Previously unrecorded hazel dormice have been found at a Southern Water site in Brede, East Sussex.
The mice were found by the company’s environmental specialists who placed nesting boxes in woodland neighbouring the water supply works.
Environmental Adviser Steve McAuliffe said: “The conservation status of the species in the UK is ‘rare and vulnerable to extinction’ so finding them on Southern Water land and confirming a new population is great news.
“Now that we know this rare and charismatic species is there, we can do some work to bolster and safeguard the population.”
The location has been registered with the Sussex Biodiversity Records Centre and studies will continue.
Steve said: “I think the finding of this species really emphasises the important role Southern Water can play in wildlife conservation.”
Dormice are the latest discovery made at the Brede site. The site is also home to several bird of prey, great crested newts and rare bee orchids.