  We demonstrate that the precessional frequencies of vortices in Bose Einstein
condensates (BECs) are determined by a conservation law, and not by the lowest
lying excitation energy mode. We determine the precessional frequency for a
single off-axis vortex and vortex lattices in BECs using the continuity
equation, and solve this self-consistently with the time-independent
Hartree-Fock-Bogoliubov (HFB) equations in the rotating frame. We find
agreement with zero temperature calculations (Bogoliubov approximation), and a
smooth variation in the precession frequency as the temperature is increased.
Time-dependent solutions confirm the validity of these predictions.
