Abstract:
Hump-nosed pit vipers (HNV) of the genus Hypnale are medically important because
they are the commonest cause of venomous snakebites in Sri Lanka. There are three
species of HNV, namely H. hypnale, H. zara and H. nepa from which the latter two
are endemic. The presence of ‘hump’ is the key identifying feature of HNV. All
Hypnale species are lookalike to the naked eye. The objective of this study was to
describe and differentiate the identification features of H. zara from the other two
species. Specimens of HNV brought by snakebite patients to hospitals were collected
from all over the country from February 2018 to January 2022. Their morphology,
including gender, lengths, scale counts, and colour variations, were recorded. Killed
specimens were preserved in 10% formalin, and live snakes were released to their
natural habitat. Data analysis was done using SPSS version 21. Seventy-one
specimens were studied, from which 45 were H. hypnale, 20 were H. zara and 6 were
H. nepa. Out of H. zara, 13 (65%) were killed specimens, and 7 (35%) were live
snakes. Twelve (60%) were males, and 8 (40%) were females. The lengths ranged as
total length 229-425mm (mean 349, SD 63), snout to vent length 201-380mm (mean
300, SD 57), head length 14-30mm (mean 21, SD 4), and tail length 27-65mm (mean
49, SD 10). The number of scale counts were ventrals-148 (IQR 142-150),
subcaudals-41 (IQR 37- 45), and mid-dorsal scales-17 (IQR 15-17). Characteristic
colour bands were observed in all specimens of H. zara on either side of the neck
compared to the other two species. These bands are thick and short, deep brownish in
colour, three or more in number and the first is longer than the others. H. zara can be
identified from the nuchal colour bands from the other two species of the genus. This
is a characteristic feature of identifying H. zara.
