Just guessing here mostly. Looking at the top graph and the way...

Just guessing here mostly. Looking at the top graph and the way the short positions either spike up or drop to zero in a day (multiple times) logic would say that it is a single entity that is doing the shorting.  That last big spike is 7 million shares or $1.75 million at 25 cents a share. I doubt that is your average mug punter.

It raises a couple of questions, who did they borrow the shares from and why did they give them back so quickly? The volume traded over those few days was fairly low  so they didn't sell that many of them in to the market before returning them (don't think chi-x is in those figures though).

If @imback is right (good chance too) then it was probably one of the big funds holding IDX that are opposed to the takeover.

As I said, just guessing