Options traders set their sights on Ctrip.com International, Ltd. (NASDAQ:CTRP - 13.59) on Tuesday, with call volume accelerating to five times the expected level. More than 5,600 calls were traded on CTRP during the course of the session, easily outstripping the 1,203 puts that changed hands.

The most active strike was the September 15 call, where 3,692 contracts crossed the tape. Roughly 84% of these calls traded near the ask price, suggesting they were purchased, and open interest jumped overnight by 3,114 contracts. Meanwhile, implied volatility on the stock's September 15 call climbed 2.9 percentage points by the close to 46.6%. In other words, it's probably safe to say that speculators were adding new long calls here on Tuesday.

The volume-weighted average price (VWAP) on the September 15 call was $0.39, which means most of these call buyers need CTRP to rally above $15.39 prior to back-month expiration. That's a gain of more than 13% from Tuesday's close at $13.59, pointing to expectations for a noteworthy short-term rally.

Taking a broader look, CTRP calls have been unusually popular lately. During the past 10 sessions, options players on the International Securities Exchange (ISE), Chicago Board Options Exchange (CBOE), and NASDAQ OMX PHLX (PHLX) have bought to open nearly 18 times more calls than puts on the travel site. This ratio arrives in the 99th annual percentile, marking a near-peak of bullishly slanted speculation.

As a caveat, though, short interest on CTRP has been ramping up steadily. The number of shares sold short rose by 14.1% over the past two reporting periods, and short interest now accounts for 8.1% of the equity's float. When short interest and call volume are rising in tandem, it can sometimes be indicative of hedging activity by the bears, rather than straightforward bullish speculation.

In fact, in a Barron's interview published over the weekend, value investor Bruce Geller said his firm is short CTRP, citing "pricing and margin pressure" as a point of concern.

CTRP is up 4.6% ahead of the bell today, as U.S. rival Priceline.com (NASDAQ:PCLN) stares down an opening drop of roughly 15.2%. Shares of CTRP are poised to challenge resistance at their 20-day moving average, but the stock's 40-day trendline still looms overhead. Together, this duo has guided the security to a year-to-date loss of 41.9%.