Under what specific condition might a tree viper exhibit heightened defensive behavior, even if normally placid?

Answer

If it is surprised or dislodged while on the ground.

When found low to the ground, arboreal snakes may react with increased defensiveness because their primary escape route, climbing, is less immediately accessible.

Under what specific condition might a tree viper exhibit heightened defensive behavior, even if normally placid?
behavioranimalTreereptileviper