Eastern Hog-nosed Snake (Heterodon platirhinos) COSEWIC assessment and update status report: chapter 11

Technical Summary

Heterodon platirhinos

Eastern Hog-nosed Snake – Couleuvre à nez plat

Range of Occurrence in Canada :

Southern Ontario

Extent and Area Information

Extent of occurrence (EO) (km²)

[A MCP was calculated using all element occurences from the NHIC database] see p. 4 : 107,100 km²

Specify trend in EO :

Declining

Are there extreme fluctuations in EO?

No

Area of occupancy (AO) (km²)

[NHIC observations from 1990 onward were overlayed with a 3x3 km grid and all squares that contained at least one observation were compiled. The total “occupied” grid area was then calculated.] See section on Abundance: 1,881 km²

Specify trend in AO :

Declining

Are there extreme fluctuations in AO?

No

Number of known or inferred current locations :

More than 126

Specify trend in # :

Declining

Are there extreme fluctuations in number of locations?

No

Specify trend in area, extent or quality of habitat :

Declining

Population Information

Generation time (average age of parents in the population) See section on Life Cycle and Reproduction :

~ 6-7 years

Number of mature individuals

See section on Abundance: (~7,524) Less than 10,000 adults

Total population trend:

Declining

% decline over the last/next 10 years or 3 generations.

Unknown

Are there extreme fluctuations in number of mature individuals?

No

Is the total population severely fragmented?

Yes, and  becoming increasingly so because of increase in roads and development (see sections on Habitat, Habitat Protection, Abundance, and Limiting Factors and Threats)

Specify trend in number of populations:

Unknown

Are there extreme fluctuations in number of populations?

No

List populations with number of mature individuals in each: 

Threats (actual or imminent threats to populations or habitats)

Mortality on roads, persecution by humans, habitat fragmentation, urbanization, collection for the pet trade, and possibly, declines in specialized food source (toads).

Rescue Effect (immigration from an outside source)

Status of outside population(s)?

USA: N5; Global: G5

Is immigration known or possible?

Not possible

Would immigrants be adapted to survive in Canada?

Probably

Is there sufficient habitat for immigrants in Canada?

Possibly

Is rescue from outside populations likely?

Very unlikely

Quantitative Analysis

Insufficient data.

Current Status

  • COSEWIC: Threatened (November 2007)
  • COSEWIC: Threatened (2001)

Status and Reasons for Designation

Status: Threatened

Alpha-numeric code: B2ab(iii)

Reasons for Designation: This species faces several threats, particularly increased mortality and severe habitat fragmentation caused by an expanding road network and increased traffic. The species is mobile for a snake, but this mobility places it at high risk when it encounters roads. The species also suffers from persecution by humans not only because it is a relatively large snake, but also because of its complex defensive threats when confronted. In southwest Ontario and south of the Canadian Shield, the species has suffered extensive habitat loss from agriculture and rapid increase in housing development. Poaching for the illegal wildlife trade is a growing threat.

Applicability of Criteria

  • Criterion A : (Declining Total Population): ( not applicable)
  • Criterion B : (Small Distribution, and Decline or Fluctuation):Meets Threatened, 2) AO<2000 km²; a) severely fragmented by roads; b(iii) loss of habitat.
  • Criterion C : (Small Total Population Size and Decline):Could meet C2a(i) &lt;10,000 adults, likely to decline, no population greater than 1000 adults.
  • Criterion D : (Very Small Population or Restricted Distribution):Population exceeds criteria
  • Criterion E : (Quantitative Analysis): Not applicable

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