hi mate , i dont know exactly how they catch mice , i take it that mice living near the river bank are sometimes swept into the water , maybe they venture into the holes made by mice along the river bank , but in the discription of the species ,stomach contents reveiled mice and rats along with what you might expect prawns crustations frogs tadpoles ect .
plus we may not be the 51st state YET , but we are getting very close , it seems this goverment does not have a mind of its own , anyway iam getting off track lol