March 17, 2014
Artist's rendition of the coastal moa, which a new paper says was hunted to extinction, along with all of its relative, by humans. Image by: Michael B. H./Creative Commons 3.0.
To find the moa's smoking gun, scientists analyzed two different sets of DNA from 281 specimens made up of four species: the South Island giant moa (Dinornis robustus), the biggest of the family; the heavy-footed moa (Pachyornis elephantopus); the eastern moa (Emeus crassus); and the coastal moa (Euryapteryx curtus). Instead of showing a slow, genetic decline, the DNA told a different story: moas were thriving even as humans arrived.
"The millenia preceding the extinction were characterized by a remarkable degree of genetic stability in all species," the researcher, headed by Morten Allentoft with the University of Copenhagen, write in the paper.
In fact, the Allentoft and his team found that some populations were even on the rise right up to the end. And the end came fast, so fast, in fact, that it left no imprint in the four species' genetics as it usually does when species genetically constrict. Just a century or two after the arrival of humans on New Zealand, all nine moa species were gone for good. The scientists call this "the most rapid, human-facilitated megafauna extinction documented to date."
A reimagined scene of indigenous people hunting the biggest moas. Scientists now believe moas would not have frequently walked with their heads upright and the Maori did not have bows and arrows. Painting by: Heinrich Harder/early 20th Century.
These results tell a very different story than a 2004 DNA study that implied the giant birds may have already been on life support before humans provided the death blow. But this research was "based on limited mitochondrial DNA (mtDNA) data," according to the new study. Here, Allentoft and his team combined mtDNA with another type of genetics analysis—nuclear microsatellite genotyping—giving them a broader view of population trends.
This squared with archaeological findings as well, which show mounds of butchered birds and eggs. Like many island animals that have known humans, the moas were likely unafraid, making them easy to approach and kill.
"You see heaps and heaps of the birds' bones in archaeological sites," Allentoft told Science News. "If you hunt animals at all their life stages, they will never have a chance."
The moa's demise took another species with them, their only predator: Haast's eagle (Harpagornis moorei). A massive predator, the Haast's eagle was likely among the heaviest raptors in the world, even if its wingspan was similar to many other large eagles. Scientists theorize that Haast's eagle quickly vanished once humans had hunted its prey to oblivion.
While the rapid extinction of nine species of giant birds and one huge raptor may seem shocking, the decline and fall of the moas could be viewed as an early episode in an ongoing extinction crisis. Many scientists believe the Earth is in the midst of a mass extinction—the sixth since life began on Earth—directly linked to a barrage human activities, such as deforestation, habitat destruction, climate change, ocean acidification, pollution, and, as with the moas, overexploitation.
Haast's eagle divebombing a pair of moas. When its prey was killed off, the Haast's eagle vanished too. Photo by: John Megahan/Creative Commons 2.5.
|AUTHOR: Jeremy Hance joined Mongabay full-time in 2009. He currently serves as senior writer and editor. He has also authored a book.|
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