Known Existence: Unknown
There are many occasions where you will cast the gate spell and the pet will go through, but you will get bumped back. Why does it happen? I have had occasions inside fire dungeon where I can gate in no problems with a pet, but other runes bump me back. This can happen with any pet and is not limited to flying creatures. The key to marking "pet friendly" runes is in the terrain. The problem most commonly occurs in T2A where the terrain is uneven. This situation only occurs when you cross servers (such as gating to another town or to a dungeon).
Solution: When marking a rune, mark it in the lowest spot you can find in the landscape. If you mark a rune on a hill in the landscape, you will get the bounce back effect.