Although black snakes are not usually social creatures, gravid females tend to gather in small groups midsummer, sometimes these groups consist of only two snakes, but more often three to six animals are involved. Occasionally a non pregnant female joins in. they share a common night time retreat and emerge and bask together.
I take issue with this statement. It is probably not common practice to keep snakes communally but there are many that can and do thrive in colonies in captivity.