TC is right the scent picture is a lot differant. You allso have to remember that when the leaves come on the weather is warmer and the moisture goes away faster. You will find out how cold of nose your dog has. Even if it has a cold enough nose to work it. If it is use to hot tracks in cold damp weather a hot track in hot dry weather is like an old track to him. A lot of dogs won't run an old track. So that is one of the reasons I don't work dogs on feeder buckets unless I have too. Them learning on older track is slower progress but it keeps you from haveing some of these problems down the road. Not saying you made that mistake. I am just saying that is what causes this problem some times.
I would do what TC said and trap and release coon waiting longer and longer before you let the dog run it. Age the track till you can hold the dog 30 minutes before letting the dog go.
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Train don't complain!!!!!
Dawg
Grady Jarvis