A few hours ago (12/22/2010) I was playing on my Minecraft server, building a simple "safe-house" outside a tunnel my friend dug. It was made of stone, three blocks high, with no roof. I put stairs on each outside and block, so that I could easily climb in. When night came, after I frolicked among the skeletons and spiders with my trusty bow and arrows, something came to my attention.
Zombies can climb ladders.
I discovered this when I fled a herd of mobs by climbing into my "safe-house", and found myself in close-quarters with a zombie. After quickly dispatching it with a round of panic-driven shooting, I turned to see the zombies behind me rising up over the edge of my wall. I quickly began jumping, placing blocks beneath me until I was safely out of reach of both zombies and skeleton arrows. I waited out the night.
When morning came, I broke down my tower (after first picking off a few wandering creepers with my bow) and tore down my ladders, replacing them with a much more zombie-proof door. At that point, it occurred to me that I could actually use these zombies' ladder-climbing abilities to make a zombie trap. So I removed the door to my safe-house, and made a larger ring of wood around it. I raised the ring of wood several blocks high, covered the outside walls with ladders (but not the inside), and built a "viewing platform" floating in the center, on the same level with the top of the walls.
After I was safely atop my viewing platform, I "paused" the game (since I was on a server, there's not really any such thing as "pausing") and went to eat dinner. Afterwards, my little sister informed me that she had heard "exploding noises" while I was away. I returned to my computer, and saw this:
And when I turned around:
It appears my viewing platform was a bit too close to the wall, as a creeper managed to get close enough to go kaBOOM (note the uneven walls, and my health). On the bright side, I now had three creepers in my pit. So zombies aren't the only mob that can climb ladders.
After getting the creeper on the wall to fall in, I jumped down onto the walls, rebuilt them, and put up new ladders. I then made a new viewing platform, higher this time, and made out of glass. Then I waited for the night, and soon:
Hey, spiders can climb ladders too!
More creepers! It's a creeper party!
This isn't just a party, it's a parTAY!
Two spiders, seven creepers, and two skeletons! All we need is...
A zombie! WooooooooooOOOO!
So yeah. Mobs can climb ladders if they want to eat you. But I'm pretty sure these ones climbed the ladders because they wanted to party.
