Waterways Ireland has warned the public to be on the alert for a very “large invasive rodent” species which has been spotted along the Royal Canal in Dublin.

Sightings of coypu, a semi-aquatic creature with bright orange teeth, a long cylindrical tail, and webbed back feet have been reported near the Ashtown area of the canal close to Castleknock.

The rodents, which can be up to a metre long and weigh up to 9kg, carry a number of diseases harmful to humans and domestic animals.

Waterways Ireland has issued an “invasive species alert” and warned the public “not to engage” the animals or make any attempt to trap them but to report any sightings, with photographs where possible.

Coypu are “highly invasive impacting on wildlife, river and canal bank stability and is a pest of agriculture crops”, Waterways Ireland said.

“Eradication programmes can cost several millions of euro and are not always successful.”

“Its appearance is similar to a very large rat; it could even be mistaken for a bulky otter at first sight,” Waterways Ireland said, but unlike an otter it does not have a fur tail but a “long rat-like tail”. Coypu are vegetarian, and particularly like carrots and parsnips.

The “invasive alien species” originates from wetlands in South America, and is thought to have arrived in Ireland about five years ago. It is believed the animal was introduced as a novelty attraction to a pet farm in Cork but some escaped in 2014 and began breeding on the outskirts of Cork city.

In 2016, 10 coypu were shot on the Curraheen river on the outskirts of the city. Sightings should be reported to Waterways Ireland and National Parks and Wildlife Service which will undertake “eradication measures”.

A successful eradication programme in East Anglia in Britain in the 1980s “took 10 years and cost several million pounds sterling”, Waterways Ireland said.