Big-tooth Whitelip (Neohelix dentifera): COSEWIC assessment and status report 2025

Official title: COSEWIC Assessment and Status Report on the Big-tooth Whitelip (Neohelix dentifera) in Canada

Endangered 2025

COSEWIC assessment summary

Assessment summary – May 2025

Common name: Big-tooth Whitelip

Scientific name: Neohelix dentifera

Status: Endangered

Reason for designation: In Canada, this large (2 to 2.5 cm shell diameter land snail is known to occur in at least six sites within mature mixed-wood forest from Perth to south of Algonquin Provincial Park in southern Ontario. It is extirpated from the rest of its historical Canadian range, which extended south to Hamilton, around Ottawa, and eastward to Quebec City where it was found in large numbers in the 1890s. It typically lives near boulders on slopes and ravines but is also found under logs in thick leaf litter. The main threats are climate change (particularly droughts and changes in freeze-thaw cycles) and logging but it is also susceptible to ecosystem modifications from invasive species (including exotic earthworms and slugs) and wildfire. The species’ restricted distribution, limited dispersal, low abundance at known sites, and continuing threats make it vulnerable to extirpation from Canada.

Occurrence: Ontario, Quebec

Status history: Designated Endangered in May 2025.

COSEWIC executive summary

Big-tooth Whitelip

Neohelix dentifera

Wildlife species description and significance

The Big-tooth Whitelip (Neohelix dentifera) is a large land snail with an olive-brown coloured shell (2 to 2.5 cm in diameter) and a pearly-white body. Only two species in the genus are found in Canada. It was historically described as one of the rarest eastern North American large land snails. The Big-tooth Whitelip is a member of the litter community and involved in litter degradation and subsequent soil formation.

Aboriginal (Indigenous) knowledge

All species are significant and are interconnected and interrelated. There is no species-specific Aboriginal Traditional Knowledge (ATK) in the report.

Distribution

In the eastern U.S., the Big-tooth Whitelip occurs in the Appalachian Mountains and the Adirondacks. In Canada, the Big-tooth Whitelip is at the northern limit of its global range. This heterogeneously distributed species historically occurred in low-abundance subpopulations along the upper St. Lawrence River and Great Lakes region from Île d’Orléans, Quebec, westward to Toronto, Ontario. Recent records are from in and near Algonquin Provincial Park, Ontario. Only two live individuals and four shells were found in five sites in 2024, despite a large recent search effort within the historical range. The continued existence of the species at one occurrence in southern Ontario based on a record from the 1990s is uncertain because it was not found in searches of this site in 2023.

Habitat

In the U.S., the Big-tooth Whitelip is associated with acidic, low-density soils in talus in high-altitude, exposed non-oak-hickory forests. It usually lives between rocks but is also found under logs in thick leaf litter. The species has been found in recent searches in Canada in mature mixed-wood forests on neutral to calcareous soils, mostly near boulders on slopes and ravines but never in floodplains.

Biology

The Big-tooth Whitelip is an egg-laying land snail. Mating and egg laying probably occur twice a year, in spring and late summer. Hibernation extends from early October to April–May. Sexual maturity may be reached after 2 years, and the species may live for 5 to 10 years. Generation time is estimated to be 5 to 6 years. Active dispersal for colonization of new areas is slow.

Population sizes and trends

The current population size is unknown. Notable abundances of the Big-tooth Whitelip were reported near Quebec City at the end of the 19th century; despite numerous surveys at that time, it appeared in low numbers elsewhere. Although the species’ range in Canada appears large, the species has always been rare, with few past occurrences. In most of the recently searched, historically occupied sites, the habitat has been altered (it was logged in the past and is now secondary forest), disturbed (by past or current human activity), or completely lost (urbanized or converted into agricultural land), which most likely has resulted in the loss of subpopulations and a decline in numbers. Currently the species is found only at a few sites within a restricted range in Ontario.

Threats

The main threats include Climate Change and Severe Weather (IUCN 11), with more frequent droughts and extreme weather events in winter (for example, freezing, storms) that increase mortality, and Biological Resource Use (IUCN 5, logging). Another low-impact threat is Natural System Modifications (IUCN 7) through wildfire, with invasive species (IUCN 8) having an unknown impact.

Protection, status, and recovery activities

The Big-tooth Whitelip is not protected by any legislation, regulations, customs, or conditions. According to NatureServe, the species is Apparently Secure to Secure globally (G4G5) and in the U.S. (N5) but Critically Imperilled (N1) in Canada. Based on historical records, the subnational rank in Quebec is “no status” (SNR), while it is Critically Imperilled (S1) in Ontario. Many states in the U.S. that have records have not assessed the species or have ranked it as “no status,” despite recent data.

Technical summary

Neohelix dentifera

Big-tooth Whitelip

French name: Hélice dentifère

Indigenous names: None proposed

Range of occurrence in Canada: Currently, only southern Ontario; range historically included Quebec

Demographic information

Requested data

Supporting explanation

Generation time (usually average age of parents in the population)

Approximately 5 to 6 years

See Life cycle and reproduction

Is there an [observed, estimated, inferred, or projected] continuing decline in number of mature individuals?

Likely

Only a few individuals (live or shells) have been found recently, in 2024. Continuing decline based on continuing threats.

[Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 3 years [or 1 generation; whichever is longer up to a maximum of 100 years]

N/A (not applicable)

Unknown

Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 5 years [or 2 generations; whichever is longer up to a maximum of 100 years]

N/A

Unknown

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last 10 years [or 3 generations; whichever is longer]

Unknown rate of decline over last 3 generations

Historical decline of uncertain magnitude inferred from the reduction in EOO and IAO; however, the decline most likely occurred more than 3 generations ago.

[Projected, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations, up to a maximum of 100 years]

Unknown

Decline of uncertain magnitude suspected based on continuing threats.

[Observed, estimated, inferred, projected, or suspected] percent [reduction or increase] in total number of mature individuals over any period of 10 years [or 3 generations; whichever is longer, up to a maximum of 100 years], including both the past and future (up to a maximum of 100 years in future)

Unknown

Decline of uncertain magnitude inferred from the past reduction in EOO and IAO and suspected in the future based on continuing threats.

Are the causes of the decline clearly reversible?

No

Climate change and habitat loss/degradation

Are the causes of the decline clearly understood?

Yes

Past and continuing habitat loss/degradation and climate change

Have the causes of the decline clearly ceased?

No

Climate change and ongoing habitat loss/degradation

Are there extreme fluctuations in number of mature individuals

Unknown

No data available

Extent and occupancy information

Requested data

Supporting explanation

Estimated extent of occurrence (EOO)

2,176 km²

Calculated based on minimum convex polygon around extant occurrences; 2,815 km² if including one uncertain occurrence.

Index of area of occupancy (IAO), reported as 2x2 km grid value

20 km²

Assuming that the species occurs in the 2 × 2 km grids around extant occurrences; 24 km² if including one uncertain occurrence.

