There are just 155 living kākāpō. But 150 years ago, there may have been between half a million and one million kākāpō living in the South Island, according to a new study.
Within a few years of stoats being introduced to New Zealand, in the 1880s, kākāpō numbers began to rapidly drop - and it wasn’t just their population size that declined. The genetic diversity of this endemic flightless bird has also suffered huge losses.
Analysis of kākāpō skins collected between 1884 and 1985, and held in museums, revealed 17 different mitochondrial haplotypes, or female genetic lineages. Today’s kākāpō population has just three.
Bruce Robertson, at the University of Otago, is a co-author of the study, published this week in the Journal of Heredity. He says that the genetic analysis identified a significant population bottleneck that started about 125 years ago, which is about five kākāpō generations. This coincides with the introduction of mustelids, such as stoats, to control introduced rabbits.
Bruce says they found no genetic evidence of any earlier population bottleneck that might have been due to hunting by early Māori. However, he is quick to point out that the 54 museum specimens that were studied all came from the South Island, and that the situation for kākāpō in the North Island may have been different.
Bruce and colleagues are currently studying ancient DNA from sub-fossil bones collected in the North Island to try and get a clearer picture of kākāpō genetic diversity before and around the time of Polynesian settlement.
Bruce reports that the first 40 kākāpō genomes have been sequenced as part of the Kakapo 125 Genome project. The next batch of 40 is due to be processed in the next few weeks, and the team hope to have all 125 genomes sequenced by mid-2017.
Kākāpō is the first species in the world in which every individual in the population will be sequenced. The sequencing is just of adult birds, and does not include the 32 chicks that successfully fledged following a bumper breeding season earlier this year.