Conchological Study
of
Norfolk Island Terrestrial Mollusca
from Fossiliferous
and
Live Populations
Fossiliferous deposit ca 800 years BP
-U N E D I T E D - D R A F T-
ROBERT V J P VARMAN PhD
=====================================================================
SUMMARY
The introduction pages discuss several fossiliferous sites containing snail shells at Kingston, Norfolk Island. The sites are grouped variously as: Fossiliferous 'Palaeo' (4000 years plus), Polynesian fossiliferous (mid- point, 800 years), pre-European (200 years plus), European (ca 200 years). A large change in species type, variety and distribution was found between fossiliferous 'Palaeo' and 'Polynesian'. The Polynesian rat (Rattus exulans) seems to be responsible for a decline but the change from Palaeo to Polynesian may need another explanation. The extinctions since European settlement has been spectacular, particularly this century; nearly all the large species have vanished.
The list presents a review of Ireland's list, listing variations and newly discovered living and fossiliferous species including some species seen only once before (in one case where the orthotype seems to be missing). It is hoped that others studying Pacific Ocean species may recognize closely related species and contact the author.
GO STRAIGHT TO THE LIST (PLEASE READ THE INTRODUCTION)
INTRODUCTION
While on Norfolk Island entrusted with the archaeological work there from 1981 to 1990, I found the indigenous snail species of the Island a very useful indicator of pre-European stratigraphy at Kingston, the location of settlement from 1788. Subtle changes were also noticed in the fossiliferous deposits which seemed to indicate the arrival of Polynesian people and the Polynesian rat (Rattus exulans).
One very ancient fossiliferous deposit indicated a subsequent reduction in the size of some species, loss of diversity and several extinctions.
The snail shells found in the archaeological deposits led to a survey of present populations on the Island as a comparison. The reduction of undisturbed habitat and the presence of the European and Polynesian rat has reduced many species to extinction or near extinction levels, particularly in the case of the larger species.
The word conchological on the title page is meant to indicate, that this is a study of shell features only. I am not an anatomist and am not even skilled at distinguishing the finer points of recognizing all species and sub-species. As an archaeologist, I am skilled at distinguishing morphological features, though mostly in regard to man-made objects. I was on Norfolk Island from 1981 to 1990 and took the time to study the plant life there (a family thing) and the snail (a consequence of my work on the Island).
From about 1987 I began corresponding with Mr Phil Colman of the Australian Museum, Sydney. Mr Coleman was able to send me copies of articles by Tom Iredale and E. R. Sykes and suggest contacts who might be able to help me.
I still don't understand many of the distinctions, particularly in regard to the minuscule species. The excessive splitting of species by Iredale was not at all helpful but I had the advantage of having access to thousands of specimens over a long period of time. I resisted Phil Colman's advice to collect and preserve live specimens for personal reasons and because live specimens for the rare species were just not forthcoming at all.
I have found at least one new species which is represented in the wild and in fossiliferous deposits, some new species only represented in fossiliferous deposits and several new sub-species or major varieties. Some mistakes were made in some of the early classification and naming of snails (mainly the result of limited samples taken from Norfolk Island and the surrounding smaller Islands). There are several introduced species never before recorded from Norfolk Island also.
There will be errors in this work. The names used are anchors to describe what was actually found. It will be up to future taxonomists to decide on the actual scientific names and carry out anatomical studies.
This is a review of a catalogue I completed in July 1991, copies were sent to the Australian Museum and the National Museum of New Zealand at the time. I made several hundred scale drawings on graph paper but not all are suitable for inclusion in this work.
Why this work? No one else seemed interested and not to pass on what I had found and observed seemed to me criminal. There has been no outside funding involved in the creation of this work, I just love it.
How did all these species evolve on Norfolk Island, in such great isolation? Like the Norfolk Pine, most of these snail species could not survive to reproduce by rafting or being carried by birds or the wind. I am interested in the theory of panbiogeology as an explanation. I believe that there has always been some part of the Norfolk Ridge above water to allow at least a small percentage of plants and animals to survive and spread out again until the next marginalization by vulcanism or rise of sea-level. Several of the species probably diversified during the isolation of the periods of high sea level and then spread out during periods of low sea level when the land mass became quite large. The lack of larger species and indigenous fresh water snails, unlike on Lord Howe Island, probably reflects the extreme marginalization during periods of high sea level and vulcanism.
