  We study of the role of major mergers (mass ratios >1:4) in driving size
growth in high-redshift (1<z<2) spheroidal galaxies (SGs) with stellar masses
between 10^9.5 MSun and 10^10.7 MSun. This is a largely unexplored mass range
at this epoch, containing the progenitors of more massive SGs on which the bulk
of the size-evolution literature is based. We visually split our SGs into
systems that are relaxed and those that exhibit tidal features indicative of a
recent merger. Numerical simulations indicate that, given the depth of our
images, only tidal features due to major mergers will be detectable at these
epochs (features from minor mergers being too faint), making the disturbed SGs
a useful route for estimating major-merger-driven size growth. The disturbed
SGs are offset in size from their relaxed counterparts, lying close to the
upper envelope of the local size -- mass relation. The mean size ratio of the
disturbed SGs to their relaxed counterparts is ~2. Combining this observed size
growth with empirical major-merger histories from the literature suggests that
the size evolution of a significant fraction (around two-thirds) of SGs in this
mass range could be driven by major mergers. If, as is likely, our galaxies are
progenitors of more massive M > 10^10.7 MSun SGs at z<1, then major mergers are
also likely to play an important role in the size growth of at least some
massive SGs in this mass range.
