Ten of The Most Invasive Animal Species in Great Britain

Invasive animal species are those not native to a region and can cause significant harm when introduced. Their presence can threaten native species, disrupt ecosystems, and even pose risks to the economy and human health. Over the centuries, various animal species have been introduced to Great Britain, either accidentally or intentionally. While some integrate without causing harm, others have proven detrimental to native species and habitats.

The following list is based on the animals’ ecological impact, rapid spread, and potential economic implications.
Ten of The Most Invasive Animal Species in Great Britain

1. Grey Squirrel (Sciurus carolinensis)

Originally from North America, they’ve played a role in the decline of the native red squirrel due to competition and disease transmission.

Signal Crayfish (Pacifastacus leniusculus)

2. Signal Crayfish (Pacifastacus leniusculus)

This North American species threatens the native white-clawed crayfish through competition and the spread of crayfish plague.

Harlequin Ladybird (Harmonia axyridis)

3. Harlequin Ladybird (Harmonia axyridis)

Introduced for pest control, it competes with native ladybirds and can become a household nuisance.

Mink (Neovison vison)

4. Mink (Neovison vison)

Introduced for fur farming, escaped minks have caused a sharp decline in water voles and affect ground-nesting birds.

Rose-ringed Parakeet (Psittacula krameri)

5. Rose-ringed Parakeet (Psittacula krameri)

Originally from Africa and South Asia, these birds can compete with native species for nesting sites.

Terrapins (e.g., Red-eared slider, Trachemys scripta elegans)

6. Terrapins (e.g., Red-eared slider, Trachemys scripta elegans)

Released into the wild from the pet trade, they predate on native species and disrupt aquatic habitats.

Chinese Mitten Crab (Eriocheir sinensis)

7. Chinese Mitten Crab (Eriocheir sinensis)

This crab can destabilise riverbanks by burrowing and competing with native species for food.

Raccoon (Procyon lotor)

8. Raccoon (Procyon lotor)

Escapees from captivity, raccoons can be potential predators of native species and can transmit diseases.

Monk Parakeet (Myiopsitta monachus)

9. Monk Parakeet (Myiopsitta monachus)

These South American birds can damage crops and infrastructure with their large communal nests.

American Bullfrog (Lithobates catesbeianus)

10. American Bullfrog (Lithobates catesbeianus)

Introduced from North America, they can out-compete and even eat native species, including protected ones.

In addition to the ecological damage, invasive animal species can lead to economic burdens, from managing their populations to rectifying the damage they cause. Conservationists, governmental agencies, and communities are working together to control these species. This includes monitoring, eradication projects, and public education. People can assist by reporting sightings, refraining from releasing non-native pets into the wild, and supporting local conservation initiatives. Vigilance and action are crucial in addressing the challenges posed by invasive animal species in Great Britain.

Further Reading & Resources

“Silent Invasion” by James Russell
GB Non-native Species Secretariat website
DEFRA’s Invasive Non-Native Species Framework Strategy

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