Is the population “severely fragmented”, that is, is >50% of individuals or >50% of the total area “occupied” (as a proxy for number of individuals) in habitat patches that are both (a) smaller than required to support a viable subpopulation, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

1. No
2. No

Number of “locations” (use plausible range to reflect uncertainty if appropriate)

1 to 5

Droughts cover a large area, while logging or fire could affect sites individually; with two occurrences approximately 2 km from each other combined.

Is there an [observed, inferred, or projected] continuing decline in extent of occurrence?

Unknown

Historical decline most likely occurred more than 3 generations ago. Continuing decline dependent on loss of peripheral subpopulations because of threats.

Is there an [observed, inferred, or projected] continuing decline in index of area of occupancy?

Unknown

Historical decline most likely occurred more than 3 generations ago. Continuing decline dependent on loss of occurrences because of threats.

Is there an [observed, inferred, or projected] continuing decline in number of subpopulations?

Unknown

Historical decline most likely occurred more than 3 generations ago. Continuing decline dependent on loss of subpopulations because of threats.

Is there an [observed, inferred, or projected] continuing decline in number of “locations”?

Unknown

Historical decline most likely occurred more than 3 generations ago. Continuing decline dependent on loss of locations because of threats.

Is there an [observed, inferred, or projected] continuing decline in [area, extent and/or quality] of habitat?

Yes

Projected decline of habitat quality due to threats.

Are there extreme fluctuations in number of subpopulations?

Unknown

Unknown

Are there extreme fluctuations in number of “locations”?

Unknown

Unknown

Are there extreme fluctuations in extent of occurrence?

Unknown

Unknown

Are there extreme fluctuations in index of area of occupancy?

Unknown

Unknown

Quantitative analysis

Is the probability of extinction in the wild at least 20% within 20 years [or 5 generations], or 10% within 100 years]

Unknown

Analysis not conducted

Threats

Requested data

Supporting explanation

Was a threats calculator completed for this species?

Yes

Overall assigned threat impact: High–Low (November 2023, updated/revised in October 2024, further modified February 2024 following SSC telecon).

Key threats were identified as:

1. Climate Change and Severe Weather (IUCN 11) – high to low impact
2. Biological Resource Use (IUCN 5) – medium to low impact
3. Natural System Modifications (IUCN 7) – low impact

What limiting factors are relevant?

• Low dispersal capacity
• Low physiological resistance

Rescue effect (from outside Canada)

Requested data

Supporting explanation

Status of outside population(s) most likely to provide immigrants to Canada.

Unknown

Status not well known, because mostly old records exist from U.S. states, SNR in Vermont and New York, and S4 in Pennsylvania (NatureServe 2025a).

Is immigration known or possible?

Unknown

Unknown

Would immigrants be adapted to survive in Canada?

Unknown

Unknown

Is there sufficient habitat for immigrants in Canada?

Unknown

Unknown

Are conditions deteriorating in Canada?

Yes

Threats for the species were identified and are continuing.

Are conditions for the source (that is, outside) population deteriorating?

Unknown

Unknown

Is the Canadian population considered to be a sink?

Unknown

Unknown

Is rescue from outside Canada likely, such that it could lead to a change in status?

No

Natural migration into Canada highly unlikely.

Wildlife species with sensitive occurrence data (general caution for consideration)

Requested data

Supporting explanation

Could release of certain occurrence data result in increased harm to the Wildlife Species or its habitat?

No

Species difficult to find.

Status history

COSEWIC status history: Designated Endangered in May 2025.

Status and reasons for designation

Status: Endangered

Alpha-numeric codes: B1ab(iii)+2ab(iii)

Numeric code for change in status: NA

Reasons for designation: In Canada, this large (2 to 2.5 cm shell diameter land snail is known to occur in at least six sites within mature mixed-wood forest from Perth to south of Algonquin Provincial Park in southern Ontario. It is extirpated from the rest of its historical Canadian range, which extended south to Hamilton, around Ottawa, and eastward to Quebec City where it was found in large numbers in the 1890s. It typically lives near boulders on slopes and ravines but is also found under logs in thick leaf litter. The main threats are climate change (particularly droughts and changes in freeze-thaw cycles) and logging but it is also susceptible to ecosystem modifications from invasive species (including exotic earthworms and slugs) and wildfire. The species’ restricted distribution, limited dispersal, low abundance at known sites, and continuing threats make it vulnerable to extirpation from Canada.

Applicability of criteria

A: Decline in total number of mature individuals

Not applicable. Insufficient data to reliably observe, estimate, infer, or suspect population trends.

B: Small range and decline or fluctuation

Meets Endangered, B1ab(iii)+2ab(iii). The EOO and IAO are both below thresholds (5,000 km² and 500 km², respectively), there are 5 or fewer locations (a), and there is a projected continuing decline in habitat quality (b(iii)) caused by a variety of threats.

C: Small and declining number of mature individuals

Not applicable. Insufficient data to determine number of mature individuals, although continuing decline is most likely.

D: Very small or restricted population

Not applicable. D1 not applicable: insufficient data to determine number of mature individuals. Meets Threatened, D2. Both the IAO and number of locations meet thresholds (20 km² and 5 or fewer locations, respectively), and the species is prone to substantial decline from the effects of human activities or stochastic events within 1 to 2 generations.

E: Quantitative analysis

Not applicable. Analysis not conducted.

Reasons for Special Concern/Data Deficient/Extirpated/Extinct

Not Applicable.

COSEWIC history

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. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions

(2025)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species is likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)**

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)***

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

*

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. Definition of the (DD) category revised in 2006.

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

Wildlife species description and significance

Name and classification

Current classification

Class: Gastropoda

Order: Stylommatophora

Family: Polygyridae

Genus: Neohelix

Species: Neohelix dentifera

Common names

English: Big-tooth Whitelip (Turgeon et al. 1998)

French: “Hélicelle dentifère” was proposed by NGSWG (2022), but Helicella is a recognized genus. “Hélice dentifère” is preferred.

Indigenous (specify language): Not known

Synonyms and notes

First described as Helix dentifera by Binney (1837) and subsequently placed in various genera, Mesodon, Polygyra, and Triodopsis (Pilsbry 1940). The current name is Neohelix dentifera following Emberton (1988) and Turgeon et al. (1998).

Description of wildlife species

This large land snail (shell up to 2.8 cm in diameter) has a thin, depressed (flattened) olive-brown shell. The whorls have a “shouldered” appearance. There is no umbilicus (hole on the ventral side of shell where whorls coalesce). The last whorl of the shell is contracted behind the lip. The lip is flatly reflected and thickened at the inner edge. There is also an easily visible parietal tooth in the shell opening (aperture, see cover photo) into which the body retreats. The body colour is pearly-white (Figure 1).