Acknowledgements
My thanks to Mr Phil Colman of the Australian Museum for patiently responding to my letters, his encouragement and for sending me literature when I lived on the Island and since my return. Mr Colman began at the Museum when Tom Iredale still worked there.
FOSSILIFEROUS TERRESTRIAL MOLLUSCA
The legendary Roy Ball, often recalled to this day on Norfolk Island, was probably the first to collect the fossiliferous snail shells at Kingston and on nearby Nepean Island. It is important to know the exact area where he found these shells because the fossiliferous deposits are not all of the same age. H. B. Preston processed Bell's finds and the results were published in 1913 in the Annals and Magazine of Natural History (Ser 8, Vol xii, December 1913) in an article entitled "Characters of the New Genera and Species of Terrestrial Mollusca from Norfolk Island".
Bell indicated the location of the fossiliferous deposit as on the "W.E. coast of Norfolk Island", which is the Kingston area. Kingston is the only area of fossiliferous deposits on the Island and the only lowlands to be found on the Island. The exact provenance of the fossiliferous finds was "Limestone quarry" or "in sand near the limestone quarry". There have been many limestone quarries at Kingston over the last 200-plus years but the only one operating during the first decade or so was the quarry near the east boundary wall of Government House. The quarry is labelled as such on the 1904 cadastral map of Kingston.
The following species collected by Roy Bell have been culled from the general list in Tom Iredale's 1945 publication, "The Land Mollusca of Norfolk Island" in the Australian Zoologist, Vol 11, Part 1, June 11, 1945 (following Preston, 1913).
FOSSILIFEROUS LAND MOLLUSC SPECIES
Spirancinea nepeanensis, Preston. Nepean Island.
(Spirancinea humerosa, Preston. Now placed with S. nepeanensis).
Norfolcioconcha iota, Preston. (Also live at Duncombe Bay).
Iredaleoconcha inopina, Preston. (Also live at Mount Pitt).
Fanulena nepeanensis, Preston. Nepean Island.
Advena campbellii nepeanensis, Preston. Nepean Island.
Mathewsoconcha albocincta, Preston. (Kingston).
Mathewsoconcha vexillum, Preston. (Kingston).
Mathewsoconcha microstriata, Preston. (Kingston)
Belloconcha elevata, Preston. Nepean Island.
Belloconcha compacta, Preston. Nepean Island.
Quintalia intermedia, Preston. Nepean Island.
Johannesoconcha miniscula, Preston. (Kingston).
Mathewsoconcha Grayi, Sykes, "found dead" (Collection, British Museum) was found very likely as a fossiliferous shell but may not have been recognized as such. This may be checked by examining the orthotype.
MY BACKGROUND ON NORFOLK ISLAND
I had been responsible for the archaeology of the Kingston area from June 1981 to about April 1990. My final report whilst living on the Island was on the fossiliferous deposits at Cemetery Bay, Kingston. For a while since 1983 I had co-operated with Charles Meredith, formerly of Monash University in regard to fossiliferous bird bones and bird bones found in 1790s stratigraphy. The later fossiliferous deposits were also sites with proof of Polynesian activity, such I reported to Dr Jim Specht, also of the Australian Museum. There was no particular interest in the Norfolk Island land mollusc shells, so I decided to study them myself.
My interest in land molluscs began in my early teens at the northern beaches, Sydney but on Norfolk Island in 1983 when I began to locate them in datable deposits in the middle of the site of the 1788-1814 township of Sydney, now the Pier Area at Kingston. Since that time I made it a study in my free time to locate both fossiliferous and 'live' sites all over the Island. I collected samples on Nepean Island in 1984 but could not use the material because I had placed them in the (Government) Museum in 1988 which I had established under a Bicentennial grant. The material on Nepean Island is exceedingly rich and deserves a separate study. Upon returning to the Australian mainland in 1990, I spent the good part of 17 months reviewing local and Norfolk snail material.
As mentioned in the Introduction, this is largely a morphological study based on shell characteristics and leave the anatomical studies to those trained in the biological sciences.
PRESENT SURVIVING FOSSILIFEROUS DEPOSITS
AT KINGSTON, NORFOLK ISLAND
Kingston has been intensively quarried for its calcareous stone and sand since settlement first began in 1788. The stone is composed of shell-based sand blown up from the greater landmass during times of rising sea level. The bulk of the stone was formed about 23,000 years ago; the dense stone, from which drip-stone filters were made, is of a much more recent date.
