Crimson Warnings: Defensive Displays in Calumma brevicorne

Calumma brevicorne is a medium‑sized chameleon endemic to Madagascar's central highlands, inhabiting humid montane forests. It is distinguished by its relatively short rostral appendage, from which its name "brevicorne" (short horn) is derived. Adults typically display cryptic green and brown coloration that blends into the canopy, but one of their most striking features lies in the throat region. The inner side of the throat in adults is colored inconspicuously: usually pinkish, yellow, or occasionally with orange hue.

In juveniles, however, the coloration is much more remarkable. Hatchlings and young individuals exhibit bright crimson red to orange gingivae. When threatened, they expose this vivid coloration to intruders, combining it with vigorous strikes and head movements. This aggressive aposematic display serves as a deterrent, signaling danger through color rather than physical combat.

Interestingly, a similar phenomenon is observed in the partly syntopic Brookesia thieli, a leaf chameleon that maintains orange coloration of the gingivae and inner mouth throughout its life. This parallel suggests that oral coloration may play a broader role in Malagasy chameleon defense strategies, though its evolutionary significance remains a subject of future studiues.