I've read on them plenty, sorry for not submitting the info.
On p1999 they are spawning during the day and they are not causing disease.
They should be spawning in packs of 3, but are currently a rare spawn (lucky to get one when killing all the pack rats).
I can't find info on it, but by memory they dropped livers about 25% of the time. It was an annoyance to loot>destroy if you weren't looking for them and like to keep the area clear of corpses while bone chip farming.
Which is a related issue someone else posted:
http://www.project1999.org/forums/sh...ad.php?t=12127