Species Profile

Gray Ratsnake Carolinian population

Scientific Name: Pantherophis spiloides
Other/Previous Names: Eastern Ratsnake (Carolinian population)
Taxonomy Group: Reptiles
Range: Ontario
Last COSEWIC Assessment: April 2007
Last COSEWIC Designation: Endangered
SARA Status: Schedule 1, Endangered

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Quick Links: | Description | Habitat | Biology | Threats | Protection | Recovery Initiatives | National Recovery Program | Documents

Image of Gray Ratsnake


The Gray Ratsnake is the largest snake in Canada. Males can reach a maximum length of approximately 190 cm from the snout to the tip of the tail. Colouration patterns on adult individuals differ considerably from one region to the next. Adults are generally shiny black with white, yellow, orange, or red on the skin between the scales. The stomach is generally white or yellowish with grey or brown patterning, often resulting in a checkerboard appearance. The Gray Ratsnake can be distinguished from other snakes by its throat, which is uniformly white or cream. In contrast to adults, juveniles have patterning on the back composed of dark grey or brown blotches on a pale grey background.


Distribution and Population

The Gray Ratsnake is commonly found in the forests of eastern and central United States. It occurs relatively continuously throughout the major part of the eastern half of the United States, along the western edge of the Appalachian Mountains, from southwestern New England to the Gulf of Mexico, westward to the Mississippi River, and northward from northern Louisiana to southwestern Wisconsin. In Canada, this species only occurs in two disjunct Ontario regions: the Carolinian forest region along the north shore of Lake Erie in the southwest, and the Great Lakes/St. Lawrence region in the southeast. Individuals from both regions comprise two separate populations divided by 300 km. The Carolinian population is made up of four very small isolated populations in Middlesex, Elgin, Haldimand-Norfolk, and Niagara counties. There are no size estimates for the Carolinian populations. However, the lack of suitable habitats and the limited number of sightings suggest that these are small populations and that they are declining. The Big Creek population just north of Long Point appears to be the largest population and the most likely to survive over the long term.



Although this species is generally associated with deciduous forests, the Gray Ratsnake seems to inhabit a wide variety of habitats, with a preference for a mosaic of forest and open habitats, such as fields and rocky outcrops. In-depth studies of habitat use by the southeastern Ontario population indicate that individuals need different habitat types in different seasons. In winter, they hibernate underground in communal hibernation sites, or hibernacula, that provide protection against freezing and dehydration. The Gray Ratsnake is extremely faithful to these hibernacula. During summer, which is when they are active, snakes seek refuge in snags, hollow logs, rock crevices, and under rocks to shed and to escape from extreme heat and predators. They must also find suitable sites to warm themselves in the sun. Females nest in the decaying material inside snags, stumps, logs, or compost piles, where the conditions are humid and the temperature is in the 30ºC range. These nests are often communal and are reused from year to year by numerous females. The Carolinian population’s habitat is dominated by agricultural land mixed with small patches of open deciduous forest and criss-crossed by a dense network of roads. Given that more than 80% of the original forest cover has disappeared, it is not known whether sufficient areas of habitat remain to support viable Gray Ratsnake populations.



The Gray Ratsnake reaches sexual maturity at seven to nine years of age. Females produce one clutch containing 10 to 15 eggs every two or three years. In Ontario, females nest from early July to early August, approximately one month after breeding season, which extends from late May to mid-June. When males encounter other males while courting, they compete in a ritualized physical combat for the right to mate with the female. Eggs hatch between late August to early October, following an incubation period of approximately 60 days. Due to the harshness of the Canadian climate, the Gray Ratsnake’s active season only lasts about six months (mid-April to mid-October). During this period, they travel up to 4 km from their hibernacula. Adults are strongly attached to their territory and often return to the same sites from year to year. The Gray Ratsnake is both predator on and prey of many species. It feeds primarily on small mammals and birds. Since it lives some of the time in trees, it is an efficient predator of bird nests. Its known predators include some large birds of prey (e.g. Red-shouldered Hawk, Osprey, and Red-tailed Hawk) and medium-sized mammals (e.g. Fisher, Mink, and Raccoon). The Gray Ratsnake can live 25 to 30 years.



Habitat loss and degradation constitute the main threat to the Carolinian population. In fact, the habitat suitable for this species in this region is very limited and extremely fragmented. It is not known whether sufficient areas of habitat remain to support viable Gray Ratsnake populations. Certain species-specific traits, such as reproducing every two or three years and at a late age, make this population particularly vulnerable to environmental disruptions. Given its low reproductive output, increased mortality caused by farm machinery could have major repercussions for this population. Other threats to this large species include the deliberate slaughter of snakes. Finally, road mortality also constitutes a significant threat to all Gray Ratsnake populations, because these snakes move slowly and may remain on the road to bask in the sun.



Federal Protection

The Gray Ratsnake, Carolinian population, is protected under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.

In Ontario, this species is protected under Ontario’s Fish and Wildlife Conservation Act, 1997.

Provincial and Territorial Protection

To know if this species is protected by provincial or territorial laws, consult the provinces' and territories' websites.


Recovery Initiatives

Status of Recovery Planning

Recovery Strategies :

Name Recovery Strategy for the Gray Ratsnake (Pantherophis spiloides), Carolinian and Great Lakes/St. Lawrence populations, in Canada
Status First posting on SAR registry



PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.

10 record(s) found.