Figure 1. Big-tooth Whitelip (Neohelix dentifera) specimen collected live at Ragged Chutes, Ontario, in September 1992 by W.J. Grimm (CMN 099317, see Table 1 for more details). Photo: A. Nicolai.

Designatable units

The species was reported from the Great Lakes Plains National Ecological Area. Evidence of local adaptations (for example, morphological differences) as well as genetic data in Canada are unavailable; therefore, a single designatable unit is recognized in Canada.

Recognized subspecies or varieties in Canada: none

Designatable units (DUs): one DU in Canada

Evidence for discreteness: not applicable

Evidence for evolutionary significance: not applicable

Special significance

The Big-tooth Whitelip has some taxonomic importance. Only two species in the genus Neohelix are found in Canada: the Big-tooth Whitelip (Neohelix dentifera) and the Whitelip (Neohelix albolabris). While the Big-tooth Whitelip is a patchily-distributed snail found in low-abundance, the Whitelip is widespread and common in southern Ontario and Quebec (A. Nicolai pers. obs.).

Big-tooth Whitelip and Tulsa Whitelip (Neohelix lioderma; Critically Imperilled and confined to Oklahoma, U.S.A.; NatureServe 2025b) are genetically close to each other (Wilkinson 2020) and form the dentifera group, based on reproductive anatomy (Emberton 1988). Indeed, they are in the same subgenus Asamiorbis (see Emberton 1995) which gives the group subgenus status and a name. Whitelip forms a paraphyletic group with the Southeastern Whitelip (Neohelix major) and the Grand Globe (Mesodon normalis; Wilkinson 2020).

Latchford (1885:230) called the Big-tooth Whitelip “one of the rarest American helices.” In Canada, the Big-tooth Whitelip is near the northern limit of its global range. Historically, 20 to 30% of its global range was in Canada (see historical distributions described by Latchford 1885; Pilsbry 1940; Hubricht 1985; Wilkinson 2020; and Examined Collections). Based on current observations, Canada is responsible for <10% of the global range, assuming no decline of the U.S. range. Fraser (2000) suggested that range-edge populations can have ecological, cultural, and economic significance because of their genetic diversity which can influence a species’ long-term survival and evolution, as well as provide opportunities for human education/recreation (for example, cryptic wildlife observations, in this case, snail watching).

Terrestrial gastropods have significance in ecosystem functioning. For instance, 2.5 to 6% of the total animal biomass of boreal forest ecosystems is composed of snails and slugs (assuming densities of 2 to 38 snails/m², Hawkins et al. 1997b; no analyses are available for deciduous forests). Snails and slugs play important roles in forest ecosystem functioning, as they:

1. aid in decomposition, nutrient cycling, and soil building processes (Mason 1970a,b; Jennings and Barkham 1979);
2. provide food and essential nutrients to wildlife (South 1980; Churchfield 1984; Frest and Johannes 1995; Martin 2000; Nyffeler and Symondson 2001); and
3. serve as hosts for parasitic worms (for example, Wilson 2012).

Gastropod declines can have an important impact on population dynamics of forest passerines (Graveland et al. 1994). Gastropod diversity can also indicate the degree of anthropogenic disturbance in an ecosystem (Douglas et al. 2013).

Big-tooth Whitelip is unknown to most Canadians, has no commercial value, and is not an agricultural or garden pest.

Aboriginal (Indigenous) knowledge

Aboriginal Traditional Knowledge (ATK) is relationship-based. It involves information on ecological relationships between humans and their environment, including characteristics of species, habitats, and locations. Laws and protocols for human relationships with the environment are passed on through teachings and stories, and Indigenous languages, and can be based on long-term observations. Place names provide information about harvesting areas, ecological processes, spiritual significance or the products of harvest. ATK can identify life history characteristics of a species or distinct differences between similar species.

Cultural significance to Indigenous peoples

There is no species-specific ATK in the report. However, the Big-tooth Whitelip is important to Indigenous Peoples, who recognize the interrelationships of all species within the ecosystem.

Distribution

Global range

The Big-tooth Whitelip occurs only in eastern North America (Figure 2), historically ranging from southern Ontario and Quebec to North Carolina, South Carolina, Georgia, and Alabama. In the U.S., the species’ range mainly covers the Appalachian Mountains, specifically towards the northwestern plateau between the ridge mountains and the Great Lakes, the Adirondacks in Vermont, and the northern highlands in Maine (Hubricht 1985).

Figure 2. Global range of the Big-tooth Whitelip (Neohelix dentifera). Counties with at least one record within a given time period are represented. Map is based on data from collections (see Examined Collections), Wilkinson (2020), and Hubricht (1985). Map created by Annegret Nicolai.

Canadian range

The Canadian range is currently confined to southeastern Ontario, but it extended historically to southern Quebec (Figure 3). Most records, except two (1992 and 1997) and those from 2024, are from 1861 to 1957. Thus, the historical range encompassed Île d’Orléans, Quebec, in the east, westward to Algonquin Provincial Park and east of Toronto, Ontario. The Big-tooth Whitelip was not found in searches of most of these historically occupied sites conducted between 2013 and 2024 (Table 1). Only a few individuals or shells were found, despite a large search effort in terms of the number of sites searched and person-hours dedicated. Most historical occurrences are considered Extirpated. In 2024, the Ontario Natural Heritage Information Centre (NHIC) conducted targeted searches in potentially suitable habitat (following training by the report writer A. Nicolai), adding five Extant occurrences where one shell or one live individual/site was found in 2024 (Table 1; records collected by A. Smith, research-grade iNaturalist records verified by report writer). One additional site is considered Uncertain because, while the record is from the 1990s and suitable habitat is still available, the species was not found in recent searches:

• Ragged Chutes, Township of North Frontenac (formerly Township of Palmerston), Frontenac County, record of a live individual collected in 1992 (preserved specimen CMNML 099317, Figure 1); site searched in 2023 but snail not found

Another record from the 1990s was initially considered Uncertain because the species was not found there in recent searches, but is now also considered historical:

• Leitrim Wetlands, Ottawa; record of one shell from 1997, but there is no voucher; not found during searches in 2022; wet forest is acidic and intact, not the typical habitat for the species; more snail-suitable, upland habitat was developed for human-use in the 2000s after the species was observed and this habitat has now been completely lost

Figure 3. Canadian range of the Big-tooth Whitelip (Neohelix dentifera) encompassing historical sites (black dots) where the species was not recently found despite searches in numerous sites in the vicinity of historical localities (see tables 1 and 2). Because the precise coordinates of historical records is unknown, the general area is indicated by a larger blue dot with black centre. One site (Ragged Chutes record from 1992) is currently considered as an Uncertain occurrence (yellow dot). There are currently five sites where the species is Extant (red dots, two overlapping). The polygons indicate extent of occurrence (EOO) based on historical records (blue polygon) and on current Extant records (red polygon), including the one Uncertain occurrence (yellow polygon). Map created by Annegret Nicolai.

