These are the changes of ARK: Survival Evolved’s Patch 188.1, grouped into categories for clarity. If not otherwise indicated, they’re quoted from the relevant Steam Thread.

New Items / New Structures

• Non-Dedicated Host Session: for small groups to play cooperatively — you use singleplayer saves with this mode, seamlessly! For the moment to Host online, you need to open ports 27015-27030 and 7777 to your computer (not necessary on LAN) — but soon tomorrow, that will be automatic using Steam NAT traversal. If you’re looking to join such a session, you’ll find these sessions listed in the “Non-Dedicated Session” filter type on the Session List UI. Or join using your Friends list, or the LAN list, if it’s a LAN game. Note that Non-Dedicated Hosting uses your SINGLEPLAYER saved world/character, so you can seamlessly switch between Hosting and playing Singleplayer 🙂 . Also, everyone but the Host is restricted to playing within a ~200 meter radius around the Host (it’s primarily for Coop-only play). For the time being, this is necessary to preserve Host performance & system memory.

Dino Changes

• Reduced Ant (Titanomyrma) aggro radius by 30%
• Phiomia can now poop

Game Changes

• Turrets no longer will target you through corpses, and they no longer have any friendly fire
• Repairing structures now only takes half as much resources as before (as further incentive to Repair rather than Replace)
• Crop plots can now be placed on very uneven ground
• Mate-boosted Tamed Dinos now have 2x chance of producing eggs
• Placeable Structures (boxes, beds, signs, etc) will no longer be destroyed when replacing the underlying structure beneath them.
• Vaults once again properly drop if the floor underneath them is destroyed
• Fortitude stat now has 1.5x the insulating effect as previously
• PvP Cave damage multiplier (default 6x) now functions in underwater caves as well

UI Changes

• There is now a repair-cost tooltip when you hover over the “Repair Structure” option, indicating the material cost to fully repair the structure

Bugfixes

• Cooked Prime Meat will no longer be eaten before Raw Meat by Tamed Dinos
• Added Tribe Name to Death Recap (so that u can know what Tribe to seek unholy revengeance upon)
• Fixed an issue in singleplayer games where you could remain sleeping forever! (sleeping beauty)

Performance

• Eliminated remaining server-side memory leak
• ~70% faster loading speed option. Choose “Experiment Fast Load Cache” launch option (use add “-usecache” to your launch commandline manually). After the first & second times that you start the game & load will be still be slow, but the third time onwards will be fast. This is testing a new caching method. If it works well, will then ship with the prebuilt cached files so that it’ll always be fast even first-time, and we’ll do this for all the maps as well.

(Original Announcement on Steam)

Here are the patchnotes of the previous patch (188.0)