Office of Law Enforcement
Pacific Region/Pacific Southwest Region



February/March 2010

We’re Being Invaded! Part I


There are many TV shows and movies depicting aliens with plans to invade or take over planets that aren’t their own.  In Independence Day, aliens travel from planet to planet, destroying all life and harvesting the planet’s natural resources before moving on.  The alien population, the Borg from Star Trek, can rapidly adapt to any situation or threat through assimilation and they threaten to take over all of the United Federation of Planets.  Both of these examples are from science fiction movies and may seem crazy and farfetched, but similar events are taking place on our earth as you read.

We have organisms, referred to as invasive species, on our planet right now that act much like the aliens described above.  Invasive species are organisms that are introduced into an ecosystem where they did not originate from and which cause, or are likely to cause, harm to the economy, environment or human health. Invasive species have many characteristics in common such as: a high rate of reproduction, short generation times, a long life span, the ability to live in many types of habitats, and abundant population in their native range, to name a few. Click here for more information.

There are a few common ways invasive species make their way into the U.S. Some have actually been deliberately imported and released to help control “pests” or solve agricultural or aquacultural problems.  Others have been imported for the pet trade, but have been released by their owners into the wild.  Often these animals have no natural predators in the ecosystem where they are released.

Sea lamprey is a snake like fish considered an invasive species
The sea lamprey is a snake like fish which is considered an invasive species in many parts of the country. Photo credit: U.S. Fish and Wildlife Service

Another way invasive species make their way into new ecosystems is by “hitching a ride” on shipments that travel long distances. For example, zebra mussels have come to our waters on ship ballast tanks and brown tree snakes have been found in cargo crates on shipments coming to the U.S. from Guam. Finally invasive species can find their way into the U.S. by travelers bringing them here without realizing how harmful the plant or wildlife is outside of its native ecosystem.

Mitten crabs have hair on their claws which gave rise to their name.
Mitten crabs have hair on their claws which gave rise to their name. Photo credit: Christian Fischer/Creative Commons

Once invasive species are introduced into an ecosystem, the negative effects that could result are numerous. For example, mitten crabs are a species of crab originally from the coastal estuaries of eastern Asia from Korea in the north to the Fujian province of China in the south. However, now the mitten crab has made its way into many U.S. waterways. Some suggest the mitten crab has entered the U.S. by being shipped here as a culinary delicacy. The crab is a famous delicacy in Shanghai cuisine and is prized for the female crab's ovaries. The crab meat is believed by the Chinese to have a "cooling" (yin) effect on the body. But its presence in our waters can wreak havoc on the environment and the economy. Mitten crabs can cause considerable damage, eroding embankments with their burrows, fowling fishing gear and clogging water intake equipment for power plants. In California and Europe, economic losses have been significant. For example, San Francisco removed 50 tons of mitten crabs from fish screens at great cost in 1998.

The U.S. Fish and Wildlife Service Office of Law Enforcement plays a role in preventing the introduction of invasive species into the U.S. through the enforcement of the Lacey Act (.pdf 1,904kb) (18 U.S.C. 42 ) and its implementing regulations (50 CFR 16).  The Lacey Act makes it illegal in the United States to import  injurious wildlife or transport such wildlife between states without a permit.

The term “injurious wildlife” refers to a defined list of species identified in either the Lacey Act itself or in the related regulations (see below). Species are placed on the list when they are determined to be injurious to: human beings; the interests of agriculture, horticulture, forestry, or wildlife; or wildlife resources in the U.S.  For more information about this process, click here (.pdf 1,904kb).

The penalty for an injurious wildlife Lacey Act violation is up to six months in prison and a $5,000 fine for an individual or a $10,000 fine for an organization.

Not all species generally considered invasive are listed as injurious under the Lacey Act.   This law only authorizes the listing of mammals, birds, reptiles, amphibians, and fish (including crustaceans and mollusks) as such.  The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, however, regulates the importation of harmful plants and some other organisms (including insects and some other non-vertebrate organisms) that do not fit into the Lacey Act definition of “injurious wildlife.”  Many States have also identified and banned specific wildlife and plant species as invasive.

Injurious species that cannot be imported into or transported across state lines in the U.S. without permits issued by the U.S. Fish and Wildlife Service as of January 2010 include:

Live wild mammals (50 CFR 16.11) please click on the link for scientific names

  • Flying fox
  • Fruit bat
  • Mongoose
  • Meerkat
  • European rabbit
  • Indian wild dog
  • Red dog
  • Dhole
  • Multimammate rat or mouse
  • Raccoon dog
  • Brushtail possum

Dhole. Photo credit: Ralf Schmode/Wikimedia Commons

Live wild birds or their eggs (50 CFR 16.12) please click on the link for scientific names

  • Pink starling or rosy pastor
  • Dioch including the black-fronted, red-billed and Sudan dioch
  • Java sparrow
  • Red-whiskered bul-bul

Live or dead fish, mollusks, and crustaceans, or their eggs (50 CFR 16.13) please click on the link for the scientific names

  • Walking catfish (alive including viable eggs)
  • Mitten crabs (alive including viable eggs)          
  • Zebra mussels (alive including veligers and viable eggs)
  • Snakehead fish (alive including its viable eggs or gametes)
  • Silver carp (alive or including hybrid species as well as its viable eggs or gametes)
  • Largescale silver carp (alive including hybrid species as well as its viable eggs or gametes)
  • Black carp
  • Uneviserated salmonid fish (dead or alive including live fertilized eggs or gametes)

Silver carp
Silver carp can jump up to 10 feet out of the water when motorized vessels pass by. This behavior has resulted in injuries to boaters. Photo credit: U.S. Fish and Wildlife Service

Live reptiles or their eggs (50 CFR 16.15)

  • Brown tree snake (live specimen or egg)

The Service may issue permits allowing importation or interstate transport of these species for zoological, educational, medical, or scientific purposes.  For information on obtaining a permit, click here

Burmese python in the Everglades
Burmese python in the Everglades. Photo credit: Public domain/Wikimedia commons

Currently, the Secretary of the Interior, Ken Salazar, is moving to list nine giant invasive snakes under the Lacey Act as injurious wildlife. They include the: Burmese python, northern African python, southern African python, reticulated python, green anaconda, yellow anaconda, Beni or Bolivian anaconda, DeSchauensee’s anaconda, and boa constrictor. This would make it illegal for anyone to import these species into the United States or transport them from one state to another.  Some of these snakes have already established themselves in the wild in Florida, where they have no natural predators and are damaging the Everglades and other ecosystems. For more information on this, click here.

The next edition of Sam Says will talk about some of the most dangerous invasive species and the damage they cause.  Stay tuned…

To contact the U.S. Fish and Wildlife Service about this piece or to report a violation you have witnessed, please go to and click on the “contact us” link at the top of the page.



Last updated: March 24, 2011

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