Ecological notes: I had noticed the gray squirrels in my yard being a bit extra frisky in mid-February during some of the warmer weather. They breed twice a year so I assumed that this was breeding behavior. Their breeding affairs are a rather violent and complicated matter. Females often have scarred ears and necks from the males biting them during copulation. As females are only in estrus for a single day, promiscuity is the rule (a less charged word might be polygyny - many males mating with a single female). Ecologists like John Koprowski (who wrote some awesome stuff on squirrel mating behavior in the early 90s), suggest that females can be seen as a limited resource and are therefore highly prized and fiercely defended (like the black walnut in my backyard come September). A dominant male will thusly defend a female (or at least access to her) during the breeding season. Part of this is behavioral male-to-male aggression. But part is physiological.
During copulation the male will ejaculate and then secrete a gelatinous substance that hardens into a plug. The male has to then fend off other males until the secretion hardens (about 20 minutes), which effectively blocks another male's sperm (gross, right?). I would assume that the reason males have such gargantuan testicles during breeding season is to have such powerful blasts of semen as to break through other male's copulation plugs (aka mating plug, sperm plug, vaginal plug, or sphragis).
If the adult in Laura's basement had been an adult then she would have mated in that mid-February warm spell, gestated for a month and a half, then given birth to little naked helpless pups in the beginning of April. It'll be less than two more months before they're fully weened and ready to tackle the world. This would put them out on their own by about June 1st, so it's not unlikely that the group of four was a mother and her three pups.
Where: Latham Ct