Overview

Brief Summary

Biology

The Brothers Island tuatara is terrestrial and primarily nocturnal, though, as an ectotherm, it spends part of its day basking in the sun outside its burrow to warm up. It does not drink water, and feeds at night on insects, worms, snails, birds eggs, chicks and occasionally even its own young (4). A special type of jaw movement allows the tuatara to shear bony prey with ease (5). In addition, the tuatara has pronounced jaw muscles due to the skull's bone arrangement: like most modern reptiles (except for turtles), this species has a diapsid skull. This means it has two holes behind the eye-holes, and a greater bone surface area for muscle attachment. As a result the tuatara's head is huge, the jaw muscles pronounced, and the bite ferocious (6). They often take over and live in bird burrows, though tuatara can and frequently do construct their own burrows (5). Several may use the same burrow, although at different times, and residents can be quite aggressive to intruders (5). Females only reproduce once every two to five years, and males compete for the right to mate, with territorial displays, aggressive fights and erected crests to make them appear larger than they are (4). Mating occurs between January and March and eggs are laid from October to December (2). About 8 to 15 eggs are deposited in small, specially constructed chambers, covered with soil and abandoned. They hatch after 12 to 15 months, which is the longest hatching time for any reptile (2) (5). The sex of the offspring is determined by the temperature: warm soil temperatures produce males, while cool soil temperatures produce females (5). Individuals reach maturity between 9 and 13 years of age, which may seem late, but these fascinating reptiles are believed to live for over 100 years (2). Their long life is the product of having an extremely low metabolic rate, and a slow growth rate, which is due to their tolerance to extremely cool weather. Indeed the activity levels of the tuatara peak at body temperatures of 12 to 17 degrees Celsius, the lowest for any reptile. This is probably why they have been able to survive in New Zealand's temperate climate for so long (4).
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Description

The Brothers Island tuatara is one of the oldest animals in the world today (4). It may look like a lizard but it belongs to the order Rhynchocephalia, which includes ancient reptiles that existed 200 million years ago. All other species in this order, apart from the tuataras, declined and eventually became extinct about 60 million years ago. Tuataras are therefore of huge interest to biologists as they represent the only living link to these ancient reptiles. The Brothers Island tuatara is one of two species of tuatara, the other being the more common Sphenodon punctatus species, which is found on the Northern Islands (5). The Brothers Island tuatara has a lizard-like body, and a long tail, stocky legs, long claws and a large head. A crest of spines runs along its back, neck and head: a characteristic which led to its Maori name, meaning 'peaks on the back,' (4) (5). Males are larger than females, with larger spines, though they look similar with olive green, grey, or dark pink body colouration, and speckles of grey, white or yellow. Newly hatched young are brown or grey, with pink tinges and a striped throat (5). This reptile has the unusual feature of a third pineal eye: This eye has a retina, a rudimentary lens and is connected to the brain by a nerve. While it is apparent in infants, it becomes covered by opaque scales in adults, so it is unknown whether the eye serves any function (4).
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Distribution

Brothers Island tuataras inhabit North Brother Island in Cook Straight, New Zealand (41°06′S, 174°26′E). Only a few hundred individuals remain on North Brother Island.

Biogeographic Regions: australian (Native )

Other Geographic Terms: island endemic

  • Cree, A. 1994. Low annual reproductive output in female reptiles from New Zealand. New Zealand Journal of Zoology, 21/4: 351-372.
  • Lutz, D. 2005. Tuatara: A Living Fossil. Salem, OR: DIMI Press.
  • Mitchell, N., M. Kearney, N. Nelson, W. Porter. 2008. Predicting the fate of a living fossil: how will global warming affect sex determination and hatching phenology in tuatara?. The Royal Society, 275/1648: 2185-2193.
  • Thompson, M., C. Daughtery, A. Cree, D. French, J. Gillingham, R. Barwick. 1992. Status and longevity of the tuatara, Sphenodon guntheri, and Duvaucel's gecko, Hoplodactylus duvaucelii, on North Brother Island, New Zealand. Journal of the Royal Society of New Zealand, 22/2: 123-130.
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Continent: Oceania
Distribution: New Zealand (North Brother Island, Cook Strait)
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Historic Range:
New Zealand (N. Brother's Island)

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Range

This rare species is only found on Brothers Island, off the coast of New Zealand. It has survived there for 200 million years because there are no natural predators. A recent survey estimated that only 400 individuals exist here (2) (5).
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Physical Description

Morphology

Tuataras generally have a lizard-like appearance, but differ from lizards in that their teeth are attached to bone, they have two temporal openings, they have no external ear, and the males lack sexual organs. Tuatara means “bearing spines”, referring to the single row of spines running along their dorsal side. The skin of this species is generally olive-brown with yellowish patches, which offers effective camouflage in their environment. When born, tuataras possess a third eye on the top of their head (called a parietal eye). This pineal spot appears somewhat functional at birth, but becomes covered with skin after several months and does not appear to serve a functional purpose thereafter. Adults are fairly large and rather slow moving, reaching a weight of 900 g and a length of 76 cm. Males are larger than females and have proportionately larger heads and crests.