Since 2013, a total of 222 localities in southern Ontario and Quebec were searched for terrestrial gastropods, with several sites being searched in some localities. The search effort was 788.5 person-hours (Figure 4, Table 2). These searches are in addition to previous search effort by M.J. Oldham between 1991 and 2012 (Appendix 1). The site searches focused on the entire gastropod community, including all current COSEWIC candidate species and species for which COSEWIC status reports are being prepared or have been completed. Between 2013 and 2024, targeted searches for the Big-tooth Whitelip at or near known historically occupied areas occurred at 73 localities, with several sites within each locality, with an effort of 223.5 person-hours.

There are many historical records from the northern cliff side of Île d’Orléans, Quebec, and the search effort in 2022 included eight person-hours in accessible cliff sites (Table 1). The rest of the island is composed of urbanized areas, private farmland, or small private woodlots; these areas were mostly deforested in the past, then were planted with Sugar Maple (Acer saccharum), and are now used for maple syrup production. Most of the island, including the northern cliff side, is private, not accessible, and not searched. Only a few accessible forested sites on the northern cliff side remain, but they were altered in the past and disturbed by human activity; the species was not found there.

The Ottawa Field-Naturalists’ Club did extensive surveys in the Ottawa region around 1900; finding a few Big-tooth Whitelip specimens was exceptional (Latchford 1885; Oughton 1948). The Ottawa region was searched in recent surveys (2013 to 2024; Table 2); the Big-tooth Whitelip was not found.

Figure 4. Map of southern Ontario and Quebec showing the search effort for terrestrial gastropods in 2013 to 2024. Map created by Annegret Nicolai.

Population structure

No studies have been conducted on spatial and genetic structure of the Canadian population which most likely consists of five separate Extant subpopulations (Crooked Lake, Mosque Lake, Kingscote, Tower Road south of Denbigh, Dickey Lake) and possibly one additional subpopulation (Ragged Chutes) that is Uncertain (Table 1, Figure 3). Because only one individual or one shell per site was found in 2024, no population studies could be conducted.

Extent of occurrence and area of occupancy

Current EOO

The current extent of occurrence (EOO) based on the five most recent Extant records is 2,176 km²(Figure 3). If the one Uncertain record from 1992 is included, the EOO is 2,815 km²(Figure 3).

Current IAO

The current index of area of occupancy (IAO) in Canada is 20 km², calculated using a 2 × 2 km grid over the five sites with recent known Extant records. If the one Uncertain record from 1992 is added, IAO is 24 km².

Fluctuations and trends in distribution

The historical Canadian EOO calculated using a minimum convex polygon encompassing all records from 1800 to 2024 is 122,101 km²(Figure 3). The decline in historical versus Extant EOO is 98%; if the one Uncertain record is included, the decline is still 98%. Assuming each historically occupied site fits in a single 2 × 2 km grid square, the historical IAO is estimated at 56 km²(14grid squares). The decline in historical versus extant IAO is 64%; the decline in IAO is 57% if the one Uncertain record is included. While there is an observed historical decline of the species’ range in Canada, the majority of the decline most likely did not occur within the most recent 3 generation status assessment timeframe (15 to 18 years, see Life cycle and reproduction).

The species’ historical range in Canada covered a large area with low human density and mainly forested habitat that could not be completely surveyed. Human activity in the past century has greatly altered and disturbed forest ecosystems at a large scale, especially in southern Ontario and Quebec, where the development of industry and agriculture along the Great Lakes shores and the St. Lawrence River resulted in an increased demand for timber from the nearby forests. It is possible that the species still occurs in remote old-growth forest remnants in mountainous areas, which should be identified and targeted for future surveys. A systematic survey program throughout southeastern Ontario and southern Quebec beyond historical records and including land outside provincial parks is required.

Biology and habitat use

Little is known about the biology of the Big-tooth Whitelip. General aspects of terrestrial snail biology are provided by the review of Barker (2001). However, information from other polygyrid snails could result in misleading conclusions because most polygyrids are common species that are not of conservation concern.

Life cycle and reproduction

The Big-tooth Whitelip is a simultaneous hermaphrodite (possessing both male and female reproductive organs) air-breathing (pulmonate) terrestrial snail (Pilsbry 1940). In general, both members of a mating pair exchange sperm and produce eggs. Self-fertilization can occur if mating probability is extremely low, as sometimes observed in the Whitelip; however, selfing results in very low reproductive success (McCracken and Brussard 2008). Clutch size in the Big-tooth Whitelip is unknown. As in most snail species, larger individuals lay more eggs than smaller ones (Heller 2001). Mating and egg laying usually occur twice a year, in spring and late summer in temperate regions, and egg clutches are deposited in shallow holes excavated in moist soil (Barker 2001). A clutch of 33 eggs of the Big-tooth Whitelip was observed, laid in a wet, rotten hemlock log in New York state (Ingram 1944). The egg’s shell is not calcified but consists only of a membrane (Ingram 1944).

Typically, gastropods are active in the morning or after rain, some are crepuscular or nocturnal, and sympatric species often have different activity patterns (Asami 1993). The hibernation period in temperate regions extends from early October to mid-April. Variations depend on local climate conditions and yearly climate variations. At the end of the 19th century on Île d’Orléans, hibernation of the Big-tooth Whitelip extended to the beginning of May (Hanham 1896). Hibernation sites of many species are shallow depressions in the forest floor covered with leaf litter or soil at depths of 5 to 10 cm (Pearce and Örstan 2006). The Big-tooth Whitelip sometimes hibernates at the soil surface with the upward pointing lip easily visible (Hanham 1896). Snails in temperate regions aestivate when exposed to prolonged heat and drought (Nicolai et al. 2011). Aestivation means that snails are inactive and seek shelter in moist microhabitats, such as in soil, under leaf litter, and under logs. During hibernation and aestivation, snails cover their shell opening with a slightly calcified epiphragm.

Snails are active from spring until fall, unless aestivating. Growth occurs in juveniles; once the lip is reflected, growth stops. In other species the same size as the Big-tooth Whitelip (for example, the Brown Garden Snail [Cornu aspersum], Roman Snail [Helix pomatia], Corsica Helix [Tyrrhenaria ceratina], and Grand Globe [Mesodon normalis]—note that only the latter is native to North America), the adult shell size (approximately 2 cm in width) is reached after 1 to 2 years, and sexual maturity, after 2 to 3 years (Nicolai 2010; Nicolai et al. 2010; Charrier et al. 2013; Foster and Stiven 1996, respectively). In the Grand Globe, the growth rate, survival during growth, and maximum adult shell diameter depend on food availability and density (Foster and Stiven 1996). Species of this size seem to be long-lived, approximately 5 years and longer in the Grand Globe (Foster and Stiven 1996). The estimated generation time for the Big-tooth Whitelip is somewhere between the age at sexual maturity and longevity, probably 5 to 6 years.

