A new species of semi-aquatic cobra, Naja nana sp. nov. has been described from Lake Mai-Ndombe in the Democratic Republic of the Congo (DRC). The new species, know as the dwarf water cobra is locally abundant and is thought to be endemic to the region. According to the researchers – Marcel Collet and Jean-François Trape – it differs from the two other local species of semi-aquatic cobras, Naja annulata and Naja christyi by a series of morphological characters, including its small size, colouration and scale counts.
Lake Mai-Ndombe (formerly Lake Leopold II) is located 290 meters (951 feet) above sea level and sits in the equatorial forest zone. It stretches from North to South for approximately 140 kilometres (87 miles) with a surface area of 2300 square kilometres (1430 square miles) and a maximum depth of 10 meters (33 feet). The banks are low, with sandy and rocky areas and the lake seasonally floods large areas of forest and secondary savannah. In the local language Mai-Ndombe means ‘black water’ owing to its dark brown colouration caused by large amounts of dissolved organic matter.
The dwarf water cobra has been known locally for a number of years and one of the authors of the study has been collecting specimens for 20 years but it has, until now, remained undescribed. According to Dr Wolfgang Wüster, a herpetologist at Bangor University, U.K., it has been exported to private collections under several names, including, erroneously as Naja christyi. Known locally as ‘Musso’, the dwarf water cobra feeds exclusively on fish and is frequently caught in the nets of fishermen. According to villagers who live around Lake Mai-Ndombe the snake can also be found amongst the boulders that line the shore and during periods of high water it can be found in the branches of flooded vegetation bordering the lake.
The dwarf water cobra, as its name suggests is a small species reaching a maximum length of 1m (3.2 feet) and the specific epithet comes from the Latin word ‘nanus’ (feminine nana) meaning small.
It has a dorsal colouration that is more or less black with small white or yellowish spots and the ventral side is mostly whitish with each ventral scale being bordered laterally in black. The underside of the tail is completely black. There are two other similar species of water cobra in the region but Naja annulata is light brown with dark bands and Naja christyi is dark brown with yellow transverse lines in the anterior part of the body. Neither of these species have a ventral colouration that is similar to Naja nana sp. nov. and both these species exceed 2.5m (8.2 feet) in length.
Naja nana sp. nov. also differs from the other species of water cobra in scale counts. Mid body dorsal scale rows are usually 19 (rarely 17 or 18 in males and 18, 20 or 21 in females) instead of 17 in Naja christyi and 21-25 in Naja annulata.
When threatened the dwarf water cobra adopts the characteristic hooded display of all cobras, raising its body to a height of one third of its total length. The toxicity of this species is not currently known but like other members of the genus it is likely to be capable of delivering a fatal bite to humans. Local reports however, suggest that the cobra is not afraid of people and fishermen and children handle it frequently. According to one snake collector who has handled more than 300 specimens and has been bitten fifteen times, the symptoms of envenomation are moderate, with mild local pain and oedema resolving in 24-48 hours.
This latest study highlights our lack of understanding of snake ecology in tropical and politically unstable regions like the Congo and its discovery brings the total number of semi-aquatic cobras in the sub-genus Boulengerina to nine. The sub-genus Boulengerina groups together the African cobras which live in or have an affinity with water. These are: Naja nana sp. nov., N.annulata, N.christyi, N.multifasciata and five species of Forest Cobra (N.melanoleuca, N.guineensis, N.savannula, N.subfulva and N.peroescobari), which until a study I was involved in were all considered to be just one wide-ranging species (Wüster et al., 2018).
Collet M. and Trape. J-F. (2020). Une nouvelle at remarquable espèce de naja semi-aquatique (Elapidae, sous-genre Boulengerina Dollo, 1886) de la République Démocratique du Congo. Bull. Soc. Herp. Fr, 173: 41-52.
Wüster W., Chirio L., Trape J.-F., Ineich I., Jackson K., Greenbaum E., Barron C., Kusamba C., Nagy Z.T., Storey R., Hall C., Wüster C.A., Barlow A. & Broadley D.G. (2018). Integration of nuclear and mitochondrial gene sequences and morphology reveals unexpected diversity in the forest cobra (Naja melanoleuca) species complex in Central and West Africa (Serpentes: Elapidae). Zootaxa, 4455 : 68-98.