While many seem to think beaver react to castor better in the spring--it is a fallacy.
They seem to act the same way no matter the time of year.The reason people think the react more in the spring has a couple of reasons.
1. A beavers activities in fall and early winter are pretty confined to gathering the winters food.For this reason you will have less traveling,I want my sets made on sighn at this time of year.
2.As the ice goes out beaver are doing a lot of pent up traveling.A short time later, the 2 year olds are kicked out and looking for new homes.As the birth of a new litter takes place, the male and young of last year go on a bit of a hiatus till after the female has delivered and adjusted to the new batch.
Because of these things, you have a tremendous amount of beaver movement--thus they seem more susceptible to castor, but in reality they are just running into your sets more often because of all the traveling.
Tom