Although it has become capable of living on land, it spends its time in the water, where its prey, fish Pokémon, are plentiful. In ancient times, it lived in warm seas. It disguised itself as seaweed to ambush its prey and devoured them whole when they got close.
Its incisors grow continuously throughout its life. If its incisors get too long, this Pokémon becomes unable to eat, and it starves to death. They will cooperate to steal eggs from the nests of bird Pokémon, but fights break out to determine which one gets to eat the eggs.
Depictions of Pokémon similar to Baltoy have been found on the walls of caves where primitive humans lived. Swellow is very conscientious about the upkeep of its glossy wings. Once two Swellow are gathered, they diligently take care of cleaning each other’s wings.