s, brown treesnakes have been purged of the parasites that typically infect them in their native range, and which likely help keep their population numbers at reasonable levels. This freedom from natural parasitic enemies may help explain at least some of the ecological success of brown treesnakes on Guam.

Researchers at the USGS Western Ecological Research Center along with collaborators in Papua New Guinea, are investigating ways to exploit the natural parasitic and disease enemies of the snake as possible additional management tools for controlling the population on Guam, if not eradicating them altogether. Although much work remains to be done before experimental studies can begin on biocontrol efficacy, the findings of the USGS researchers to date are encouraging, and more exploratory work is on the horizon.

Eradicating this snake on Guam would have tremendous ecosystem, human health, and economic benefits, and would reduce the risk of invasion for other islands and the U.S. mainland.

Stalking Snakes:

Days (and Nights) in the Life of a Brown Treesnake Rapid Responder (contains a cool find-the-snake page to demo how difficult it is to see them!)

The Brown Treesnake on Guam

Brown Treesnake FAQs

Snakes in the Wrong Places: Gordon Rodda’s Career in Invasive Species Research

An American alligator and a Burmese python locked in a struggle to prevail in Everglades National Park. This python appears to be losing, but snakes in similar situations have apparently escaped unharmed, and in other situations pythons have eaten alligators. Photo by Lori Oberhofer, National Park Service.

Mid-sized mammals in Everglades National Park are getting a big squeeze from invasive Burmese pythons, according to a USGS co-authored study published in the Proceedings of the National Academy of Sciences. These pythons, large constricting snakes native to Asia that can reach more than 20 feet in length and upwards of 200 pounds, are now found throughout much of southern Florida, including all of Everglades National Park. Since the recognition 11 years ago that these invasive, exotic snakes were breeding in the park, formerly common mammals there have declined dramatically.

The status of species that are rare, patchily distributed, active during the day, or that don’t cross roads was not assessed in this new study.

The university and federal scientists who conducted the study found that the most severe declines in mammals appear to have occurred in the remote southernmost regions of the park, where pythons have been established the longest.  In this area, observations of raccoons dropped 99.3 percent, opossums 98.9 percent and bobcats 87.5 percent.  Marsh and cottontail rabbits, as well as foxes, were not seen at all in recent years, despite having been present in the 1990s.

The authors suggested that one reason for such dramatic declines in such a short time is that these prey species may be “naïve” to large constrictor snakes — that is, they are not used to being preyed upon by pythons since such large snakes have not existed in the eastern United States for millions of years. In addition, some of the declining species could be both victims of being eaten by pythons and of having to compete with pythons for food.

Florida Everglades. Photo by: USGS Florida Cooperative Fish and Wildlife Research Unit, U.S. Geological Survey

Pythons have increased dramatically in both abundance and geographic range in South Florida since 2000. Based on the geographic extent of the Burmese python population in Florida and knowledge of detection rates for other snakes, experts estimate that a population of at least tens of thousands now live in the wild in Florida, but stress that this estimate is extremely rough.  Population size may have dropped somewhat as a result of the severe cold snap of early 2010, but the population is expected to quickly recover from this unusual event.

Burmese pythons have traits that increased their risk of establishment and that make their eradication difficult. Specifically, Burmese pythons:

• grow rapidly to a large size (one over 16-feet long was captured in the Everglades in January 2012);
• are habitat generalists (they can live in many kinds of habitats);
• are dietary generalists (can eat a variety of mammals, birds and reptiles);
• may be arboreal (tree-living) when young, which puts birds and arboreal mammals such as squirrels and bats at risk and provides another avenue for quick dispersal of the snakes;
• are tolerant of urbanization (can live in urban/suburban areas);
• are well-concealed “sit-and-wait” predators (difficult to detect and difficult to trap due to their infrequent movements between hiding places);
• mature rapidly  and produce many offspring (females can store sperm and fertilize their eggs —which can number more than 100 — when conditions are favorable for bearing young);
• achieve high population densities (resulting in a greater impact on native wildlife); and
• serve as potential hosts for parasites and diseases of economic and human health significance.

As a result, Burmese pythons pose considerable challenges for the ecosystems of South Florida and many of the animals that live there, including threated and endangered species. Federal and state agencies or institutions are working hard to deal with the serious threats caused by this invasive species.  USGS research aims to help managers preserve and restore the Everglades’ ecosystems.

