* Yahoo's board approves $1.1 bln Tumblr acquisition -WSJ
* Actavis to acquire Warner Chilcott in stock-for-stock deal
* Futures off: Dow 5 pts, S&P 0.9 pts, Nasdaq 2.25 pts
NEW YORK, May 20 U.S. stock index futures were little changed in light volume on Monday as investors search for catalysts after major U.S. equity indexes closed Friday for a fourth consecutive week of gains.
* Acquisitions including Yahoo's $1.1 billion bid for Tumblr indicate that companies continue to search for growth through acquisitions despite record highs, a bullish sign for the market.
* The S&P 500 and Dow industrials finished Friday at fresh record highs and the Nasdaq Composite is at its highest since late 2000.
* A light economic and earnings calendar could leave the market vulnerable for a pullback, but those have been shallow and short-lived as investors take any weakness as a new chance to increase long positions.
* S&P 500 futures dipped less than a point and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 5 points, and Nasdaq 100 futures shed 2.25 points.
* Yahoo shares rose 2.8 percent in premarket trading after a report its board has approved a deal to buy blogging and social networking site Tumblr for $1.1 billion in cash. The Wall Street Journal report on Sunday cited people familiar with the matter.
* Actavis confirmed it will acquire Warner Chilcott Plc in a stock-for-stock transaction valued at approximately $8.5 billion. Actavis shares rose 3.8 pct in premarket trading.
* Solar products maker JA Solar Holdings reported another quarterly loss on lower prices for panels that convert sunlight into electricity, but its operating loss nearly halved from the first quarter of 2012.
* China's housing inflation accelerated to its fastest pace in two years in April, a hurdle for policymakers trying to cool the property sector while supporting economic expansion.
* The Japanese government upgraded its assessment of the economy on Monday, as emerging signs of an upturn in exports and factory output added to growing evidence that Prime Minister Shinzo Abe's aggressive polices are beginning to reignite growth.