Lake Erie watersnake COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

Lake Erie Watersnakes require specific habitat during the active season to forage, bask, court, mate, and give birth to young; they also require suitable habitat for hibernation. Essential summer habitat is composed of rocky shorelines or those made of limestone or dolomite shelves and ledges with cracks and some sparse vegetation (King 1987; King 1989; USFWS 2003). Summer habitat in Canada also includes sandy areas with associated debris or vegetation as well as cobblestone beaches and berms (D. Jacobs pers. comm. June 2005). Lake Erie Watersnakes also use areas with gravel, bare sand and/or exposed bedrock (King 1986, 1989; NatureServe 2005). Plants, loose rocks, and limestone shelves provide cover, and utilization of these structures depends on vegetation density, proximity to the shoreline and availability of basking areas (USFWS 2003). Logs and anthropogenic debris (e.g. metal sheets, cardboard, etc.) can also provide cover for Lake Erie Watersnakes (M.J. Oldham pers. comm. October 2005).

In all habitats, King (1986, 2003) reported 75% of observations of Lake Erie Watersnakes to be within 13 m of the water's edge on Ohio islands. Similar shoreline habitat occurs on Pelee, East Sister, and Middle Islands in Ontario, although Pelee Island does have sandy beaches that do not occur on the other Islands and are not as attractive to the watersnakes as rocky shorelines (D. Jacobs pers.comm. September 2005). However, actual distance from the water’s edge was dependent on availability of cover such as vegetation or fallen debris, rather than a fixed distance (D. Jacobs pers. comm. November 2004). Nevertheless, this species is rarely found more than 100 m inland (King 2003). Availability of prey, presence of predators, and suitable basking and escape areas influence whether Lake Erie Watersnakes will use interior portions of islands (USFWS 2003; King 2004a). Ponds and wetlands found in the interior of islands are used by a small number of individuals during the summer active season. Similarly, flooded quarries and drainage ditches in the interior of the islands are used by Lake Erie Watersnakes during the summer active season (M.J. Oldham pers. comm. October 2005).

Lake Erie Watersnakes also use inland locations as hibernation sites (King 2003; D. Jacobs pers. comm. November 2004). Lake Erie Watersnakes may hibernate in natural areas or human-made structures. These sites usually contain soil and rock substrates and possess openings or fissures, which can include cracks in bedrock, rock piles, tree root masses, animal burrows (King 2003), abandoned and active quarries (Campbell et al. 1991; King 2004a; D. Jacobs pers. comm. November 2004), rock-filled timber, or steel crib docks and riprap (broken stones used for a foundation) (USFWS 2003). In Canada, radiotelemetry studies indicate that there is a significant amount of communal hibernation, whereas this has not been observed to any great extent on the U.S. islands (D. Jacobs pers. comm. September 2005).

Habitat trends

Inland habitat is infrequently used during the summer active season, but is important for hibernation sites (King 1998, 2003; D. Jacobs pers. comm. November 2004), suggesting that Lake Erie Watersnakes use a full range of island habitat and that all areas are potential snake habitat (King 1998, 2003). Increasing shoreline development, such as construction of homes, roads, docks, marinas, and structures for erosion protection on these islands threaten the Lake Erie Watersnake’s survival (USFWS 2003). Although snakes can use some human-made structures, other construction such as sheet steel docks and poured concrete for erosion control are not utilized by snakes and decrease suitable habitat (USFWS 2003). Watersnakes may adapt to some human development, but King (1998) found a higher proportion of snakes in more extensively vegetated areas. These sites had relatively less gravel, sand, and bare soil and more debris, suggesting that locations with greater onshore cover are preferred and that areas with a lower degree of human disturbance are more attractive (King 1998).

Habitat protection/ownership

In 1991, the Lake Erie Watersnake was added to Ontario's Endangered Species Act, which protects the snake’s habitat from willful destruction or interference. Under the Conservation Land Tax Incentive Program, the Ontario Ministry of Natural Resources (OMNR) offers tax rebates to landowners who possess at least 0.2 ha of endangered species habitat (such as Lake Erie Watersnake shoreline habitat) (OMNR 2004; D. Jacobs pers. comm. September 2005). In 1999, the Nature Conservancy of Canada successfully bid for the purchase of Middle Island (15 ha) and then turned it over to Parks Canada in 2001, with the island becoming part of Point Pelee National Park (it is now managed as a Zone 1 Special Preservation Area – the highest level of protection in the National Parks system) (D. Jacobs pers. comm. September 2005, V. McKay pers. comm. October 2005). East Sister Island is protected as a Provincial Nature Reserve (D. Jacobs pers. comm. September 2005).

Pelee Island contains three nature reserves: Fish Point and Lighthouse Point (combined 114 ha), established and managed by the Ontario Ministry of Natural Resources, and Stone Road Alvar, owned by the Nature Conservancy of Canada, Ontario Nature, and Essex Region Conservation Authority. A small portion of Mill Point (1.5-2 km of shoreline habitat) is also under the protection of the Essex Region Conservation Authority and Ontario Nature (B. Porchuk pers. comm. November 2004; D. Jacobs pers. comm. September 2005).

Although additional islands and island habitat deemed critical for Lake Erie Watersnakes are privately owned and zoned for environmental protection, experience has shown that designating legal habitat protection often reduces cooperation by landowners, who deny researchers access to properties (USFWS 1999; King 2004a). In 2003, OMNR researchers attempted to confirm the presence/absence of the Lake Erie Watersnake on three privately owned Canadian islands (Hen, Middle Sister, and North Harbour) but were refused access by the landowners (in one case, the refusal was specifically due to concerns over potential restriction of activities) (D. Jacobs pers. comm. September 2005).

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