Wataru Kojima is Associate Professor in the Faculty of Science at Yamaguchi University, affiliated with the Graduate School of Sciences and Technology for Innovation. His research centers on the evolutionary ecology of insects, with a primary focus on the Japanese rhinoceros beetle Trypoxylus dichotomus. Studies examine regional variations in life-history traits such as larval growth rates, egg size, and body size, as well as adaptations to different host plants and latitudinal clines. Additional work investigates defense mechanisms against avian and mammalian predators, including physical and chemical traits of beetle exoskeletons, and mating behaviors, including evidence that most females mate only once in their lifetime.
Kojima has received several awards, including the Inoue Research Encouragement Award in 2013, the Japan Zoological Society Paper Award and Fujiwara Award in 2015, and an excellence award at the 59th Science and Technology Film Festival in 2018 for educational content on beetle life cycles. He has authored or co-authored numerous peer-reviewed papers in journals such as Functional Ecology, Ecology, Current Biology, Animal Behaviour, and Biological Journal of the Linnean Society. Notable publications include work on latitudinal clines in larval growth (2020), horn length and lifting strength evolution (2023), and age-dependent decline in fighting performance (2025). He has also written books for general audiences on rhinoceros beetles. Kojima maintains an active laboratory studying insect evolutionary ecology and contributes to public science communication through presentations and media.