Habitat requirements

In the U.S., the Big-tooth Whitelip is associated with “acidic, anionic, deep, low-density soils in talus in high-altitude, exposed, non-oak-hickory forests” and usually lives between rocks (Emberton 1991:112) but is also found under logs in thick leaf litter (Hubricht 1985). Nekola (2010) lists the Big-tooth Whitelip among the species found only in neutral/calcareous sites, but the sample size appears too small to draw such a conclusion on habitat preference. In recent Canadian surveys, the species was found in mature mixed-wood forest on neutral-to-calcareous soils, mainly close to boulders on slopes and ravines, never in floodplains. The elevation of the records ranged between 300 and 450 m above sea level. Nothing is known about habitat requirements for particular life stages (Appendix 2). In most forest species, adults may explore more open adjacent habitat to forage.

Movements, migration, and dispersal

Distances moved by the Big-tooth Whitelip are unknown, but other Polygyridae of similar size move between 120 and 220 cm per day within a home range of 80 to 800 m²(measured with a spool with thread attached to snail’s shell) in the Whitelip and the Whitelip Globe (Mesodon thyroidus), respectively (Pearce 1990). These snails are homing and use the same hibernation sites in consecutive years.

Dispersal distances (that is, displacement of home range) are small in land snails, for example, 32.2 m over a 3-year study of the Oregon Forestsnail (Allogona townsendiana; Edworthy et al. 2012). Eggs and immature stages are not known to be dispersed by wind, but birds may transport snails. Some snails can survive the passage through bird intestines (Wada et al. 2012) and be dispersed by bird migration (Kawakami et al. 2008). Some snails can survive short periods in water, in hypoxia (Nicolai and Ansart 2017), and snails in riparian habitats were observed to disperse by rafting on floating objects (Vagvolgyi 1975) or by fish (Altaba 2015). The likelihood of aerial or aquatic transport of the Big-tooth Whitelip is probably small because the species lives on higher ground. However, the distribution of some snails along rivers and lakes suggests that aquatic transport drives long-term interpopulation dynamics.

Interspecific interactions

Diet

Details of diet and feeding behaviour are unknown. Similar to other litter-dwelling species such as the Broad-banded Forestsnail (Allogona profunda) and Banded Tigersnail (Anguispira kochi; COSEWIC 2014, 2017), the Big-tooth Whitelip may eat decaying plants or microfungi. In general, snails require calcium for shell formation.

Predators and competitors

Potential predators have been reviewed by Jordan and Black (2012:7):

Gastropods are an important food source to a vast number of species, including salamanders, frogs, toads, turtles, snakes, lizards, birds, shrews, voles, moles, rats, mice, chipmunks, and squirrels. Invertebrate predators of terrestrial mollusks include sciomyzid fly larvae, firefly larvae, parasitic wasp larvae, carabid and staphylinid beetles, ants, spiders, and harvestmen.

Glass Snails (Oxychilusspp.) are an introduced species and are commonly observed in southern Ontario (A. Nicolai pers. obs.). They include native snails in their diet (Örstan 2006) and can negatively affect native land snail communities (Curry et al. 2016). In general, introduced predators or an increase in abundance of native predators because of ecological disturbance can increase snail mortality by predation.

Host/parasite/disease interactions: parasites are known from other snail species

Trematodes (Barger and Hnida 2008; Barger 2011)

Free swimming or attached flagellates (Current 2007)

Parasitic mites: can cause high mortality, reproductive perturbations, and reduced cold hardiness in some snail species (Baur and Baur 2005)

Nematodes: increase mortality rate in juveniles (Morand et al. 2004) and in adults in a confined space (Örstan 2006), although are inefficient in controlling pest gastropods in an urban green space (that is, open space, Fredon Inc. unpubl. data).

Other interactions

Competition for food and shelter is a possible interaction with other terrestrial gastropods, including exotic species, but has not been documented. The Grovesnail (Cepaea nemoralis) and various species of slugs, mainly the Grey Fieldslug (Deroceras reticulatum) or the Dusky Arion (Arion subfuscus/fuscus), are introduced into many natural areas in Ontario (A. Nicolai pers. obs.). They may be in direct competition for food as these species may have similar diet preferences.

Physiological, behavioural, and other adaptations

Plasticity and adaptability of physiological responses to environmental factors have not been studied intensively in Polygyridae.

Habitat parameters, such as calcium availability, influence the snail species richness of an area (Nekola 2005) and physiological processes, such as heat resistance in eggs (Nicolai et al. 2013). Snails accumulate heavy metals and pesticides in tissues, which may disturb physiological processes (Barker 2001).

Snails generally aestivate in buffered refuges and avoid evaporation in regions with prolonged periods of drought and heat by sealing the shell opening with a dried mucus layer (Barker 2001; Pearce and Örstan 2006). During aestivation, biochemical stress reactions may protect cellular architecture and processes (such as membrane fluidity, osmoregulation, and enzyme activity) and hence maintain survival mechanisms. In temperate regions, many species aestivate only in dry/warm summer conditions for a short period. If hot/dry periods become longer and more frequent with climate change, mortality may be increased, for example, up to 70% in the Roman Snail right after arousal from hibernation (Nicolai et al. 2011).

Different, somewhat plastic, strategies have evolved in snails to enable survival at sub-zero temperatures (see review by Ansart and Vernon 2003). Strategies vary among species of the same family (Nicolai and Ansart 2017), but winter mortality is usually around 40% and drives population dynamics (Peake 1978; Cain 1983). Snails hibernate in buffered microsites insulated by snow (Nicolai et al. 2011). Burch and Pearce (1990) suggest that the availability of refuges that buffer environmental conditions, such as temperature and humidity, drives snail abundance.

Limiting factors

Limiting factors are generally not human-induced and include intrinsic characteristics that make the species less likely to respond to conservation efforts. Limiting factors may become threats if they result in population declines. The main limiting factor for the Big-tooth Whitelip is a low dispersal ability, which restricts gene flow among subpopulations. Low physiological resistance to fluctuating environmental factors such as temperature and humidity and a dependence on the availability of moist refuges that buffer environmental fluctuations is probably a limiting factor for the population growth and persistence of land snails in general at particular sites (Burch and Pearce 1990).

Population sizes and trends

Data sources, methodologies, and uncertainties

The comprehensive set of available data on the Big-tooth Whitelip consists of presence-absence data compiled from verified museum and collection records. All the historically occupied areas and their vicinities were searched in field surveys in 2013 to 2024. Only two live individuals and four shells were found during these surveys.

Abundance

No abundance data were collected during surveys in 2013 to 2024. In the five localities where the species is considered to be Extant only one to two shells or one live individual per site were found during the searches. Therefore there are no quantitative data to estimate the current overall Canadian population size. Similarly, there are no quantitative data on historical abundances (see Long-term trends).

