Visual Contrast and Intensity Affect Perch Choice of Brown Tree Snakes (Boiga irregularis) and Boa Constrictors (Boa constrictor).

•Snakes use visual cues to select between alternative destinations when crossing gaps.•Snakes prefer the mechanically advantageous destination when color is constant.•For mechanically similar destinations, snakes prefer the darker destination.•With both white and black backgrounds, brown tree snakes prefer black destinations.•Some preferences for darker destinations override those for mechanical benefits.