Billionaire George Soros is not the only marquee investor who is hedging against a stock market crash these days.

Soros' latest 13F filing with the Securities and Exchange Commission shows he hiked his position in SPDR S&P 500 exchange-traded fund (ETF) puts in the latest regulatory reporting period by more than 600 percent to a whopping $2 billion holding.

Raul Moreno, chief executive of iBillionaire, an index that tracks investment choices by big investors, told MarketWatch it represents Soros' largest such put position since 2008. But since Soros is still 80 percent long equities, he noted the stake is likely a hedge against disaster rather than a firm conviction the market is headed for a freefall.

Another large investor's 13F filing showed a huge bearish position on homebuilders. Chase Coleman's Tiger Global Management held 23.5 million put options on the SPDR S&P Homebuilders EFT as of June 30, a stake with a market value of $770 million.

Billionaire Carl Icahn, meanwhile, boosted his stake in CVR Energy Inc. by 8 percent to a total of nearly 77.2 million shares as of the end of the second quarter, a stake with a market value of about $3.58 billion.

"We have seen an increase in energy stocks, particularly those with a high dividend yield, and we see them as some protection against a potential downfall," Moreno said.

Icahn and another major U.S. investor, Appaloosa Management's David Tepper, have been sounding cautions about high stock valuations in recent months.

Icahn warned last week of a "major asset bubble" and Tepper suggested earlier this year that it might be wise for investors to take some profits.

However, Moreno noted both Icahn and Tepper appeared to maintain their long positions in the market, at least through the second quarter.

Soros' funds kept major bullish stakes in energy firm YPF SA, SPDR S&P 500 ETF calls, Teva Pharmaceuticals and Tibco Software, among others, MarketWatch reported.

Some big hedge fund operators actually raised their long exposure by the end of the second quarter, according to Maz Jadallah, founder of research firm AlphaClone.

For instance, he told MarketWatch, Ray Dalio's Bridgewater Associates saw long exposure increase by 9 percent, and John Burbank's Passport Capital raised its long positions by 44 percent.

"That doesn't look like they're running for the hills," Jadallah said.

If there was much doubt that many hedge funds tend to have a follow-the-herd mentality, it could be dispelled by the some of AlphaClone's latest data cited by CNBC.

The largest total stock investment by hedge funds is in Icahn Enterprises, followed by Allergan, a takeover target being pursued by billionaire investor Bill Ackman's Pershing Square Capital Management, according to AlphaClone's analyses of approximately $1 trillion in assets managed by more than 250 hedge funds.

The next largest hedge fund holdings were in Vanguard FTSE Emerging Markets ETF, General Dynamics and Microsoft, AlphaClone's 13F filings analysis showed.

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