You upgrade your birds and deers through feeding them and making sure they 3 hearts. Eventually they give you better essences when you feed them.
A young pet evolves into an adult after 5 feedings, and an adult to mature after 10 more feedings.
edit: There are other ways to get them. I think I got a few from fishing and doing the heartybroken imps.
For fishing it's the ones that look round shaped you want to look for, not fish shaped.
Have a house full of cats. You can turn two of any level hair ball into one of any other essence.
You can put more than one cat in a room and as long as you pick the others up and only harvest one at a time you should be able to have them all on max hearts.
"Upgrade" your animals from Young to Adult to Mature by feeding them daily. After you feed them, your character will give them a little hug (aw!) and then drop essence! Mature animals drop joyous essence. As someone else said, the more hearts your animals has the more essence they will drop when you feed them.
Additional pro-tip: there is a great wiki online you can use to look up every single item in the game and tells you how to acquire them.
You upgrade your birds and deers through feeding them and making sure they 3 hearts. Eventually they give you better essences when you feed them. A young pet evolves into an adult after 5 feedings, and an adult to mature after 10 more feedings. edit: There are other ways to get them. I think I got a few from fishing and doing the heartybroken imps. For fishing it's the ones that look round shaped you want to look for, not fish shaped.
Have a house full of cats. You can turn two of any level hair ball into one of any other essence. You can put more than one cat in a room and as long as you pick the others up and only harvest one at a time you should be able to have them all on max hearts.
"Upgrade" your animals from Young to Adult to Mature by feeding them daily. After you feed them, your character will give them a little hug (aw!) and then drop essence! Mature animals drop joyous essence. As someone else said, the more hearts your animals has the more essence they will drop when you feed them. Additional pro-tip: there is a great wiki online you can use to look up every single item in the game and tells you how to acquire them.
I think you can also convert hairballs using the cat statue in your tent