This hedge fund has gone to the dogs.

Activist hedge fund Jana Partners said on Thursday that it will ask retailer PetSmart to explore a sale and other means of creating shareholder value, prompting the stock to pop 13 percent.

Jana Partners, run by Barry Rosenstein, has been building a 9.9 percent stake in PetSmart since early May and is now the company’s largest single shareholder, according to a regulatory filing.

The stock — which had been down almost 18 percent this year — surged 13 percent to $67.60 in trading Thursday morning on news of the activist’s stake.

Phoenix-based PetSmart last month slashed its sales forecast for the full year, citing a “challenging and volatile consumer environment and a competitive market.”

The hedge fund said it plans to hold meeting with the company’s board and management as well as shareholders to discuss ways to boost the share price, including returning cash to shareholders and improving operations.