Dogs recognise voice tones.
A moderately intelligent dog should be able to spot a 'threatening' tone.
( Amorous Badger NAKED BEA ARTHUR PHOTOS 4U, Wed 20 May 2009, 14:51, archived)

I was wondering more about the use of an ultimatum

( Gooch Is neither here nor there, Wed 20 May 2009, 14:54, archived)