Hi Pam! It's been a while! Both boys are very healthy. Thor being slightly over weight which we are working on. They all had kitty colds about 4 months ago and besides that(which they are all better from) they are as fit as can be.
Loki lives up to his name. He runs circles around our other 2 cats when it comes to energy. He is non stop. Usually when Thor mounts Loki makes the terrible crying sounds which alerts us to whats going on. Usually it starts with a deep grow but turns into crying quickly. We separate them as fast as possible. We have never noticed the tufts of fur or scaring on Loki's neck when we are gone. Thor seems to do it almost exclusively while we are there. Can't be 100% sure, it just seems that way.
There is a random cat that will come by. A black cat that looks almost identical to Loki. No idea if its a male or female or if its been fixed or not. It comes by maybe once every 3 months or so. Walks by and wanders off. Never sticks around or anything.
I bough Thor da bird a while back. He loved it for about 15mins then moved on. He did LOVE to watch it though. Same with laser pointers. He sits there as low as he can go and chirps away, rarely attacking. That was about a year ago and Loki has already destroyed it so I just ordered another one for him. I'm on a deployment right now over seas so I'll have my wife report in on how he likes it.
So far actually his favorite toy had been that raccoon tail we got from the show when he was a kitten. Someone recommended a place(can't find it for the life of me) online that sells larger ones as well as lamb fur plush toy with catnip inside but he never really took to it the same.
Oh I forgot. One of the best ways I get him to really engage his inner hunter is a game I made up for him. He LOOOOVES turkey, duck and chicken hearts. It's the only raw food he will really touch. So when he is asleep or in another room I take his treat and hide it in some random easy to get to spot like his cat tree or window sill. He figures out real quick there is the smell of treat in the air and hunts it down.
Mounting other cats is a dominance ploy, and very common in cats of both genders, including spayed and neutered pets.
I assume both boys are healthy....occasionally cats show dominance over another when there may be a health issue going on with the one being picked on. Is it possible there is a stray cat coming around outside your home...possibly an intact female that is in heat?
Are Loki and Thor of about equal energy level now that they are adults? Since Thor is a typical Savannah in the energy department, you could consider adding another high-energy level kitty to your crew, and this need not be a Savannah.
How does Loki react when Thor mounts him...and how do you react? You may have to separate them when you are not at home to monitor their activity, especially since Thor is leaving marks on poor Loki...
Have you tried Da Bird wand toy to help expel excess energy for Thor ? His grandmother Tart also is very picky about toys, but she cannot resist Da Bird!
I hope your deployment is soon over! 