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National Invasive Species Awareness Week: Snakes, Starlings, and Swine, Oh my!

Posted by Gail Keirn, USDA APHIS Public Affairs Specialist in Animals Plants
Feb 21, 2017
A brown treesnake, European starlings and feral swine
Brown treesnakes, European starlings and feral swine are just a few of the invasive species whose damages are lessened by Wildlife Services activities. Photos by USDA.

This month USDA highlights some of the important partners that work with us to care for our land, air, water, and wildlife.  The National Invasive Species Council is one such group.

When you hear the word “invasive,” most people automatically think of bugs and weeds. Unfortunately, invasives (or non-native pests) can also include wildlife, such as birds, reptiles, amphibians, and mammals.

It is estimated that 50,000 animal and plant species in the United States are non-native, meaning they are not naturally found here. Approximately 5,000 are considered invasive because of the ecological and economic damages they cause. That’s why the National Invasive Species Council and APHIS Wildlife Services (WS) are raising awareness about the negative impacts caused by invasive species in America as a part of National Invasive Species Awareness Week.

“Invasive species present some of the greatest challenges to conservationists. Brown treesnakes, European starlings, feral swine, and nutria are just a few of the more than 50 invasive wildlife species we work with,” states WS Deputy Director for Wildlife Operations Steve Kendrot. “Our experts use a variety of tools and strategies to identify and measure the economic and biological impacts of invasives, prevent their spread, and reduce their damage to agriculture, natural resources and property.”

Below is just some of the research and operational work being done by WS professionals to reduce the impacts of invasive wildlife.

Brown treesnakes: The brown treesnake (BTS) was accidentally introduced to Guam in the late 1940s. With no predators, the snake's population has grown to an estimated 1 to 2 million. BTS are responsible for the extinction of most native bird, bat, and lizard species on the island and have caused extensive damage to the island's economy and electrical grid. The unintentional movement of BTS through shipping or travel represents a very real danger to other Pacific islands and sections of the U.S. mainland. The potential BTS colonization of the Hawaiian Islands alone could cost as much as $2 billion annually. Since the late 1980s, WS has collaborated with other agencies on Guam to reduce BTS numbers, prevent their spread, reclaim natural areas for the reintroduction of native wildlife, protect endangered species, improve public health, and protect power stations and other sensitive locations from intrusion. To achieve these aims, WS research encompasses the development of repellents, attractants, toxicants, fumigants, reproductive inhibitors, and improved trapping and baiting methods— including a new aerial bait delivery system.

European starlings: European starlings easily adapt to a variety of habitats and food sources. More than 200 million starlings live in North America. Often gathering in large flocks and roosts, they can damage crops, cause sanitation and disease problems, compete with native birds, and consume and contaminate livestock feed.

During 2014, WS specialists removed more than 1.1 million European starlings and dispersed an additional 7.8 million from areas where they were not wanted. Techniques vary from hazing devices, such as propane cannons and other noise makers, to repellents and toxicants. WS researchers are investigating new management tools, as well as the role starlings play in disease transmission, particularly at feedlots and dairies.  Additionally, WS economists are highlighting the impacts of these birds by calculating damage estimates related to crop loss, livestock feed consumption, and disease transmission.

Feral swine: Introduced to America in the 1500s, feral swine were not considered a threat until the early 1980s when their populations expanded and their damage and disease threats increased dramatically. These invasive species are known to contaminate watersheds, damage and eat crops, compete with native wildlife, and transmit diseases. To address this growing problem, APHIS recently established the collaborative National Feral Swine Damage Management Program with the goal of reducing feral swine damage in every state with a recognized population. WS leads this national effort. To accomplish its goal, the program works closely with local, state, and federal agencies. It also partners with WS researchers to improve control efforts, conducts outreach to raise awareness, and leads a national population monitoring and disease surveillance effort to better understand feral swine distributions and impacts to America’s resources.

Nutria: These semi-aquatic South American rodents cause significant environmental and agricultural damage in coastal marshes. WS is part of a multi-agency partnership to eradicate nutria at and around Blackwater National Wildlife Refuge in the Chesapeake Bay. Since 2002, nutria have been nearly eliminated on 250,000 acres of wetlands in the Bay, with the last removal in the spring of 2015.  For the final phase, WS is providing five teams of handlers and scat-detection dogs as part of a 12-member crew searching to confirm the absence of nutria on the Delmarva Peninsula.

To learn more about invasive species control and prevention efforts, please visit the following websites:

NOTE: For an interactive look at USDA's work in conservation and forestry over the course of this Administration, visit

Category/Topic: Animals Plants

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Laurella Desborough
Feb 22, 2016

I did not see feral cats on the list of invasive species. These feral cats are a serious threat to native wildlife, birds, small mammals, including baby rabbits, lizards and just about anything they can manage to catch. It seems to me that there needs to be a lot more attention paid to the removal of feral cats from wild areas and requiring all ferals that are caught to be kept in secured facilities, not returned as in TNR.

ed frankel
Feb 23, 2016

As to feral cats, a very emotional subject which I am very well aware of. As a veterinarian involved in wild life care, survival,destruction, and euthanasia I have very strong negative opinions of TNR and even maintaining feral cat colonies in the wild. With a first hand view of numerous viral and parasitic diseases afflicting feral cats, zoonnotic diseases, starvation, and lack of veterinary care.Suffering.

Virginia Currie
Mar 02, 2016

what about protection of a native cat, Puma concoloris? A hunter shot and killed a cougar in bradley county arkansas in October 2014 without any repercussions from the fish and wild life. although the cat was just walking by the hunter's deer stand, because this person claimed he feared for his life, he was able to kill an endangered apex predator no problem. if people were more educated in the roles that our native species played, particularly keystone species and apex predators--maybe we could help mitigate some of the other issues we face

Ben Weaver
Mar 09, 2016

@Virginia Currie - thank you for your comment. The management of wildlife species, such as the mountain lion, is primarily the responsibility of State natural resources or fish and game agencies. USDA-APHIS Wildlife Services partners with these agencies to help reduce problems that may arise between people and our native wildlife, as well as invasive species. Wildlife Service works at the request of other groups.