The eyelash viper occurs in a wide range of colors, including red, yellow, brown, green, even pink, as well as various combinations thereof.

Although these species are very closely related, this restricts the range of B. schlegelii sensu stricto to Colombia, in primarily highland regions.

After dark, the eyelash viper awakens and awaits the presence of small, tree-dwelling animals that may cross its path, including mammals (rodents, bats), amphibians (tree frogs), birds or lizards (anoles, geckos, juvenile iguanas).

In some cases, individuals have been known to select specific ambush sites, returning each year in-time for the spring bird migration.

[1] Sometimes, B. schlegelii (especially juveniles) will employ what is known as "caudal luring", wriggling their tail in a "worm"-like fashion to entice potential prey, such as hungry frogs or lizards, to move within striking-range.

The eyelash viper is not known to be an aggressive snake towards humans, and is likely to be avoidant of creatures larger than itself, but will not hesitate to strike if repeatedly harassed.

[15] Snakebites inflicted by B. schlegelii in humans are characterized by pain, edema, and ecchymosis at the site of the bite, rarely with blisters, local necrosis, or defibrination.

[16] Some investigations using venom samples of B. schlegelii from the northern region of Colombia have reported a typical bothropic envenomation characterized by pain, rapid local tissue damage, edema and inflammatory reactions at the site of the bite, followed by systemic alterations such as coagulopathy and acute renal failure.

[2] In 2024, a systematic revision of B. schlegelii through DNA-sequencing finally split it into an additional number of species: B. klebbai, B. rasikusumorum, B. khwargi, B. rahimi, and B. hussaini.

At the same time names that were previously synonyms were revalidated: B. nigroadspersus (Steindachner, 1870), B. nitidus (Günther, 1859), and B. torvus (Posada Arango, 1889a).