The Tuataras of New Zealand

The Tuataras Of New Zealand
Tony Jones

Tuatara pic to follow

Tuatara pic to follow

In September 2000 I flew to Christchurch on the South Island of New Zealand.  This was to be a bit of a first for me as I had promised my girlfriend that this trip was to be a real holiday instead of spending two weeks trekking around the undergrowth looking for animals.  I did not pack a field guide, did not call any zoos, did not make contact with any local herpers and did not even look to see what herps were to be found in New Zealand.  However, despite all of my non-preparations, I knew in the back of my mind that no trip to this unique habitat would be complete without an encounter with one of the real enigmas of the reptile world….. the tuatara.

New Zealand must indeed be unique for it is only here that the single representative of an ancient order of reptiles has survived.  Its nearest relatives died out at least 60 million years ago leaving only the tuatara to remain isolated to New Zealand and its nearby islands.   Often described as a “living fossil”, the tuatara is now restricted to a handful of islands off the coast of New Zealand, having been eradicated from its habitats on the mainland.  This is mainly due to the introduction of Pacific rats (which out-compete the tuatara for food) and pigs which had been introduced by Europeans.

Tuataras were originally thought to be related to Agamid lizards and were classified here by John Gray of the British Museum in 1831.  Gray had been in receipt of a single tuatara skull and had noted the chisel like marks made by the upper mandible, leading to the use of the Latin  Sphenodon, meaning “Wedge Tooth”  Incidentally Gray later received a whole tuatara skeleton and, not realising this was from the same animal as Sphenodon, named it Hatteria punctuata and still grouped it with the Agamids.

Although subsequent scientists soon realised that the tuatara was certainly not a lizard it has been the responsibility of recent DNA work by Dr Charles Daugherty at Victoria University that has (almost) settled the arguments surrounding the tuatara.  There are now two recognised species of tuatara; Sphenodon punctuatus, and the much less common, Sphenodon guntheri. (Gunther 1867)

It is understandable that Gray thought the tuatara to be an Agamid lizard.  The similarities are astonishing.  Even when armed with knowledge to the contrary, as I held a tuatara in my hand it was difficult to conceive that this animal is not a lizard.  It has many typically saurian features; its back sports a row of spines and their diet is typically lizard like.  Even upon close scrutiny, it looks more like a lizard than some lizards do!  At least the tuatara has legs!  So what’s the difference?  There are many but here are some of the major differences.

•    Tuataras have no copulatory organs.
Male tuataras have no penis.  Copulation is similar to that of lizards with the male subduing the female by grasping the back of her neck with his jaws and twisting his tail around hers until the cloacas are aligned.  From here things change slightly. As the tuatara has no penis, fertilisation is achieved by sperm flowing directly from the male’s vent into the female.
•    Tuataras have a parietal eye.
Ok so your iguana has one too.  However, in tuataras, the degeneration of this organ is less complete.  It has a rudimentary retina and lens and has a chemical connection to the brain.  It is thought to be associated with the pineal gland and appears to help in the early development of tuataras and have some role as a general biological clock!
•    Tuataras have a stronger skull.
The skull is more robust and is more like that of a crocodile than a lizard.  There are also more holes in a tuatara skull than in those of a lizard.
•    Tuataras have skeletal similarities they share with birds.
Their vertebrae and ribs have features that they share with birds and a few extinct fossil reptiles, namely the hook like structures that attach the muscles and ribs.
•    Tuataras have a beak.
This feature is less pronounced in tuataras but is more noticeable in the skulls of extinct relatives.  (The sphenodontida were at one time thought to be the dominant reptile group during the age of the dinosaur.)

The specimens that I had the opportunity to handle were on display at Orana Park in Christchurch, New Zealand.  The animals were housed in a simple enclosure within the small reptile house at the park.  All told there were around a dozen or so enclosures of various sizes, most of which housed native species such as common gecko, common skink and green gecko.  There were two non-native species, an Australian lace monitor and a pair of Australian shingle back skinks.  Two of the larger enclosures housed tuataras.  The décor and set up were quite basic with a dirt/mulch substrate and a large ceramic water-bowl.  In addition to the various bark hides that littered the floor of the enclosure, there was also a short length of corrugated tubing which was buried at a 45 degree angle.  This led to a shelter beneath the floor of the enclosure which was accessible from above through a trap door.  This underground lair seemed to be a favourite spot for the tuataras as this was the first place the keeper looked when trying to find the animals.  In the wild tuataras often co-habit, sharing burrows with birds such as prions and other nesting sea birds.

Although tuataras are essentially nocturnal, they often emerge from their burrows to bask when necessary. (As do many other species of nocturnal reptile.)  In the wild their diet consists of many insects along with worms, snails, spiders, beetles and the like.  Tuataras will also eat small seabird chicks and eggs, particularly those with which they share their burrows.  The tuataras at Orana are fed a typical variety of commercial live-foods including mealworms, wax worms and wax moths and are treated with an occasional pink mouse.  I was surprised to hear that crickets do not feature in the diet although I could not ascertain if this was by design or because they were not available.

Tuataras are tolerant of much cooler temperatures than many lizards or snakes would prefer.  Indeed, tuataras are active at temperatures below 7 degrees C.  This is reflected in the design of the enclosure which is almost completely glass apart from a large wire mesh section which vented directly outdoors.  On the day we visited the park during New Zealand’s mid spring, the weather was particularly cold and we were wearing coats and hats.  Even during the winter months, the tuataras at Orana Park are not provided with any supplemental heat. When I held the animal I could feel that it’s body temperature was very cool, even though my hands were not particularly warm anyway.  If this had been a lizard in my collection I would have been quite concerned.  Fortunately, this was no lizard.  Unfortunately, it wasn’t in my collection either!