Brothers Island tuataras belong to the order Rynchocephalia, which contains only one other living species, Sphenodon punctatus (spotted tuataras). Brothers Island tuataras are characteristically smaller and have longer reproductive cycles than spotted tuataras.

Range mass: 900 (high) g.

Range length: 76 (high) cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: male larger

  • Pope, C. 1956. The Reptile World. London: Routledge & Kegan Paul Ltd.
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Ecology

Habitat

Brothers Island tuataras are one of the few reptiles with the ability to thrive in cooler conditions. They are nocturnal and physically capable of withstanding temperatures as low as 9°C, with humidity in the range of 70 to 80%. High humidity and low temperatures allow tuataras to maintain healthy shed cycles and live longer life spans, due to their effects on heart and metabolic rates. During the day, most individuals inhabit burrows along cliff faces. Their burrows can measure about 5 meters in length and 30 centimeters in depth, and are sometimes taken over from previous inhabitants. Burrows are typically found in open areas featuring low coastal vegetation, and usually offer both shade and sunlight to aid in heat regulation. Certain cliffs and other areas of the island that provide different types of terrain are often inhabited by birds or other animals that can compete with tuataras for territory.

Range elevation: 87 (high) m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: chaparral

  • Nelson, N., S. Keall, S. Pledger, C. Daugherty. 2002. Male-biased sex ratio in a small tuatara population. Journal of Biogeography, 29/5-6: 633-640.
  • Ramstad, K., N. Nelson, G. Paine, D. Beech, A. Paul, P. Paul, F. Allendorf, C. Daughtery. 2007. Species and cultural conservation in New Zealand: Maori traditional ecological knowledge of tuatara. Conservation Biology, 21/2: 455-464.
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Habitat and Ecology

Systems
  • Terrestrial
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Inhabits low forest, scrub areas and rock stacks on Brothers Island, and is found between zero and three hundred meters above sea level, where the climate is cool (2) (5). The island is also occupied by petrel and shearwater birds, which provide the tuatara with many benefits (5).
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Trophic Strategy

Tuataras are carnivorous and will eat whatever they can catch. They often prey on beetles, worms, lizards, and other tuataras. They prefer to eat wetas (Deincrida rugosa), an insect species that is endemic to New Zealand. Occasionally, tuataras will eat sea bird eggs located in borrows close to their territories.

Animal Foods: birds; reptiles; eggs; insects; terrestrial worms

Primary Diet: carnivore (Eats terrestrial vertebrates, Insectivore )

  • New, T. 2008. Insect Conservation and Islands. Springer.
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Associations

Tuataras prey mostly on invertebrates. As tuataras and sea birds may live in close proximity, tuataras occasionally steal eggs from the birds. The main predators of tuataras include birds (Falco novaezeelandiae and Circus approximans), dogs, and rats. A species of tick (Amblyomma sphenodonti) has been documented as an external parasite of this species. As the specific epithet of this tick indicates, it is only found on tuataras.

Commensal/Parasitic Species:

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Sea bird species that inhabit North Brother Island sometimes attack tuataras, often for territorial reasons. However, swamp harriers (Circus approximans) and New Zealand falcons (Falco novaezeelandiae) are known to catch and consume younger tuataras. Invasive species like rats also predate on tuataras. Young tuataras are diurnal, which, along with their faster speed, helps them avoid being prey to older members of their species. Tuataras may also drop and regenerate their tails in order to escape predation.

Known Predators:

Anti-predator Adaptations: cryptic

  • Ching, R. 1986. New Zealand Birds: An Artist's Field Studies. Cornell University: Reed Methuen.
  • Meads, M. 1990. Forgotten Fauna: The Rare, Endangered, and Protected Invertebrates of New Zealand. University of California: DSIR Pub.
  • Seligmann, H., J. Moravec, Y. Werner. 2008. Morphological, functional and evolutionary aspects of tail autotomy and regeneration in the ‘living fossil’ Sphenodon (Reptilia: Rhynchocephalia). Biological Journal of the Linnean Society, 93/4: 721-743.
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Life History and Behavior

Behavior

The pupils of the tuatara readily expand and contract to help them see diurnally and at night. Although they have no external ears, they are still able to hear. They are also able to use touch, smell, and taste to perceive their environment.

