CBS has put the kibosh on Survivor: The Amazon winner Jenna Morasca's plans to star in PETA's new anti-fur ad. Sources confirm that the reality champ was all set to don a faux fur bikini for PETA's new campaign, "Wear Fake for the Animals' Sake," but Eye execs — citing Moraska's "contractual obligations" with the network — nixed the deal. According to a PETA rep, CBS initially OK'd the idea, as long as the word Survivor was not mentioned in the ad. PETA conceded, but the network still said no. The about-face came as a surprise to the animal rights org, which just completed a successful anti-fur campaign with American Idol finalist Vanessa Olivarez. Says the rep: "PETA encountered no problems with the folks at Fox, as Vanessa was also still under contract."