Oxybelis aeneus is built for visual ambush in vegetation. The head tapers into a long point and carries a shallow furrow along each side, running from the eye forward to the snout tip. The eye can sight along this channel, so the head does not block the forward view.
The pupil is horizontal and drawn out into a keyhole shape. Together these features give the snake a substantial region where the visual fields of both eyes overlap, the basis for judging distance by stereopsis. Depth judgement matters because the snake strikes at lizards from a coiled, extended posture across open space, with no chance to correct a misjudged reach.
Defence is postural. Held motionless and swaying slightly, the snake resembles a dead vine closely enough that predators pass it by; provoked, it gapes to show a dark mouth lining and may inflate the forebody. Its rear-fanged venom subdues lizards, and bites to humans have produced only local swelling in recorded cases.