ALL EXTINCTIONS ARE OUR FAULT
March 10, 2013
need not look far on conservation websites to find that this species
or that is headed toward extinction because of human activities. Nonetheless,
millions of species have gone extinct naturally, so it is not always
our fault. A column I wrote several years ago about the plight of the
tuatara makes the point.
are the sole surviving members of an otherwise extinct taxonomic group
of reptiles. For comparison with other living reptiles, several thousand
species of snakes and lizards are alive today. A hundred million years
ago, tuataras would not have been considered rare because, as verified
by the fossil record, hundreds of species thrived throughout the world.
Today they are restricted to living on a few cold, undeveloped islands
off the New Zealand coast.
look like big brown lizards but differ by having distinctive dental,
skull and skeletal features. Their blood cells are larger than any other
living reptile. Tuataras have the remnants of a third eye in the center
of the skull; its function remains unclear to scientists. Another tuatara
trait 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.
physiological difference between tuataras and all other living reptiles
is that they require cool temperatures to survive. A well-known characteristic
of other reptiles is that they are only active when they are warm, usually
at temperatures between 70 and 80 degrees F. Some desert lizards thrive
at temperatures above 100. But a tuatara tolerates temperatures near
freezing, is active around 45 degrees, and will die at temperatures
much above 80.
reach lengths greater than two feet. They eat mostly small animals,
along with bird eggs and a few small seabirds that nest on their islands.
Tuataras are classified as endangered and are carefully protected. They
are not allowed to be transported out of the country, even to zoos.
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
have a long life span. One was kept in captivity 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 can take 15 months to hatch.
greatest threats to the remaining tuataras are nonnative rats that have
been inadvertently introduced to the islands. A slow-growing reptile
with a low reproductive output that has evolved without natural predators
can become dependent on extended longevity to ensure successful reproduction.
The arrival of a predator that can kill tuatara eggs and young could
become a serious threat to the reptile's continued existence. Sadly,
these unusual reptiles are already extinct on some of the islands invaded
by rats. Some conservation biologists contend that humans are culpable
for the introduction of rats and subsequent decline of tuataras. Sure,
we have probably caused the disappearance of some tuataras, but these
last remnants of this bizarre group of reptiles were on the way to extinction
long before humans appeared on the scene. Most species of tuatara disappeared
millions of years ago.
represent a conservation situation different from ones that pit economics
against the environment or self-serving individuals against public sentiment.
Humans protect today's tuataras as well as a wild animal can be protected.
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, it is somehow gratifying to know
that we really should not blame ourselves.
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