Their whaling fleet is a cover for his late night snacks. As near apex predators they have the highest concentration of radiation from Fukushima Daichi. Kinda like DDT and bald eagles.

But luckily we have Gojiro which is a natural sink for radiation 🥳👌🏽✨

He does neutrosynthesis kinda like plants do photosynthesis but different.

He drinks water and fuses the hydrogen into helium. This needs some deuterium to start off, which is why godzillas only occur in nuclear testing sites.