George Soros, Steve Cohen's SAC Capital Advisors and John Thaler's JAT Capital Management were among the few that disclosed owning Facebook stakes as of June 30. Chase Coleman's Tiger Global Management, which invested in Facebook before it went public, also listed a stake of almost 2 million shares.

Many more funds are rumored to be betting against Mark Zuckerberg's creation. Funds and other large investors are not obligated to disclose short positions in their quarterly filings.

Shares of Facebook have tumbled 46 percent since the company's initial public offering at $38 a share on May 18. The shares on Tuesday shed almost 6 percent to close at $20.38 after online daily deal provider Groupon posted disappointing quarterly results.

Facebook's $16 billion IPO was one of the largest ever and valued the company at over $100 billion. Facebook's lockup agreement, which prohibited further selling by insiders holding some 1.9 billion shares, begins to expire on August 16, which could put further pressure on the share price.

Managers may also have bought Facebook shares at the IPO in May or later, but sold them before June 30.

(This story is repeated to specify date lockup expires in 5th paragraph)

(Reporting by Aaron Pressman; editing by Leslie Adler, Gary Crosse)

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