In 1993 was ascertained that there was an decline of the flora and fauna of the country estate Fraeylemaborg in Slochteren. The estate council decided to take measures. The mowing of meadows was adapted and more dead wood was left behind. These appeared to be good measures of which especially the stinse-plants and bats took advantage.
In 2004 a stock list has been made up of the plants and animals and progress compared to 1993 is ascertained.
Holwortel, Maarts violet, Kievitsbloem and Lenteklokje that nearby had disappeared are present in abundance again. Further the Gele anemoon started spreading over the estate .

Disappeared is the Kale vrouwenmantel, probably she became a victim of a cleaning of a ditch. ‘It is not a disaster, she will come back’, says the administrator Gerard de Haan. ‘ For in the biotope nothing has changed’.
Bird brooding in caverns use the estate extensively. They are so numerous because there are many old dead trees on the estate. In there live: Grote bonte specht, Holenduif, Gekraagde roodstaart, Bonte vliegenvanger, Koolmees, Boomklever and Boomkruiper.

Use of the hollow trees is made also by the Pink bats, a colony of them is on the estate. Further live on the estate: the watervleermuis, the Gewone grootoorvleermuis, the rare Baardvleermuis, the Ruige dwergvleermuis and the Laatvlieger. Meervleermuizen are seen in the Slochter-harbour and above the Slochterdiep and will, so says the editor of the report 'the Stichting tot Behoud van Particuliere Historische Buitenplaatsen' (Foundation PHB), also be present on the castle terrain.
Also on provincial level the population of bats on the landgoed Fraeylemaborg is important.
The bats are so numerous and the species so diverse that the Foundation PHB advises to name the Fraeylemaborg as Protected Area for bats. The board of the estate investigates if such an qualification is among the possibilities.

The investigation for the Nature-values of the estate Fraeylemaborg was made possible by a contribution of the VSB-Fund.