Stone was quarried for building and for making into lime. Sand quarrying is a more recent phenomenon and was and is used for mixing to make mortar, levelling paving and for fill in laying service pipes. Thousands and thousands of tons were removed in 1942 to use in creating the present airport. Most of the material came from the calcarenite ridge from Point Hunter to Cemetery Bay, permanently transforming the landscape. With the advent of trucks and mechanical excavators there was no limit on the amount of stone and sand that could be removed. The resident naturalist, Owen Evans remembers his astonishment at the vast numbers of bird bones that emerged from depressions within the ridge when the 1942 quarrying took place.
It can be fairly said that despite every effort and petition to the local government since the early 1980s to stop the quarrying of fossiliferous sand, the government has consistently refused to act. The removal of about 4000 cubic metres of fossiliferous sand from Cemetery Bay in 1990 to use in laying bedding for sewerage pipes would be the most cynical exercise by any government or public authority I have ever had the misfortune to witness. The heritage laws were suspended by an unprecedented act by the then Administrator. The sand is still being quarried (1997), though once again, 'regulated'. The deposits are unique to Kingston and needless to mention, the world. There was no lesson to be learned by what happened.
HISTORIC AND PRE-HISTORIC DEPOSITS
There are several very reliably dated deposits located at Kingston which survive as witness to the initial clearing of the land at the Pier Area in 1788 supported by contemporary accounts. Historic and pre-historic is intended to signify deposits that could not be classified as fossiliferous.
PIER AREA, KINGSTON
An 170 metre trench I was responsible for excavating through the First Settlement Township in 1983 revealed an ordered stratigraphy with undisturbed loam layers, over former reefs, with rich land mollusc shell deposits to disturbed deposits without a single snail shell to be seen but still dating to the initial Settlement period. There was evidence of flooding after the removal and burning of the rich lowland vegetation and then the ingress of sand. The 1790 -1792 period was distinguished by the phenomenal numbers of broken bird bones, the result of systematic exploitation of mainly migratory birds during near-starvation times, as recorded in contemporary journals. The close of the First Settlement period was marked by a thick black band of charcoal, the result of the burning of the settlement, to discourage American whalers and the French from using the Island as a base. The During the 1825-1856 period quarrying took place mainly to level the site and volcanic clayey soil was dumped over the sand to consolidate the surface. The dating of the stratigraphy could confirmed by the types of ceramics, glass and metals found.
Polynesian
Early Polynesian activity was suggested by pre-European ash lenses, burned bird bones and the appearance of Polynesian rat bones (the European convicts ate the rats too as evidenced by the numbers of bones found with the bird bone strata higher up). The deposits were wind blown and were caught in small depressions in the ground, typically composed of the burned bones, charcoal, indigenous snail shells and pumice. The presence of pumice suggests that the area may have been cleared by burning and pumice blew up from the nearby sea. These depressions in the sandy loam were covered over by sand and eventually became part of the soil profile. During early European times the land was cleared and again pumice was blown up from the sea, whereas normally the dense growth would have stopped the pumice from blowing in.
Natural Environment
The evidence of the dense vegetation so close to the sea (protected by sand dunes) is based on the very high loam content of the calcareous sand and the abundance and variety of snail shells found in those deposits. This indicates a fairly dense, diverse and moist forest environment, which is confirmed by the earliest European written and illustrated documentation and parallel sites elsewhere on the Island (particularly the low land forest at Hundred Acre).
Below the loam deposits were sandy layers mixed with broken pieces of calcarenite rock, some worn very smooth, others jagged suggesting a long period of calm and a short period of destruction reflecting a period of sea ingress. There was some evidence that the area served as a partially submerged reef during a geologically recent period of high sea level. Curious calcarenite formations in the shape of tree branches or perhaps even roots were washed loose from the fossil dunes (calcarenite rock) and laid down with the other rock fragments. These strange formations may still be seen in situ at Point Hunter, possibly the result of when the sand was blown up into bushland about 20,000 years ago. The sand dunes gradually turned to stone leaving hollow tubes which were consolidated by lamination of soluble lime which built up along the tubes by the action of rain water. Although the hint of a snail shell might be found in the fossilized sandunes of the Pier Area, the main fossiliferous shell deposits occurred later.
The Massive Calcarenite along the present shore, a dense sandstone without the layering found in the fossiliferous sand dunes, is of various ages, no earlier than five thousand years because it overlies the swamp deposit dated beyond that time and some upper layers within the last thousand years because the stone has been found to incorporate Polynesian stone tools and stone chips. I found snail shells and 'decomposed' pumice incorporated in some of this stone (below the Boatshed to Flaghouses area).
