Can a prison staff member retaliate against an inmate for filing a grievance?

The complaint is rife with allegations that the "Green Wall Staff Prison Gang" is retaliating against Plaintiff for his grievances by stealing his mail. Under the First Amendment, prison officials may not retaliate against prisoners for initiating litigation or filing administrative grievances. Rhodes v. Robinson, 408 F.3d 559, 568 (9th Cir. 2005). A viable claim of retaliation entails five basic elements: (1) an assertion that a prison official took some adverse action against an inmate (2) because of (3) the inmate's protected conduct; (4) the adverse action chilled the inmate's exercise of his First Amendment rights; and (5) the adverse action did not reasonably advance a legitimate penological purpose. Id.; Barnett v. Centoni, 31 F.3d 813, 816 (9th Cir. 1994).