Lake Sibolla, truly a mosaic of different ecosystems, is an important habitat for the many species of vertebrates associated with water, in particular fishes, amphibians and numerous birds.

Over the last few years, in fact, one of the most beautiful heronries in Tuscany has become established at Sibolla,  with as many as 5 regularly nesting species including the Night Heron (Nycticorax nycticorax) and the Great White Egret (Casmerodius albus).

Among the other species nesting in the reserve, mention should also be made of the  Marsh Harrier (Circus aeruginosus), Coot (Fulica atra), Water Rail (Rallus aquaticus) and the Green Woodpecker (Picus viridis).

Ducks are far less common, but the number of nesting Mallard (Anas platyrhyncos) is on the increase. 

The poor quality of the water, due to widespread pollution over all the area, and the prolonged partial drying prior to 2004 on the contrary have drastically reduced the ichthyic component of the fauna which, except for a few allochthonous species like the Black Bullhead (Ameiurus melas) and Mosquito or Gambusia Fish (Gambusia sspp.), today only counts a few individuals of Common Carp (Cyprinus carpio) and European Eel (Anguilla anguilla).

The introduction of other species is planned but so far has not been put  into effect
Among the reptiles, the recent sighting in the Lake Sibolla of some individuals of the European Pond Terrapin (Emys orbicularis) deserves mention, as it has never been reported before in these areas.