2k of draw calls

I’m stuck with a serious problem. I have made Open world (streaming levels) and in one of the sub levels I have created a huge scene with more than 1000 static meshes. My Other sublevels are empty. Mountains are made by sculpting landscape. As I know engine did not use for rendering any invisible objects including that completely hides behind other objects. When I play my game in UE4 editor everything is fine, count of draw calls corresponds to visible meshes. When I go with my character to other empty sub level, everything is ok too. А few Count of draw calls are there.

But, when I package my project to Android, everything is going wrong. It is not important whether static mesh is fully behind other object or not (one object completely hides other(s) object(s)). I am receiving a bunch of draw calls even when I stand in front of a big wall. When I go to another empty level I receive the following result about draw calls:

  1. When I turn to way where there are no any object behind the mountains, I have a few draw calls.
  2. When I turn to way where there are a lot of bunch static meshes (but they are invisible, they are beyond the mountains) I have more than 2k draw calls.

Situation, when a few draw calls:

Situation when more than 2k draw calls

Is it a bug or it is normal? How to avoid that situation?
Please help