EXTINCTION OF TUATARAS WILL NOT BE OUR FAULT
by Whit Gibbons
April 7, 2003
The tuatara of New Zealand is a species on the verge of extinction.
Unlike with most other pending extinctions around the world, humans
are not to blame.
Tuataras are the sole surviving members of an otherwise extinct taxonomic
group of reptiles. For comparison among living reptiles, crocodiles
and alligators have the smallest number of species, with fewer than
25. The turtles have more than 250 species, the snakes more than 2,700,
and the lizards more than 4,400. Tuataras are distinctive in being lonely
reptile relicts of the past. A hundred million years ago, tuataras would
not have been considered particularly unusual because, as verified by
the fossil record, hundreds of species thrived throughout the world.
Today they are restricted to living on only a few cold, undeveloped
islands off the New Zealand coast.
Tuataras look somewhat like iguanas that are brown instead of green
but differ from all lizards by having distinctive dental, skull, and
skeletal features. They also have blood cells that are larger than any
other living reptile. Tuataras have the remnants of a third eye in the
center of the skull, and although a similar structure has been studied
in some lizards, the function remains unknown. Another tuatara trait
also found in a few lizards is vocalization. Hearing a tuatara croak
on a cold, drizzly night on an uninhabited island a thousand miles from
Australia would presumably bring back some strange emotions related
to our own evolutionary past. They reportedly make a cricket-like sound
when picked up.
A distinctive physiological difference between tuataras and all other
living reptiles is that they require cool temperatures. A well-known
characteristic of other reptiles is that they are only active when they
are warm. Most reptiles do well at temperatures between 70 and 80 degrees
F, and some desert lizards thrive at temperatures above 100. But a tuatara
will die at temperatures much above 80, are active at temperatures around
45, and can tolerate temperatures near freezing with no problem.
Tuataras reach lengths greater than two feet but eat mostly small animals,
such as insects, snails, and frogs. They also eat bird eggs and a few
small seabirds that nest on their islands. Tuataras are classified as
endangered and are carefully protected. They cannot even be transported
to zoos, and the few captives living in zoos today are often not on
display. Most Americans have never seen a live one, and most New Zealanders
have never seen one in the wild, as the islands themselves are practically
Tuataras have a long life span. One was kept as a captive for 77 years,
and documentation that some individuals live more than a century would
come as no surprise. Other age-related phenomena of importance are that
these bizarre animals take up to two decades to reach maturity and more
than half a century to attain full adult size. Female tuataras lay about
a dozen eggs, but at intervals of four years. The eggs take as many
as 15 months to hatch.
One of the greatest threats to the remaining tuataras are non-native
rats that have been inadvertently introduced to the islands. A slow-growing
reptile with a low reproductive output that has also evolved without
natural predators can become dependent on extended longevity to assure
successful reproduction. The presence of a new predator that can kill
eggs, young, and possibly even adults could become a serious threat
to the tuatara's continued existence. In fact, the sad news is that
these unusual reptiles are already extinct on some of the islands invaded
Tuataras represent a conservation situation different from ones that
pit economics against the environment or politicians against public
sentiment. Humans protect today's tuataras as well as a wild animal
can be protected. But all the species of tuataras have been on their
way to extinction for millions of years, and the majority have already
Other species of wildlife and other environments have been woefully
neglected or actively mistreated by humans in many ways on a global
scale, but when the last tuatara dies, we really should not blame ourselves.
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