Fiddler crab a vital role in the preservation of wetland environments; by sifting through the sands, they aerate the substrate and prevent anaerobic conditions. Fiddler crabs live rather brief lives of no more than two years (up to three years in captivity). Male fiddler crabs use the major claw to perform a waving display as a form of female courtship. Females choose their mate based on claw size and also quality of the waving display. In many fiddler crab species, the female occupies the burrow of their mate while she lays her clutch of eggs. Research shows that the male major claw
Invasive species which were brought to control insects upon the introduced grain crops, have displaced native birds as have rainbow lorikeets and cockatoos (both from Australia) which fly free around areas west of Auckland City such as the Waitakere Ranges. In much of New Zealand, the Australian black swan has effectively eliminated the existence of the previously introduced mute swan. Two notable varieties of spiders have also been introduced: the white tail spider and the redback spider. Both may have arrived inside shipments of fruit. Until then, the only spider (and the only venomous animal) dangerous to humans was the native katipo,