[2] It is native to southern Russia, Kazakhstan, and potentially northern Mongolia and China.

[3][4] The Hungarian birch mouse (S. trizona) and Nordmann's birch mouse (S. loriger) were previously thought to be subspecies representing isolated western populations of S. subtilis, but phylogenetic and anatomical evidence supports them being distinct species.

[4][5] A 2018 study detected a distinct, previously unknown genetic lineage of S. subtilis in the North Caucasus.

From head to rump it measures from 56 to 72 mm, with a tail from 110 to 130% of the main body length.

The southern birch mouse is pronouncedly a steppe dweller.