I agree, but perhaps more that it was probably a bit overwhelming for him with the atmosphere of a party and in an enclosed space - don`t feel bad though as you did`nt go there determined to join in regardless of how Jack might have felt, you did`nt know he would be so atmosphere-sensitive !
The same happened with my Fluke when I took him to an agility competition for the first time soon after I adopted him. It was a bit of an over-load to him and while I was surprised that he was so reactive I can understand it but had I not taken him I would not have known he would find it so un-nerving - imagine if I`d just been training him in agility then turned up for a competition with him never having faced that atmosphere before - he would have been demented about it
Because I found out how stressy it was for him I have been ale to work on careful gentle desensitisation, including using an anxiety wrap for him, [ he actually became the agility warehouse photo model for the wraps` advert there
], so that he can acclimatise to very large gatherings of dogs and the high level of activity which goes with it.
It may be that he will be be a veteran before he feels comfortable enough to compete and thats fine by me, because if he ever does get to compete it will not be for the sake of that for me but testament to his character to be willing to trust me in us working on it together and thats how fear aggression should be worked on imo - as a team striving to overcome whatever place or atmosphere causes a dog to be unsettled, to build confidence for the sake of that dogs inner well-being.
Now that you know Jack lacks confidence in the setting of the hall, [ I`m assuming it was a hall ? ], you have the opportunity to piece together the elements which contributed to his discmfort, including :
the flooring - did he feel vulnerable if the floor was slippy in places
no escape - was he too `hemmed in` because of too many dogs between him and a comfort zone [ outside the door / entrance ]
Or was he too near the door and felt there was a stream of dogs, [ to his perception ], which would naturally look toward him when coming in, and in his mind any one of them may have had negative intent
volume of dogs - literally so many dogs he felt the need to try to watch in case any of them might have a go at in [ in his perception ], in a closed space, lots of dogs milling around, if feeling vulnerable he could have felt unable to cope with trying to keep an eye on all of them all of the time just in case`, and may have felt isolated `against the world`
sound magnification - the noise bouncing around indoors of presumably many barky dogs and human voices / laughter / excited tones, [ especially if there were party games too ], for some dogs it can be such a cacophony to their hearing, that alone could create fear where there might usually be none on a `normal` training night which would be calmer and would have nowhere near as much going on
Yes, thousands of dogs are perfectly fine about any or all of those things, but for those which are`nt so comfortable it can be very difficult for them.
But had you not gone and not seen his reaction to that atmosphere, you would not have gained the opportunity to identify what to work on to help him
Whether it was any of the above individually or in combination, or anything else you will be able to piece together when sitting down and considering how he reacted at particular times to specific stimuli - that might sound like an impossible task but believe me you and Chris are in tune with him, you will be able to sift through the evening to pinpoint some `trigger moments` - trust your instincts
It may be that taking him to the venue when empty of other dogs, then gradually building up with one, then two, then three etc of the dogs which can be trusted to be laid back toward him, could be what will get him through this - perhaps the trainer might be happy for you to go to class nights early before other dogs are expected to arrive so you can take him in, do a little basic obedience and rewarding in complete relaxation then out again, until ready to arrange for a trusted dog to arrive a few minutes in to you doing this, and so on, [ it would depend on how helpful the trainer is and how soon he or she arrives at the venue to prepare before students start arriving ].
Doing something like that would give Jack the opportunity to change his perception of `the place` and what happens inside, to make it more positive for him, and even hopefully get him to the point where the arrival of other dogs is a trigger to fun brain-work through which instead of feeling like its `him against the world`, it can become his family unit having a good time as `part` of that world, which can in turn translate to other venues and other situations