The little rodent turns out to be a (baby) Bank Vole.
After the UK mainland broke its ties with continental Europe, from the coastal area of Western France, those land animals which found themselves on the broken on landmass, were stuck. By the time the western rock broke itself off, a lot of these UK mammals had not found their way west. (yet) and so, like before, we have ended up with a lower number of mammals. We have no Moles, nor any Weasels, nor Wildcat, to name but a few. Neither have we got a Field Mouse/Vole and no Water Vole.
The result of having so few of these smallish rodents, is that there is not enough food for predators such as Owls, and this little Vole therefore, is a great addition to the menu of not only Owls, but also Foxes.
In 1925, for the damming of the Shannon, a German company was asked to come and do the job. Loading their own heavy earth moving machinery, the Germans set sail to the west of Ireland.
39 years later, in Listowel, county Kerry, a German student spotted a little Bank Vole, discovering the island's first such Vole. The fact that a new species made its entree in the west was highly unusual. Usually, new ones are discovered in the east where they set foot first after coming here from the UK. They can easily be transported in cargo crates, lorries, or any other way of hitching a ride. The way this little Vole made it to the country is a lovely story, if ever there was one. It has colonised the south west of Ireland, and is now moving east at 4kilometres a day.