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
Distribution: New Zealand (North Brother Island, Cook Strait)
New Zealand (N. Brother's Island)
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
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.
Habitat and Ecology
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 )
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.
- tuatara ticks (Amblyomma sphenodonti)
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.
- brown rats (Rattus norvegicus)
- swamp harriers (Circus approximans)
- New Zealand falcons (Falco novaezeelandiae)
Anti-predator Adaptations: cryptic
Life History and 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.
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
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.
Status: wild: 100 (high) years.
Status: wild: 60 to 100 years.
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
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
IUCN Red List Assessment
Red List Category
Red List Criteria
- Needs updating
- 1994Endangered(Groombridge 1994)
Date Listed: 06/02/1970
Lead Region: Foreign (Region 10)
Where Listed: Entire
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
Relevance to Humans and Ecosystems
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)
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