Keelbacks are one of the most common and diverse snake groups in Thailand. Named for the ridges (keels) on their dorsal scales, these snakes are mostly semi-aquatic species that feed on frogs, fish, and invertebrates in and around the water. Keelbacks fall into a few major groups quite distinct from each other.
The Fowlea genus has medium-large, aggressive keelbacks with checkered patterns that are very comfortable in the water. They hunt frogs and fish in marshes, mangrove swamps, canals, rice paddies, ponds and lakes. The Yellow-spotted Keelback is found across the country while the Checkered Keelback is more prevalent in the north and the White-spotted Keelback appears limited to Ranong Province. The closely related Triangle Keelback and Malayan Spotted Keelback from the Xenochrophis genus are found in south Thailand.
The Rhabdophis genus are brightly-colored keelbacks that don’t spend quite so much time in the water but still frequent very moist environments like marshes and lake shores. Several of these species are quite venomous and extreme care should be taken around them. The most dangerous may be the Red-necked Keelback, found in lowland wetlands across the country and linked to several near-fatal reactions. The Blue-necked Keelback and Orange-necked Keelback are found in similar lowland habitat in the south and may be similarly dangerous. The Black-banded Keelback is more a species of the forest hills, though concentrated in frog habitat near streams and moist areas. In the south the Speckle-bellied Keelback is found in these same hills. The Buff-striped Keelback, found in fields and marshes throughout Thailand, is a similar species from the Amphiesma genus.
The Hebius genus of keelbacks are small terrestrial snakes, usually found near streams in hilly forest regions. They are dark in color with a variety of drab stripes and spots, often including a distinct light lip stripe. In northern Thailand you will mostly encounter Deschauensee’s Keelback and the Khasi Hills Keelback, with the Two-striped Keelback occurring at the tops of the very highest mountains. In eastern Thailand you will see the Tai-yong Keelback and possibly the White-lipped Keelback near the border. Groundwater’s Keelback is only known from Ranong Province but hasn’t been seen in nearly 100 years, so the only species currently found in south Thailand is the Malayan Mountain Keelback.
Finally, there are a few species of rare, highly aquatic keelbacks which are only found in a few mountain streams. The Yunnan Water Snake is a heavy-bodied banded species found in the mountains of the north. Angel’s Stream Snake is a dark, similarly heavy-bodied species found only at two sites on the Laotian border. Boomsong’s Stream Snake is a mid-sized brown snake that has only been found three times, all in Loei Province. Spencer’s Mountain Stream Snake is a slender species that has only been found in a couple streams in northeastern Thailand. And the related Yellow-spotted Mountain Stream Snake is only known from a single specimen found in 2007.