Snakes, Hibernation, and Man

by Frank Groves


With so much of their natural habitat being destroyed by rural development, some Maryland snakes have begun to utilize man-made structures as wintering quarters. Over the past 20 years or so, 28 cases of adult black rat snakes found in basements of residences have come to hand. Most of these were in unheated areas, in the 40 - 50oF range, where the snakes were generally inactive, though not torpid, moving sluggishly when disturbed. Apparently, they were in some state of semi-hibernation. In a few cases the snakes were in heated basements and normally active, possibly feeding on field mice that often inhabit such places in winter. A juvenile black rat snake was found by a repair man between inner walls of a church that was heated only on Sundays. The snake was active enough to bite the man when he tried to capture it.

Some snakes have taken to digging in alongside the foundations of buildings thus receiving some heat passing through the walls. During an unseasonably warm period in February 1992, an adult black rat snake was seen emerging from a heavily mulched area alongside the home of my neighbor in Carroll County. In October 1978 five ring-necked snakes were observed over a period of a week congregated on the cinder block steps leading to my basement. When disturbed they disappeared into small cracks in the steps. The steps are against the building foundation and must receive some heat from the house. After the weather cooled they were no longer seen. Evidently the steps were being used as a hibernaculum. In late December 1977 a ring-necked snake was found about 18 inches below ground close to the foundation of a home in Anne Arundel County by a man digging out a burst water pipe.

There are a few records of black rat snakes hibernating in wells. In April 1969 a Howard County resident reported a gathering of these snakes in and around his well-house over a period of several weeks. As many as 15, including an albino specimen, were counted on one day. As the weather warmed the snakes disappeared. The well-house was an 8 x 10 wooden structure inside of which a ladder descended to a depth of about 20 feet from the floor of the lower level. Many crannies between the stones formed chambers in which the snakes hibernate. This site was visited in October 1969 when 3 snakes were captured in the well-house and another was seen between the stones about 5 feet down into the well.

In early spring of 1970 a large black rat snake was seen emerging from an unused well a few miles from the first sire and in May 1979 two specimens were captured in another well, also in Howard County. In late November 1979, near Towson, Baltimore County, two were found in a well-house similar in construction to the first. These were lying in the open on the cement floor of the lower level and were in a near-torpid state.

By pursuing such tactics as described above, some snakes may be able to extend their survival in an environment that is becoming increasingly hostile.