North American Beaver
Castor canadensis
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Photo credit: WWF © Sarah Pietrkiewicz
Castor canadensis - North American Beaver
Description:
Habitat:
Origin and Distribution:
Impacts:
Is it found in Northern Ireland?
How could it get here?
Prevent Spread
Current legislative position (Enters into force: 07 August 2027): This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.
For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email: invasivespecies@daera-ni.gov.uk
Castor canadensis - North American Beaver
Description:
- A large, herbivorous, semi‑aquatic rodent reaching up to 1.20m in length and 18–47 kg in weight
- Fur colour ranges from yellowish‑brown to black, with reddish‑brown the most common
- Long coarse guard hairs overlay dense, lead‑grey underfur
- Distinctive broad, scaly, flattened tail, dark in young animals and lighter with age
- Strong swimmers
- Robust incisors and powerful jaws for felling trees and manipulating woody vegetation
Habitat:
- Always found near water, including ponds, lakes, rivers, and still or slow‑moving streams
- Requires surrounding forest for both food and building materials (especially willow and aspen)
- Builds characteristic wood‑and‑mud lodges either in open water or on pond/lake edges
- Constructs watertight dams to create ponds suitable for lodge building
Origin and Distribution:
- Native to North America, historically widespread across Canada, the United States, and parts of northern Mexico
- Introduced intentionally in several regions, including Finland, Poland, and Tierra del Fuego (southern South America)
- Some introductions resulted from mistaken reintroduction programs meant to restore the European beaver (Castor fiber)
- Established populations present in Finland, northwestern Russia, and a Western European cluster covering parts of Germany, Belgium, and Luxembourg
Impacts:
- Considered a powerful ecosystem engineer, altering hydrology, vegetation, nutrient dynamics, and geomorphology
- Deforestation accelerates erosion, sedimentation, and loss of riparian tree regeneration
- Beaver‑created ponds increase aquatic productivity, but drastically reduce macroinvertebrate diversity
- Alters water chemistry: increased nitrogen concentrations, organic material accumulation, and changes in sediment composition
- Beaver dams can block fish migration, cause flooding, and increase water temperature in impounded areas
Is it found in Northern Ireland?
- It is not currently present in Northern Ireland
How could it get here?
- Human‑mediated translocations primarily motivated by fur trade interests or mistaken conservation efforts
Prevent Spread
- Prevention via enforcing the IAS (Enforcement and Permitting) Order (Northern Ireland) ensuring that Castor canadensis is not introduced to Northern Ireland
- Reporting any sightings so that Rapid Response can be instigated
- You can help by reporting any sightings: @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.
Current legislative position (Enters into force: 07 August 2027): This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.
For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email: invasivespecies@daera-ni.gov.uk