Identification of hybrids between the Japanese giant salamander (Andrias
japonicus) and Chinese giant salamander (Andrias davidianus) using deep
learning and smartphone images
Abstract
Biological invasions are recognized as one of the factors causing
biodiversity loss. Incomplete reproductive isolation with a closely
related species can result in hybridization when a non-native species is
introduced into a new habitat. Management of hybrids is essential for
biodiversity conservation; however, the distinction between the two
species becomes a challenge in cases of hybrids with similar
characteristics to native species. Although image recognition technology
can be a powerful tool for identifying hybrids, studies have yet to
utilize deep learning approaches. Hence, this study aimed to identify
hybrids between native Japanese giant salamanders (Andrias japonicus)
and non-native Chinese giant salamanders (Andrias davidianus) using
EfficientNet and smartphone images. We used smartphone images of 11
native individuals (with 5 training and 6 test images) and 20 hybrid
individuals (with 5 training and 15 test images). In our experimental
environment, an AI model constructed with efficientNet-V2 showed 100%
accuracy in identifying hybrids. In addition, highlighting the regions
that influenced the AI model’s predictions using Grad-CAM revealed that
salamander head spots are responsible for correctly classifying native
and hybrid species. The results of this study revealed that our approach
is one of the methods that enable the identification of hybrids, which
was previously considered difficult without identification by the
experts. Furthermore, since this study achieved high-performance
identification using smartphone images, it is expected to be applied to
a wide range of low-cost identification using citizen science.