Which bones form the expanded hood that cobras display when threatened?

A cobra’s expanded hood is formed by elongated ribs in the neck region.

When threatened, a cobra spreads several long ribs behind its head. The ribs push outward the loose skin on the sides of the neck, creating the familiar hood. Muscles control the movement, allowing the snake to expand and relax the display rapidly.

The hood is primarily a defensive signal that makes the cobra appear larger and more imposing. Its shape and markings vary among species, so the hood alone cannot identify one particular cobra. Some unrelated snakes can flatten their necks as well, but the classic broad hood is strongly associated with cobras.

The hood is not a separate anatomical structure and does not result from inflating the body with air. Cobras may combine the display with hissing, an elevated posture, or a forward strike if the perceived threat continues.