Purpose This study aims to test a multirotor unmanned aerial vehicle (UAV) paired with a thermal imaging camera for detecting big game species such as Eurasian elk, red deer, European roe deer and Eurasian wild boar. Design/methodology/approach The research work was carried out in the Czarna Bialostocka Forest District (Podlaskie Voivodeship, Poland). A thermal imaging camera E20Tvx Yuneec with a view angle of 33° × 26.6° and a thermal sensor resolution of 640 × 512 pixels was selected for the research. The Yuneec H520E hexacopter was chosen as the lifting vehicle. The flights for the study were conducted between the autumn of 2021 and the winter of 2022. The UAV was flown at two different altitudes, 120 and 80 m above ground level, which provided a ground sampling distance of 11 and 7 cm, respectively. Findings The results so far have shown the potential of commercially available thermal imaging cameras for detecting and identifying big game species, such as Eurasian elk and red deer. Moreover, in the winter season of 2022 on the 7th and 13th of March, it was also possible to determine the sex of red deer distinguishing between males and females. The results of the survey made with the thermal camera were compared to the assessment from the standard method for the determination of the game population in the Czarna Bialostocka sub-district. In the case of red deer, the results of the research carried out during the winter exceed five times the numbers obtained as a result of the traditional inventory. That is most likely due to the gregarious occurrence of this species in the winter season. Originality/value The use of thermovision to estimate the population and sex of animals is a relatively new issue, especially in Poland, where the use of thermal imaging is not the official method of research of big game species yet.