Tuataras have not been bred at Orana Park, but at the most southerly tip of New Zealand’s South Island is the world’s leading tuatara breeding project.  Invercargill is home to the Southland Museum, which houses the “Tuatarium”.  I managed to contact Lindsay Hazely, a leading authority on tuatara husbandry and breeding having worked with these animals at Southland Museum for thirty years.

The entire collection is housed on display in the 200 square metre enclosure, which is divided into several separate areas to house the different sizes and age groups.  Here are housed four adult tuatara (Sp. punctuatus) from which Lindsay has produced over 60 living offspring, the oldest of these being 16 years old.  In addition to this the Tuatarium has also raised 7 Brothers Island tuatara (Sp guntheri) which are now 10 years old.

To the un-initiated, thirty years to produce 60 offspring may not seem like much of an accomplishment.  However, when you consider that tuataras may not reach sexual maturity until between 18 and 22 years of age, the picture becomes a little clearer.  In the indoor enclosure at the Tuatarium, both heat and food are provided at optimum levels.  This allows the developmental process to proceed a little more quickly, with breeding success being achieved at around 14 years.  Accelerated sexual maturity is not the only benefit of the artificial environment.  The tuataras at Southland are the first to achieve annual breeding, a feat that was never thought to be possible.  Wild tuataras have a biennial breeding cycle (at the most) which is certainly one of the major reasons there are declining wild populations. (Think on that for a while!)

Tuataras were first bred at the Tuatarium in 1984, and since then the centre has become the worlds most successful tuatara breeding project.  Of the sixty or so young the centre has produced,  Southland has supplied 32 tuatara to other institutions, with a re-introduction programme as the ultimate goal.  And the project goes from strength to strength.  No captive hatched tuatara has itself produced young, but in 1998 a 14 year old captive raised female at the Tuatarium produced eggs. Although the eggs were not viable, this event was the first of its kind in captivity and helps to confirm that tuataras can be sexually mature at 14 years of age.

Lindsay attributes the success of the tuatara breeding project at Southland Museum to a number of contributing factors.  The first and most important being temperature.  Although the arrival of humans and non native predators has accelerated the demise of the tuatara; (They are now only represented in 0.1% of their former range!) Lindsay also cites a dramatic climate change.  Having looked at historic weather patterns and comparing them with the present day it appears that the current climate in New Zealand may have the tuatara struggling.  Indeed Newman & Cree (1991) observed that 25% of females gravid in the wild lay once every four years.  The prime conditions in the artificial environment at Southland have seen the average female gravidity rate soar well above the wild rate of 21%.  Moreover, such conditions seem to allow juvenile tuatara to reach sexual maturity within its physiological possibility.

Secondly and related to the provision of optimum temperatures is the abundance of food.  By maintaining the mean air temperatures at 16-17 Degrees Celsius the females at Southland are able to consume an average of 100-150 grams of food each year.  The longer, warmer “summer” allows for a more active metabolism and an increase in food consumption.  These extra calories and nutrients are then made available for egg production.  This is thought to be a major contributing factor in the annual production of eggs.

Lastly but interestingly is the provision of UV light.  Lizard producers have long known of the importance of UV and its role in vitamin D3 and calcium metabolism.  The provision of UV for these purposes seems consistent with the breeding and rearing of tuatara.  However, experiments with captive hatched tuatara have led Lindsay to explore the influence of UV on the pineal gland.  As we know the degeneration of the parietal eye in tuatara is less complete and is thought to have a relationship with the pineal gland. (The body’s time clock)  In newborn tuatara the parietal eye is visible under the skin but becomes covered with less transparent scales over a period of 6-12 months.  After experiencing a 50-80% mortality rate in newborn tuatara, in 1992 Lindsay started to experiment with UV and tuatara hatchlings. The primary cause of death had been a chronic calcium deficiency, which had not responded to dietary supplementation.  He now achieves 100% rearing success!  This can only be good news for the survival of this fascinating and biologically important reptile.

Although the North Island has a greater diversity of wild species than the rest of New Zealand, the South Island has its own attractions.  Apart from the obvious attraction of collections such as that at Orana Park and Southland Museum, the Island itself is exceptionally beautiful.  It was impossible to discipline myself and not come home with enough landscape photos to fill an entire album!  The scenery, fauna and flora make a trip to New Zealand one that I would highly recommend.

Thanks to Korina Ferguson at Orana Park Christchurch, New Zealand for allowing access to their Tuataras.

Huge thanks to Lindsay Hazely at The Tuatarium, Southlands Museum Invercargill. New Zealand, for all the info, advice and corrections, not to mention the photos.

Literature Cited.
Gill B &Whitaker T: New Zealand Frogs & Reptiles.
Parkinson B : The Tuatara
Hazley L : UV and Life
Hazely L : Annual Breeding of Tuatara (abstract)

Published: REPTILES magazine.


~ by Tony's Desk on March 10, 2009.

One Response to “The Tuataras of New Zealand”

  1. Hello!
    Very Interesting post! Thank you for such interesting resource!
    PS: Sorry for my bad english, I’v just started to learn this language 😉
    See you!
    Your, Raiul Baztepo

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