Monday, November 10, 2014

It only takes a few humans to kill off easy prey like moa, and maybe Hawaiian monk seals.

A new study suggests that it takes very few humans to kill off a large, easily-caught food species.

There were only about 2,500 Maori in New Zealand by the time they killed off the last of the moa—that giant bird which, along with the dodo, is emblematic of lost wildlife.

(Image: A representation of an upland moa, Megalapteryx didinus. Credit: George Edward Lodge.)

“Both the Polynesian settlement of New Zealand and moa extinction are recent enough to be dated with a high degree of precision.

“In addition, the founding human population can be estimated from genetic evidence,” says an article published in Nature Communications, by Richard Holdaway, of the Universiity of Canterbury and Palaecol Research Ltd., and his New Zealand and Australia co-authors Morten Allentoft, Christopher Jacomb, Charlotte Oskam, Nancy Beavan and Michael Bunce.

What they found was that the moa were hit by a multi-part human impact: The big, long-necked birds were killed directly, their eggs were collected, and their habitat was destroyed.

“Polynesians exterminated viable populations of moa by hunting and removal of habitat. High human population densities are not required in models of megafaunal extinction,” the authors write.

In a press release from the University of Otago, the researchers said they used radiocarbon dating from 270 sites around New Zealand.  

“Analysis of 210 of the ages showed that moa were exterminated first in the more accessible eastern lowlands of the South Island, at the end of the 14th century, just 70-80 years after the first evidence for moa consumption. Analysis of all 270 dates, on all South Island moa species from throughout the South Island, showed that moa survived for only about another 20 years after that."

The entire population of moa was gone between the first signs of human activity in South Island, which was no earlier than 1314 BC and the loss of the last moa in 1425, give or take a decade.
Is there a Hawaiian equivalent? Hawai`i had its own moa, the moa nalo, which was a giant flightless duck, and it also disappeared early. This thick-beaked species had different species on several islands, three of them in the genus Thambetochen. The massive Kaua`i version, Chelychelynechen quassus, was known as the turtle-jawed moa nalo.

They would have been a little harder to locate than the 500 pound, 12-foot New Zealand moa, but they were all extinct by the time Europeans arrived.

Additionally, the Hawaiian monk seal was killed off early in the main Hawaiian Islands--so early that its bones are only known from a very few early archaeological sites. Seals were still found in the Northwestern Hawaiian Islands, and from there they began the slow process of repopulating the main islands.
For early Hawaiians, the seals, which sun themselves and raise their pups on the beach, would have been very easy and nutritious prey.

© Jan TenBruggencate 2014

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