I did several internet searches and came up empty. The only two references I pulled up were a glossary that referred to the book series I was reading, and a medal of some sorts that a Japanese (I think) man received.
The book series I read talked about a donbeag as if it were some sort of small furry creature, a rodent perhaps. Is this a real creature, or did the author make it up? It’s a fantasy series, so that’s possible. And does anyone know of any pictures if it is a real creature?
Other than that, I dunno. It’s not in any of my on-line dictionaries, nor in my 20 pound hardcover Webster’s Deluxe Unabridged, so obviously it’s not a real critter. If it was a real animal, Google would have brought SOMETHING up. There’s no animal so strange that it doesn’t have its own web page somewhere. I’d say the author either made it up, or appropriated some obscure Gaelic term that only folklorists would know about.
Since even my search on “alactaga” (another small, obscure furry animal) brought up 72 hits on google, I think we can conclude that your critter is fictional.
I emailed the author and she responded that the donbeag is indeed just a figment of her imagination, though she said it is similar to an Australian sugar glider.