The Eternal Cylinder

To get the Deimatic Trunk mutation, you must have a Trebhum eat a Tuba Tuber, which grow on the end of long tentacle-like plants with tubas on the end of them. The plants occasionally make trumpeting noises when nearby and are fairly common in early areas of the game.

Once equipped with a Deimatic Trunk, press the B button with your water sac highlighted in the hotbar to let out a trumpet noise. The noise will scare away certain predators.

Tonglegroplets resemble large pink slugs with legs, and a big green water sac around their midsection. Just walk up to one, wait for it to notice you, and blast it with your trumpet to scare it away.