PRESENT GOVERNMENT HOUSE AREA
This area was cleared for farming during the 1790s and certainly thoroughly cleared during the construction of the 1803/1804 government house (and reconstruction during 1828).
Upon excavating down below the construction period deposits, a very rich loamy calcareous sandy soil was discovered. The soil contained many specimens of shells from a range of indigenous snail species, the deposits being almost identical to those found in the Pier Area.
SLAUGHTER BAY SHORE
Rich loam deposits overlain by building and cultural debris, overlain by beach sand drift may be seen midway along the beach, across from the former Convict Barracks. This largely pre-European deposit extends under the road and the Barracks. The deposits seen are not quite as rich as those found at the Pier Area and Government House but the area has been greatly modified since 1788.
CEMETERY BAY FOSSILIFEROUS DEPOSITS
This huge deposit extended from just south of the Cemetery as part of a barrier dune system to the rocky commencement of the low calcarenite stone cliffs leading to Point Hunter. The deposit is long and wide, bounded by the seaside dunes to the east and the golf course to the west.
The deposit of greatest interest is a dense layer of calcarenite sand with a light (leached?) loam content. The deposit is so consistent that it couldn't be mistaken for any other deposit in the area. The deposit is covered by a layer of fairly loose calcareous beach sand between one or two metres thick dating within the last eight hundred years, judging by dates derived from charcoal in the dense layer below. A stone road was built over the sandy layer during convict times but was subsequently covered by sand drift due to the clearing of scrub in the area.
Under the dense loam layer was a deposit of very white powdery calcarenite sand. The sand appears to have undergone a chemical change akin to bleaching. Sharply angled decomposing calcarenite stone fragments were found throughout this deposit. The layer is associated with a large number of number of bivalve shells Arcopagia (Pinguitellina) robusta, particularly at the horizon of the layer above. Most of the shells were chipped as if opened by some agency. The upper half of the deposit was tinged with an orange-yellow hue, the result of a layer of disintegrated (disintegrating) pumice. The shells suggest an estuarine environment during a period of slightly higher sea levels. There is nothing on or around the Island these days that produce such numbers of the bivalve shells. Below this, in stark contrast, is a thick mat of Norfolk Pine roots, perhaps taking advantage of the early swamp deposit. The water table is at the level of the pine roots.
The dense deposit mentioned in the first paragraph of this section, is the fossiliferous deposit. The upper horizon is remarkably straight in line, as anyone familiar with the sand quarries can attest to. The deposit is about a metre thick, though it seems a little thicker where it is closer to the sea. The upper half has overwhelmingly higher loam content than the sandy lower half and suggests a period of gradual colonization by plants. Large pockets of pumice have been found. The upper layer is astoundingly rich in a great variety of indigenous snail species, the larger of which are now extinct or near extinct on Norfolk Island. The deposit is also very rich in bird bones, charcoal. Two Polynesian stone tools were found in this deposit.
The charcoal lenses in the fossiliferous deposit have caught the attention of a number of scientists. Dr Charles Meredith collected a number of carbonized twigs from the 'old sand quarry', since tragically filled with garden rubbish, volcanic soil and creek dredgings (PhD thesis, Monash University, page 22). In 1982 the following 'before present' year figures were obtained, 715 years plus or minus 75 years; 840 years plus or minus 160 years; 850 years plus or minus 50 years; and 800 years plus or minus 50 years.
The old sand quarry, new sand quarry and the huge sand quarry for the laying of the Norfolk sewerage pipeline all contained evidence of charcoal lenses. Some of the charcoal had fallen down old bird burrows and into depressions caused by the burning or decay of large trees that grew there. Charred bird bones were also found scattered about but so were charred snail shells, suggesting accidental contact with fires. Some of the bones may have been the result of Polynesian feasts but one would need a better context to determine that for sure. A minor question is how were these fires started considering that bush fires on the Island by lightening or accident, at any time in recorded history, are virtually unknown. Europeans used fire to help clear land, so it is not impossible that Polynesian people did the same on a smaller scale. Considering that the deposit was laid down some hundreds of years before the arrival of European settlers, it seems very probable that Polynesian people were responsible for the charcoal. The destruction of the rich plant life, as evidenced by the snail shells, tipped the balance in favour of a scattered scrub and sand dunes regime.
