BIG CAN AN EAGLE GET?
October 4, 2009
animals serve as a reminder that despite what some people like to think
about humans being special, some predators view us as simply another meal.
Sharks, crocodiles, and giant snakes are clearly in the top 10 of animals
that under the right circumstances would view us as just another prey
species. A Komodo dragon, the largest lizard in the world, in Indonesia
and a pet Burmese python in a Florida residence each killed someone this
year, presumably considering the people as potential prey.
article in the September issue of the Journal of Vertebrate Paleontology
by R. Paul Scofield of Canterbury Museum in New Zealand and Ken W. S.
Ashwell of the University of New South Wales in Australia adds a new dimension
to the potential list of human predators. Information collected during
their study suggests that a giant eagle, now extinct but alive in New
Zealand as recently as 500 years ago, may have preyed occasionally upon
children and small adults. The scientific emphasis of the published study
was on other aspects of the ecology and evolution of the eagles, but an
aerial predator capable of swooping down and carrying someone off for
a meal is a chilling thought.
information about Haast's eagle, as the predator is called, is based on
skeletal material the scientists examined. As with modern birds of prey,
including hawks, owls, and eagles, females typically got larger than males.
A male Haast's eagle is estimated to have reached a body weight of 27
pounds. The females are believed to have weighed in at just over 39 pounds.
Because the estimated weights of Haast's eagle are based on only a few
specimens, it seems safe to say that the largest ones were probably over
Forty pounds is huge for a flying bird. To put their size in perspective,
the largest bald eagles are around three feet in body length, have an
outstretched wingspan of slightly under eight feet (which is right big
in itself), but average under 15 pounds in total weight. That's pretty
paltry compared to 40 pounds. Haast's eagles are indisputably the largest
eagles known to science.
comes to mind that the Maoris, the original settlers of New Zealand, probably
got cricks in their necks from keeping a close watch on the skies for
incoming eagles. But the primary target of Haast's eagles were flightless
birds native to the islands--the moas.
are the largest birds on earth today. Moas were even larger; they were
the biggest birds ever known to have lived on earth. Some of the species
were over 10 feet tall and weighed more than 400 pounds. Haast's eagles
were the only natural predator of the moas, which used their enormous
legs to move around quickly, like modern-day ostriches and emus. One advantage
of flight is the ability to escape ground predators. About 10 species
of moas had evolved on the islands of New Zealand because, without flying,
they were able to fend off any natural predators--except the eagles. Things
would probably have persisted for centuries in equilibrium, with big eagles
eating big flightless birds, if the Maoris had not arrived in New Zealand
in the late 1200s. The Maoris could easily capture and kill the moas,
which had never encountered such a relentless land predator and had never
evolved the ability to fly. So by the time Columbus landed in America,
all species of giant moas had been extinct for a century.
Haast's eagles are gone now, the former because of relentless hunting
and the latter because its main prey base was driven to extinction. An
aerial predator that can swoop down and carry off a small human is a staple
of certain myths, fairy tales, and speculative fiction. But such a creature
wasn't mythical; it was real. Knowing that a bird twice the size of a
bald eagle once existed is an intriguing thought. But the idea that one
might swoop down and carry away your walking partner goes one step beyond
what feels comfortable.
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