Results tagged “tuataras” from

Tuataras: The Endangered "Living Fossil"

ttara.jpgThe tuatara is the last member of an order of reptiles that lived, along with the dinosaurs, 225 million years ago. The order is rhynchocephalia, which comes from Greek and means "beak head." The tuatara is called a "living fossil," but in some ways this is the wrong name for it. Although in some respects it seems a little more primitive than some of the more modern reptiles, scientific experiments have proven that its rate of molecular evolution* is quicker than that of any animal yet tested.

The Maori word "tuatara" has been translated in many different ways, but the most common meaning is that tua means 'back,' and tara, 'spine.' Both the males and the females have spines (actually just flaps of skin), but the males' are larger and can be stiffened in order to attract a mate or fight another male.

There are two types of tuataras. For a long time, the Cook Strait tuatara (also called the common tuatara) was the only kind known to exist. Then, a second one, the far rarer and slightly smaller Brothers Island tuatara, was discovered. Today, the classification of tuataras is controversial, with some people arguing that there are two species, while others hold that it's one species, just slightly adapted to its environment. One way to distinguish the two types is that the Brothers Island species is olive-green with yellow speckles, while the Cook Strait tuatara, which is usually mottled and always has white spots, varies from green to grey, dark pink, or brick red. It can also change color throughout its lifetime. Additionally, when caught by a predator, a tuatara can drop its tail which continues to wriggle, allowing time for escape. Their tails do grow back, but they are often a different color plus shorter. They also can lose spines and regrow them and will shed their skin annually.

The adult tuataras are nocturnal and as a result eat mainly insects that are active at night. Beetles are their favorite food, but they sometimes eat lizards, birds, and bird eggs. They do not have real teeth as humans do. Instead, their teeth are sharp protrusions of their jaw bones. Tuataras have two rows on their upper jaws and one row on bottom. The lower teeth fit between the top teeth when the tuatara's mouth is closed and are useful for eating hard insects. Tuataras are the only animal with this kind of dental arrangement. Unfortunately, having built-in teeth means that they can't replace them as they wear down. Older tuataras have to switch to soft food, like larvae, slugs, and earthworms, and eventually make do with smooth jaw bones.

Adult tuataras can go for an hour without breathing if they need to -- even if they don't need to, a resting adult may take only one breath an hour. Although they are cold-blooded, tuataras prefer cool weather to hot. They stay active in 50° weather, while many lizards don't. Like many other reptiles, tuatara eggs are very sensitive to temperature. If the eggs are incubated at 70° F, they have an equal chance of being male or female. At 64°, they are guaranteed to be female and above 72°, they are almost always be male. One threat from global warming is that the weather will be too hot for female eggs to incubate and the remaining males will not be able to find mates. Even if the eggs are laid, that's no guarantee that they're going to hatch because many predators enjoy eating them. If a theoretical tuatara had just laid a fresh clutch of eggs today, and no one was going to eat them, it would still take more than a year for them to hatch (incubation takes 13 to 16 months because they stop developing when they get too cold).

At 13 to 20, they reach maturity, but they don't stop growing until they're thirty. That is a long childhood, but it is not exactly an ideal one. Tuatara moms are not very attentive. They lay their eggs once every four years and then leave. The hatchlings must hunt in the day to avoid being eaten by adult tuataras at night. Then, they have to dig their burrow for protection. Burrowing is much easier for an adult tuatara, because they do not mind staying in 'hotels.' Whenever they sense danger, they dart into the nearest burrow, which is often inhabited by nesting seabirds. The birds go fishing during the day, and the tuatara goes hunting at night. The birds do not seem to mind this arrangement -- except in the occasional case where a tuatara eats one of their chicks.

One feature visible in tuatara hatchlings is their "third eye," also called a "parietal eye." This comes with its own lens, cornea, retina, and non-functional connection to the brain, which makes scientists think that it evolved from a real eye. This can be seen through the skin on top of the tuatara's head until it is a few months old, when scales and pigment will have covered it. One possible use is to tell the time of day or the season. Interestingly, tuataras also have three eyelids. The first closes from the top, the second from the bottom, and the third horizontally. This last is a clear one, called a nictitating membrane, which protects and moistens the eye while still allowing the tuatara to see. Their eyes also focus independently.

The chief reason tuataras are endangered is that introduced species, such as the rats and dogs first brought by the early Polynesian settlers, prey on tuatara eggs and hatchlings. The Europeans brought more of these pests, as well as cats and ferrets. In 1895, New Zealand's government fully protected the tuataras, but their population continued to plummet as rats reached one island after another. Even as late as 1984, they killed all of the tuataras on a 25-acre island. For a long time, tuataras lived only on 32 remote islands. On the mainland, where captive release programs have been operating, one nest and one hatchling have been discovered in the wild. Many fenced preserves also keep tuataras, which also benefits other endangered species, such as kiwis, other birds, lizards, and the giant weta, a flightless insect. More than 60,000 tuataras are estimated to live worldwide, which means that this remarkable reptile can resurge in the wild.

Kiwi Conservation Club
San Diego Zoo

*Molecular evolution means that the DNA is changing over time, which is, simplified, the same thing as evolution, only on a tiny scale.


Find recent content on the main index or look in the archives to find all content.