The peer-reviewed publication for this dataset has now been published in Animals, an MDPI journal, and can be accessed here: https://doi.org/10.3390/ani12060692. Please cite this when using the dataset. The images have been taken at the polar bear enclosure at Nuremberg Zoo, which is home to two mature animals (Vera, female adult and Nanuq, male adult). The three on-site cameras acquire videos with a frame rate of 12.5 fps and a resolution of 3840×2160 pixels. For the aim of this project, a period of five days of data (27 April - 1 May 2020) has been selected. During this period, the polar bears shared both enclosures and thus might both be present in a single image. A total of 4450 frames were randomly selected and stored for further labeling. Three biologists annotated all images to provide labels of high quality by assigning labeled bounding boxes to the animals visible in the picture. We provide the resulting mean annotations. As the 4450 images were randomly selected from the video data, only 2099 instances show one or more animals. 167 images show both animals, 1932 only one. 2266 bounding boxes are provided, 1082 for the male and 1184 for the female bear.