well yes, I'm pretty sure they would, although I've not heard of it specifically. rats predominantly eat grains, berries, insects and the like, but also eat small mammals, birds, eggs, even fish and shellfish. read more
video footage has been found of rats diving down to mussel beds, retrieving mussels and eating them by the waterside, leaving the shells behind. rats are highly competent swimmers (although many a domestic rat thinks themselves tortured if you wash them ;) :P ) and I am quite sure that fish and water based ambphibians must be on the menu occasionally, as rats can easily catch them and if they can, they would happily eat them. read more
(What Do Rats Eat) The giant white-tailed rat which is found in the rainforests of north-east Queensland eats fruits but it largely survives on omnivorous diet. It is known to eat insects, fruits, small vertebrates, nuts, eggs when available; whereas its close relative melomys species are generally herbivorous as they eat shoots, leaves, fruits, and roots. read more