Fluctuations and trends

Habitat loss and degradation have most likely led or contributed to the 98% decline in EOO and 57 to 64% decline in IAO within the last 30 to 100 years, which have most likely resulted in a population decline. No data are available to estimate a recent decline within the last 3 generations, or 15 to 18 years. Nothing is known about the number of mature individuals within subpopulations.

Continuing decline^{Footnote 1}in number of mature individuals

The decreases in EOO and IAO indicate historical declines in the number of mature individuals. Continuing threats are likely to result in a continuing decline in snail numbers.

Evidence for continuing decline (1 generations or 3 years, whichever is longer, usually up to 100 years)

It is unknown whether there will be a continuing decline in this timeframe. If the currently occupied sites are not altered in the future, the past historical decline may not continue. Ragged Chutes is a privately owned woodland where logging is not excluded. The Algonquin Provincial Park site (south of Kingscote Lake) and the other four sites in this area on Crown land (Table 1) can be logged within the next 10 years.

Evidence for continuing decline (2 generations or 5 years, whichever is longer, usually up to 100 years)

See above regarding a decline in 1 generation or 3 years)

Evidence for past decline (3 generations or 10 years, whichever is longer) that has either ceased or is continuing (specify)

Past large-scale historical decline from habitat changes which occurred well before the past 3 generations (or 15 to 18 years) has ceased. Decline within the past 3 generations is likely but not quantifiable.

Evidence for projected or suspected future decline (next 3 generations or 10 years, whichever is longer, up to a maximum of 100 years)

A future decline is suspected. It is uncertain whether the remaining habitat currently occupied by the species will be preserved in the future. Logging in the Algonquin area may destroy or alter the species’ habitat within the next 10 years. Climate change may impact the species. The threat assessment predicts an overall threat impact of High–Low, which equates to a projected population decline of 0 to 70% over the next 3 generations (or 15 to 18 years).

Extinction risk based on quantitative analysis

Analyses were not done.

Long-term trends

Unknown. The lack of estimates of historical abundance prevents long-term trends from being calculated.

Historical abundances in southern Ontario from intensive surveys done by the Ottawa Field-Naturalists’ Club are either not mentioned because finding the snail was exceptional (for example, Latchford 1885; Taylor and Latchford 1890) or only single shells were found (for example, La Rocque 1933). Notable abundances of the Big-tooth Whitelip were reported from the vicinity of Québec City at the end of the 19th century. Île d’Orléans was described by Hanham (1896:98) as “the only rich collecting ground in species,” that is, multiple species were observed in the district around Québec City. On an “old unused path on the cliff side” with northern exposure, 71 Big-tooth Whitelip individuals were observed on May 27, 1893 (Hanham 1896:100). Latchford (1892) reported seven individuals found in one hour in 1891 on the island. Following other surveys done during May 1893, the Big-tooth Whitelip was “rather common” in “the swampy forest off the Ste. Foy Road” and formed a “small colony on the cliff side” at Saint-Romuald (Hanham 1896:100, 99 to 100, respectively). While the Big-tooth Whitelip seemed to be historically abundant on the cliffs of the St. Lawrence River near Québec City, stretching from Saint-Romuald on the south side to Boischatel on the north side and particularly on Île d’Orléans, it appears to have been rare everywhere else despite numerous surveys at the end of the 19th century.

Population fluctuations, including extreme fluctuations

Unknown in this or other polygyrids.

Severe fragmentation

The species appears to be heterogeneously distributed over a large area. Occurrences are small patches with few individuals; the species has always been rare in historical surveys (see Long-term trends). This suggests that there is no severe fragmentation.

Rescue effect

The likelihood of dispersal from the U.S. is extremely small, given the limited distribution in the U.S. and the snails’ poor dispersal capabilities. A potential northern expansion of the peripheral Canadian population or even the U.S. population could be largely negated by historical and current habitat loss and degradation, important factors to consider for range peripheral species under climate warming (Gibson et al. 2009). The Big-tooth Whitelip is extremely scarce and unlikely to be transported by human activity, such as with horticultural or agricultural products (Robinson 1999; Robinson and Slapcinsky 2005). The large Great Lakes water bodies and the St. Lawrence River make immigration from U.S. states such as New York and Pennsylvania unlikely in the short term. One Vermont state county at the Quebec border has old species records (prior to 1990, Figure 2). If the species is still extant there and the habitat is connected to that in Canada, dispersal from the U.S. may be possible. However, there are no current extant occurrences in Quebec, and it is uncertain whether the ecological continuity required for dispersal is still available between the U.S. and Canada.

Threats

Historical, long-term, and continuing habitat trends

Even though the historical species’ range in Canada appears large, the actual number of occurrences was already small in the past, because the species lives at higher elevations, on rocky slopes and ravines, and in mixed-wood neutral-to-calcareous forests. The habitat has been altered (it was logged in the past and is now secondary forest), disturbed (by past or current human activity), or completely lost (urbanized or turned into agricultural land) in and near the recently searched historically occupied sites.

Current and projected future threats

The Big-tooth Whitelip is vulnerable to the cumulative effects of various threats. The nature, scope, and severity of these threats are described in Appendix 3, following the IUCN-CMP (International Union for the Conservation of Nature – Conservation Measures Partnership) unified threats classification system (see Salafsky et al. 2008 for definitions and Master et al. 2012 for guidelines). The threat assessment process consists of assessing impacts for each of 11 main categories of threats and their subcategories, based on the scope (proportion of the total population exposed to the threat over the next 10-year period), severity (predicted population decline within the scope during the next 10 years or 3 generations, whichever is longer up to approximately 100 years), and timing of each threat. The overall threat impact is calculated by taking into account the separate impacts of all threat categories and can be adjusted by the species experts participating in the threats evaluation.

The overall threat impact for the Big-tooth Whitelip at the five Extant and one Uncertain site is considered to be High–Low, corresponding to an anticipated further decline of between 0 and 70% over the next three generations by the threats acting in the next 10 years. These values are to be interpreted with caution, as they may be based on subjective information, such as expert opinion, although efforts have been made to corroborate the scores with available studies and quantitative data. Threats that scored with at least a low or unknown impact are discussed below, from highest to lowest impact, then unknown impact. See Appendix 3 for comments about the non-scoring threats and those that scored as having a negligible impact.

