Greetings from Slovenia (the place where this issue was written) as Impurest’s Guide to Animals hits the big 4-0. Last week the horrifically violent Humboldt Squid was in the spotlight. This week’s animal is (mercifully) very different; still don’t take it lightly, not if you value your fingers

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Issue #40 Big Headed Turtle

Kingdom – Animalia

Phylum – Chordata

Class – Reptilla

Order – Testudines

Family – Platysernidae

Genus – Platysternon

Species – megachephalum

Related Species - Big Headed Turtles are the only member of the Family Platysernidae (1)

Range - Big Headed Turtles are found in a number of counties in South East Asia including China, Vietnam, Laos and Thailand

A Big Head Indeed

Big Headed Turtles have a carapace length of around 20cm and live in shallow fast flowing streams bordered by thick forest. As the name suggests the species has an enlarged head, which is so big that the turtle can’t pull it into its shell. To compensate for this the species has a reinforced roof of bone on it’s skull to deter predators. Big Headed Turtles are poor swimmers and use there enlarged claws to grip rocks. In fact they are so accomplished at climbing, using their jaws and tail in conjunction with their claws, that it’s not uncommon to see an adult Big Headed Turtle sunning itself on a low tree branch (2).

Like most freshwater turtles the Big Head is primarily carnivorous, coming out at night to hunt for freshwater crustaceans and molluscs. While only a few species within the turtles range prey on it both Leopards (Panthera paradus) and Mugger Crocodile (Crocodylus palustris) are strong enough to try. When threatened the turtle uses it’s bony tail to shield its head and legs since they are too big to be fully withdrawn into its shell.

Sadly Big Headed Turtles are among the species readily exported for the Oriental Food Trade throughout much of its range. Coupled with a slow reproduction and growth rate there is a very slow turn-over in the population making individual removal from the environment particularly devastating.

Ecology 101 - A Guide to Environmental Mechanics

When pollution and its negative impact on the environment are mentioned the mind usually jumps to massive disasters such as oil slicks or local examples such as littering. As such Light Pollution is often overlooked, despite the horrific consequences it has on the biota of a number of species. The darkness of the night sky is ranked on the Bortle Scale with a true Dark Sky having a Naked Eye Limiting Magnitude (which measures the faintest level of stellar object visible) of 7.0 to 8.0. In contrast most urban areas have a Naked Eye Limiting Magnitude of only half that (3).

As such creatures those navigate using stellar cues or by lunar position such as Marine Turtles are easily confused and mislead by sky-glow. There are many instances of the light produced by a city at night drawing pregnant female turtles away from their nesting beaches and deep into the urban centre. Turtles aren't the only nocturnal navigators affected this way; fireflies, salamanders and bats all use the moon and stars to navigate, and are all affected this way.

For Salamanders, it’s theorized, that the effects can be even more disturbing, an increase in UV light (such as that created by light pollution) can cause deformities such as mutation in the eye and skin as well as the growth of additional limbs (4). The effect on birds however, is not theorized but proven fact. In the United States alone over four million birds are killed by being drawn astray by light pollution. Those birds that migrate at night are particularly vulnerable often being drawn into city centres and then becoming too exhausted or stressed to escape (5).

Bibliography

1 - www.arkive.org

2 -. http://www.turtlerescues.com/platysternidae.htm

3 - O'Hanlon, Larry (1 May 2013). "Turn Yourself into a Skyglow Meter". Discovery News

4 - Blaustin A.R, Johnson P.T, (2003) The Complexity of Deformed Amphibians, Front Ecol Environ

5 - http://physics.fau.edu/observatory/lightpol-Birds.html

Picture References

1 - http://cdn2.arkive.org/media/BB/BB05DC6F-563F-42E1-8097-390A4A212ED4/Presentation.Large/Big-headed-turtle-.jpg

2 - http://www.cydoniamall.com/pets//pictures/PmegacephalumTR2.jpg

3 - http://www.utah3d.net/og/salt-flats-night-og.jpg

4 - https://news.uns.purdue.edu/images/+2008/williams-salamander.jpg

And in a flash (that lasts the entire night) the Big Headed Turtle crawls off to sleep the day away. Next weeks animal is a bone cracking foe that would gladly take on the turtle if it was to find one. Until then critic, comment and check out Past Issues in the Bestiary of er Past Issues

Many Thanks

Impurest Cheese