Originally Posted by
flch1ck
I hate to admit this but I did a study on this and keep a chart.
The earning rates from lowest to highest are: fire, nature, earth, water, dark, electric, and legendary with the holiday themed animals somewhere between water and dark.
Also (as can be expected) common earns the least with ultra rare (in the case of legendaries) the highest. The ultra rares we earn such as Easter Bunny and Maid Mareian... I don't have enough of to complete that chart and so can't help there.
When the animal is dual-element, the earn level is always based off of the highest element i.e. Fairy Ferret (Fire/Nature) earns very little but Fire Glider (Fire/Electric) earns decent.
My strategy has been to always feed the electric type animals first and work my way down through the ranks. So I would feed a Super Rare Electric before a Super Rare Fire and a Rare Dark before a Rare Nature.