Use of citizen science to assess the success of reintroduction of Red Squirrels Sciurus vulgaris on Mersea Island, Essex

The Eurasian Red Squirrel is the only native tree squirrel in Europe and is widely dispersed throughout the Palearctic but is heavily threatened in Britain and parts of Europe by habitat loss, disease and, in particular, by competition from introduced Grey Squirrels. Red Squirrels have now been replaced by Grey Squirrels throughout the majority of Britain and only remain in areas of Northern England and Scotland, and small regions in Wales and Southern England. Mersea Island was a site of a reintroduction programme, with a total of 29 Red Squirrels being released in batches at three different sites between 2012 and 2015. Squirrels were monitored by members of the public who recorded their sightings on social media pages. This study analysed these sightings from September 2012 to August 2017. The population of Red Squirrels rose steadily over the study period, as did interest from the public. Sightings were biased to areas of increased human habitation, but the distribution of Red Squirrels still appeared to be increasingly widespread across the island over the years. The density of Red Squirrel sightings significantly positively correlated with density of greenery cover, and was significantly affected by type of habitat (rural versus suburban). Most reported fatalities were anthropogenic in nature. The reintroduction project on Mersea has been relatively successful, but areas for improvement could include connection of woodland fragments, increased public awareness and monitoring of genetic diversity, to improve the chance of maintain and maximising the population size of Red Squirrels on the island