Artist rendering of giant eagle attacking unsuspecting moas. Art: John Megahan via Bunce et al, 2005.
Like I said over at PLOS blogs, I first saw a moa fossil skeleton in the Smithsonian’s Museum of Natural History. I was curious about that tall bird with no semblance of wings. I searched for the label to find out if that skeleton was incomplete, in the hope to find more information on that bird’s perhaps long lost wings. It is not uncommon for partial skeletons to be found and displayed – smaller, more fragile bones decompose faster and are not left behind. Many skeletons seen in museums are a collage of bones from many different specimens, and several parts are artificially built (for example, one rib can be a plaster-made, mirror image of another). However, the label on the moa skeleton explained that this huge bird did not even have vestigial wings. Without the need to fly, its wings completely disappeared throughout the course of evolution. They would have left no trace, wasn’t for the bird’s unmistakable similarity to an ostrich.
The ostrich is today’s largest bird, and it belongs to the ratite (flightless) group of birds. Many species of ratite bird are extinct, including the moa and the elephant bird of Madagascar, but still living are the ostrich, emu, cassowary, rhea, and their tiny relative, the kiwi.
The wiki image above is a great example of the size difference between the kiwi, ostrich, and moa (Dinornis). In fact, the moa was for years believed to be part of the ostrich family, until the little detail of “no wings” came to light. Earlier moa archeologists were surprised after finding one leg bone after the next, but never an arm. One massive bone (which can be seen on the ostrich’s thorax, on the above picture) is missing from the moa and kiwi. That’s a bird’s keel, which is responsible for anchoring a bird’s wings. Many ratites do have wings (like ostriches and emus), even though they are not so helpful. The moa and the kiwi do not.
The moa’s enormous femur bones were first to be found. Twice the circumference of a human femur, those fossils helped recreate the image of this massive bird. After the discovery of many moa fossil sites and skeleton reconstructions, it is now known that the moa came in 9 species, reached up to 12 ft. tall and could weigh over 500 lbs – heavier than a gorilla. Currently we have an even better understanding of this animal. For example, we can tell its diet consisted of at least 74 different species of plants and that it fought its only predator pre-human settlement (the giant eagle). Researchers have also been able to extract pieces of its DNA from its fossil bones.
The moa used to live in New Zealand before extinction, when it disappeared shortly after Maori settlement in the 13th century. This bird was New Zealand’s largest herbivore. There were no land mammals – unless you count the three species of bat. The moa roamed freely, unaware of predators except for giant eagle (Haast’s Eagle). Much like a modern day eagle, it grabbed and killed prey with a strike of its talons – claw marks are preserved in many moa fossils. Moas were easy catch for the settler tribes – having never seen humans before, there was no reason for fearing them. On the course of a few hundred years they were all eaten and only bones were left to tell the story. Imagine the size of those drumsticks: even though moas were eaten, historical reports claim it did not taste so good (and supposedly tasted tough and stringy, and some admit it might have been similar to a kiwi). With no land mammals or other domesticated animals, life in New Zealand must have been difficult. Today however, it serves as an interesting cautionary tale for animal species survival or man-driven extinction.