The man's predicament is self-evident. We've all been in the tree, out on a limb. Some hold on. Others let go.
I let go.
The dog, however, seems open to interpretation.
If the dog represents fear, I like to think I outran it.
If the dog represents security, concern and support on the way --- as in, what are you doing way up there so far out on the limb? Come down! I'll be here when you fall! I'm a man's best friend -- we have nothing to fear by letting go.