Follow in Nigel's Footsteps

Trimeresurus fucatus...

Like most families in natural history, reptiles are constantly undergoing dramatic changes in their classification due to improved genetic analysis of mtDNA, which has brought to light many interesting splits and new species. The Asian green pit vipers are just one such family. In the last 20 years they have been split, renamed and split again on several occasions, some species being in an almost constant state of flux. They are, without doubt a complex group and in some parts of South-East Asia there can be several very similar species with overlapping ranges. Differences in scalation and hemipenes shape are distinctive but field marks allowing ID to species level which don't involve intimate handling, are not always consistent or reliable.

In Peninsula Malaysia there are about half-a-dozen or so pit viper species present, some more northerly towards the border with Thailand others scattered throughout. Altitude as well as distribution can help identify some species too. The only two 'green' species found within the areas we visited are Trimeresurus nebularis (Cameron Highland Pit Viper) and Trimeresurus fucatus (Siamese Peninsula Pit Viper). T. nebularis was only confirmed as a separate species in 2004 (VOGEL, DAVID & PAUWELS), named after the small highland area that it was thought to be confined to (it's Latin name 'nebularis' means 'from the clouds' in reference the cloud forests it inhabits). T. fucatus (Popeia) has a wider distribution being found in Malaysia, Thailand and parts of Myanmar and was confirmed from a Holotype in 1990 from Thailand.  Prior to that it was thought to be a subspecies of Trimeresurus popeia (Pope's Pit Viper). To complicate things T. nebularis was recently confirmed at Fraser's Hill to the south of its known limit.

There's still a lot to learn about the Trimeresurus genus complex.

I recently managed to see several specimens of Trimeresurus fucatus on a field trip to Peninsula Malaysia, some straightforward but one that raised a question or two for me.

Trimeresurus fucatus, immature female
Bukit Fraser, Pehang, Malaysia
I initially thought this was T. nebularis based on
field marks I was aware of but subtle differences
in eye colour as well as a more matt appearance
to the scales point towards T. fucatus

Trimeresurus fucatus, immature female
Bukit Fraser, Pehang, Malaysia

Trimeresurus fucatus, immature female
Bukit Fraser, Pehang, Malaysia

Trimeresurus fucatus, immature female
Bukit Fraser, Pehang, Malaysia

Me with T. fucatus
Bukit Fraser, Pehang, Malaysia

Sheer delight! How I spotted this among the
greenery, I'll never know. Pure luck.
Green pit vipers are generally arboreal but will descend lower at night to sit and ambush small mammals and reptiles  (lizards, geckos etc.). They will sit motionless for hours but don't let that fool you, when they sense their prey with the heat sensing pit (situated half way between their eye and nostril), they can strike with incredible speed. As they do their hollow fangs swing forward from the roof of the mouth (solenoglyphous) and in a fraction of a second they bite and inject just the right amount of venom deep into the tissue of their prey.

Trimeresurus fucatus, male, Bukit Fraser

Trimeresurus fucatus, male, Bukit Fraser

Trimeresurus fucatus, male, Bukit Fraser
Males can be very handsome and well marked like this individual.

Trimeresurus fucatus, female, Bukit Fraser

Trimeresurus fucatus, female, Bukit Fraser

Trimeresurus fucatus, female, Bukit Fraser
Portrait showing head scalation.

Venom is basically an evolutionary modified saliva packed with enzymes - peptides, polypeptides, metalloproteinases to name but a few, all designed to have a targeted effect on the snake's preferred prey. Some venoms attack the nervous system (neurotoxins), live cells (cytotoxins), muscles (myotoxins), blood (haemotoxins), kidneys (nephrotoxins) or the coronary system (cardiotoxins and sarafotoxins) - depending on the species/family of snake. They are complicated and incredible secretions and many venoms have more than one effect on its intended victim (eg. shock, haemorrhaging, paralysis and pre-digestion). These complex components can be collected, separated and used to try and find cures in modern medicine.

In the case of most Asian green pitvipers the venom is primarily haemotoxic or blood (platelet) destroying and also causes painful blistering, bleeding and necrosis at and around the bite site. Not necessarily lethal in its own right but secondary infection is the real problem and digits or limbs can be lost if medical help is not sought and antivenom administered to halt further damage.

Thankfully none of the vipers seen on our trip were particularly aggressive, although the female pictured above did look particularly grumpy and I certainly wouldn't have liked to have been bitten by her.

No comments:

Post a Comment