Last Week's Top Hedge Fund Moves: D.E. Shaw, OZ Management & Lone Pine

Tracking hedge fund activity is key to many investment strategies. Here is a look at some of the most relevant moves from some of the largest hedge funds last week.

D.E. Shaw

David E. Shaw’s D.E. Shaw & Co. continues to increase its exposure to Tesoro Corporation TSO, a $12 billion market cap independent petroleum refining and marketing company.

As of the end of the last reported quarter, the fund held 5,135,819 shares of the company’s Common Stock. Over the past couple of months, it presented four 13G filings with the SEC, disclosing surges in its wage on the company. As of July 30, D.E. Shaw declared ownership of 6,824,328 shares of Common Stock, up from 6,848,291 shares disclosed 20 days before.

The current stake comprises 5.4 percent of the company’s shares outstanding, and makes of the fund one of the largest institutional investors in the refiner. A bigger investor is The Vanguard Group, which last said to own 11,214,975 shares, representing an 8.88 percent stake in the company.

OZ Management

Starwood Hotels & Resorts Worldwide Inc HOT felt Daniel S. Och's OZ Management’s bullishness this week. After adding 6,188,232 shares of Common Stock to its holdings, the fund declared ownership of 8,630,835 shares, or 5.05 percent of the company.

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This stake is worth almost $690 million at current stock prices, and makes of OZ Management the second-largest institutional investor of record in the hotel and leisure company. The only fund with a larger bet on Starwood is The Vanguard Group, which last disclosed holding 9,480,309 shares. Among hedge funds, Senator Investment Group is a noteworthy investor, with 5,650,000 shares, representing 3.16 percent of the total shares outstanding.

Lone Pine Capital

Finally, Stephen Mandel’s huge hedge fund disclosed a new position in Horizon Pharma PLC HZNP, a $5.6 billion market cap specialty biopharmaceutical company that saw its stock surge more than 190 percent year-to-date. According to a 13G SEC filing, the fund now owns 8,353,668 shares of the company, representing 5.4 percent of the outstanding stock.

In early May, FMR LLC disclosed ownership of 17,590,380 shares (up from 8,709,848 shares as of the end of the last reported quarter), which make it the largest institutional investor in the company.

Among hedge funds, James E. Flynn’s Deerfield Management has the largest exposure. After increasing its stake by 10 percent over the first quarter, Deerfield disclosed ownership of 12,792,689 shares, or 10.76 percent of the company.