Pantherophis spiloides
Gray ratsnake
Image of Pantherophis spiloides

Photo by Jim H. Harding 

Key Characteristics

The Gray Ratsnake is the largest snake in the Great Lakes region, with total adult lengths ranging from 40-101 inches (102-257 cm). Adult Gray Ratsnakes are black or dark brown in color often with remnant dark blotches from their juvenile color pattern. The belly is white or yellow with dark checkerboard markings on the forward part of the body becoming gray or brown toward the mid-body or tail. The labial scales ("lips"), chin and throat are also white. The young are yellow, white or pale gray in color and strongly patterned, with dark gray or brown blotches or saddles on their backs alternating with smaller blotches on the sides.

Status and Rank

  • State Status: SC
  • State Rank: S2S3
  • Global Rank: G4G5

Occurrences

County NameNumber of OccurrencesYear Last Observed
Allegan32010
Barry12002
Berrien72014
Cass52013
Clinton12014
Hillsdale11985
Jackson11985
Kalamazoo11977
Lenawee21999
Muskegon42014
Oakland11992
Saginaw11995
St. Joseph11989
Van Buren42011
Washtenaw11996
Distribution map for Pantherophis spiloides

Updated 1/31/2017. Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.

Habitat

Gray Ratsnakes usually occur in forested habitats, primarily deciduous forests, but they also use adjacent open habitats including shrubby fields, prairies and marsh and bog edges. Gray Ratsnakes also are often found in or around barns, outbuildings, old foundations and trash dumps. The Gray Ratsnake is a very good climber and often climbs trees to eat nestling birds or eggs. Gray Ratsnakes hibernate in mammal burrows, root networks, rock crevices or other burrows or crevices that provide refuge from freezing temperatures. Gray Ratsnakes deposit eggs in loose soil, rotted stumps or logs, sawdust piles or cavities under rocks, boards or other cover.

Specific Habitat Needs

Downed woody debris needed in Emergent marsh, Wet-mesic sand prairie, Bog, Mesic southern forest, Dry-mesic southern forest, Dry southern forest, Oak openings, Oak barrens, Mesic sand prairie, Mesic prairie, Dry-mesic prairie, Dry sand prairie

Natural Community Types

Methodology

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Feel free to send questions and comments to Brad Slaughter at slaugh14@msu.edu.

Management

Protecting known populations and maintaining large, contiguous forested habitat complexes or mosaics of forested and open habitats are essential for conservation of this species. These snakes rapidly disappear with deforestation, but they may persist in patches of forest. Partial timber harvest techniques and low-intensity agricultural uses that create mosaics of forested and open habitats would benefit this species. Management activities that have potential to cause take or adverse impacts on Gray Ratsnakes (e.g., timber harvesting, use of heavy equipment, mowing) should be conducted when the snakes are inactive or less active (i.e., November to March) to minimize the potential for adverse impacts. To reduce habitat fragmentation and road mortality, construction of new roads through suitable habitat complexes for Gray Ratsnakes should be discouraged or minimized, and closure of existing roads through suitable habitat complexes should be considered. Surveys and research are needed to determine this species' status and distribution and investigate this species' ecology and conservation and management needs in Michigan. Public education also is needed to communicate the harmless nature of this snake, demonstrate the value and benefits of maintaining this species (e.g., its consumption of rodents makes it useful in agricultural areas) and discourage persecution and harassment.

Active Period

Active from fourth week of April to fourth week of October

Breeding from first week of May to second week of June

Nesting from fourth week of June to fourth week of July

Survey Methods

The best time to survey for this species is in May and June during the mating season. An effective way to survey for this species is with funnel traps and drift fences. Drift fences and funnel traps should be placed throughout areas with suitable habitat and should be checked daily or more frequently, if possible, during the survey period. Visual encounter surveys also can be conducted for this species, although they may be difficult to see when they are above ground in tree branches, particularly after leaf out. Visual surveys should be conducted during appropriate weather conditions, generally between 60-80 or 85 degrees F, partly sunny or cloudy skies, and little to no wind.

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Mar 30, 2017]

More Information

See MNFI Species Abstract

References

Survey References

Technical References