Go here for a series of amazing photos of a heron capturing a gopher.
I'm not accustomed to seeing herons hunt rodents, much less rodents of
unusual size! Also, check out the way the prey has been speared .
I agree that a gopher is a rather large prey for a Ardea herodias. However
it's very close european relative Ardea cinerea will happily eat just about
anything it can kill and swallow. Mammalian prey includes mice, water-voles
(which are largish, up to ca 200 mm), field-voles, water-shrews and even
moles! They can be really serious predators on Little Grebes.