The aurora often appears as an approximately oval shape surrounding the magnetic poles, and is a visible manifestation of the intricate coupling between the Earth’s upper atmosphere and the near-Earth space environment. While the average size of the auroral oval increases with geomagnetic activity, the instantaneous shape and size of the aurora is highly dynamic. The identification of auroral boundaries holds significant value in space physics, as it serves to define and differentiate regions within the magnetosphere connected to the aurora by magnetic field lines. In this work, we demonstrate a method to detect and model the poleward and equatorward boundaries in global UV images. Our methodology enables analysis of the spatiotemporal variation in auroral boundaries from 2.5 years of UV imagery from the IMAGE satellite. The resulting dataset reveals a root mean square boundary normal velocity of 149 m/s for the poleward boundary and 96 m/s for the equatorward boundary and the velocities are shown to be stronger on the nightside than on the dayside. Interestingly, our findings demonstrate an absence of correlation between the amount of open magnetic flux and the amount of flux enclosed within the auroral oval. Furthermore, we highlight the inadequacy of a simplistic generalization of the expanding-contracting polar cap paradigm in explaining temporal variations in the auroral oval area, underscoring the imperative for an enhanced understanding of equatorward boundary fluctuations.