Wildlife experts are warning that a virus is killing endangered Red Squirrels in Anglesey.
The red squirrels Wales Trust says that tests carried out on dead red squirrels on the island revealed that a lethal strain of the Adenovirus was present in 65 percent of the animals.
Newborough, Pentraeth, and Holy Island have been identified as Anglesey's hotspots for the virus.
The Trust's Project Manager, Dr Craig Shuttleworth, says infected red squirrels look perfectly normal a few days before they die, with the virus affecting their digestive systems.
– Dr Craig Shuttleworth, Red Squirrels Wales Trust
If you were to take a photo a few days before it dies, the infected red squirrel would look perfectly normal.
But then 24 hours later, it will have diarrhoea and it will drop down dead the next day.
The virus causes legions in the Squirrel's gut.
The cause of the virus has yet to be identified, but mice and grey squirrels on Anglesey have also been found to have the disease.
However, Dr Shuttleworth says that there is not yet any sign the virus can be passed on to humans or domestic pets such as cats, dogs, or guinea pigs.
A threat to the species
Red squirrels were re-introduced to Anglesey 15 years ago in an effort to save the endangered species.
The island is Wales' refuge for Red Squirrels, whose numbers are threatened by the grey squirrel.
Between just 400 and 500 red squirrels remain on Anglesey, where a programme to eradicate the grey squirrel is in place.
Dr Craig Shuttleworth says the further hit to the red squirrel population posed by the virus would be substantial:
– Dr Craig Shuttleworth
This is just the tip of the iceberg. Most of the red squirrels that are dying from the virus will not be discovered.
Although this is not an epidemic, our research suggests a significant, ongoing background of mortality all the time.
We could have a scenario with clusters of the virus causing local extinction, or perhaps killing the only female in that forest.
As seed dispersers who help to germinate and spread forestation, the red squirrel is a vital part of Anglesey's ecosystem.
But their value to the local community is also economic, as an attraction for tourists.
– Dr Craig Shuttleworth
The red squirrel in Anglesey is like India's Tigers - you might not see them when you're there, but just knowing they exist adds to your experience.
Our Correspondent Carole Green reports on the threat posed to Wales' largest single population of red squirrels by this mystery virus.