London, May 12 (ANI): Elisabeth Fritzl's five-year-old son Felix is making an amazing recovery, say doctors treating him.

The little boy, who had never seen daylight while caged in a windowless underground cellar by father Josef is now showing improvement and has stopped communicating by grunts. He is also walking normally.

"The grunts and growls it was suggested he and his brother Stefan used appear only to have been the excitement of their release," Mirror quoted a source, as saying.

While all the doctors treating Felix are surprised by his ready wit and enthusiasm for everything new in his transformed life, they are captivated by how he reacts to sunlight.

Every morning, with the rising sun, he is seen with a radiant smile wearing his special protective goggles.

Meanwhile, Felix and his mother Elisabeth and his other five siblings are seen bonding like a new family. While three of the kids were caged with their mother, the other three lived upstairs after being adopted by Fritzl and wife Rosemarie.

"Only Elisabeth and Felix have increased photosensitivity and need goggles. The boys are making a good recovery, especially Felix. Both are polite and seem to have had respect instilled into them," Mirror quoted Dr Berthold Kepplinger, senior consultant at the Landesklinikum in Mauer, outside Amstetten, as saying.

He added: "They do exactly what their mother tells them and have the basics of reading and writing. Felix has a keen intelligence which shows with his enthusiasm for everything. We love his wit and outgoing personality." (ANI)