Buster did it again....alerting to possible danger

Last night I was standing in the yard talking to my brother in law while Buster played. I wasnt watching the pup as close as I know I should have been (he was leashed, couldnt get more than 20' from me). Next thing we know Buster is barking at something on the neighbors back step. Big brother headed over to see what the pup was alerting us to and said "Its an opossum, keep him away". No problem, Buster didnt want anything to do with that nasty creature! He alerted us but stood there keeping the leash completely loose.

A couple things were strange about the encounter, he barked and he made no move to chase.

Barking is something Buster does during play only, last night was the first time he barked outside since coming home 3 months ago. He let out 3 barks...granted he has a big bark... we responded and he went back to being silent.

He chases wild rabbits out of the yard every time I take him potty, he wanted nothing to do with the opossum last night. He stood there very alert but never took even a single step towards the creature...almost as if he knew it was a dangerous animal and not to approach it.

Should have added...Buster was praised very well for alerting and not chasing. As soon as we knew the reason for his barking, we headed into the house for some yummy treats.