Kiwi wait millions of years to go blind

[…] Natural evolution could be making New Zealand’s iconic bird blind as its natural habitat and way of life renders sight unnecessary for survival.

Three kiwi have been found to be profoundly blind in a South Island forest and an article in the New Scientist has suggested this could be an indication the flightless nocturnal birds may be evolving to lose their eyesight.

A study of 160 Okarito brown kiwi in the Okarito forest in New Zealand’s South Island found a “very high prevalence of birds with eye lesions”.

Te Papa Museum researcher Alan Tennyson said a third of the birds had eye problems.

The three completely blind birds had no other clear physical problems.

Tennyson said no other birds were known to have a free-living population of blind members.

However, he told the New Scientist, plenty of other animals such as moles and cave-dwelling fish, have evolved blindness.

“Vision is not essential for survival in all animals.”

He said the most likely explanation the kiwi were becoming blind was because of where and how they lived.

“Kiwi are flightless and generally nocturnally active, and have very good senses of smell, hearing and touch, so it seems that vision is not essential for their survival, at least for some individuals,” Tennyson said.

The New Scientist said other researchers have speculated that a gene called Sonic hedgehog might be responsible for the loss of vision.

The gene could also enhance the touch and smell sensors in the birds’ long beaks.

Researchers suggested the loss of sight was “collateral damage” as kiwi adapted to their nocturnal lightless niche within which normal, functioning eyes were not a necessity. […]

-NZ Herald

According to another source on the Internet

[…]  the oldest known fossil is a femur, about 1 million years old, found in coastal deposits near Marton, in the North Island. […]

[…] During periods of isolation in ice ages, the birds south of the glaciers gradually evolved into the various forms of Tokoeka we know today, with Stewart Island birds separating from the rest about 4 million years ago. […]

[…] When the islands split again, some birds became isolated on the North Island (about 2.5 million years ago) and evolved into today’s brown kiwi species. […]

-NZ Herald

Starting from a common ancestor we now have five separate species of kiwi: Brown kiwi; Great spotted kiwi/roroa; Little spotted kiwi; Rowi and Tokoeka.  Through geographical separation, this evolution has taken millions of years to generate the different species.

But we are told that scientists are now watching evolution happen before our very eyes since the brown kiwi have finally decided that after being nocturnal birds for millions of years they now no longer need the ability to see.

Really …?

What took these birds so long to come to this momentous, and eminently sensible, conclusion?  Were they waiting for the special votes to be counted?

I imagine a grant application for more funds to study this phenomenon is in the post.  In the meantime, my BS meter is slammed against the right-hand stop.


This post was written by Intern Staff


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