I haven't read the Spanish-language article, but in the Guardian piece, the gallery owner states that the dog was actually fed at intervals by the artist (when the public was not present) and that it 'escaped', rather than died. In other words, a provocation and ultimately, a hoax - all for 'artistic' purposes.
Given the photo documentation - which lacks any images of a deceased dog (and which normally would have included this, given the way the event had been documented up until that point) - there may be some reason to believe that this was true and that the dog did not die.
In terms of provocation, the installation was certainly a success: the Guardian claims a half-million signatures of protestation (on another petition?), plus numerous death-threats against the artist.