This section temporarily contains information copied directly from Bulbapedia, and needs to be rewritten so not to be classified as plagiarism.
“Alolan Rattata’s form changed as a result of their battle for territory with Yungoos. Unlike ordinary Rattata, urban areas are Alolan Rattata’s main habitat. They are nocturnal and live in nests of several dozen. Alolan Raticate serve as their bosses. As a countermeasure to the exploding Rattata population in the Alola region, Yungoos were imported and released. To better avoid Yungoos, Rattata changed their preferred environments and circadian rhythms. These adaptations to their new environment led to a changed form. Alolan Rattata have an excellent capacity for sniffing out delicious fresh foods in Alola. They pay no attention to foods that aren’t fresh.”
In Alola, Rattata became nocturnal to evade the diurnal Yungoos imported to the region to contain their numbers. Its fur is black, with hair tufts on the ears, tail, and near their nose. The insides of its ears are purple.