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. (Cree, 1994; Lutz, 2005; Mitchell, et al., 2008; Thompson, et al., 1992)
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. (Cree, 1994; Lutz, 2005; Mitchell, et al., 2008; Nelson, et al., 2002a; Ramstad, et al., 2007)
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. (Cree, 1994; Lutz, 2005; Pope, 1956)
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. (Cree, 1994; Lutz, 2005; Pope, 1956)
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. (Cree, 2002; Lutz, 2005; Mitchell, et al., 2006; Nelson, et al., 2002a; Nelson, et al., 2010)
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. (Cree, et al., 1991; Cree, 1994; Lutz, 2005; Newman, et al., 1994)
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. (Cree, et al., 1991; Cree, 1994; Hall, 2007; Hemphill, 2012; Newman, et al., 1994)
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. (Hall, 2007)
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. (Lutz, 2005; Nelson, et al., 2002b; Ramstad, et al., 2007; Thompson, et al., 1992)
The weather plays a role in tuatara activity levels. Even though they are capable of withstanding lower temperatures than most other reptiles (as low as 9°C), their activity level will decline in colder weather. There is some debate as to whether tuataras actually hibernate, but it is believed that on colder nights they can maintain a sort of torpor. Humidity on North Brother Island is typically 70-89%; lower percentages can result in activity suppression and a preference to remain in burrows. (Hall, 2007; Lutz, 2005; Walls, 1983)
Older tuataras are active from dusk until dawn and emerge from burrows mostly at night. Young tuataras are often diurnal, as their faster speed allows them to escape predation. Older tuataras are will set up territories that they defend with displays or physical attacks. The most commonly performed territorial displays include forward approaches, inflation of the body, raising of the crest, head bobbing from side to side, and mouth gaping. (Gillingham, et al., 1995; Terezow, et al., 2008)
Despite being territorial, tuataras typically live in close proximity to each other. Males become aggressive when other male tuataras enter their territory. Females will also become aggressive towards other females, but often permit males into their territory. Territory sizes are 11.5 to 86.7 m^2. Female territories are typically half the size of males' and in some cases overlapping territories can occur between sexes. (Gillingham, et al., 1995; Hall, 2007; Lutz, 2005; Terezow, et al., 2008; Walls, 1983)
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. (Lutz, 2005; Naskrecki, 2011; O'Shea and Halliday, 2002)
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. (Gillingham, et al., 1995; Lutz, 2005)
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. (Hall, 2007; Mitchell, et al., 2008; Naskrecki, 2011; New, 2008)
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. (Ching, 1986; Lutz, 2005; Meads, 1990; Seligmann, et al., 2008; Terezow, et al., 2008)
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. (Lutz, 2005; Ramstad, et al., 2007; Terezow, et al., 2008)
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. (Lutz, 2005; O'Shea and Halliday, 2002; Ramstad, et al., 2007)
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. (Cree, et al., 1991; Hoare, et al., 2006; Lutz, 2005; Nelson, et al., 2002a; Ramstad, et al., 2007)
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. ("Tuatara Recovery Plan 2001-2011", 2001; Lutz, 2005)
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. ("Tuatara Recovery Plan 2001-2011", 2001; Nelson, et al., 2002b)
A recent molecular study utilizing microsatellite and mitochondrial DNA concluded that the genus Sphenodon contains only one species, and that Brothers Island tuataras represent a geographic variant of this more broadly distributed species. Despite this study, many researchers and government agencies continue to recognize Brothers Island tuataras as a distinct species. (Hay, et al., 2010)
The Maori tribe have few legends based on the Brothers Island tuatara. Of the people that subscribe to these legends, some believe tuataras are blessings while others believe tuataras act as omens. (Naskrecki, 2011; Ramstad, et al., 2007)
Amanda Johns (author), Radford University, Karen Powers (editor), Radford University, Kiersten Newtoff (editor), Radford University, Melissa Whistleman (editor), Radford University, Jeremy Wright (editor), University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
Animals with indeterminate growth continue to grow throughout their lives.
An animal that eats mainly insects or spiders.
animals that live only on an island or set of islands.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
having more than one female as a mate at one time
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
uses sight to communicate
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