A female Burmese python (Python molurus) on her nest with eggs. Photo by Jemeema Carrigan, University of Florida. Courtesy of Skip Snow, National Park Service. Used with permission.

Everglades Restoration Includes the Management of Invasive Species

Invasive species are plants or animals that are non-native to a given ecosystem and which pose economic or ecological threats to native plants, animals, ecosystems, and sometimes people. In the case of the Burmese python, the new study shows that pythons appear to have begun to markedly alter the Everglades ecosystem by changing food webs through depleting or eliminating vulnerable native species. If enough animals are lost, entire ecosystem processes could be disrupted.

Scientists found little support for alternative explanations for the mammals’ decline, such as disease or changes in habitat. Scientists also ruled out predation by black bears and Florida panthers as the cause, since these populations have not grown in size during the past 15 years. Additionally, researchers ruled out mid-sized predators, such as foxes and bobcats, as the cause of these mammal declines since these two species have also experienced significant declines.

Can the Everglades be Rid of These Pythons?

The odds of eradicating an introduced population of reptiles once it has spread across a large area are very low, pointing to the importance of prevention, early detection and rapid response.  And with the Burmese python now distributed across more than a thousand square miles of southern Florida, including all of Everglades National Park and areas to the north such as Big Cypress National Preserve, the chances of eliminating the snake completely from the region is low. However, controlling their numbers and preventing their spread are critical goals for South Florida land managers. For example, a number of Burmese pythons have been found in the Florida Keys, but there is no confirmation yet that a breeding population exists in the Keys.  Given a recent USGS study that showed the python’s apparent ability to disperse via salt water, island residents and resource managers need to stay vigilant so as to be able to detect and eliminate arriving pythons before they become established.

On Jan. 23, 2012, the U.S. Fish and Wildlife Service published a rule in the Federal Register that will restrict the importation and interstate transportation of four non-native constrictor snakes (Burmese python, northern and southern African pythons, and the yellow anaconda) that threaten the Everglades and other sensitive ecosystems. These snakes are being listed as injurious species under the Lacey Act. In addition, the FWS will continue to consider listing as injurious five other species of nonnative snakes: the reticulated python, boa constrictor, DeSchauensee’s anaconda, green anaconda and Beni anaconda. For more information about the Lacey Act and the listing of these four constrictors as injurious, please visit this FWS News and Resources site.

How does USGS Research Help Managers Deal with Invasive Species?

Fishing guide Camp Walker, Catalyst Charters, of Islamorada, Fla., took this photo of a Burmese python swimming in Florida Bay from the end of Twisty Channel toward End Key on Nov. 16, 2011.

According to the USGS Invasive Species Program, the U.S. is under an economic and ecological siege by having to deal with more than 6,500 harmful non-native species estimated to cause more than a hundred billion dollars in damage each year to the U.S. economy. These costs are borne by farmers, ranchers, businesses, and local, state, tribal and federal governments battling to control the economic, health and environmental threats these invaders pose.  Invasive species adversely affect every state in the country,  in both urban centers and wilderness areas. Increased global travel and trade provides pathways for both intentional and unintentional introductions of invasive species.

Experts note that Florida has the largest number of established non-indigenous reptile and amphibian species in the entire world. Fifty-six are established including three frogs, four turtles, one crocodilian, 43 lizards and five snakes.

Researchers with the USGS Invasive Species Program work collaboratively on all significant groups of invasive organisms in terrestrial and aquatic ecosystems in all regions of the United States.  USGS plays an important role in Federal efforts to combat invasive species by providing tools, technology and information to assess, prevent, contain, control, and manage invasive species nationwide. Key components of invasive species activities include prevention, monitoring and forecasting threats, and control and management of established invaders.

For more information, see the USGS Invasive Species Program Web site.

Multi-Media:

News Releases & Other Info:

USGS News Release: Severe Declines in Everglades Mammals Linked to Pythons

USGS News Release: Salt Water Alone Unlikely to Halt Burmese Python Invasion

Everglades and Python Prey Study FAQs

Video:

Title: Constrictor Snakes
Description: Video footage (B-roll) of Everglades National Park biologists hunting and capturing a Burmese Python in Florida.

URL: http://gallery.usgs.gov/videos/169