Tuataras become territorial at about 6 months of age. Males often inflate their bodies, chase off rivals, head bob, gape their mouth, and raise their crests in order to defend their territories. During breeding season males may croak, which is used as a mating call to alert females to their presence.

Communication Channels: visual ; acoustic

Perception Channels: visual ; tactile ; acoustic ; chemical

  • Naskrecki, P. 2011. Relics: Travels in Nature's Time Machine. Chicago and London: The University of Chicago Press.
  • O'Shea, M., T. Halliday. 2002. Reptiles and Amphibians. Pennsylvania State University: Dk Pub.
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Life Cycle

In tuataras, incubation temperatures above 22°C tend to produce males, while temperatures of 20°C and below result in more female offspring. Young tuataras escape their eggs by using an egg tooth. This structure is located on the tip of their head between the nostrils and is lost after the first couple of weeks. Newly hatched tuataras resemble miniature versions of adults, and grow very slowly, taking as long as 35 years to reach adult sizes.

Development - Life Cycle: temperature sex determination; indeterminate growth

  • Cree, A. 2002. Tuatara. Pp. 210-211 in T Halliday, K Adler, eds. The New Encyclopedia of Reptiles and Amphibians. Oxford, UK: Oxford University Press.
  • Mitchell, N., N. Nelson, A. Cree, S. Pledger, S. Keall, C. Daugherty. 2006. Support for a rare pattern of temperature-dependent sex determination in archaic reptiles: evidence from two species of tuatara (Sphenodon). Frontiers in Biology, 3/9: doi:10.1186/1742-9994-3-9.
  • Nelson, N., J. Moore, S. Pillai, S. Keall. 2010. Thermosensitive period for sex determination in the tuatara. Symposium: Reptile Reproduction, 5/2: 324-329.
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Life Expectancy

There is some debate regarding the full extent of tuatara lifespans, but they are known to be able to live for over 100 years. Their longevity is mainly due to their slow metabolism and low body temperatures. Little is known about the lifespan of tuataras in captivity, as they are not generally kept as pets.

Range lifespan

Status: wild:
100 (high) years.

Typical lifespan

Status: wild:
60 to 100 years.

  • Nelson, N., S. Keall, D. Brown, C. Daugherty. 2002. Establishing a new wild population of tuatara (Sphenodon guntheri). Conservation Biology, 16/4: 887-894.
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Reproduction

Little is known about the social structure of mating systems in tuataras, but males tend to be highly territorial and mate with multiple females if given the chance. Male tuataras generally outnumber females in their native environments. Copulation consists of a male mounting a female and excreting sperm from the cloaca.

Mating System: polygynous

Female tuataras reach sexual maturity at 10 to 20 years. Tuataras have long life spans and prolonged reproductive cycles. Females usually dig nests in soil located on cliff edges. Tuataras on North Brother Island produce an average of 1.27 eggs per year for each mature female. The mean clutch size of Brothers Island tuataras is approximately 6.5 eggs. Each egg has a mean weight of 4.9 grams, and the shell has a white coloration with a rather soft texture. Tuataras may lay eggs as often as every 2 years, but most lay eggs every 4 to 5 years. They mate in late summer (December through February in New Zealand), with eggs being layed the following spring.

Breeding interval: Tuataras typically breed every 4 to 5 years.

Breeding season: Tuataras mate in late summer and lay eggs during the spring. Eggs undergo an incubation period of 12-16 months.

Average number of offspring: 6.5.

Range gestation period: 8 to 10 months.

Range age at sexual or reproductive maturity (female): 10 to 20 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous

Females invest energy in their young via the production of egg yolks and shells. Once the eggs are laid, neither parent protects the eggs. There is also no parental investment post-hatching.

Parental Investment: no parental involvement

  • Cree, A. 1994. Low annual reproductive output in female reptiles from New Zealand. New Zealand Journal of Zoology, 21/4: 351-372.
  • Cree, A., C. Daugherty, S. Schafer, D. Brown. 1991. Nesting and clutch size of tuatara (Sphenodon guntheri) on North Brother Island, Cook Strait. Tuatara, 31/1: 9-16.
  • Hall, D. 2007. The Ultimate Guide to Snakes and Reptiles. Edison, New Jersey: Chartwell Books, Inc.
  • Hemphill, K. 2012. DK Eyewitness Travel Guide: New Zealand. Penguin.
  • Lutz, D. 2005. Tuatara: A Living Fossil. Salem, OR: DIMI Press.
  • Newman, D., P. Watson, I. McFadden. 1994. Egg production by tuatara on Lady Alice and Stephens Island, New Zealand. New Zealand Journal of Zoology, 21/4: 387-398.
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Conservation

Conservation Status

Human development and introduction of invasive species on North Brother Island appears to have caused the most damage to population numbers in tuataras. Even though population numbers are low and Brothers Island tuataras exhibit a male-oriented sex ratio, long-term survival is probable. Tuataras do not reproduce often, although their long life spans helps with their overall conservation.

