Ark DevKit Beaver Dams not spawning


i starting to make my own Map with the Devkit and there are some Problems for me.

The First and most important one are the Beaver Dams. I made a Biome Zone with the Custom Tag “Beaver” also tried “Beavers”) and into this i made the NPCZoneVolume, NPCSpawnZoneVolume and the NPCZoneManager. The Beavers are spawning but no Dams, is there some Resource the Beavers need to make a Dam. The Colission of the Landscape is “Ground Terrain”. I looked into The Island Map and i saw no Different . What i doing wrong?

And the other Problem are if i download my Map and play it, there are no Water Textures the Physic Volume works. I used a SharedLake Waterplane and the LakeWater_CenterRedwood_MIC Material for the lake and put it in a seperate Folder for Textures.