T A N E 20, 1974

MOLLUSCA IN MAORI MIDDENS ON SLIPPER ISLAND

by R.C. Willan*

SUMMARY

A list of land and marine molluscs observed in Maori midden sites at South Bay, Slipper Island is presented. The probable origins of the shellfish are discussed. Using land snails taken from the middens it is possible to describe broadly the vegetation types that existed on pre-European Slipper Island. The presence of two interesting gastropod species in the midden is recorded; Cellana denticulata (Martyn) and Papusuccinea archeyi (Powell), both rep­resenting new locality records.

INTRODUCTION

For a considerable distance along the fixed dunes backing South Bay, the wind and tides have exposed profiles of Maori midden. Molluscan shells as well as bones of fishes and mammals are scattered amongst the charcoal lumps and flakes of obsidian in darker layers of these sand dunes. It appears that foraging parties of Maoris disposed of the remains of their meals by throwing them into pits or sand hollows at the back of the beach. These people would have been either permanent inhabitants of the pa on Slipper Island or parties travelling up or down the coast.

METHODS

Marine shells observed in the exposed midden profile were listed while still in situ, land molluscs were collected for later identification. A search was made of scrub vegetation on the sand dunes for live land snails, and only the introduced European Helix aspersa M'uller and Vallonia excentrica Sterki were found.

*Zoology Department, University of Auckland.

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MOLLUSCAN SPECIES LIST

Molluscs recorded from the middens: AMPHINEURA:

GASTROPODA Prosobranchia:

Pulmonata:

BIVALVIA:

Sypharochiton pelliserpentis (Quoy & Gaimard, 1835) Eudoxochiton nobilis (Gray, 1843)

Haliotis iris Gmelin, 1791 Patelloida corticata (Hutton, 1880) Cellana denticulata (Martyn, 1784) Cellana radians (Gmelin, 1791) Cellana ornata (Dillwyn, 1817) Melagraphia aethiops (Gmelin, 1791) Zethalia zelandica (A. Adams, 1854) Lunella smaragda (Gmelin, 1791) Cookia sulcata (Gmelin, 1791) Nerita melanotragus (Smith, 1884) Maoricolpus roseus roseus (Quoy & Gaimard, 1834) Thais orbita (Gmelin, 1791)

= Neothais scalaris (Menke, 1829) Haustrum haustorium (Gmelin, 1791) Cominella adspersa (Bruguiere, 1789) Cominella maculosa (Martyn, 1784) Thalassohelix zelandiae (Gray, 1843) Laoma (Phrixgnathus) phrynia (Hutton, 1883) Laoma (Phrixgnathus) sublucida Suter, 1896 Paralaoma pumila (Hutton, 1883) Elasmias subperforata (Suter, 1909) Rhytida greenwoodi greenwoodi (Gray, 1850) Delos jeffreysiana (Pfeiffer, 1853) Papusuccinea archeyi (Powell, 1933) Perna canaliculus (Gmelin, 1791) Dosinia ? subrosea (Gray, 1835) Chione stutchburyi (Gray, 1828) Amphidesma australe (Gmelin, 1791) Amphidesma subtriangulatum (Wood, 1828)

DISCUSSION

The occurrence and origin of the species present will now be examined, with emphasis on ecological and prehistoric implications, dealing firstly with the marine molluscs:

The most abundant species were Lunella smaragda, Chione stutchburyi (tuangi), Amphidesma australe (pipi), Cellana radians and Cellana ornata, all of which had undoubtedly been used as food. The coiled gastropod shells had their spires broken off, the animals had apparently been prized out. Such breakage patterns can only be explained by assuming the shells were cracked open and used as food by the Maoris. No natural mechanisms would account

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for the general breakage patterns observed. The bivalve shells appeared to have been baked until the valves opened. Criteria used to justify this statement are the characteristic fractures and shell discolouration seen on pipi and tuangi valves.

Less common were Cominella adspersa, Thais orbita, Haustrum haustorium, Cookia sulcata, Nerita melanotragus and Melagraphia aethiops; many of these shells had been cracked open, again apparently by the Maoris.

Finally some shells were only rarely observed, and these were not cracked or burnt. Presumably such species as Zethalia zelandica, Patelloida corticata and Maoricolpus roseus roseus were not eaten but had been accidentally gathered. For example the limpet Patelloida corticata may have been collected while attached to a mussel shell.

The rocky shore adjacent to South Bay would most probably have provided many of the species noted in the middens, such as Lunella smaragda, Cellana ornata, Cellana radians, Nerita melanotragus, Haustrum haustorium, and Perna canaliculus. Amphidesma subtriangulatum however, could have been dug out from the clean sand when the tide was low. Species such as Chione stutchburyi and Amphidesma australe are typical dwellers of harbours and estuarine flats, and not offshore islands. Since such bivalves are not living at present on Slipper Island, it is probable that large quantities of them were gathered on the coast and brought to offshore islands to be used as an additional food source. This statement is supported by Moore's observations on the Aldermen Islands.5 Pipi valves were found amongst midden on Ruamahua-iti Island, but pipi and tuangi do not live around the Aldermen Islands.

Since the smaller land molluscs were not eaten, one must speculate on their presence in the middens. Some species (Elasmias subperforata, Papusuccinea archeyi) can live amongst the sparse plant growth on fixed sand dunes,7 while others (Paraloama pumila, Thalassohelix zelandiae) can survive in coastal flax and scrub vegetation. Specimens of Thalassohelix zelandiae and Laoma sublicida were most common. Other species such as Rhytida greenwoodi, Delos jeffreysiana and Laoma phrynia are typical inhabi­tants of native bush, being found amongst damp leaf litter on the forest floor.

