Definitions of terms used in the Conservation Strategy for the Butler's gartersnake

The following habitat definitions are important to understand the habitat requirements of the Butler's gartersnake and to appropriately implement the Conservation Strategy.

Suitable Habitat Patch:

This is defined as undeveloped areas that include both wetland and adjacent upland habitat. The patch is not based on a project's site but the area of contiguous suitable snake habitat. To be considered as potential Butler's Gartersnake habitat:

• The wetland habitat may be any classification except permanent open water. Lakes, streams, and deep ponds are not considered suitable, nor are permanent stormwater management ponds. A 100' edge of forested wetland where it abuts or is adjacent to suitable upland habitat is also considered suitable, as crayfish burrows are likely to be present in this habitat.
• The upland habitat must be within 300 feet of over-wintering wetlands AND have intact ground vegetation (grasses, forbs) AND have less than 75% canopy closure. The upland habitat must be directly connected to the wetland in at least one location. Closed canopy forests where ground vegetation is very sparse are not considered suitable, but old fields with significant invasion of woody shrubs and trees is suitable if grasses and forbs are still largely intact. Lawns and fields in active agriculture row crops or in crop rotation are not considered suitable. Fields that remain fallow for more than one year may be considered suitable habitat. Pastures will be included as suitable habitat if more than 50 percent of the acreage had an eight-inch or greater canopy height.

Suitable Habitat Size:

The habitat patch size assumes that as size increases the potential for snakes to persist increases because larger sites tend to be better buffered against localized effects and have the potential to support larger Butler's populations. Larger sites tend to also support a greater diversity of microhabitats that afford better buffering against wholesale invasions of exotic plant species. Exotic plants, like reed canary grass, often grow in dense stands that prevent crayfish from burrowing. Crayfish burrows provide essential overwintering habitats for Butler's gartersnake. Increased patch size often provides more snake-friendly edge habitat between uplands and wetlands. Edges appear to be especially important for Butler's gartersnakes.

Suitable Habitat Quality:

Poor: Habitat is considered to be poor quality if more than 75% of the wetland habitat component is dominated by dense cattail (Typha sp.) beds or dense stands of exotic species (i.e. reed canary grass, Phalaris arundinacea; purple loosestrife, Lythrum salicaria; giant reed grass, Phragmites sp.); and/or more than 75% of the ground cover (grasses and forbs) in the upland habitat component is relatively sparse and likely to become sparser through ongoing natural succession.

Moderate: Habitat is considered to be moderate quality if 50-75% of the wetland habitat component is dominated by dense cattail (Typha sp.) beds or dense stands of exotic species (i.e. reed canary grass, Phalaris arundinacea; purple loosestrife, Lythrum salicaria; giant reed grass, Phragmites sp.); and/or 50-75% of the ground cover (grasses and forbs) in the upland habitat component is relatively sparse and likely to become sparser through ongoing natural succession.

Good: Habitat is considered to be good quality if less than 50% of the wetland habitat component is dominated by dense cattail (Typha sp.) beds or dense stands of exotic species (i.e. reed canary grass, Phalaris arundinacea; purple loosestrife, Lythrum salicaria; giant reed grass, Phragmites sp.); and/or less than 50% of the ground cover (grasses and forbs) in the upland habitat component is relatively sparse and likely to become sparser through ongoing natural succession.

Isolated:

A site that does not exchange genetic material with other sites, due to being physically separated from other suitable habitat patches. Barriers may include impassable physical structures (paved roads, parking lots, walls), or resistant terrain (mowed lawns, golf courses, forests, agriculture). Resistant terrain is land use that a snake could still physically pass through, but would do so only occasionally, with risk of predation, desiccation, and lack of shelter from the elements. Where resistant terrain connects suitable habitat patches, resistant terrain of over 1000 feet should be considered an impassable barrier.

Temporary Habitat Disturbance:

Defined as a disturbance of Butler's gartersnake habitat that will be restored to its pre-activity condition or a condition that improves habitat for the Butler's gartersnake following completion of the activity.