Some bvr live in bank dens on river or pond banks and some build lodges of wood and mud ect... sometimes the bank dens will have some wood and mud pulled up on bank over den roof and doesnt look like much... usually in fall you will see new work on lodges or dens in banks so keep an eye out.... if water is clear you can walk banks and see where bvr runs come into bank as mud in channel will be cleaner than rest of mud in bottom of water and you know bvr are swimming in and out of channel..