The snail shells, in addition to bird, Polynesian rat and lizard bones, are extremely well preserved. In areas where the loam was richer within the deposit, the colours and stripes of the snail shells were better preserved. Incipient petrification was noticed in areas of rich loam.
After the destruction of the forest, there was no longer a homogenous development of deposits into layers and features. The later deposits are not well compacted and have no significant loam content. The lowest layers do contain indigenous snail shells attesting to perhaps a sparse forest or it might just be the result of wind-blown material. The layers above the level of the 1830s stone-based convict road are fairly free of snail shells. The road is a useful indicator of pre-1830s deposits.
The snail shells from the Cemetery Bay sand quarry pits date broadly between 160 and about 1,000 years ago. The dense fossiliferous deposit appears to be earlier than European settlement, there being no indication of European activity. Carbon dating in layers rich in snail shell deposits seems to point to a date around 800 years ago. The rich community of plants, as indicated by the number and variety of snails, and birds came to an end sometime between 800 and 200 years ago when sand dunes and scrub, with the odd pine, dominated the scene. What caused the demise of the plant community is not certain, though the presence of fire might point the finger at Polynesian settlers.
The beginning of the fossiliferous deposit may not be earlier than one to two thousand years, probably somewhere in between, certainly not earlier than 4,000 years, the youngest date obtained from the saprophytic marsh deposit below the 'estuarine' deposit (below the fossiliferous deposit).
OVERVIEW
The range and number of fossiliferous remains was extraordinary, particularly in the snail shell and bird bone categories. It was terrible to have witnessed thousands and thousands of little shells and bones dumped all along the sewerage trenches of the Island in 1990. The fossiliferous sand was used as bedding for sewerage pipes. I believe it was the first time that an administrator used his special powers to override the law, in this case heritage laws relating to Kingston.
The sand was quarried using large mechanical excavators. As the fossiliferous sand was scooped out, upper layers of sand collapsed into the earlier layers below, mixing shells from later introduced snail species such as the tiny Valonia sp., with the fossiliferous material. Charcoal lenses, even Polynesian material was destroyed (I found a part of a stone tool there during the work). I had to refuse to supervise the mass destruction so they brought in a poor PhD student (Palaeontology) from Canberra to witness the farce. There is a fascinating story just waiting to be written about the politics of the Island based on this case alone (but not by me though, it was enough to witness it all).
The range of the snail species matched, as far as it is possible to ascertain, the shallow deposits at Point Hunter, Slaughter Bay and the Pier Area, with the exception of a couple species.
The snail shells found at the Cemetery Bay quarries should be regarded as lowland assemblages, as several species which are undoubtedly endemic and common in the forests of Mount Pitt and Mount Bates were not represented at all at Kingston. Also, a number of species found at Kingston are not represented at the higher altitudes of the Island, several of these are now extinct.
The fossiliferous deposit is significant also in that it is testimony to the extinction of a lizard species (eggs and bones) on the Norfolk mainland and the introduction of the Polynesian rat at an early stage. It is to be wondered what the impact of the introduction of the Polynesian rat had on the extinction of a number of the larger snail species. The introduction of the European rat (Rattus rattus) during World War II appears to have been the final straw for the larger snail species, as well as a number of bird species.
It is important to distinguish the fossiliferous deposits here discussed from the older deposits about to be discussed because of the different extinctions and varieties within species as evidenced from the various deposits.
SLAUGHTER BAY 'PREHISTORIC' LENS
This lens was discovered at the east end of Slaughter Bay after a large calcarenite boulder, near ground level, broke away from the greater mass. This seems to have liberated a compact lens of shells, possibly washed in by rain over a long period of time. The deposit is likely to be considerably earlier than the nearby shallow loam layer deposit which extends from that area under the 1830s or earlier convict road. The youngest part of the loam deposit could be no later than about the 1790s because the area became the focus of lime burning, the bulk of the deposit must date to before then. The area was also the focus of intensive rock quarrying from an early period.
The 'prehistoric' lens contained a species (in large numbers) of a snail not found in the shallow loam deposits noted so far or the Cemetery Bay fossiliferous deposits. Some species were more numerous than found in other sites at Kingston and some species showed greater variability in size than found elsewhere and at present.
SLAUGHTER BAY MASSIVE CALCARENITE SNAIL SHELL INCLUSIONS
Snail shells have also been found IN the more recently formed massive calcarenite (Dripstone) deposits along the shore at the west end of Slaughter Bay. Only a few species were noted: these were associated with bands of pumice. See earlier comments.
