A small dent or ''wrinkle'' in the trunk in an unexpected location based on the curve of the trunk. Musth-Trunk-Wrinkles are typically seen on the trunks of male in musth. We are not able to say whether the Musth-Trunk-Wrinkle has any function or why it may occur during musth.
References: Kahl & Armstrong 2002. (Full reference list)
This behavior occurs in the following context(s): Advertisement & Attraction, Aggressive, Courtship