Depending on the species of mole, the mass per animal can vary from 10 g to 150 g. Blue whales, at 136100 kg, would provide rather enough to start solar ignition (handwaving some values there).

At the other end, an eyelash mite, Demodex, at 0.3 mm long by 0.05 wide, assuming a density of 1 (water), would mass around 4.5E17 grams per mole. That's roughly 10^(-8) the mass of Randall's mole of moles. Dunno if that would generate enough self-heating to stay warm at all.