Black Rat snakes (Elaphe obsoleta) were mainly recorded at the base of Point Pelee National Park in forested areas but they have been absent from the park since 1960. However, suitable habitats still seem to exist throughout the dryland areas.
Since the point is part of what is known as the Carolinian Forest it should not be surprising to hear that the Black Rats, according to JD Wilson et al, are “the most common of the large snakes encountered in North Carolina.” According to Natural Resources Canada its habitat is “open woodlands, fields, and abandoned buildings” but its status is “rare and local in southeastern Ontario, and even rarer in southwestern Ontario where it has declined with loss of forest cover.”
Carolinian Forest:
Carolinian Canada recounts that C.H. Merriam “used isotherms - 8°C (46°F)- as well as plant and animal ranges to define a Carolinian Area in Canada ranging from “the north end of Lake St. Clair to the west end of Lake Ontario.” Carolinian Canada would like the label to be used “for those associations within the Deciduous Forest Region in which Sassafras and Tuliptree are dominants. Some Flowering Dogwood in the understorey would be nice. Such an association would likely have had a lot of American Chestnut at one time. Co-dominants would include Black Walnut, Black Oak, White Oak, Red Maple, Pignut Hickory, and Black Gum." In essence, it would include “species which are largely restricted to well drained, sandy, often acidic, soils.”
Status of Black Rat Snake:
According to Parks Canada the Black Rat Snake is "common and secure in its American range (priority 5). In Canada and Ontario it is designated as rare (priority 3)." It is threatened in the West St. Lawrence Lowland region.
This species has not been recorded in the Park since the early 1960's, and is assumed to currently be extirpated (eradicated).
Requirements for Black Rat Snakes include:
- dry land- although they can swim
- edge habitats
- old outbuildings for nesting and ecdysis (shedding)
- basking areas- to raise body temperature
- sufficient area to range- 100 to 900 meters in diameter
- bird nestings and eggs for food
- mice and voles for food
- loose earth, decaying logs, sawdust piles for laying eggs
- rock fissures, tree roots, abandoned wells and cisterns for hibernation (hibernacula)
Causes of Extirpation and Management Problems:
Park officials believe this species probably became extirpated because of human intolerance. Farming in the park may have actually enhanced the habitat for this species by opening woodlots, providing hibernation sites and increasing the number of rodents. However, an increase in the human population probably ended the existence of this menacing looking snake.
It is not known if current habitats in the Park are suitable in terms of quality and size for this species. Any re-introduced population would be isolated.
Prospects of Species Introduction:
T.M Clarke and Rom Westrum, in Environmental Management, point out that “reintroduction of animals to the wild to establish free-ranging viable populations is a valuable conservation tool, but ecological skills alone are not enough to ensure a successful reintroduction; also needed to do the work are effectively designed and managed programs.
Presently at Point Pelee, the park conservation plan ranks the reintroduction of extirpated species as a priority C project (i.e. a desirable project if and when funds become available to do it). If decided upon for the Black Rat Snake, the site for reintroduction would be an upland area of mature forest along the DeLaurier Trail.
However, other things need to be considered. For instance, are there rare or breeding species that might be affected by the introduction of the snakes? Parks Canada’s program of environmental assessments at Point Pelee National Park conducted by students, asks them to choose the species that they think might be at risk, and then to gather information and make an educated decision (e.g. the Appendaged Waterleaf which is rare in Ontario).
Environmental Assessment:
Following are segments of a student-generated environmental assessment screening report. The key points were as follows:
- estimated cost- $77 490 in 2010 dollars (staff $62 730; other $14 760)
- estimated staff time- 450 hours
- description- obtain, transfer, medically examine, mark with liquid nitrogen, implant six individually with radio transmitters, and then check on-site acclimatization for 30 days; and finally the release of snakes on site followed by radio monitoring of the population from April 1st to Sept. 30th for two seasons with infrequent 3/day/year monitoring after the second season.
- Site suitability for project- excellent except for hibernation sites (limited), and public access bisecting area.
- Impact on site resources- greatest impact will be upon the Yellow-Breasted Chat, and possibly on the Eastern Mole which are part of the diet. Hibernation sites could possibly be provided.
- Long term consequences- a reintroduction of species to restore the parks ecological integrity is a very desirable goal (although studies suggest physical integrity at risk)
- Screening decision- approved pending modifications; which may include periodic closing of trail to protect hibernation sites
Educational Opportunities:
An educator could use the ideas presented and enpower the students to develop a similar proposal at an accessible natural area. They could perhaps include:
- An interpretive display: type and proposed location (impacts), or
- Develop a similar proposal at an accessible natural area, but with a ‘site description’ component (class field study)
Sources:
- J.D. Wilson et al. Rat Snake. Davidson College
- Carolinian Species and habitats. Carolinian Canada
- Black Rat Snake. Natural Resources Canada
- Point Pelee National Park Environmental Assessments: Senior Class Projects- Eastern Ratsnake Reintroduction. Parks Canada
- Point Pelee in Peril, Study Finds. Windsor Star. Mar. 17, 2008.
- Tim W. Clark and Ron Westrum. High-performance teams in wildlife conservation: A species reintroduction and recovery example. Environmental Management. Vol. 13, No. 6. 1989. pgs. 663-670.
James Gibson - James Gibson is a retired teacher and small business owner. He is a published writer and has a wide spectrum of interests.
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