Dodos were descendents of a type of pigeon which settled in Mauritius over 4 million years ago. With no predators to attack them, they lost their need and ability to fly. They lived and nested on the ground and ate fruits that had fallen from trees. There were no mammals on the island and a high diversity of bird species lived in the dense forests.
In 1505, the Portuguese became the first humans to set foot on Mauritius. The island quickly became a stopover for ships engaged in the spice trade. Weighing up to 50 pounds, the dodo was a welcome source of fresh meat for the sailors. Large numbers of dodos were killed for food.
Later, when the Dutch used the island as a penal colony, pigs and monkeys were brought to the island along with the convicts. Many of the ships that came to Mauritius also had uninvited rats aboard, some of which escaped onto the island. Before humans and other mammals arrive the dodo had little to fear from predators. The rats, pigs and monkeys ate dodo eggs in the ground nests.
The combination of human exploitation and introduced species significantly reduced the dodo population. Within 100 years of the arrival of humans on Mauritius, the once abundant dodo became a rare bird. The last one was killed in 1681.