Climate change (IUCN 11; overall threat impact high–low)

Ontario is projected to have more extreme weather events, including droughts, floods, and temperature extremes, under climate change models (Varrin et al. 2007); therefore, the scope is pervasive because all Extant sites and the one Uncertain site are exposed to the effects of climate change. With increasing average temperatures, spring frost is more frequent (Augspurger 2013), which can cause spring mortality, as observed in snails when snow cover is absent (for example, up to 90%, Nicolai unpubl. data). Tornados and ice storms have occurred in the Big-tooth Whitelip’s range, but they are unpredictable. Droughts can cause high mortality in some gastropod species depending on the presence of shelter (for example, 75% in the Roman Snail, Nicolai et al. 2011). Flooding may be an issue at all sites but only if the species seeks moist habitat on lower ground. Following the framework for assessing species’ vulnerability to climate change by Foden et al. (2013), the Big-tooth Whitelip can be considered highly vulnerable because (i) it is exposed to climate change (spring frost, absence of snow cover, droughts); (ii) it is sensitive (specific microhabitat conditions); and (iii) it has a low adaptive capacity (low intrinsic and extrinsic dispersal possibilities because it lives in “islands” of natural habitat).

Biological resource use (IUCN 5; overall threat impact medium–low)

Logging and wood harvesting (IUCN 5.3)

Large-scale logging (clear cutting or shelterwood, that is, the gradual removal of trees by a series of cuttings over several years, allowing natural regeneration) can lead to habitat loss, while low-intensity selective logging has only a slight impact. All sites are subject to logging. Personal wood harvesting by the landowner currently occurs at Ragged Chutes; the intensity or strategy of logging could change with the current or future landowner. The Algonquin Provincial Park site is under the Algonquin Park Forest Management Plan (FMP), while all the other Crown land sites are within the Mazinaw Lanark FMP. Both FMPs are for the period 2021 to 2031, so any planned harvest indicated in the FMP could occur within that time. Kingscote in Algonquin Provincial Park is designated as a renewal and tending area and can be logged after 2031, which is within the 10-year timeframe. Crooked Lake is already partially logged and will be further logged (shelterwood), while Tower Road and Dickey Lake are proposed in the FMP for clear-cut/shelterwood harvesting and selective harvesting, respectively. The harvesting has not started yet. No harvesting is planned before 2031 at Mosque Lake, but it may be in a future FMP. The severity was scored as moderate–slight because the species can occur on slopes which are often not harvested.

Natural system modifications (IUCN 7; overall threat impact low)

Fire and fire suppression (IUCN 7.1; low impact)

Climate warming in the Northern Hemisphere has increased fire risks because of drought. In the last decade (2010 to 2019) the extent of forest fires has increased (2 to 5 million ha/year) compared with 1980 to 1989 (1 to 2 million ha/year), while their number has slightly decreased (CNFDB 2023). However, Ontario is still subject to a moderate fire risk. Burning directly and indirectly affects the survival of ground-nesting animals, litter-dwelling organisms, and soil invertebrates (Nekola 2002). Fire reduces and modifies organic substrates and residues, which are sources of nutrients and which buffer and shelter these organisms. Fire also changes the microclimate when post-burn bare soil is heated by the sun, thereby increasing soil evaporation (reviewed by Saestedt and Ramundo 1990; Knapp et al. 2009). Fire destroys the upper part of soil habitat, the litter and uppermost humus layer, which is the most important factor affecting survival for litter-soil organisms (Bellido 1987).

Other ecosystem modifications (IUCN 7.3; unknown impact)

There are several highly invasive plants in southern Ontario, including the Garlic Mustard (Alliaria petiolata). It was observed displacing native vegetation and altering soil nutrient cycles, thereby slowing restoration (Catling et al. 2015). The impact of invasive plants on the Big-tooth Whitelip is unknown.

Non-native earthworms have invaded parts of Canada relatively recently and have altered forest floor habitats by reducing or eliminating the natural leaf litter layer and digging up and mixing the mineral soil with the organic surface layer (CABI 2016). While direct evidence of the effects of exotic earthworms on terrestrial gastropods is lacking, Norden (2010) and Forsyth et al. (2016) suggest that invasive earthworms could indirectly alter terrestrial gastropod communities. Earthworms such as the Asian genus Amynthas, that removes the surface leaf litter (Qiu and Turner 2017) where gastropods live, would be a particular threat (see also Dobson 2017 and Lee 2017 for photographs of the effects of exotic earthworms on soil duff layers). Other indirect effects could result from earthworms’ feeding on forest plant seeds (Cassin and Kotanen 2016) or altering plant–fungi mutualism (Paudel et al. 2016), thereby affecting understorey vegetation composition (Drouin et al. 2016) and potentially reducing available food fungi. This change in forest floor structure profoundly affects plant- and litter-dwelling invertebrate communities (Addison 2009; Dobson and Blossey 2015) as well as bird abundance and nesting success (Loss et al. 2012). Invasive European earthworms are present in the Leitrim Wetlands (A. Nicolai pers. obs. 2022) and are generally observed in Carleton County, as well as potentially being present in other sites, given that they have been recorded in Frontenac County (Reynolds 2014). Recreational fishing activities introduce exotic earthworms. Algonquin Provincial Park has a great deal of recreational fishing activity, and the Crown land site can also be used for fishing. All these sites potentially have exotic earthworms.

In the Ragged Chutes site, the former land owner mentioned that there were many more snails and less moss 50 to 60 years ago. Mosses indicate soil acidification that can be due to acid atmospheric deposition or wood harvesting (McLaughlin and Wimmer 1999). Snails that rely on calcium for growth and reproduction may be negatively affected by such changes in the soil system.

Number of threat locations

The likely number of threat locations, based on the COSEWIC definition (that is, geographically or ecologically distinct areas in which a single threatening event can rapidly, for example, within a single generation or three years, whichever is longer, affect all individuals present, resulting in population decline) for the Big-tooth Whitelip is 1 to 5. The most serious and plausible threat is IUCN threat 11, Climate Change (High–Low impact), which could affect all Extant sites and one Uncertain site simultaneously (= 1 location), or each site differently (= 5 locations), with Mosque Lake and Crooked Lake being one location because they are within 2 km of each other (see overlapping dots in Figure 3). The second-highest impact threat (Medium–Low impact; Logging and Wood Harvesting, under IUCN threat 5, Biological Resource Use) would probably affect each occupied or potentially occupied site differently.

Protection, status, and recovery activities

Legal protection and status

The Big-tooth Whitelip is not protected by any legislation, regulations, customs, or conditions. It is not listed under the Species at Risk Act (2002), under any provincial legislation, or under the U.S. Endangered Species Act of 1973. It is also not listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES 2022).

Non-legal status and ranks

The Big-tooth Whitelip is not on the IUCN Red List (IUCN 2022). NatureServe (2025a) provides the following status ranks for the snail:

• Global rank: G4G5 – Apparently Secure to Secure (last reviewed May 24, 2024)
• National rank (U.S.): N5 – Secure
• National rank (Canada): N1 – Critically Imperilled

Subnational ranks (S-ranks) as provided by NatureServe (2025a) are as follows:

• SNR (not ranked): Connecticut, Maine, Maryland, Massachusetts, New Hampshire, New York, Ohio, Vermont
• S5 (Secure): West Virginia
• S4 (Apparently Secure): Pennsylvania
• S3S4 (Vulnerable to Apparently Secure): North Carolina, Virginia
• S2 (Imperilled): Kentucky
• S1 (Critically Imperilled): Ontario
• SNR: Quebec

There are no status ranks for Arkansas, Minnesota, Alabama, Illinois, Indiana, South Carolina, Georgia, or Tennessee.

