There's no way to disable Ewecus in world gen settings.

I think hunts are supposed to surprise you with either a koalafant, an ewecus or a varg. You would need three different hunt options you can set to less, default, more and lots. This might be rather a feature request than a bug

5 hours ago, plotmissed said:

I think hunts are supposed to surprise you with either a koalafant, an ewecus or a varg. You would need three different hunt options you can set to less, default, more and lots. This might be rather a feature request than a bug

Or it could be like how they do it in DST, where there's a label for "Hunt Surprises" I think. It might be called something else, but it's basically what it says on the tin: set it to high and you'll be more likely to be surprised with a Varg or an Ewecus, set it to none and you'll never be surprised and always get Koalefants.