  We have measured the quantum-Hall activation gaps in graphene at filling
factors $\nu=2$ and $\nu=6$ for magnetic fields up to 32 T and temperatures
from 4 K to 300 K. The $\nu =6$ gap can be described by thermal excitation to
broadened Landau levels with a width of 400 K. In contrast, the gap measured at
$\nu=2$ is strongly temperature and field dependent and approaches the expected
value for sharp Landau levels for fields $B > 20$ T and temperatures $T > 100$
K. We explain this surprising behavior by a narrowing of the lowest Landau
level.
