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Myocastor coypus
they look like beavers but they have long tails like a rats tail. this family was eating grass on the river bank.
river bank
I think they could be Nutria - In the UK regarded as an introduced pest: they used to cause flooding at small river banks by undermining the banks by their burrowing. Were eventually trapped and eliminated in Norfolk in the 1970's.
I think kbergh1 is right, looks like Nutria to me..
Nice animals, I was never able to get a good picture of them..