The bug
When any living entity falls into the space of a ladder or vine block, their fall distance resets and they 'climb' down the ladder/vine. For certain entities, such as players, endermen and zombies, this is consistent. For entities like pigs and sheep this is not consistent though: real pigs and sheep can't climb ladders, neither up or down.
A more consistent solution would be to separate living entities in those that can climb and those that can not climb:
What entities should definitely climb
Player
Cat
Ocelot
Snow Golem
Villager
Wandering Trader
Enderman
Zombie Pigman / Zombified Piglin
Spider
Cave Spider
Iron Golem
Creeper
Drowned
Evoker
Husk
Pillager
Skeleton
Stray
Vindicator
Witch
Wither Skeleton
Zombie
Zombie Villager
Piglin
What entities should definitely not climb
Cow
Donkey
Fox
Horse
Mooshroom
Mule
Parrot
Pig
Rabbit
Cod
Salmon
Sheep
Skeleton Horse
Squid
Tropical Fish
Turtle
Pufferfish
Bee
Dolphin
Llama
Panda
Polar Bear
Wolf
Blaze
Elder Guardian
Guardian
Phantom
Ravager
Other entities don't really make sense whether they do it or not.
To reproduce
Place a column of climbable blocks
Spawn a pig on top of the column so that the pig falls down
❌ See the pig climbing down: pigs can't even climb...
Comments 10
This should absolutely be considered a change request, and is hiding behind the word "inconsistent". It is not inconsistent, it's just not matching real life animal abilities, that doesn't constitute a bug.
All mobs, except those that fly, can use climbable blocks, the only reason flying mobs can't is because they can fly up anyways. This is very much consistent across the whole game, and requesting to get that changed to match real life is exactly that, a change request.
I agree; inconsistency with real life is not a bug, since the game doesn't claim or want to mimic real life. Please post this to the feedback site instead: https://feedback.minecraft.net
Please check if this is still an issue for you in 1.16 Release Candidate 1 or later.