c.2013 New York Times News Service

c.2013 New York Times News Service

Hertz, one of America’s biggest car rental companies, is battening down the hatches.

The company has adopted a one-year shareholder rights plan, commonly known as a “poison pill,” to thwart an investor from gaining control of the board.

The move, which Hertz attributed to “unusual and substantial activity” in the company’s shares, comes as activist investors are becoming more successful in campaigns to pluck directors of company boards and replace them with their own candidates. Activist investors buy shares in a company with the intention of shaking things up.

The shareholder rights plan would be triggered by any investor acquiring a 10 percent stake or more of the company’s shares.

The company, based in Park Ridge, N.J., said it had been talking to shareholders, without naming any, and “welcomes their input towards the goal of enhancing shareholder value.”

Hertz’s largest listed shareholder is Wellington Management, which holds 9.15 percent of the company’s shares. Hedge fund York Capital Management also has a 2.75 percent stake.

Hertz said the plan would allow management to continue “strategic initiatives,” including the integration of its recent $2.6 billion acquisition of Dollar Thrifty. Hertz acquired Dollar Thrifty last year after a protracted battle with its rival Avis.