The Kākāpō Makes Survivalistic Comeback

New Zealand bird survives extinction through genetic bottlenecking


JakeOsborne Flickr Photo

Endangered species: there are so many that there is a list for them that could honestly be made into a book series. 

One endangered species is a small and cute flightless bird called the Kākāpō. This bird is native to New Zealand and has been described as a green flightless owl that is about the size of a small turkey.

The bird is a nocturnal flightless parrot that is currently endangered, and you may be asking why that is, or you could already have an idea. 

Humans are the cause of this but it is not due to humans directly hunting them, but instead small invasive mammals such as rats and stoats, which are small weasels. They primarily went after the birds’ chicks and eggs, drastically decreasing the number of the Kākāpō. 

These birds never had to worry about predatory mammals coming after them, so they essentially did not know how to face such a challenge. 

It is said that in 1995 about 51 Kākāpō were left in the wild, on one island in New Zealand. That number stayed steady for a good amount of time until a conservation group called Kākāpō Recovery started helping their numbers to increase. 

Today there are about 201 of the adorable flightless birds due to the help of this conservation group. Though they are starting to see an increase in numbers, it is not all good news. 

Scientists think that due to there being such a small bottleneck of the species, the birds could have some negative effects due to inbreeding since there may not be enough genetic diversity in their population. 

In an article released on Sept. 8 called “Population Genomics of the Critically Endangered Kākāpō”, scientists went to Stewart Island in New Zealand to analyze the genome of the population on this small island. 

In total, they looked at 35 modern genomes and were also able to take a look at 14 extinct genomes from the main island of New Zealand and what they found was interesting, to say the least. 

Though their genetic variation is low due to the bottleneck, the scientists found that the small population left over on Stewart Island have a low mutation load. Mutation load is what determines the fitness of a species and in this case, having a low mutation load is a good thing. 

Compared to the extinct population from the mainland, the genomes of those found on Stewart Island showed that their average fitness is higher than those that were once on the mainland. 

There are some explanations as to why the Island genes have better fitness than the mainland genes. In the discussion setion of the article, the authors assert that “One explanation for this reduced mutational load is that random genetic drift led to a loss of alleles that were at low frequency before the decline in population size on Stewart Island. However, while most deleterious alleles at low frequency will be lost due to random drift, a small proportion will be fixed, meaning that the average frequency of deleterious alleles will not change.” 

Another explanation could be that the inbreeding is actually helping their genome weed out these alleles that would reduce the population’s fitness. 

Though the future of the Kākāpō is a bit uncertain on how well their population will be due to the bottleneck, right now they seem to be on a long road to recovery, and may once again be able to reclaim the islands of New Zealand that they used to call home.