Brothers Island tuataras are protected by the government of New Zealand. It is unlawful to collect tuataras for pets or kill them for any reason. Due to low population numbers, many organizations have recognized that scientific research on captive tuataras is necessary to conserve this species and keep their genetic diversity as high as possible. Victoria University is actively involved in the long-term survival of the tuatara through studies of captive tuataras individuals.

Translocation of Brothers Island tuataras has been attempted. However, there is much debate as to whether this is the most useful method for increasing their population size. Nutrients and territory on North Brother Island are limited and too many tuataras might be relocated in the same place. This could potentially harm native and new tuatara populations. If food and territory are not limiting, translocated tuataras appear to adapt well to their new environment.

US Federal List: no special status

CITES: appendix i

State of Michigan List: no special status

  • New Zealand Department of Conservation. Tuatara Recovery Plan 2001-2011. Threatened Species Recovery Plan 47. Wellington, New Zealand: New Zealand Department of Conservation. 2001.
  • Hoare, J., S. Pledger, S. Keall, N. Nelson, N. Mitchell, C. Daugherty. 2006. Conservation implications of a long-term decline in body condition of the Brothers Island tuatara (Sphenodon guntheri). Animal Conservation, 9/4: 456-462.
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IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
D1+2

Version
2.3

Year Assessed
1996
  • Needs updating

Assessor/s
Australasian Reptile & Amphibian Specialist Group

Reviewer/s

Contributor/s

History
  • 1994
    Endangered
    (Groombridge 1994)
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Current Listing Status Summary

Status: Endangered
Date Listed: 06/02/1970
Lead Region: Foreign (Region 10) 
Where Listed: Entire


Population detail:

Population location: Entire
Listing status: E

For most current information and documents related to the conservation status and management of Sphenodon guntheri , see its USFWS Species Profile

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Status

Classified as Vulnerable (VU) on the IUCN Red List (1), and listed on Appendix 1 of CITES (3).
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Threats

Evidence suggests that the tuatara cannot persist in areas where rats are present due to competition with these fast breeding rodents. They do not occur on Brothers Island but there is concern that Polynesian rats, Rattus exulans, which occur on other islands, may spread by boats and on driftwood to Brothers Island (7). Tuatara are also predated on by introduced animals such as dogs and cats (8). Furthermore, scientists warn that climate change could have significant impact on this species as the eggs are sensitive to small changes in temperature that could alter the sex ratio and unbalance the reproductive success of a population. Tuatara have, however, survived 200 million years, so may have mechanisms to cope with climate change, though it is feared that the climate change of the future may occur at a faster rate than tuatara can adapt, physiologically or behaviourally (9).
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Management

Conservation Actions

Conservation Actions
It is listed on CITES Appendix I.
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Conservation

Brothers Island tuatara is one of the oldest animals in existence and is heavily protected under the Wildlife Act in New Zealand. The island it occurs on is designated as a Wildlife Sanctuary and as a Flora and Fauna Reserve, and permits are required for visits (2). Every precaution is taken to prevent rodents gaining access to this island and threatening the populations, although this cannot be guaranteed (2). New Zealand's Wildlife Service has been running a long-term research programme on the ecology of the two tuatara species and factors affecting their survival, in order to best decide on conservation measures (7). While these measures are considered adequate, there are concerns that any threat could have significant impacts on this species due to its incredibly slow reproductive rate and poor adaptability. As a precaution, in 1995, 68 Brothers Island tuataras were introduced to Titi Island in Cook Strait (8). Following this success another 54 individuals were introduced to Matui island, where tourists are able to view them and learn more about the need to protect this rare species (8). In 2001 a recovery plan was published for the tuatara which focuses on developing current initiatives and monitoring the gene pools of each population (8). Conservation and continued research is essential to ensure that we do not lose the oldest living reptile in the world (2).
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Relevance to Humans and Ecosystems

Benefits

There are no known negative economic effects of Brothers Island tuataras on humans. When threatened or handled, they are capable of delivering a painful bite.

Negative Impacts: injures humans (bites or stings)

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Tuataras' unusual physical characteristics and low population numbers attract attention and funding from scientists and conservationists. However, there are no known positive benefits of tuataras to natives of the islands where they are found. Although tuataras are illegal in the pet trade, they have been placed on the black market for thousands of U.S. dollars.

Positive Impacts: research and education

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