These small land snails can be used as good indicators of the type of vegetation existing at the time of pre-historic Maori occupation on Slipper Island. The snails fall into two groups depending on the situation in which they live, one group is typical of coastal forest, the other of sand dunes. Because of the presence of snails in the midden from both these habitats it appears that a major change in the coastal vegetation must have taken place.

An explanation is presented by Powell 7 based on studies of similar coastal sites in Northland. It is suggested that initially the area was covered in coastal forest as can still be seen on adjacent Shore and Rabbit Islands1. This forest supported growth of typically bush-living land snails such as Delos jeffreysiana, Rhytida greenwoodi and Laoma phrynia. These conditions were followed by a presumed dry period when coastal rain forests died and allowed the formation of drifting dunes and the development of a sand-grass community with the snail Papusuccinea archeyi. The sedge Desmoschoenus spiralis and grass Spinifex hirsutus are characteristic plants of such dunes.

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Papusuccinea is an excellent indicator of these coastal xerophytic conditions because of its extremely specialized habitat and narrow tolerance limits. 7

Ultimately this species was eliminated under conditions with the succession to the fully developed scrub dune community, with Coprosma, Meuhlenbeckia and Cassinia species dominating. Typical land snails of this community are Paralaoma pumila and Thalassohelix zelandiae. The latter is the youngest community and one would expect the majority of land snails in the midden to belong to it; this was found to be true.

These changes took place then, in pre-historic Maori times. The Maoris could well have contributed to this successtion by extensively clearing the coastal forest, at least in the south west sector, to meet timber requirements for palisading and to satisfy the need for cleared arable land. 2

Finally record must be made of the presence of two molluscs in these Maori midden sites. Slipper Island is a new locality record for both species: 1. Cellana denticulata (Martyn, 1784), sometimes called the Cook Strait Limpet, this species is abundant around Wellington and further south.6 In the northern part of the North Island it has been recorded to occur spasmodically on prominent land features and offshore islands, specimens have been found at the Three Knights Islands, Poor Knights Islands, North Cape, Cape Maria van Diemen, Mayor Island and the East Cape Region. 4 ' 9 In the far north large dead shells have been collected from exposed foredune middens at Spirits Bay (R.C.W. 28/12/1965) and Tapotupotu Beach (R.C.W. 20/1/1970), revealing their earlier existence at these localities. The presence of two shells found in the South Bay midden (lengths 39mm, 43.5mm) can be explained in the same way as these above-mentioned occurrences have been. This is by sporadic northern settlement of larvae of this species from cooler southern waters; these specimens generally do not achieve stable breeding populations in northern waters. ' 8

2. Papusuccinea archeyi (Powell, 1933) is New Zealand's single species of amber snail, typically found amongst vegetation on coastal foredunes. This species, as already explained, is a useful indicator of past xerophytic phases in respect to post-glacial climate.7 Specimens have been recorded only from the east coast of the North Island, in the north at Spirits Bay, Tokerau Beach, Taipa Beach and north of Whananaki7'1 0 and in a block of localities further south in the Bay of Plenty and on the Coromandel Peninsula. Specimens have been found at Whangamata , Mount Maunganui 1 0 ' 1 1 and Papamoa Beach.1 1

The specimens collected from the middens at South Bay (nine in all), are thus a new locality record in the southern area of the distribution of Papusuccinea archeyi. An unsuccessful search for live specimens was made on the surrounding dunes.

ACKNOWLEDGEMENTS

Mr Jeremy Spencer and Miss Janette Underwood assisted cheerfully with the field work. Thanks must also go to Mr N . Gardner for identification of some of the small land snails and to Mr R. Cassels (Department of Anthro­pology) who read the manuscript and provided useful criticisms.

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REFERENCES

'Court, D.J. 1974 Botany of Shoe Island and the Slipper Island Group - Coromandel Peninsula. Part 1. Vegetation. Tane 20 (this volume).

2Edson, S.C. 1973. Human Ecology and Prehistoric Settlement of some Offshore Islands (East Cape to Cape Reinga). Unpublished MSc. thesis, University of Auckland.

3Jones, A .H . 1954. At Whangamata. Conchology Section of the Auckland Museum. Bull. 10: 9-10.

4Milligan, E.N. 1953. Marine Molluscs. Tane 6: 127-141. 5Moore, P.R. 1971. Evidence of Former Maori Occupation of the Aldermen Islands.

Tane 19: 21-29. 6Morton, J.E. , Miller, M.C. 1968. "The New Zealand Sea Shore". Collins, London. 638pp. 7Powell, A.W.B. 1950. Life History of Austrosuccinea archeyi, an Annual Snail and its

Value as a Post-Glacial Climatic Indicator. Rec.Auckland Inst. Mus. 4(1): 61-72. 8Powell, A.W.B. 1961. "Shells of New Zealand". Whitcombe & Tombs Ltd. 203pp.

Fourth Edition. 9Powell, A.W.B. 1973. The Patellid Limpets of the World (Patellidae). Indo-Pacific.

Mollusca3(15}: 75-206. 1 0Thomson, W.P. 1952. Austrosuccinea archeyi (Powell) at Mount Maunganui. Auckland

Museum Conchology Club Bull.8: 9-10. "Thomson, W.P. 1959. Austrosuccinea archeyi (Powell) - Further Records. Conchology

Section of the Auckland Museum. Bull.15: 19-20.

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