Image acquisition
In this study, 11 native individuals and 20 hybrid individuals were used (Supplementary Figures 1 and 2). The Hiroshima City Asa Zoological Park, where these individuals are kept, has been researching and trying to breed Japanese giant salamanders since 1971 and is one of the leading facilities in Japan for research and conservation on this species. Native individuals were already kept at the Japanese giant salamander conservation and breeding facility. Hybrids were captured in the wild in Hiroshima Prefecture in May 2022 and were kept in the same facility.
11 native individuals were photographed on August 20, 2022, at 11:00 AM. Each individual was recorded for approximately 30 seconds using an iPhone 11 with a 12-megapixel camera. We photographed the Japanese giant salamanders in the water from above (Supplementary Figure 3). The videos were converted to ten still JPEG images (1920 × 1080) per second using the Free Video to JPG Converter.
20 hybrid individuals were photographed on November 19, 2022, at 2:00 PM using an iPhone SE equipped with a 12-megapixel camera. The method of image collection was the same as for the native individuals.