Baby oPossum explosion - my boys are interested

As some may recall, I have a small backyard fenced in to allow Espy
and Nipsy to go outside. Well, a few days ago I see Nipsy in the hall
playing with his toy mouse. No, it's a live, or rather, dead mouse.
Burial at sea time.

Outside, a bit later, I see Nipsy playing with something, and it's
another mouse. I get that one away from him and drop it through the
fence into the yard next door. The next day I come home (they've been
inside the whole day because they only go out when I'm home) and
there's a dead mouse in the hallway. I guess one of them brought it in
the day before. Those were definitely mice.

Today is, as far as I can tell, baby opossum day. I think they're
opossums. They're not mice, or rats. Not voles I don't think, or
shrews. No, having seen an adult opossum (the THING in the backyard
thread of a few months ago), I think these are babys.

One ended up in the hall , where the dead mice were. It was still
alive so I set it free. Now I've seen one in a neighbor's yard, and
freed two more from the cats. I was just outside and Espy is parading
around with a fairly large grey thing in his mouth. I got it away and
sent it next door.

I'm bringing the boys in now. I realize this is what cats do, but I
don't have to be very happy about it. Mice and opossums are actually
pretty cute.