We've had Winston for just about a year, we got him as a baby.
When we got him we already had two grown mice (all caged separately but next to each other) and all was well. We (my son and I) held/hold our mice for an hour each day and they come straight out each time and don't want to be put back at the end.
In march we lost our two older mice over the same weekend and Winston definitely noticed they were gone. We continued to hold him each day for an hour but he was always on the side of his cage and seemed to be looking for Hamilton.
A couple of weeks ago we got a new mouse Wilbur and put him in Hamilton's old cage. Winston freaked out and ever since, even though we hold Winston first and keep him away from Wilbur and his smells, he has started biting A LOT. Winston was used to other mice before but and he seems to be fine with Wilbur now when they both meet up on the side of their cages together but he is still biting me (my son is afraid to hold him). He even tries to reach around the treats to bite my finger through the bars when we give treats during non-holding times. He seems squirly in general, he is less than a year old and this is his first spring, is it mating season or something?
How do I get him to calm down and stop biting? Thanks