The South Island is divided along its length by the Southern Alps. The Fjordland's steep mountains and deep fjords record the extensive ice age glaciation of its south-western corner. The North Island is less mountainous but its geography is marked by ancient volcanic activity.
The moa, a large flightless bird, had no fear of humans. It quickly became a source of food, supplementing the agricultural products they brought with them. Prior to the Maoris arrival the moa's only predictor was a large eagle which attacked from the air. The moa's defense was to stand perfectly still and take advantage of it's natural camouflage to protect itself from the eagle seeing it. As you might imagine, that defense didn't work well with the Maoris and they quickly became extinct.