We visited two crocodile farms near Bangkok, at Samut Prakan in Sriracha in Bangkok and Sriracha, in Chonburi Province on the eastern side of the Bight of Bangkok, where my contributor Yosapong Temsiripong was based.
At Samut Prakan croc farm many Siamese and Saltwater crocodile are kept together,
with inevitable hybridization
A Sriracha croc farm the Siamese crocodiles are kept in small groups away from other species to maintain their pure-blood line
We did not see Samut Prakan's most famous resident "Yai"
We filmed and examined Saltwater crocodiles (Crocodylus porosus), Siamese crocodiles (C.siamensis) and hybrids between the two. There are 16 external morphological differences between the two species, the best being the absence of post-occipital scutes in the saltwater crocodile, so pure-bred crocs are easy to tell apart, but hybrids blur these differences and it may be impossible to identify a pure Siamese crocodile by eye when they are mixed with saltwater crocodiles.
Identifying the Siamese Crocodile
Crocodylus siamensis at Sriracha croc farm
Yos has pure-bred adult Siamese crocodiles at Sriracha crocodile farm, so we caught one adult and took blood - this is not difficult with a crocodile and very little blood is required for DNA analysis in reptiles.
Blood is most easily from the blood vessel posterior to the rear of the skull
Many of the enclosures at the crocodile farms have crocodiles of all sizes and probably both species mixing freely, with the result that hybridization is rampant and specific identification of crocodiles becomes difficult in the extreme. I photographed crocodiles which morphologically appeared to be Siamese crocodiles or Saltwater crocodiles but mindful of the hybridization problems I tended to label them all 'cf.' ('confer' in Latin, meaning 'most like').
Siamese crocodile, Crocodylus cf. siamensis at Samut Prakan crocodile farm
Siamese crocodile, Crocodylus cf. siamensis at Sriracha crocodile farm
Siamese crocodile, Crocodylus cf. siamensis at Phetchaburi crocodile farm
Saltwater crocodile, Crocodylus porosus X Siamese crocodile, Crocodylus siamensis at Samut Prakan crocodile farm
Saltwater crocodile, Crocodylus porosus X Siamese crocodile, Crocodylus siamensis hybrids at Sriracha crocodile farm
Crocodiles 'gape' to loose heat and cool down. They clearly cannot sweat, not possessing mammalian sweat glands and being in possession of a thick skin. They also cannot extend the tongue to 'pant' so they spend much of their time on land gaping, mouth open wide.
Possibly a reason they cannot extend the tongue is because it serves another purpose, the back of the tongue forming a value which seals with the roof of the mouth when underwater, thereby preventing ingress of water down the throat into the stomach and lungs. This is why crocodiles elevate their heads well above the water level before releasing the valvular flap and swallowing prey items.
Crocodile gape to loose heat
Kait with one of the Sriracha Siamese crocodiles
Around the crocodile farm at Sriracha we saw Common rice-paddy frogs (Fejervarya limnocharis), IndoPacific house gecko (Hemidactylus garnotii) and Common garden lizards (Calotes versicolor).
Common rice-paddy frog,
Common garden lizard, Calotes versicolor
We also filmed at a crocodile temple known as Wat Chakrawat in Bangkok. This temple reputedly held a pair of genuine Siamese crocodile that predated the hybridization of the crocodile farms. When we arrived we discovered both large crocodile were in a low cave behind their pool and could not be filmed. Roger asked me to go into the cave and encourage the two crocodiles to leave and enter the pool. This I eventually accomplished, armed with a Midwest Stump-ripper and a head-torch, the former to guide the crocs to the entrance and to protect me from their jaws and tail, the latter so I could see what I was doing in the blackened, low-roofed cave and also keep an eye on crocodile two as I drove crocodile one out of the entrance. It was not easy.
Crocodylus siamensis at Wat Chakrawat