Sixty-five million years ago ‘proto-New Zealand’ separated from the ancient supercontinent Gondwanaland and took a group of existing plants and animals with it. Those animals included insects, amphibians, reptiles and birds. However, this separation of landmasses occurred before the evolution of mammals.
Consequently – with the exception of three species of bat – there were no land mammals in New Zealand before the arrival of humans. Because of this, our plants and animals have not developed the necessary defence mechanisms to deal with mammalian predation. For example, the leaves of our plants do not contain poisons to deter browsing mammals, while many of our birds and insects have lost the ability to fly.