Bungarus slowinskii – Red River Krait

Background story of the first record of the Red River Krait (Bungarus slowinskii) in Thailand

Maybe I was being greedy, but I just couldn’t call it a night when I crossed paths with a Parafimbrios lao early in the evening in Thailand’s northern province, Nan. A rare snake that was only fairly recently (2017 by A. Teynié & S. Hauser) reported for the first time on Thai soil. What a great sighting! It made the very long drive to this region totally worth it, and little did I know what would follow after…
The area I was exploring had proven to host various interesting snakes that were previously only known from neighboring countries. My good friend Sjon Hauser had made several exciting discoveries of species previously not known to occur in Thailand. He was the first one who had found that first live Parafimbrios lao and he had shown me the right spots.
Based on the known similarities of snake fauna with the region of Northern Laos and Vietnam, I had been brain storming with Sjon and also Parinya Pawangkhanant what more surprises could potentially be found there. And it was these dreams that got me excited to explore the region. But what I came across next had never crossed my mind, not even in my wildest dreams.

After photographing the Parafimbrios, I drove to another location to park the car and start herping on foot.
Despite the elevation, the temperatures were fairly mild and every now and then there was a little bit of rain. The weather got me more excited. And as I walked along a roadside drain filled with leaf litter, black and white bands caught my eye.
The head of the snake was hidden in a hole, seemingly foraging for food. But I immediately knew I found something very special. And then the head came up and the unmistakable markings on its head became visible. I just couldn’t believe my eyes.
Who would have thought that this rare snake – only known from several records in Vietnam and one record in Laos – would occur on Thai soil?
It was the first Red River Krait for Thailand, known to science as the Bungarus slowinskii named after the herpetologist that lost his life to a Many-banded Krait bite on a field expedition in a remote region of Myanmar.

What an unbelievable night!

Knowing the importance of the sighting, I took my time to photograph the snake from all angles. The results will follow, below.

Little is known about the Red River Krait (Bungarus slowinskii). The species was first described in 2005 by Ulrich Kuch, David Kizirian, Nguyen Quang Truong, Robin Lawson, Maureen A. Donnelly and Dietrich Mebs. In a later publication, a few more records from Vietnam and one from Laos were reported. But other than that there seem to be very few reports of this species.
But here follows some of the information based on my specimen and other sources.

facts

Dangerous?	Fixed front-fanged. Venom has not been studied to my knowledge but likely to be potent like the other Bungarus species. The fact it’s so rare, means this is probably a species nobody needs to worry about. And adding to that, the specimen encountered was calm, never tried to bite, only hissed shortly upon first encounter.
Venom	Most likely neurotoxins
Length	Can reach over 150cm
Diet	Snakes. An Ovophis tonkinensis and Protobothrops mucrosquamatus were recorded from the stomach contents of a specimen. Kharin et al. 2011
How easy to find	Being a first country record, and the relatively small number found in Vietnam and Laos, it is probably safe to say this is a very rare snake.
Best time of year	Most likely wet months. I found it active in September.
Best time of day	At night
Threats	Not known, though deforestation is definitely a problem in general in Northern Thailand.
Notes:	I found the first specimen known from Thailand in September 2018. And together with Sjon Hauser, we officially published the record on 24 June 2019 in Tropical Natural History Issue Vol 19 No 2 (2019): https://www.tci-thaijo.org/index.php/tnh/article/view/170942/137366

Description

The Red River Krait – Bungarus slowinskii is black with white bands. The scales in the white bands have black edges. The tail has a blunt tip, similar to the Bungarus fasciatus. The head in the specimen we encountered was quite distinct from the body and has white markings on the side and top that form a distinct v-shaped pattern. The tongue is pink with light tips. The specimen found in Thailand was approximately 125cm in total length, and fairly heavy built.

Similar-looking species

Confusion would be most likely with the harmless large-toothed or wolf snakes, or the other species of krait. If you intend to handle any of the black and white snakes in Thailand, please, stay safe and always consider it to be a krait unless you are 200% positive it is one of the harmless species.

• Bungarus candidus – Blue or Malayan Krait
  
  

  Blue Krait (Bungarus candidus) typically hiding its head under its body in Kaeng Krachan district, Phetchaburi, Thailand

  This species (up to 160cm) is the most similar to the Red River Krait, however the white bands are generally wider and the Bungarus candidus often has black spots on the white scales, whilst the Bungarus slowinskii will have black edges but clean white in the center. The tail of the Malayan Krait tapers towards the tip, whilst the B. slowinskii has a blunt tail tip. And Bungarus candidus lacks the white markings on the head seen in the B. slowinskii.
• Bungarus fasciatus – Banded Krait
  
  

  Banded Krait – Bungarus fasciatus

  The Banded Krait is in most cases easy to distinquish from the Bungarus slowinskii simply by color. The Bungarus fasciatus usually has black and yellow bands. However in some cases this species can be similarly black and white. Both species have a stump tail. The black scale edges of the white scales in the Bungarus slowinskii are not found in the Banded Krait. The marking on the head of the Bungarus slowinskii is clearly white-dotted, forming a line over the nose and a v-shaped marking on the back of the head. In the Bungarus fasciatus there is a v-shaped marking on the head, but usually this is more continuous, not dotted. And the stripe across the nose is not present in the Bungarus fasciatus.
• Lycodon septentrionalis – Northern Large-toothed Snake
  
  

  White-banded wolf snake (Lycodon septentrionalis) adult in Nan, Thailand

  This species (up to 1.2m) is similar in coloration, but has thin white bands and no white markings on the head. And it lacks the enlarged scales on the vertebral ridge that are found in the Red River Krait.
• Lycodon subcinctus – White-banded Wolf Snake
  
  

  White-banded Wolf Snake (Lycodon subcinctus), the best Blue Krait-mimicking species, easiest to keep apart by the lack of enlarged scales on the dorsal ridge.

  This species (up to 100cm) is similar in coloration. As with the L. septentrionalis species, this wolf snake lacks enlarged vertebral scales, which are very distinctly larger in the krait. And has no markings on the head.

Behaviour

The Red River Krait is known to be nocturnal, and terrestrial. Actively searches for prey, primarily other snakes species. Two viper species (Ovophis sp. and Protobothrops sp.) have been found in the stomach contents of a specimen in Vietnam, reported by Kharin et al. 2011.

Range & habitat

The first Bungarus slowinskii was found in Nan province in Northern Thailand. Elevation 1461m. In evergreen submontane forest within fairly close proximity of a stream.

How to find this species in Thailand?

Being such a rare snake, it is not likely to be an easy task to find one. Currently only known from one location in Nan province. Unsure if it is found elsewhere in the region. As with most kraits, it is likely just a matter of spending enough time (potentially a LOT of time) in the right area.