Castoroides are passive. If you see one check the immediate area for beaver dams. Beaver dams give you wood, cementing paste, and rare mushrooms/flowers. Beaver dams offer one of the fastest cementing paste gathering rates in the game. Once you open a beaver dam all castoroides become hostile so be quick. When you grab cementing paste from the beaver dam inventory make sure to dump all the wood or excess thing you will not collect. This is important because more cementing paste will not spawn once it's taken, a new dam needs to be created. By dumping all items the beaver dam is destroyed and a new one will be created later. Wild beavers are not worth killing. They offer little pelt if any and leave a mean bite.
How to VERY easily tame Beavers (or any medium dinos with high torpor) on single player :
Step 1: Build a 4x4 trap with 2 high walls built with door frames (add ramps on one side if you don’t have an argy)
Step 2: Carry one with an argy or lure it into the trap with aggro if you don’t have an argy
Step 3: Leave it there but don’t go out too far so it won’t despawn, wait for night, put sleeping bag down and sleep for 4 hours. This step is to drain it’s food.
Step 4: Knock it out with tranqs and feed it berries or carrots (you can get plenty with a trike or stego, if not then parasaur is also good)
Step 5: Enjoy having a beaver then cry that you need to be level 61 to make a saddle for it…
Pros: Insanely fast starve tame method, doesn’t use any narcs of any kind for a level 145, doesn’t reduce much taming efficiency like the old starve tame method where you have to knock it out THEN let it starve, almost always gets 80-90% taming effectiveness.
Cons: Have to be in the area for a long while so it won’t despawn and wait for night time, it eats a lot and if you don’t check on it, it will eat everything you put in if you wanted to save stuff like crops or prime meats, you have to trap it for it to starve so will cost a lot of building mats to start.