Yes they are on the map. They are in multiple locations. You will find them near swamp/river areas of the islands. Sometimes near the beach - least I know of one area where they actually are beach side. Rest of the time they are at the mouths of rivers and similar areas

cant find any at all

even if dino count is set to 1.0 for multiplier - there will be a lot. Looking at the map - Try the island on the far left - jungle island - Western most island - there are rivers that empty out facing the big center island (the one with redwoods and desert). Anyway on average there should be several in the mouth of the river with plenty of dams. Then the big island - desert end of the island as you move along the coast - there was some that spawned there - not sure if that got changed - the are other places - that is just a few.

I came across 3 beavers when I was on my boat...I had been loking for them all over near rivers and gave up a few days ago. Shame i had no tranqs at the time of seeing them otherwise I would of had one. Saw them in the desert at about 60 Lon, 80 Lat. Not exactly where I would have looked for them.

60/15