IMO, there are two instances that you can use present participle to modify the sentence.
1) The present participle modifies the sentence that contains a logical subject of an action. As in the case above, "sleeping 15 hrs and moving blah blah" logically modifies the subject of the action "the sloth."
2) The present participle is used to modify the entire sentence, indicating a result of a sequence of action. For instance,
"The price of beef has gone up 50% percent since Nov., leading many people to speculate that the price will increase further."
-- by 会员 silent7706 (2010/6/20 12:20:36)