In order for this egg to hatch, this bonsai tree must be pruned, watered, and well cared for. Otherwise, the growing creature inside will perish!
Surtles themselves are extremely easy creatures to care for. Feed them a vegetarian diet and ensure that water is within a few feet of them and they'll be just fine. They also move extremely slow like tortoises, so they haven't went far if you've lost yours! Just keep searching and be mindful of how they can blend in with rocks and boulders.
The real joy of having a Surtle, though, is the art of caring for the bonsai tree attached to its shell. The well-being of this bonsai tree directly affects the well-being of the creature itself. So be sure to prune the tree when it needs it!