is there a way to transport animals like yaks and donkeys across oceans? and what should I do so I can breed yaks in a place near the south pole
If you do not happen to have cages, you could always tame the animals and build a bridge over the ocean so you could ride them over it.
and they won’t die from the cold?
Yaks shouldn’t, donkeys might but if you have a lot of carrots it shouldn’t be a problem as long as you keep feeding them.
what do yaks even eat?
They eat wheat which can be found in a lot of places.
Contain them using cages, it’s efficient use of transporting donkeys and yaks.
The yaks will enjoy wheat.
A cage allows you to store your donkey, yak, dodo, or other creature within your inventory for easy relocation. When your animal is in a cage you don’t have to worry about feeding them. The animal will have the same level of both hunger and health when released as it was when first put in the cage, regardless of the amount of time it was contained.