Tuatara tale a tell-all

University of Otago associate professor of zoology Alison Cree has just published  <i>Tuatara:...
University of Otago associate professor of zoology Alison Cree has just published <i>Tuatara: biology and conservation of a venerable survivor</i>, which documents almost 800 years of human contact with tuatara. Photos supplied.
Alison Cree.
Alison Cree.
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tuatara_tale_a_tell_all_541bd04b04.JPG
The book.
The book.

The tuatara may be regarded as a national treasure but don't call it a living fossil, biologist Alison Cree tells Shane Gilchrist.

The tuatara has graced postage stamps, the New Zealand 5c coin (until inflation put paid to that in 2006) and the cover of a 1985 Flying Nun music compilation, as well as beer and wine bottles.

Sculptures of its distinctive form crop up in schools, playgrounds and public spaces throughout the land; it is regarded as taonga, treasure, by a number of Maori iwi.

Yet, it's an animal that remains something of an enigma to many.

Alison Cree hopes to change that.

An associate professor of zoology at the University of Otago, she has just published Tuatara: biology and conservation of a venerable survivor (Canterbury University Press), a ''long overdue'' update on the subject.

Documenting almost 800 years of human contact with the spiny creature, Dr Cree also presents and adds to nearly 200 years of published research, including how the lineage leading to tuatara came to be isolated in New Zealand.

Ever since she began studying the tuatara as a postdoctoral researcher in the 1980s, Dr Cree has harboured the idea of producing a comprehensive book, believing it would help a variety of people ''from researchers in New Zealand and around the world, students doing assignments, and the many people who are now involved in the conservation of tuatara''.

An author of more than 100 scientific publications (she has also studied the biology of New Zealand lizards and frogs), Dr Cree admits to a sense of both relief and pride that Tuatara appears to be a balancing act between an exhaustive scientific treatise and a reference book that might also appeal to others, be they passionate or merely curious.

''The reward will be if people working with tuatara in the future find the book useful.

''I don't mean just my contemporaries. There are many groups in the community who are becoming involved in the management of tuatara habitats, translocations, ecosanctuaries, islands, captive populations and so forth,'' Dr Cree says, adding she has enjoyed great support from various iwi to work with live tuatara.

''Professionals like me have access to journals and specialist publications. But for others, it's not so easy to get information, or if they do get hold of scientific articles, they may not be so easy to understand.''

Known formally to scientists the world over as the genus Sphenodon, the tuatara is represented today by the sole living species Sphenodon punctatus.

Formal study began with the first published description in 1831, but advanced greatly from 1867 when tuatara became recognised as the only surviving example of rhynchocephalians, one of the four orders of living reptiles.

That led to what Dr Cree labels an ''evolutionary conundrum''.

The tuatara is clearly living today and is therefore a modern reptile.

Yet it is often described as a ''living fossil'', as if it has been directly transplanted from Mesozoic times.

''That idea of a 'living fossil' has no precise meaning for a professional biologist,'' she says.

''One common understanding of the term - in the public's eye - is of an animal that hasn't changed in many millions of years.''

In her book, Dr Cree points out that, in fact, the oldest described fossils of tuatara - the genus Sphenodon - are no more than about 34,000 to 100,000 years old.

''Although the discovery of Miocene fossil jawbones resembling those of tuatara could push this back further (by up to 19 million years for the subfamily), it is apparent that the fossil record for tuatara is not an especially ancient one.

"Compared with its Mesozoic relatives, Sphenodon must be viewed as an essentially modern genus,'' she writes.

''When talking about antiquity, it is important to make a distinction between tuatara in particular and rhynchocephalians in general.

''The fossil record for rhynchocephalians dates from at least 220 million years ago in the Triassic, and tuatara clearly share some characteristics with the earliest forms.

"But tuatara are not identical to Mesozoic species, having their own unique combination of specialised characters,'' she notes in a breakout box early in her book.

''The view of tuatara as ... a species unchanged for hundreds of millions of years, perhaps even ancestral to other living reptiles, is now viewed as quaint by the majority of scientists. Yet it still emerges in some publications and continues to hold tremendous popular appeal.''

