What makes Billy think that the coon isn’t the same one his dogs had been trailing at first?

From the text:

During the meal I told Grandpa I didn't think that the coon in the big tree was the same one my dogs had been trailing at first.

"What makes you think that?" he asked.

I told how the coon had fooled us and how Little Ann had seen or heard this other coon. I figured he had just walked up on my dogs before he realized it.