Land tenure and ownership

Ragged Chutes is privately owned without public access. Kingscote is part of Algonquin Provincial Park and managed by Ontario Parks. The sites at Crooked Lake, Mosque Lake, Dickey Lake, and Tower Road south of Denbigh are within the Mazinaw Lanark Forest (Crown land).

Recovery activities

Not applicable

Information sources

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Collections examined

• GBIF.org (September 16, 2022) GBIF Occurrence Download
• GBIF.org (March 23, 2023) GBIF Occurrence Download
• Biodiversity occurrence data published by Invert-E-Base Portal (accessed through the Invert-E-Base Portal
• Biodiversity occurrence data published by Invert-E-Base Portal (accessed through the Invert-E-Base Portal
• Verifications of specimens in the following collections: Academy of Natural Science Philadelphia, Canadian Museum of Nature, Royal Ontario Museum, and Florida Museum of Natural History.

Authorities contacted

• Michael G. Oldham, Ministry of Natural Resources and Forestry (MNRF), Ontario
• Graham Cameron, MNRF, Ontario
• General data request, Natural Heritage Information Centre (NHIC), Ontario
• Alison Smith, NHIC, Ontario
• General data request, Données sur les espèces en situation précaire, Centre de données sur le patrimoine naturel du Québec, Gouvernement du Québec (Isabelle Gauthier, Coordonnatrice provinciale des espèces fauniques menacées et vulnérables, and Nathalie Desrosiers, Direction générale des écosystèmes et des espèces menacées ou vulnérables, Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs
• Frederick W. Schueler, request for data in private collection, Ontario
• John Mesman, Michelle Cavanagh, Erin Thorne, South Nation Conservation Authority, Ontario
• Sarah Lamond, David Legros, Algonquin Park, Ontario
• Kevin Kemmish, Patrick Moldowan, Algonquin Wildlife Research Station

Acknowledgements

Funding for the preparation of this report was provided by Environment and Climate Change Canada. The authorities listed above provided valuable data and advice. Special thanks to Valérie Briand who helped in field work and data collection, Alison Smith for field surveys that found new occurrences in and near Algonquin Park in 2024, and Robert Forsyth for advice and discussions on specimens and historical material.

Biographical summary of report writer(s)

Annegret Nicolai is an independent ecologist at the Living Lab CLEF, France. She holds a Ph.D. from the University of Bremen, in Germany, and from the University of Rennes 1, in France. Her research involves investigating eco-physiological questions in terrestrial snails, specifically about the impact of climate change and resource availability on the physiology and reproduction in endangered and invasive species. She has very specific knowledge about the biology, anatomy, physiology, and ecology of terrestrial gastropods. In Germany she developed a captive-breeding program for the protected Helix pomatia, and in France she was a coauthor of the national action plan for the conservation of Tyrrhenaria ceratina in Corsica. In the Sinclair Lab at Western University, in Ontario, she investigated the overwintering strategy of the invasive species Cepaea nemoralis. Since 2012, she has been surveying terrestrial gastropods in Ontario, participating in the “barcoding of life” project at the University of Guelph, and writing nine species status reports and five recovery strategies. She became a member of the Mollusc Species Specialist Subcommittee of COSEWIC in 2014.

Appendix 1. Location of general terrestrial gastropod surveys by M.J. Oldham in 1991 to 2012 with 2,349 georeferenced collection records that reflect a recent and historical search effort

Additional surveys were done by J.M. Bowles in 1994 (113 georeferenced collection records) and by A. Nicolai in 2012 (364 georeferenced collection records). Map created by M.J. Oldham

Appendix 2. Summary of essential functions, habitat, and detail of habitat for the Big-tooth Whitelip (Neohelix dentifera) in Canada by life stage

^a Life stage: stage of the life cycle of the species (for example, seed; egg, seedling, juvenile, larva, pupa, adult).

^b Habitat function: How a habitat supports a life-cycle process of the species (for example, habitat that supports spawning, breeding, denning, nursery, rearing, feeding/foraging, migration, flowering, fruiting, seed dispersing, germinating, seedling development).

^c Habitat: The structural or biological features of the area or type of site needed for a species to carry out its life processes.

^d Detail of habitat: detailed information such as measurable properties or characteristics of the habitat.

Appendix 3. Threats assessment for the Big-tooth Whitelip (Neohelix dentifera)

Species or Ecosystem Scientific name: Neohelix dentiferaBig-tooth Whitelip

Date: 11/7/2023

Assessor(s): Annegret Nicolai (writer); Dwayne Lepitzki (facilitator and responsible Co-chair); SSC members: Daelyn Woolnough (also recorded comments), Cam Goater, Andrew Hebda, Tim Rawlings; Colin Jones (COSEWIC member for ON); Michelle Cavanagh (South Nation Conservation in Eastern Ontario); Fred Schueler (Research Director/Curator for Fragile Inheritance); Elisabeth Shapiro (CWS at ECCC); Jennifer Wilson (COSEWIC Secretariat)

References: Draft threats calculator (4 June 2023) accompanied draft COSEWIC status report sent for review; telecon held 7 Nov 2023. Google Earth Pro screenshots shown during the threats assessment. Threat assessment updated by the report writer to include the five additional occurrences from 2024, reviewed by the Molluscs SSC during the 20 February 2025 teleconference.

Assigned overall threat impact:

BD = High - Low

Overall threat comments:

The two sites where live individuals were found in 2024 (Kingscote in Algonquin Park, Crooked Lake) are considered to have 20% of the population each. In 2024, only shells were found at three additional sites (Tower Road south of Denbigh, Dickey Lake, Mosque Lake), each considered to have 15% of the population. There is one uncertain occurrence, at Ragged Chutes (1 live, in 1992, approximately 15% of the Canadian population). The Leitrim Wetlands site (Ottawa suburb, 1 shell in 1997, no voucher, original collection information confirmed by F. Schueler as part of the original threats assessment) was initially included in the threats assessment but then removed. It is unlikely that the species still occurs there: the snail is not a wetland species and development has subsequently occurred in the upland part of the area where the species probably occurred. Gen time 5 to 6 years; therefore, timeframe for severity and timing is 15 to 18 years into the future. Additional field verification summer 2023 casts doubt on historical record from Hamilton (misidentification); two people searched Ragged Chutes for a full day in 2023 with no Big-tooth Whitelip found, but other snails were. Landowner suggested many snails there 50 to 60 years ago but now more mosses. Habitat seems intact at Ragged Chutes. No trends in snail abundance available.

Classification of Threats adopted from IUCN-CMP, Salafsky et al. (2008).