It is thought that the nene evolved from the Canada goose (Branta canadensis), which most likely arrived on the Hawaiian islands about 500,000 years ago, shortly after the island of Hawaiʻi was formed. This ancestor is the progenitor of the nene as well as the prehistoric Giant Hawaiʻi goose and nēnē-nui (Branta hylobadistes). The nēnē-nui was larger than the nene, varied from flightless to flighted depending on the individual, and inhabited the island of Maui. Similar fossil geese found on Oʻahu and Kauaʻi may be of the same species. The Giant Hawaiʻi goose was restricted to the island of Hawaiʻi and measured 1. 2 m (3. 9 ft) in length with a mass of 8. 6 kg (19 lb), making it more than four times larger than the nene. It is believed that the herbivorous Giant Hawaiʻi goose occupied the same ecological niche as the goose-like ducks known as moa-nalo, which were not present on the Big Island. Based on mitochondrial DNA found in fossils, all Hawaiian geese, living and dead, are closely related to the giant Canada goose (B. c. maxima) and dusky Canada goose (B. c. occidentalis).