Common in the early years of European colonisation, the "brown duck" (as it had been often referred to) was heavily harvested as a food source.

This is an evolutionary response to natural diurnal predators such as the New Zealand falcon, Eyles' harrier, or skuas further south in their range.

Brown teal have no defense against introduced cats, dogs, stoats & ferrets, which can kill adults & ducklings, or against rats which eat eggs.

Small species such as pipi (Paphies australis) and large wedge shell (Macomona liliana) are eaten whole and crushed in the gizzard.

[12] This species is endangered and occurs predominantly on offshore islands but also in predator-proof sanctuaries on the mainland such as Tawharanui Regional Park.

Formerly, it was widespread on the New Zealand mainland, but it disappeared there due to introduced predators like cats, dogs and rats, which easily preyed on this unwary, weakly flying bird.

Apart from Fiordland's Arthur Valley, there is only one other site in the South Island where brown teal live in the wild: since 2017, the Department of Conservation and Project Janszoon have released just under 300 of the waterfowl in the Awapoto River in Abel Tasman National Park.