COSEWIC Status Reports

  • COSEWIC Assessment and Update Status Report on the Gray Ratsnake (Elaphe spiloides) in Canada (2007)

    The Gray Ratsnake (Elaphe spiloides) is the largest snake in Canada, reaching a maximum snout-vent length (SVL) of approximately 190 cm. The colour pattern of adult Eastern Ratsnakes is widely variable across the species’ range. Throughout all populations in Canada, adult Gray Ratsnakes are typically plain, shiny black with white, yellow, orange or red colouration on the skin between the scales. The ventral surface is typically white or yellowish with a clouded grey or brown pattern, often resulting in a checkerboard appearance. Ratsnakes can often be distinguished from other snakes by their throat, which has a plain white or cream colour. In contrast to adults, juveniles are dorsally patterned with dark grey or brown blotches on a pale grey background.

COSEWIC Assessments

  • COSEWIC Assessment - Gray Ratsnake (2007)

    The species was considered a single unit and designated Threatened in April 1998 and in May 2000. Split into two populations in April 2007. The Carolinian population was designated Endangered in April 2007.

Response Statements

  • Response Statement - Gray Ratsnake, Carolinian population (2007)

    This population consists of only 4 highly disjunct subpopulations in southwest Ontario, all of which are small and isolated, and surrounded by agricultural and developed terrain. Their slow rate of reproduction and late age of maturity makes them especially vulnerable to increases in adult mortality from road traffic and agricultural machinery.

Recovery Strategies

  • Recovery Strategy for the Gray Ratsnake (Pantherophis spiloides), Carolinian and Great Lakes/St. Lawrence populations, in Canada (2017)

    The Minister of Environment and Climate Change and Minister responsible for the Parks Canada Agency is the competent minister under SARA for the Gray Ratsnake (Carolinian population) and the Gray Ratsnake (Great Lakes/St. Lawrence population) (henceforth referred to as the Gray Ratsnake (Carolinian and Great Lakes/St. Lawrence populations) and has prepared the federal component of this recovery strategy (Part 1), as per section 37 of SARA. SARA section 44 allows the Ministers to adopt all or part of an existing plan for the species if it meets the requirements under SARA for content (sub sections 41(1) or (2)). A single document has been prepared to address the recovery of the two Gray Ratsnake populations (Carolinian and Great Lakes/St. Lawrence) under SARA. The Ontario Ministry of Natural Resources (now the Ontario Ministry of Natural Resources and Forestry) led the development of the attached recovery strategy for the Gray Ratsnake Carolinian and Frontenac Axis populations (Part 2) in cooperation with Environment and Climate Change Canada and the Parks Canada Agency. In this federal addition, “Frontenac Axis population” has been replaced by the term “Great Lakes/St. Lawrence population” because of how the species is listed under SARA, and these terms may be used interchangeably. The Province of Ontario also led the development of the attached Government Response Statement (Part 3), which is the Ontario Government’s policy response to its provincial recovery strategy and summarizes the prioritized actions that the Ontario Government intends to take and support.


  • Order Acknowledging Receipt of the Assessments Done Pursuant to Subsection 23(1) of the Act (2008)

    This Order acknowledges receipt by the Governor in Council of the assessments of the status of 30 species made pursuant to paragraph 15(1)(a) and in accordance with subsection 23(1) of the Species at Risk Act by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).
  • Order Amending Schedule 1 to the Species at Risk Act (2009)

    Her Excellency the Governor General in Council, on the recommendation of the Minister of the Environment, pursuant to section 27 of the Species at Risk Act, hereby makes the annexed Order Amending Schedules 1 to 3 to the Species at Risk Act.
  • Order Amending Schedule 1 to the Species at Risk Act (2012)

    The purpose of the Order Amending Schedule 1 to the Species at Risk Act is to add 18 species to Schedule 1, the List of Wildlife Species at Risk (the List), and to reclassify 7 listed species, pursuant to subsection 27(1) of SARA. This amendment is made on the recommendation of the Minister of the Environment based on scientific assessments by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and on consultations with governments, Aboriginal peoples, stakeholders and the Canadian public.

COSEWIC Annual Reports

  • COSEWIC Annual Report - 2007 (2007)

    2007 Annual Report to the The Minister of the Environment and the Canadian Endangered Species Conservation Council (CESCC) from the Committee on the Status of Endangered Wildlife in Canada.

Consultation Documents

  • Consultation on Amending the List of Species under the Species at Risk Act - Terrestrial Species (2008)

    As part of its strategy for protecting wildlife species at risk, the Government of Canada proclaimed the Species at Risk Act (SARA) on June 5, 2003. Attached to the Act is Schedule 1, the list of the species that receive protection under SARA, also called the List of Wildlife Species at Risk. Please submit your comments by March 25, 2008 for species undergoing normal consultations and by March 27, 2009 for species undergoing extended consultations.

Recovery Document Posting Plans

  • Environment and Climate Change Canada's Three-Year Recovery Document Posting Plan (2016)

    Environment and Climate Change Canada’s Three-Year Recovery Document Posting Plan identifies the species for which recovery documents will be posted each fiscal year starting in 2014-2015. Posting this three year plan on the Species at Risk Public Registry is intended to provide transparency to partners, stakeholders, and the public about Environment and Climate Change Canada’s plan to develop and post these proposed recovery strategies and management plans. However, both the number of documents and the particular species that are posted in a given year may change slightly due to a variety of circumstances. Last update March 31, 2017