|Top. Trimeresurus gunaleni. Below its habitat|
Vogel et al. (2014) investigated morphological variation in 126 specimens from at least 67 populations of Trimeresurus sumatranus. They found two distinct taxa: Trimeresurus sumatranus (Raffles) and Trimeresurus gunaleni sp. nov. They selected a neotype for Trimeresurus sumatranus and restricted its type locality to the vicinity of Bengkulu, Bengkulu Province, Sumatra. The second taxon Trimeresurus gunaleni represents a distinct, previously unnamed species. The holotype of Trimeresurus gunaleni is from Mt. Sibayak, ca. 1,500–2,200 m ASL, west of Brastagi (Berastagi), Karo Regency (Kabupaten Karo), Sumatera Utara Province, Sumatra, Indonesia. The new species differs from Trimeresurus sumatranus by a lower number of ventrals in males (162–179 against 178–185) and females (164–171 vs. 175–191); a distinctly longer tail in males; the also differ in the color of the tail, the color of the eyes: (green in the new species, vs. dark grey in T. sumatranus), the color of the ventrals, which are green with a pale posterior suture in the new species and pale with dark posterior suture in T. sumatranus. The new species Trimeresurus gunaleni lives at higher elevations than T. sumatranus and seems to be endemic to the higher mountain ranges of western Sumatra and inhabits regions typically covered with tropical moist montane forests, from 1,500 m to as high as at least 2,000 m, perhaps as much as 2,200 m, where it has been observed by local insect collectors. There is no record of populations lower than 1,500 m. On Mount Sibayak, Trimeresurus hageni occurs at elevation of 500 m, and Tropidolaemus wagleri at 200 m. Trimeresurus gunaleni is clearly isolated as a high montane dweller. The female holotype of T. gunaleni was collected during the daytime in dense humid montane forest scattered with tiny springs. The snake was resting on the ground under tree roots. In another instance, a male was seen perched at night on a tree branch about two meters above the ground. None of the specimens were found.
Vogle G, David P, Sidik I. (2014) On Trimeresurus sumatranus (Raffles, 1822), with the designation of a neotype and the description of a new species of pitviper from Sumatra (Squamata: Viperidae: Crotalinae). Amphibian & Reptile Conservation 8(2): 1–29.