Whole Foods Market (WFM) shares spiked up 10% on Monday after activist investor Jana Partners' Barry Rosenstein launched an insurgency campaign at the organic grocer, seeking to press the company to consider selling itself and make other share-price improving changes.

Specifically, Jana Partners, which has frequently launched director-election proxy contests in the past, reported acquiring a 9% Whole Foods Stake. The fund said in a securities filing that it wants to see Whole Foods initiate a review of strategic alternatives, adding that the grocery store chain has been "unwilling to engage in discussions with third parties" about M&A alternatives.

The fund also said it was "prepared" if necessary to nominate director candidates to the company's board if it didn't move to consider strategic alternatives shortly. The fund noted that it had already signed agreements with some potential director candidates it was willing to nominate.

The comments suggests that Jana Partners could launch a contest if no review is forthcoming.

Jana Partners has launched 39 activist campaigns and seven proxy fights since 2001, according to FactSet. It has also threatened to launch a proxy fight in nine instances.

The deadline for shareholders—read Jana Partners—to launch a director contest at Whole Foods 2018 annual meeting is Sept. 6. Whole Foods typically holds its annual meetings in February.

Jana Partners campaign comes after TheStreet's Brian Sozzi in February suggested that Whole Foods could become the target of an activist investor after its earnings missed estimates by 9 cents a share and executives chopped their full-year outlook.

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The fund also wants Whole Foods to change up its board and senior management composition. It also is seeking to "optimize" its real estate and capital allocation strategies, which likely means the fund is seeking more stock buybacks and dividends. 

The organic grocer had already raised the ire of many of its institutional investors in 2015 after it pushed to set up a mechanism that appeared to enfranchise shareholders, even though upon closer inspection it did not. The organic grocer sought and initially received regulatory approval to set up a mechanism that appeared to allow shareholders the ability to nominate one or two director candidates onto the company's board in an inexpensive manner.

The Whole Foods proposal sought to allow one investor—not a group—which has held a 5% stake for five years, to nominate essentially one director onto a corporate board. Upon the agency's approval of the Whole Foods proposal, roughly 25 other companies offered up similar corporate proposals, a move that set off a firestorm of criticism among investor groups and ultimately drove regulators and companies including Whole Foods to rewrite its proposals so that they are more shareholder friendly.

Jana Partners acquired its Whole Foods stake between Feb. 9 and April 10 at prices ranging from $28.50 and $31.77. Jana signed possible nomination agreements with three potential director candidates, Thomas Dickson, Meredith Adler and Glenn Murphy. Jana Partners also set up a consulting agreement with two individuals, Diane Dietz and Mark Bittman.

According to relationship mapping service BoardEx, a service of TheStreet, Dickson, 61, a grocery chain expert, is on three public company boards—Conagra Brands (CAG) - Get Report , CST Brands (CST) and Brixmor Property Group (BRX) - Get Report . He also is a former CEO of Harris Teeter Supermarkets.

Adler is on the board of Performance Food Group PFGC and had previously served as a managing director at Barclay's Capital. Murphy had previously served as CEO of GAP (GPS) - Get Report .

Jana Partners has had a string of director installation successes of late that haven't resulted in a need to go the distance with a proxy contest. Bristol-Myers Squibb (BMY) - Get Report added three directors to its board and announced a fast-tracked share buyback program in the wake of discussions with Jana Partners. Jana Partners also recently reached a settlement with Tiffany (TIF) - Get Report , adding three new directors to its board. The activist fund owns about 5.1% in Tiffany.