I agree with wysiwyg. It can be misleading to attribute Jake's behaviour to "dominance" or wanting to be top dog in this situation. The article in the link provided by wysiwyg is very good & explains the social interactions between dogs very well.

The changes in Jake's behaviour towards Sam could be either triggered by Jake's own age, needs, wants & perceptions, or by Sam's changing behaviour as he gets older & adjusts to having less visual acuity, or by a mixture of both. It is also possible that the relationship between the dogs has not always been as "good" as it appeared & maybe underlying tensions were suppressed until now.

I think that Jake needs some training on calm, quiet, attentive & confident behaviours & emotional states so that he can learn to interact with Ailsa & Sam is a calmer manner. Perhaps giving Jake some one to one training using positive reinforcement to build confidence, & selecting for calm & static behaviours would help.

Another thing you can do is to ensure that all dogs have lots of the things they consider important, e.g. toys, chews, comfy beds etc. This way they are less likely to start guarding things or thinking that these things are in short supply & need guarding. If there are issues over food then feeding in separate rooms should sort that one out & make Sam feel safer to enjoy his dinner in peace.

And remember, you are also a very important resource to your dogs so you need to ensure that they all get individual attention at times when the other dgs are not so needy. So if Jake has a chew, perhaps use this time to give Sam or Ailsa a cuddle?

The sooner you can sort this out the better as there is a possibility it could get worse & the relationships between the dogs could alter more permanently.

Agree with Wilbar and WYS

The more the younger dog gets to practise his bullying and getting rewarded for it (rewarded by the other dog doing what he wants) then the more he will do it
I used to believe in the whole inter pack dom thing, I heard so many people talking about how they let the dogs just sort things out for themselves and support the 'alpha' one

But then when it was happening to Ben by a dog that was supposed to be a foster then I seen it for what it really was
an insecure bully trying to get their own way

For a short while I watched them like a hawk and distracted them before anything started. I worked hard on training them together so the bossy one got to learn that Ben getting treats was a sign that nice things were just about to happen to her (I can now scatter treats on the floor and they happily share)
and if she ever got too bolshy or was trying to control Ben too much then she had some time out on the naughty step

Deff get help, but while you are waiting try and manage the situation so hhe cant get to practise being a bully, feed seperate and be proactive in stopping things happening

Seems we all agree on this one. Although I usually do agree with Ben & Wys's posts anyway.

I also wanted to emphasise the "no practice" part for unwanted behaviours in dogs. Not only is this important from the learning theory side of things (i.e. behaviours that are rewarded are more likely to recur), but also from the physiological side of things.

The more the physiological responses linked to certain behaviours are activated, the more the neural pathways associated with those behaviours are sensitised. When the neural pathways are sensitised by use (i.e. the "firing of one cell in a neural pathway, causes the next cell to fire etc), the more likely they are to be activated in similar situations. Then these slightly different pathways are sensitised & more easily triggered, then the unwanted behaviours start to generalise to other situations & get even more ingrained. It can be a downward spiral which makes the original problem even more difficult to solve.

Neural cells fire more strongly with strong emotional reactions, e.g. fear responses are usually associated with a strong neural cell response. We've all seen cases where an exposure to fireworks causes a huge fear response & before you know it, the fear of fireworks has generalised to guns, cars backfiring, other loud noises, going out after dark etc etc.

This process is called "long term potentiation" or LTP, & as the neural cells trigger firing in slightly different but linked pathways, the process is called "associative long term potontiation" or ALTP. This is the result of learning at the cellular level (Hebb's Rule) and goes a long way to explaining how most animals learn on the subconscious level.

The upshot is that the more dogs are exposed to things that frighten them, leading to neural fear responses, the more sensitised their neural pathways become & the more likely they are to trigger in future in similar situations. So this is why the best way to deal with unwanted behaviours, particularly fearful behaviours, is to avoid them! Then you can begin to start a programme of desensitisation & counter-conditioning whereby you are changing the sensitivity of neural pathways in certain situations from fearful to calm.

I don't know if I've explained this very well (or if I'm "preaching to the converted"!) but if anyone's interested in the physiology side of things I can recommend the "Physiology of Behaviour" by Neil Carlson. Plus if you google Long Term Potentiation there is lots of info about the cellular basis of learning. I find it interesting but I totally understand if I'm the only one who does!

Thank you for your replies, they were very interesting and informative. I do quite a lot of the things you have advised but will up my game. Unfortunately poor Sam was taken very ill last night (see post of Sam is v. ill) and it's a very
worrying situation at the moment. I will re read your posts at a later date too I know there will be good things in there that I have missed by reading too quickly.
Unfortunately there is both a lack of behaviourists and good trainers here and lack of money on my part so will just have to continue on my own buoyed up by good advice.

The more the physiological responses linked to certain behaviours are activated, the more the neural pathways associated with those behaviours are sensitised. When the neural pathways are sensitised by use (i.e. the "firing of one cell in a neural pathway, causes the next cell to fire etc), the more likely they are to be activated in similar situations. Then these slightly different pathways are sensitised & more easily triggered, then the unwanted behaviours start to generalise to other situations & get even more ingrained. It can be a downward spiral which makes the original problem even more difficult to solve.
Thank you Wilbar - I think that this is a very interesting subject. Humans often control their responses and override their natural impulses, (feelings, wants, drives, etc.). Most of us work at it all the time. I don't think dogs and other animals are able to do this. Food for thought (and bedtime reading)

I am sorry to hear that Sam is not well (so there may be something going on that we as humans are not aware of and the dogs are). I hope everything works out for Sam - perhaps now he does need his own space/peace and quiet a bit more than he used to.

I'm so sorry to hear about Sam ~ best wishes to you both & I hope he makes a speedy recovery.

Yes I think humans have better cognitive skills that can override pure emotional reactions & the flight/fight responses. Dogs & other animals also have cognitive/reasoning skills too but nowhere near as well-developed as ours, so they're more likely to be governed by the emotional & automatic responses. But they can learn to overcome their natural reactions ~ look at the ways some dogs can be trained jump through hoops of fire!!!

Could we close this post please, Sam died a little while ago.
Thank you for your help. Gill