Short-term traders are positioning for a possible decline in Suncor Energy by the end of tomorrow's session.

optionMONSTER's tracking program detected the purchase of 2,698 May 26 puts in one print for $0.18 yesterday. Volume surpassed the strike's open interest of 615 contracts, indicating that this is a new position, and follows heavy buying in the May 25.50 puts on May 5.

Long puts lock in the price where a stock can be sold, so they make money if shares decline. Investors use them to hedge long positions or to speculate on a drop. (See our Education section)

SU fell 2.98 percent to $26.37 yesterday. The energy producer, which completed its acquisition of Canadian Oil Sands in March, missed quarterly earnings expectations on April 28. .

Overall option volume was about average in SU yesterday, but puts outnumbered calls by a bearish 5-to-1 ratio.