On 21 June 2012 at 1320 h we observed an adult male U. guentheri on a trail in primary forest within the Monteverde Cloud Forest Preserve, Costa Rica (approx. 10.3001°N, 84.7474°E, datum WGS84; elev. ~1000 m). While handling the snake with minimal force, the tail broke ~3 cm posterior to the cloaca. Upon breakage, the snake began to roll its body in an apparent attempt to escape my grasp. Simultaneously, the detached tail began to writhe, and the bright ventral color was a potent visual stimulus. When I released the snake it ceased rolling and began pressing its head low and attempting to burrow under leaf litter. This be- havior reduced the visual stimulus provided by the snake’s ven- ter, while the tail continued to flash bright orange as it thrashed in the leaf litter.