Invasion Risks

Invasive alien species (harmful non-native organisms) are considered one of the major threats to native wildlife and habitats worldwide. The escape and release of former pets has been identified as a source (pathway) for the introduction of invasive animals into natural environments. Not only can these former pets become invasive, but so can other organisms associated pets and pet care.

Possible sources of invasive alien species introduction through the pet trade pathway include:


• Release of unwanted pets or live pet food (e.g., feeder fish, crickets);

• Outdoor disposal of unwanted plant material associated with aquariums, terrariums, or water gardens that house pets;

• Outdoor disposal of pet food containing viable seeds or rootable plant material;


• Escape of pets or live pet food that are poorly contained;

• Introduction of pathogens and parasites that “hitchhike” on pets or organisms used for live pet food that are released or escape; and

• Introduction of plant material, pathogens, or parasites when pet housing (e.g., aquariums/terrariums, bird cages), toys, feeding dishes, and other supplies are cleaned outdoors.

Many (perhaps most) pets and associated organisms that escape or are released into the natural environment are unable to survive due to inappropriate climatic conditions, predation, or the hazards of human development (e.g., road traffic). However, under ideal conditions, not only do these organisms survive, they thrive and become invasive alien species - causing significant harm to the environment, human and animal health, and/or the economy.

The greatest risks for the introduction of animals through the pet trade pathway are likely to be associated with:

• Release by/escape from consumers (pet owners). Commercial businesses have an economic interest in protecting their “inventory;”

• Non-regulated direct sales – such as sales through the internet and newspapers, hobbyist shows, flea markets, etc. This is a rapidly growing segment of the pet industry. People who purchase pets in this manner may be making “spontaneous purchases” that are not well thought through and they may be more likely to receive animals that are in poor condition (i.e. more likely to have pathogens or parasites);

• Pets that are free or inexpensive. Because there is relatively little financial investment in these animals, the owners may be more included to release them when they no longer wish to care for them;

• Species which grow large, reproduce easily and in large numbers in captivity, have specialized dietary or other husbandry requirements, and have aggressive temperaments. These animals require a relatively greater investment of care and money. Owners who are not prepared to meet the animals’ needs may choose to release them; and

• Species ecologically suited to the geographic region in which they are maintained as pets. When these animals enter the natural environment they have the potential to survive the weather conditions. If they can reproduce, they might establish a viable population and spread

Escaped/released pets can predate upon and compete with native wildlife, threatening entire ecosystems. They can also spread pathogens and parasites to people, livestock, pets, and wildlife. In some cases, former pets can become agricultural pests.

When plants (including seeds) associated with pet care enter the natural environment, they can establish and spread to such an extent that they outcompete native plants and cause wide-scale disruptions to ecological systems. Some invasive aquatic plants have become so abundant that they hinder boating and recreational fishing.

Examples of invasive alien species that were likely introduced, intentionally or unintentionally, into natural environments through the pet trade pathway include:

• Red-eared turtles (Trachemys scripta elegans) (also human food pathways)

• American bullfrogs (Lithobates catesbeianus; formerly Rana catesbeiana) in water gardens (also human food pathways and bait)

• Monk/Quaker parakeets (Myiopsitta monachus)

• Lionfish (Pterois volitans) (also possible introduction by divers and public aquarium)

• Feral domestic cat (Felis domesticus/Felis catus)

For more information on the pet trade pathway in general, we invite you to read the attached article entitled, HabitatittudeTM: Getting a Backbone about the Pet Release Pathway.

For more information on the pet trade pathway and disease, we invite you to read the attached article entitled, All Creatures Great and Minute: A Public Policy Primer for Companion Animal Zoonoses.



Key Terms



Alien species

Species, subspecies or lower taxon, introduced outside its natural past or present distribution; includes any part, gametes, seeds, eggs, or propagules of such species that might survive and subsequently reproduce (CBD Guiding Principles)

Sometimes also called: non-native species, non-indigenous species, or exotic species

Invasive alien species

An alien species whose introduction and/or spread threaten biological diversity (CBD Guiding Principles). Some definitions also include threats to human health, animal health, and the economy.

Sometimes also called: invasive species, invasive non-native species, injurious wildlife, noxious weed, plant pest, or unwanted organism


The movement by human agency, indirect or direct, of an alien species outside of its natural range (past or present). This movement can be either within a country or between countries or areas beyond national jurisdiction (CBD Guiding Principles).

Risk assessment

The evaluation of the likelihood of entry, establishment or spread of a pest or disease within the territory of an importing Member according to the sanitary or phytosanitary measures which might be applied, and of the associated potential biological and economic consequences’ (WTO-SPS Agreement).

Environmental biosecurity

Protection of the environment and social amenity from the negative effects associated with invasive species; including weeds, pests and diseases. It occurs across the entire biosecurity continuum: pre-border preparedness, border protection and post-border management and control (Australian biosecurity policy)







US Aquatic Nuisance Species Task Force


Convention on Biological Diversity.


Convention on International Trade in Endangered Species of Wild Fauna and Flora


European and Mediterranean Plant Protection Organization


European Union


Global Invasive Species Programme


International Plant Protection Convention


IUCN Invasive Species Specialist Group


International Union for the Conservation of Nature


US National Invasive Species Council


World Organization for Animal Health


CBD Subsidiary Body on Scientific, Technical and Technological Advice


WTO Agreement on the Application of Sanitary and Phytosanitary Measures


United Nations Environment Programme


World Trade Organization



"Anyone who has accustomed himself
to regard the life of any living creature
as worthless is in danger of arriving also at the idea of worthless human


 - Albert Schweitzer, Alsatian Theologian, Musician, and Medical Missionary


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