Bright-eyed and bushy-tailed,
the mammals have finally arrived in force.
Australian possums.
Imported for their fur two centuries ago,
they soon reached plague proportions,
stripping trees of their vegetation.
A war is being waged against them.
Traps set and poison scattered.
And yet they are now far more numerous than the kakapo ever were.
A staggering 70 million possums overrun New Zealand's forests,
where a bird failed, a mammal has succeeded.
But why?
The possums were unwitting immigrants,
while the kakapo have lived here for millennia,
perfectly adapted to this forest.
It's an irony that is by no means unique to the kakapo and the possum.
Right across the Pacific, similar scenes have been unfolding.
Tiny islands off the coast of New Zealand
are the last refuge for a host of animals
now vanished from the two main islands.
This is Stephens Island,
one square mile of rock protruding from the ocean. （