The Kozjača forest (e.u. 30 a) is located in the immediate vicinity of the town of Karlovac, so we can safely say that Kozjača is one of the most valuable parts of the town of Karlovac. Located in central Croatia with a moderate continental climate, mild winters and the surrounding landscape dotted with meadows, fields and orchards, it greatly contributes to the quality of life of the surrounding population. It was the combination of a favourable climate and habitat conditions that made room for the development of the stag beetle. Stag beetle monitoring was carried out in a forest stand of white oak and common hornbeam, which in this case proved to be a valuable habitat for stag beetle. This work includes processed data from two years of stag beetle monitoring. The work also covers habitat conditions, which have changed significantly in just a few years. Changes caused by anthropogenic activity are becoming more and more difficult for nature to absorb, and when we add climate changes that greatly affect our lives, it becomes unclear how sensitive species such as stag beetle will adapt to the new habitat conditions.