The spitting behavior of two species of spitting cobras

Abstract

Spitting cobras defend themselves by spitting their venom in the face of a harasser. Although it is common belief that spitting cobras direct their venom at the eyes of an aggressor, this has never been investigated. Here, we show that the spitting act of cobras (Naja nigricollis and N. pallida) can readily be triggered by a moving human face or by a moving real size photo of a human face. In contrast, a stationary human face (real or photo) or a moving or stationary human hand does not trigger the spitting act. If threatened, spitting cobras aim their venom, ejected either in two distinct jets (N. pallida) or in a fine spray (N. nigricollis), either between the eyes or at one eye. In both cobra species investigated, the width and height of the area hit by the venom was independent of eye distance (test range 5.5 cm and 11 cm). During the spitting act the cobras performed fast undulating head movements that lead to a larger distribution of their venom. This behavior increases the probability that at least one eye of the aggressor is hit.