Swamp Fossil Deposit
The Bell Hill Vineyard fossils were deposited 1000 - 2000 years ago along a small, spring-fed stream flowing beneath a forest dominated by matai (Prumnopitys taxifolia).
Fossil trunks, branches, and seeds of this tall native pine are very common in the deposit, which formed where the stream crossed an area of soft clay.The thixotropic clay in the deposit trapped the animals and, once they had drowned, the high lime (carbonate) content of the clay helped preserve their bones. In other parts of the deposit, animals may have been able to stand on a firm stream bed beneath the clay, but the clay held them fast and they would not have been able to escape. Eventually they would have starved to death.
A few metres down the stream from the main concentration of large bones are the bones of small birds and other vertebrates, including the tuatara (Sphenodon), that were dropped into the stream by extinct giant harrier hawks (Circus eylesi) feeding in the branches overhead. Some of the bones of the native pigeon (Hemiphaga novaeseelandiae) still carry beak marks from the predator hawks. The hawks themselves were caught occasionally, either while trying to drink from the stream or attacking prey in the streambed.
The giant harrier was not the only bird of prey at Bell Hill Vineyard. The moa were food for the giant Haast’s Eagle (Hieraaetus moorei). A hole ripped into one of the recovered moa skulls shows the power of the eagle’s huge claw. Yet, for all its strength, sometimes the killer died with its prey - eagle bones have also been found in the swamp. Altogether, the remains of 19 species of native bird have been identified from the Bell Hill Vineyard deposit, ranging in size from parakeets and quail to the Giant Moa. Bones of the introduced Pacific rat (Rattus exulans) have also been found.
The deposit continued to develop after the forest was destroyed by fire early in the Polynesian period (beginning around AD 1300). The New Zealand quail (Coturnix novaezealandiae) inhabited the shrublands and grasslands that replaced the forest.
Fossils of three species of birds introduced by Europeans and the spur-winged plover which reached New Zealand by itself in the 20th Century show that the sticky clay was still trapping and preserving animals up to the time it was excavated.
Although only part of the deposit was excavated, nearly 300 individual moa have been identified. All four species of moa found in the lowlands of Canterbury are represented. The most abundant species is the Giant Moa (Dinornis robustus), of which over 150 (43%) are juveniles. Next most common is the Eastern Moa (Emeus crassus), with at least 40 adults, followed by the Stout-legged Moa (Euryapteryx geranoides), with 33 adults. Least common is the second-largest species, the Heavy-footed Moa (Pachyornis elephantopus), of which only 16 adults have been identified. All ages are also represented, from eggs and hatchlings to old birds that were perhaps 40-50 years old.
Carbon dates show that moa were trapped in the Bell Hill Vineyard site from at least 2000 years ago to the time of Polynesian settlement. The deposit is therefore of major importance as a ‘snapshot’ of the way North Canterbury was when people first explored it, 700 years ago.
As part of ongoing research programmes, the Bell Hill moa remains are being used in studies investigating the ecology and environment of the moa. Bones from Bell Hill Vineyard were also included in a study showing that female Giant Moa were twice as heavy as males. The DNA of the Bell Hill bones was well preserved, allowing the birds to be sexed and body size calculated from leg bone dimensions. The large sexual dimorphis resulted in a reduction of the number of moa species from 11 to 10 which was proven through the DNA testing – so an extinct species became extinct – the Dinornis giganteus is no longer, now included in the Dinornis robustus group.