Saturday, September 09, 2006

Third Eye Blind(ish)

The Tuatara (Sphenodon punctatus) is a reptile that is also grouped into the "living fossil" category (see footnote on the lungfish). They belong to order Rhynchocephalia, which has existed worldwide about 220 million years ago, and the tuataras themselves look about the same as they did 140 million years ago. They aren't exactly worldwide anymore, as they are confined to New Zealand, and being an island species is never good news in terms of population.
Image from Wellington Zoo

While superficially resembling lizards, there are various characteristics separating the two groups, such as lack of external ears, another set of teeth, and a developed pineal eye1. This "third eye" may help in temperature regulation, circadian regulation, Vitamin D absorption, or something completely different.

Tuataras are nocturnal and able to function at much lower temperatures than most reptiles. They have long lifespans, taking 20 years to reach maturity and living up to 100 years. Like many predators, they subscribe to the idea, "Is it animal matter, smaller than my head, and easy to catch? Then it's food." Hunting by ambush, they will eat insects, lizards, eggs, and seabird chicks.

The endangerment of the tuatara starts out fairly textbook. After millions of years isolated on islands, humans interfere and begin habitat destruction, removing them from the New Zealand mainland. Europeans bring rats, which eat the eggs and the young. However, there is a newer problem facing the tuatara. Like many reptiles, incubation temperature determines the sex of the offspring. Too warm (above 71.6 degrees Fahrenheit for the tuatara) and the nest is all males, too cold (under 69.8 degrees) and the nest is all females. What happens when global warming comes into play? One female can only parent one litter at a time (and four years apart), so this hurts the population much more than if fewer males were being hatched.

There is hope for our spiny little friends. Breeding and release programs are working on bringing the tuatara back to the New Zealand mainland, with the help of rat-proof fencing. Various studies are being conducted to determine the extent of global warming's effect.

1Though not near as developed as this guy's, who I came across while searching for images.


Drew said...

In the whole scheme of Global Warming, isn't it more accurate to talk about global climate change? It is my understanding that global climate change means more extreme temperatures, be it hot or cold. So, couldn't the climate change actually help this creature?

Garfman said...

Having more than 50% females wouldn't really help the tuataras, just wouldn't be as detrimental as having more than 50% males. Also, they seem to have found more males as of late, and are probably monitoring temperature closely, so the temperature is probably generally increasing in that area of the world.

Raging Wombat said...

Great blog and great post. I like your academic approach. Ugly animals need more advocates.

Trish said...

This little guy is (a) indisputably adorable and (b) one of my favorite animals (I am an advocate of little-known unusual animals). Thanks for showcasing him, even though he is cute.

RE: the term "Living Fossil". Aren't we all, strictly speaking, living fossils? And if your physical form hasn't changed in many many millions of years, shouldn't that mean you WIN at natural selection?