Squirrel Pox

The survival of native Red Squirrels is threatened by a disease spread by Grey Squirrels.

Red Squirrels are native to Great Britain - at the beginning of the 20th Century they were the only squirrels found here.  After Grey Squirrels were introduced the range of the reds reduced dramatically.  Initially it was thought that this was as a result of competition for food and other resources, however it is now believed that the transmission of the disease 'Squirrel Pox' played an important role.

Grey Squirrels are carriers of Squirrel Pox, but it doesn't kill them.  It does kill Red Squirrels and so when an outbreak occurs the Greys are able to quickly take over from the dying out Reds.
Native red squirrel on a branch
Native red squirrel suffering from squirrel pox

Thin strip of image show tree trunk and bark