Pain in the ass to tame. If you want a large egg, tame a Mouschops, way easier.

How to tame?

Go to a small lake, they are usually there.

Check the water temperature in the lake *at night*. You're going to be in this water for a very long time. If there are sabertooth fish in the lake, it is a significant bonus.

Clear the lake of any predators, you're going to be there for at least three hours unmounted, so be prepared.

Enter the water and start killing fish. Take their bodies and arrange them on the beach. Take one corpse and approach Hespronis from behind. Feed him the fish's body. Continue like this for three hours, as you chase him like a madman in the water throughout the day and night.

Put it on your shoulder, smile.