Spiny softshell turtle (Apalone spinifera) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Spiny Softshell Turtle
Apalone spinifera

Description

The softshell is a medium to large-sized freshwater turtle. Males can reach a carapace length of up to 21.6 cm. Females can reach up to 54.0 cm, weigh as much as 11.7 kg and are, on average, more than 1.6 times larger than males (Harding 1997). The carapace is olive to tan in colour, flat, round, keelless, and leathery with inconspicuous, spiny projections present along the anterior edge. The surface of the carapace may be slightly roughened like sandpaper, particularly in juveniles. Adult males retain the juvenile pattern of ocelli, spots, and lines, whereas females develop a mottled or blotched pattern which is slightly noticeable even at the time of hatching (Fletcher pers. obs.).

Distribution

Apalone spinifera spinifera ranges from New York to Wisconsin, down the Tennessee and Mississippi Rivers, and north to southern Ontario and Quebec (Harding 1997). The centre of abundance and continuous distribution for this subspecies is the Mississippi River-Ohio River system and the lower Great Lakes (Bleakney 1958, Conant and Collins 1991).

In Canada, A. s. spinifera was formerly found throughout the lower Great Lakes/ St. Lawrence watershed from upper St. Lawrence to lower Lake Huron including some tributaries. Presently the spiny softshell can only be found in isolated locales throughout this historic range. The Canadian population can be divided into two subpopulations. The first is located in the Ottawa River, St. Lawrence River, and the Richelieu River-Lake Champlain system, with the majority of individuals located in Lake Champlain. The second much larger subpopulation is located in Lake St. Clair, Lake Erie (including major tributaries e.g. Thames and Sydenham Rivers), and western Lake Ontario. The majority of the individuals in this subpopulation can be found in the Thames and Sydenham Rivers and at two sites on Lake Erie (Rondeau and Long Point).

Habitat

A. s. spinifera inhabits a wide variety of aquatic habitats including rivers, marshy creeks, bayous, oxbows, lakes, and impoundments. Common habitat features include a soft bottom with some aquatic vegetation as well as sandbars or mudflats (Ernst et al. 1994). Five habitat components that appear to be essential are: sandy or gravelly nesting areas that are close to the water and relatively clear of vegetation, shallow muddy or sandy areas to bury in, deep pools for hibernation, basking areas, and suitable habitat for crayfish and other softshell food sources (Fletcher et al. 1995).

Population sizes and trends

Research conducted since the completion of the original status report in 1985 (Campbell and Donaldson) suggests that the southwestern Ontario subpopulation has a size of approximately 800-1000 individuals (M. Fletcher unpub. data.).  There is currently no estimate for the size of the Quebec subpopulation, but, based on the observation that there have not been more than 100 individuals encountered in one season, it is in the low hundreds (P. Galois pers. comm.). The sections of the Ontario subpopulation that have been consistently observed over the past 5 years appear to be stable, but it is difficult to estimate overall trends for the Canadian population. There are few published historic estimates of densities for the population and only scattered sighting and survey records prior to 1994 (Gartshore and Carson 1990). It would appear that the population has decreased dramatically if one compares a 1792 journal entry from the Chatham area of the Thames River which states that “hundreds of soft-shelled river turtles were scooped off floating logs to make supper that everyone enjoyed” (Gray 1956) to 1997 survey work which located fewer than 10 individuals in the same area (Fletcher 1997).

Limiting factors and threats

Although habitat loss was probably the most significant factor causing the historic decline of this species, habitat degradation is the biggest current problem. Several of the largest remaining nest sites are also heavily used for human recreation and activity on these sites appears to be increasing. Softshells are easily disturbed during nesting so increased recreational use of these sites may result in decreased nesting success. Environmental contamination may also be having an effect on nesting success. High numbers of infertile eggs at some sites in Ontario have prompted the need for analysis of contaminant levels in eggs. Egg samples collected from 1997-1999 are currently being analyzed for contaminant levels.

Existing protection

Currently, the eastern spiny softshell is listed by COSEWIC as Threatened. In Ontario, this species is currently protected under the Ontario Fish and Wildlife Conservation Act 1999. The habitat of this species also receives some protection through the natural heritage component of the Provincial Policy Statement under Ontario’s Planning Act. This Act protects significant portions of the habitat of all threatened species. Several nesting sites are also protected, to varying degrees, as they are located on provincial or federally owned land. In Quebec, new legislation is currently under review that will prohibit the capture, holding, transportation or sale of any subspecies of Apalone spinifera (P. Galois, per. comm.).

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) determines the national status of wild species, subspecies, varieties, and nationally significant populations that are considered to be at risk in Canada. Designations are made on all native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fish, lepidopterans, molluscs, vascular plants, lichens, and mosses.

COSEWIC Membership

COSEWIC comprises representatives from each provincial and territorial government wildlife agency, four federal agencies (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biosystematic Partnership), three nonjurisdictional members and the co-chairs of the species specialist groups. The committee meets to consider status reports on candidate species.

Definitions

Species
Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.

Extinct (X)
A species that no longer exists.

Extirpated (XT)
A species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A species facing imminent extirpation or extinction.

Threatened (T)
A species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*
A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR) **
A species that has been evaluated and found to be not at risk.

Data Deficient (DD)***
A species for which there is insufficient scientific information to support status designation.

* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
** Formerly described as “Not In Any Category”, or “No Designation Required.”
*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994.

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list.

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

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