What happens when an alkylborane is treated with acetic acid? In the hydroboration reactions of alkenes I've seen so far, they were always followed by oxidation with $\ce{H2O2/NaOH}$ (to yield alcohols). 

Today I found a peculiar reaction in which acetic acid-d1 was added after hydroboration to give a deuterated product:



I don't quite understand what exactly happens after the hydroboration part. Can someone enlighten me here?
Acetic acid effects protonolysis of the borane:



If AcOD is used then RD (instead of RH) is formed.