Dr Cree also dissects the evolution of tuatara research, pointing out how scientific interest has changed in focus, from initial studies on unusual anatomical features, through research into ecology and environmental relationships, to today's concern with conservation.

Although the Department of Conservation recently carried out a survey in which the tuatara was identified as one of 10 species that define New Zealand, human interaction has not always spawned favourable results.

Humans and tuatara have been in contact for almost eight centuries following the settlement, from about 1200, of voyagers from east Polynesia, who brought with them the Pacific rat, or kiore, believed to have preyed on tuatara eggs and juveniles and competed for similar food sources.

Yet Pacific rats were not the only eaters of tuatara.

Middens provide evidence that Polynesians harvested them for food at a range of locations, including at Kakanui, in North Otago, and Long Beach, north of Dunedin.

''Tuatara jawbones, which are pretty distinctive, have been found in various middens, the inference being they were being eaten by Polynesians who settled. That might not be well-accepted today, but I think that's what any humans would have done,'' Dr Cree says.

The environmental impact of Polynesian settlement was considerable, she notes.

By the late 1700s, when Europeans first arrived, nearly half the mainland forests had gone.

The implications for not only tuatara but a range of species are well-documented (extinct: Haast's eagle, moa ...).

European settlement then added rats, dogs, cats, rabbits and other animals to the mix.

Fast-forward to the 1990s, by which time 34 species of land mammals, 33 species of birds, 20 species of freshwater fish, about 1500 species of insects and a similar number of plant species had been added to the list of alien arrivals.

''Now, wild tuatara are estimated to number between 60,000-100,000, of which at least half are estimated to be on one island - that is, Stephen's Island (Takapourewa) in Cook Strait,'' Dr Cree says.

''As to captivity, as of July 2010 there were more than 380. Those numbers fluctuate as, for example, some juveniles have since been released to the wild and others come in as eggs from the wild that then hatch. Captive numbers are now likely to be in the low hundreds.

''Tuatara are sufficiently numerous in the wild not to be categorised as a threatened species, though they are clearly much reduced in distribution and numbers compared with pre-human times, and some populations on small islands are at risk of local extinction.

''It would be fair to note that many New Zealand lizards have a higher level of concern in terms of risk of extinction ... and that tuatara can be a bit of a flagship for these.''

Fortunately, tuatara can survive in quite modified habitats, Dr Cree points out.

''They are quite adaptable animals, but they need shelter from warm temperatures. Hence the need to burrow to find cool areas as well as come out and bask safely. But they don't require too much food.''

The tuatara could also be regarded as research-friendly: it is small enough to be manageable by hand, yet its body is large enough to enable the attachment of a radiotransmitter and to have blood or other tissues taken; it is not poisonous or particularly dangerous; and it lives for a long time, allowing for extended studies of the same individuals.

Still, patience is required.

Dr Cree says tuatara that have been visible in captivity have often frustrated observers.

According to a lighthouse keeper of 1913, one tuatara held indoors, and around which a pencilled outline was drawn on the floor, did not shift its position for more than six weeks.

And that apparent disinclination for activity extends to the tuatara's mating habits.

''They don't reproduce often; they take a long time to mature sexually. Therefore they need to live for a long time in order for there to be a population 'recruitment'.

''One interesting aspect that has conservation repercussion is the discovery that a tuatara's sex is determined by temperature.

"The basic idea is that the sex of an embryo is not decided when a sperm and egg meet.

"It happens later, when an embryo is partway through its development. If soil temperature is relatively cool, it will become a female; if warm, it will be male.

''You can see that population ratios can become skewed if soil temperatures are in a narrow range,'' Dr Cree says.

''However, knowing that, it is possible to manipulate soil temperatures in a captive situation. On the other hand, we are not sure what is happening in the wild.''

 


The book

Tuatara: biology and conservation of a venerable survivor, by Alison Cree, is published by Canterbury University Press ($89.99).


 

 

 

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