What is happening in the first five minutes
Group walks start with a pile-up of triggers: several dogs arriving and greeting, leads and harnesses appearing, voices calling instructions, and the whole party moving off at once. A young or excitable dog who mouths a sleeve or seizes his own lead is usually not being rude on purpose — his arousal has risen past the point where he can use his trained behaviours, and his mouth goes to the nearest moving target. It tends to fade once the walk settles into a rhythm, which is your clue that the problem is the launch, not the walk itself.
Lower the launch temperature before the group forms
Arrive a few minutes early and spend them away from the gathering point. Let him sniff a verge thoroughly, scatter a handful of his food in grass to search for, or play a quiet find-the-toy game, so the first wave of excitement discharges through his nose instead of his mouth. Join the group from the edge or the back rather than the middle of the greeting scrum, and keep his lead loose and his space generous for the first stretch. If the organiser allows it, walking parallel at a distance and closing in gradually suits arousable dogs far better than a stationary huddle of excited dogs.
Give his mouth a legal job he already knows
Alternatives only work if they are fluent before you need them, so build them on solo walks first. Teach him to carry a soft toy or a retrieved dummy for the first minutes of a walk, or to bump your hand with his nose on cue for food — both occupy the mouth and the brain without a struggle. Practise the hand target until he offers it eagerly in the garden and on quiet streets, then ask for it at the group walk start. When he does grab the lead or a sleeve, go still, avoid a tug-of-war, wait for the release, and immediately offer the known alternative; wrestling the fabric back turns the grab into the best game of the day.
Read the escalation and step out early
Learn his personal early signs — faster panting, fixating on other dogs, lead biting that gets harder, jumping up between grabs — and treat them as information, not defiance. Stepping ten metres aside, letting the group move ahead, and rejoining once he can take food and look at you is a training success, not a failure. Repeatedly letting him practise the full mouthing routine at peak arousal teaches the routine; repeated calm starts, even shorter ones, teach the calm. Be honest with the group organiser about what he needs; most would rather adjust a start than manage a wound-up dog for an hour.
When mouthing is more than excitement
Mouthing that breaks skin, targets other dogs rather than fabric, or comes with hard staring and stiffness is a different conversation and needs a one-to-one assessment before group walks continue. The same applies if a previously steady dog suddenly starts — pain, including sore teeth or a sore neck from the collar or harness, can lower a dog's tolerance sharply. Your veterinarian is the first check in that case, followed by a qualified behaviour professional if the all-clear comes back.
With KinsLe Care Teams, the pre-walk sniff routine, his chosen mouth-job cue, and notes on which group sizes he copes with can be assigned to whoever walks him, so every group walk starts the same calm way.