EMILY BAY 'PALAEO' FOSSILIFEROUS DEPOSIT
This deposit, which I have dubbed 'palaeo' because of its obvious great age, is distinct from all the other fossiliferous sites so far uncovered.
The deposit is within a fissure in the about 22,000 year old calcarenite outcrop at Emily Bay between the new and convict creek outlets into Emily Bay. The new creek outlet was dug between 1929 and 1945 and cut through this deposit.
The fissure is covered by a layer of rock, rubble and sand not related to the stone quarrying activities of the European period. The closing of the top of the fissure appears to be of great age. The fissure remained hollow as evidenced by the distribution of the snail shell deposit. The shell deposit is in reverse position to what one normally finds--most of the shells were tightly packed at the top of the fissure!!!
The scenario seems to have been that the shells gradually accumulated in the fissure. The fissure was blocked off by some event and the area was inundated by a rise in the sea level. The fissure was filled with water causing the whole shells (trapped air) to rise to the upper cavity. The water pressure must have been great because the floating shells were wedged so tightly that they are difficult to dislodge without breaking. The shells had a 'washed' appearance, as opposed to the dusty appearance of those found in the usual fossiliferous deposits.
The nature of the shell assemblage was different also. There were none of the usual marine inclusions, as found at all the other fossiliferous sites near the sea. Could it be an indication that the deposit was a considerable distance away from the sea when the shells were deposited, unlike the present day situation? The marine exception was a layer of yellowish sludge at the base of the fissure which appears to be decomposed pumice--that might have an origin earlier than the shell deposit
The snail shells, after sorting into species and variations, revealed a disproportion to the species frequencies found at the other sites at Kingston.
Several species were noticeably larger than their present day counterparts and those found in the later fossiliferous sites. In one case, the average shell was smaller than in the other deposits!
At least one common species in the palaeo deposit is absent from all known fossiliferous and live populations and not previously recorded.
No Polynesian rat bones were found, though bird and lizard bones were present.
The question is what could be the date of this deposit, was it created before the sea reached, say, Nepean Island (also very rich in fossiliferous snail shells). More to the point, since the deposit was formed "What Happened!!??". When did the sea rise so as to cover the present day Emily Bay area?
The shells have to be later than the calcarenite stone of the fossilized sand dunes of 22,000 years ago but certainly earlier than 1000 years ago. I suspect that Palaeo deposits may also be found on Nepean Island.
POINT HUNTER ANCIENT DEPOSIT
This is a lens on the east side on top of the ridge that has become exposed because of erosion. The snail shells became mixed with calcarenite stone debris and in places has fused with that debris. More samples will need to be studied to compare with the Palaeo deposit of Emily Bay.
POLYNESIAN AND EUROPEAN RATS
I have found numerous rat bones in deposits dating between 200 and 800 before the present at Kingston. One finds at the beginning of European settlement that rats were a huge problem (Philip Gidley King's journal). The excavations at the Pier Area found rat bones in contexts dated to the 1790s--some burned some not (but in midden deposits with thousands of bird bones). The bones were identified by Charles Meredith as Rattus exulans, hence it is reasonable to conclude that the rats which annoyed the first European settlers were Polynesian rats (it was too soon for European rats to have made an impact). The rash of extinctions and near-extinctions (bird species) since World War II seems attributable to the introduction of Rattus rattus when an American vessel became wrecked near the Pier at Kingston and was disassembled on the reef. I think it was Owen Evans who first proposed this theory of the late introduction of the European rat. Curiously even up to the late 1980s outside experts thought that the Polynesian rat was extinct on the Island (and is listed as such in a number of publications) yet rat traps of the time often ensnared Polynesian rats.
In Norfolk Nature Notes of March 1992, Vol 8, number 1, an article on rat control trials (Ian McFadden, New Zealand Department of Conservation, 1990 and 1991) showed that the Polynesian rat was very common in the National Park, though Rattus rattus more so. My collection of snail shells in the Park indicated that the larger snail species were close to extinction.
PRESENT DAY LIVE POPULATIONS
This section will be written at a later stage. The author collected specimens in all the locations mentioned by previous collectors, and in addition areas of remnant forest and in particular Hundred Acre and the National Park.
It was noted that in areas of healthy tree regeneration such as at Hundred Acre, snail species were numerous whereas they were almost absent in areas of poor regeneration (spindly unhealthy trees) such as at Steele's Point (below High Point).