For much of last century, in the days before genetic research, kiwi were classified according to their body structure.
Because scientists could only work from what they could see, up to the 1980s just three species of kiwi were formally recognised – the great spotted kiwi, the little spotted kiwi and the brown kiwi.
With the brown kiwi species, three varieties were also recognised: North Island brown, South Island brown and Stewart Island brown.
Delving into kiwi DNA
Genetic research in the 1980s changed all this. It allowed kiwi DNA (deoxyribonucleic acid) to be studied. DNA contains the genetic instructions used in the development and functioning of all known living organisms.
For the first time, scientists could read the ‘essence’ of kiwi, not just what the scientists’ eyes could see.
By comparing the DNA of different kiwi species, geneticists have been able to infer their evolutionary history, and this is more complex than suggested by studying their anatomy alone.
From three to five species
The genetic research confirmed the great spotted and little spotted kiwi as separate species.
But it also split brown kiwi up into three distinct species – brown kiwi, rowi and tokoeka.
Thanks to DNA, today five kiwi species are formally recognised.
And, with further genetic research under way, even more species and/or subspecies may be identified in future, especially within tokoeka.
In 2016 a paper published by researcher from Toronto university and the Department of Conservation looked deeper into the different lineages of the five recognised species.
The five species
The five formally described kiwi species are:
- little spotted kiwi/kiwi pukupuku (Apteryx owenii) on several offshore islands and two mainland sanctuaries
- great spotted kiwi/roroa (A. haastii) in the northwestern South Island and around Arthur’s Pass
- brown kiwi (A. mantelli) in the North Island
- rowi (A. rowi) at Okarito, on the West Coast of the South Island
- tokoeka (A. australis) in the South Island (Fiordland, the Haast Range and Rakiura (Stewart Island)).
Different varieties add to the complexity
To add to the complexity, 2 of the 5 kiwi species (brown kiwi and tokoeka) have different varieties within them, making a total of 10 ‘kinds’ of kiwi. The varieties have arisen because populations of brown kiwi and tokoeka live in quite separate geographical areas, so have not interbred for a very long time.
For simplicity’s sake, researchers often use the term ‘taxa’ (singular: taxon) to refer to the 10 different kinds of kiwi.
Within brown kiwi, four distinct taxa have been distinguished based on both where they live and their genetics: Northland, Coromandel, western and eastern.
Within tokoeka, three distinct taxa have been identified based on geography and genetics: Haast, Fiordland and Rakiura/Stewart Island.
Unlike brown kiwi and tokoeka, the current little spotted kiwi, great spotted kiwi and rowi species show no clear geographical genetic differences, but recently extinct taxa are known for both little spotted kiwi and rowi.
Population numbers – a best guess
|Taxa||2015 population estimate||% under active management||Actual number of kiwi actively managed||2030 population estimate||Predicted % increase over 15 years|
|Great spotted||14,800||12.6%||1,858||12,428||-1.6% decline|
|Fiordland tokoeka||12,500||8.8%||1,100||10,722||-1.0% decline|
|Rakiura (Stewart Island) tokoeka||13,000||1.9%||250||9,962||-1.8% decline|
Kiwi researchers’ best estimates are that New Zealand’s kiwi population was 67,550 in 2015. That is fewer than the estimated 73,000 in 2008. Their estimate is that, if the current management of each taxa is maintained for the next 15 years, the total kiwi population will be more or less stable.
The size of individual kiwi populations is not precisely known because we don’t yet have a cost-effective way to count kiwi. We do know that the biggest threat the birds face is being killed by pest mammals, particularly stoats, and also ferrets, dogs and cats. Protecting habitat without reducing the number of predators will not save kiwi.
Since 2000, population declines have been turned around for the four rarest (rowi, Haast tokoeka, Coromandel brown kiwi and little spotted kiwi) and reduced for others. However, fewer than a quarter of New Zealand kiwi (24%) live in places where predators are controlled. More than three-quarters of kiwi do not enjoy this level of protection and many populations continue to decline.
Across all 10 kiwi taxa, the proportion of each population under active management varies greatly, as shown in the table below. In general, the bigger the population, the smaller the percentage under active management.
The taxa with the largest number of birds under active management is the Northland brown – an estimated 4075 kiwi, nearly 50% of the population. The taxa with the smallest number actively managed is the Rakiura (Stewart Island) tokoeka – with just 250 birds out of an estimated population of 13,000, just 1.9%.
The table below also shows that, if we keep managing kiwi in the same way, three taxa are predicted to decline in number over the next 15 years – great spotted kiwi, Fiordland tokoeka, and Rakiura (Stewart Island) tokoeka.
More information about population trends for each of the 10 kiwi taxa can be found through the links below.