A composite particle consisting of an even (odd) number of fermions behaves like a boson (fermion).
Swapping $^3He$ atoms involves swapping an odd number of fermions (3 nucleons and 2 electrons). Swapping $^4He$ atoms involves swapping an even number of fermions (4 nucleons and 2 electrons).
The same applies to other atoms: $H$ = 1 proton and 1 electron = 2 (even) fermions: bosonic, $D$ = 2 nucleons and 1 electron = 3 (odd) fermions: fermionic, etc.