A sure sign that something has invaded the yard is when Boots barks.  She doesn’t care if other dogs in the area are barking.  She simply ignores that (fortunately).  But she will sound the alarm if something is in her yard. 

So this morning I came out to find out what the ruckus was all about and discovered this specimen:

It was up on the fence because Boots had been chasing it.  At first I was concerned because it appeared to be drooling excessively, which had me thinking rabies.  But it appears that this may be one of its natural reactions to extreme fear (Wikipedia entry on opossums, Virginia Opossum), which includes excessive saliva, among other interesting symptoms: 

But with enough stimulation, the opossum will enter a near coma, which can last up to four hours. It lies on its side, mouth and eyes open, tongue hanging out, with green fluid emitting from its anus, and emitting an odor putrid to most predators. […]  As a result of this unusual behavior, opossums that are discovered apparently dead with no obvious fatal injuries should be given the benefit of the doubt as to avoid inadvertently burying them alive.

‘E’s not dead.  ‘E’s just restin’ 

I guess in this case he was getting ready to fall over and “die” if I hadn’t brought Boots back into the house.