Adult males of P. kaulbacki may attain a total length of 134 cm (53 in), which includes a tail 22.5 cm (8.9 in) long. Females may grow longer: maximum total length 141 cm (56 in), tail 23 cm (9.1 in). Dorsally, it is green, with a vertebral series of dark angular spots, which may be joined to form a zigzag stripe. The top of the head is black with yellow stripes. Ventrally, except for the whitish throat area, it is gray with large squarish or crescent-shaped yellow spots.[9] Scalation includes 25 rows of dorsal scales at midbody, 201–212 ventral scales, 66–78 subcaudal scales, and 8 supralabial scales of which the third is the largest.[4]
P. kaulbacki is oviparous. The adult female lays a clutch of 6–32 eggs in a hole in the ground, and then remains with the eggs to guard them. Eggs measure 48–53 mm x 26–27 mm (about 2 in x 1 in). Each hatchling is 26–27 cm (about 10½ inches) in total length.[9]
^Guo, Peng (2007). "New evidence on the phylogenetic position of the poorly known Asian pitviper Protobothrops kaulbacki (Serpentes: Viperidae: Crotalinae) with a redescription of the species and a revision of the genus Protobothrops ". Herpetological Journal17 (4): 237–246.
^ abSmith MA (1943). The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-region. Reptilia and Amphibia. Vol. III.—Serpentes. London: Secretary of State for India. (Taylor and Francis, printers). xii + 583 pp. (Protobothrops kaulbacki, p. 512).
^Rao D, Zhao E (2005). "A New Record from China – Protobothrops kaulbacki (Reptilia, Serpentes, Viperidae)". Acta Zootaxonomica Sinica30: 209-211.
^Harrington, Sean M.; de Haan, Jordyn M.; Shapiro, Lindsey; Ruane, Sara (2018). "Habits and characteristics of arboreal snakes worldwide: arboreality constrains body size but does not affect lineage diversification". Biological Journal of the Linnean Society125 (1): 61–71.
Kraus, Fred; Mink, Daniel G.; Brown, Wesley M. (1996). "Crotaline Intergeneric Relationships Based on Mitochondrial DNA Sequence Data". Copeia1996 (4): 763–773. (Protobothrops kaulbacki, new combination).
Smith MA (1940). "The Amphibians and Reptiles obtained by Mr. Ronald Kaulback in Upper Burma". Records of the Indian Museum42: 465–486. (Protobothrops kaulbacki, new species, p. 485, Plate VIII, Figure 5).