New research finds Kiwi evolved to cope with nocturnal life
Kiwi may have been driven into night-time living to avoid competition with the giant moa.
New genetic research has pinpointed some of the adaptations New Zealand's native flightless bird developed to live life in the shadows.
Researchers at the University of Leipzig and the Max Planck Institute sequenced the entire genetic makeup of two North Island brown kiwi. They found one of the largest bird genomes sequenced to date and a few hints on how kiwi evolved their nocturnal lifestyles.
University of Leipzig evolutionary biologist Diana Le Duc said the adaptations seemed to have happened about 35 million years ago – shortly after the kiwi's ancestors were thought to have arrived in New Zealand.
She said moa were already in New Zealand and the giant herbivores were thought to have monopolised resources during the day. That might have forced the early kiwi to become nocturnal to avoid competition.
The findings, published on Thursday in Genome Biology, showed that kiwi do not see in colour but can smell a wide range of odours – which could help with night-time foraging.
Le Duc said the changes in vision and smell were similar to adaptations found in nocturnal mammals.
The five species of kiwi, all endemic to New Zealand, are the smallest of ratites – a group of birds that includes emu, ostriches and moa. They are the only nocturnal ratites and have a highly-developed sense of smell, huge eggs compared to their body size and a low metabolic rate.
Only about 3 per cent of bird species are nocturnal. Nocturnal animals tend to have low metabolic rates and the researchers found genetic changes in the kiwi related to energy expenditure, reserves and metabolic processes.
University of Canterbury evolutionary biologist Dr Tammy Steeves said a high-quality genome for a species like North Island brown kiwi was an exciting advancement.
"Of the more than 10,000 bird species worldwide, a mere 50 of them have a readily available genome."
Since all five kiwi species are considered endangered, Le Duc pointed out that the diversity they found among the two kiwi genomes was similar to that seen in inbred species.
Steeves said it was essential to preserve the genetic diversity of endangered species to enable them to adapt to future environmental changes.
The new genomic data would provide a starting point for more studies that could measure genetic diversity and inform conservation management of the rare birds, she said.