Non-Native Invasive Species


Potentially harmful, invasive, non-native species are as much a threat in the Isle of Man as in other parts of the world, with the increase in the transport of plants and animals by human activity and through climate change. The UK has developed a strategy for coping with these harmful species with a very helpful website, newsletters and regular alerts.

This page will provide information relevant to the island as it becomes available.

Skunk Cabbage

Is this wetland plant likely to spread and become an invasive nuisance? It has escaped from more than one garden in the north of the Island. It is Lysichiton americanus. Its common name is American or Yellow Skunk Cabbage. This photograph, from a wetland in Norfolk (South Walsham Broad), shows how dominant it can become.

Chinese Mitten Crabs

Found in rivers, brackish water estuaries and rarely along marine inshore coast. Not yet seen around the island but has spread across the UK. See the Mitten Crab Recording project website.


Flatworms, sometimes known as Planaria, are small and slimy but also quite mysterious, with a hermaphrodite sex life. They particularly like the damp mild climate of the north western areas of the British Isles.  There are two groups of flatworms, those with two eyes include the four probably native species (Microplana spp.) and those with multiple eyes, which are all introduced. The introduced species pose a potential threat to native earthworm populations. There are now at least ten of these alien species in the British Isles.

Five species of flatworms have been recorded in the Isle of Man, three of which are potentially harmful  invasive aliens. These are:

Invasive flatworm species:

Arthurdendyus triangulatus

New Zealand flatworm

5-20cm long. Dark brown or purple/brown with pale spotted margin or underside. Shiny black egg capsules. It is an offence under the UK Wildlife and Countryside act to knowingly distribute this species in the UK because of the damage it can do. See pictures.

Australoplana sanguinea

Australian flatworm

2-8cm long. Orange or pinkish with many minute eyes showing as black dots. Eats earthworms and is therefore a potential threat. See picture.

Kontikia andersoni

1-2.5cm long, pale brown with 3 rows of darker brown spots, unknown origin. Scavenges small, dead invertebrates. See picture.

Native flatworm species:

Microplana terrestris

Two-eyed, 1-2 cm long, black, dark grey to brown, the most common UK species. A scavanger, feeds on dead slugs and earthworms.

Microplana scharffi

Two-eyed, 2-5 cm long, bright yellow sometimes yellow grey or pinkish. Apparently a scavanger.