7.1 Definition

Animal movement corridors are elongated, naturally vegetated parts of the landscape used by animals to move from one habitat to another. They exist at different scales and frequently link or border natural areas. Animal movement corridors encompass a wide variety of landscape features including riparian zones and shorelines, wetland buffers, stream and river valleys, woodlands, and anthropogenic features such as hydro and pipeline corridors, abandoned road and rail allowances, and fencerows and windbreaks. The Natural Heritage Component of the Provincial Policy Statement states that "natural connections between natural features should be maintained and improved where possible".

7.2 Ecological function/effects of loss

Animal movement corridors allow animals to travel freely and safely across the landscape by providing cover, shelter from harsh weather conditions, and by minimising encounters with predators and people. They are especially important to animals that require a variety of habitats to survive.

Animals move for several reasons. Often a particular area does not satisfy all seasonal habitat requirements of a species. For example, some forest salamanders spend the summer and winter in forest soils but, in spring, breed and lay their eggs in ponds, marshes, or temporary pools that may or may not be located in forest. Larvae mature in the aquatic environment, emerge as adults, and then move back to the forest. Large mammals often must travel over large areas for all of their needs.

Other animals move in response to seasonal changes in climate (white-tailed deer, moose, caribou, and migratory birds). Often these animals follow traditional migration routes or corridors. For example, the north shores of Lake Ontario and Lake Erie form an important migratory corridor for land birds flying south during fall migration.

Subadult animals of many species disperse from their place of birth to establish territories of their own. In order for populations to persist, enough individuals must be able to move among suitable habitats to balance local extirpations and ensure genetic diversity.

Corridors often provide permanent dwelling habitat for some plants and animals. For example, a creek connecting two wetlands may support amphibians and reptiles that are also found in the wetlands; or some corridors connecting patches of forest can provide the entire required habitat for smaller forest mammals such as chipmunks and mice.

Adding corridors to a natural heritage conservation system may increase dispersal abilities of many wildlife species and help maximise biological diversity within a given planning area. They are one way to help offset the negative impacts on wildlife of highly fragmented landscapes, and in some situations, may increase habitat and populations of some species. They may also function as buffer zones, by protecting natural areas and their ecological processes from adjacent land-use activities.

Loss of wildlife movement corridors makes species more vulnerable to predation and disturbance. Local populations of some species (e.g. white-footed mice) may even be extirpated when re-colonisation is impossible due to an absence of corridors.

7.3 Identification of animal movement corridors

In many municipalities in southern Ontario, corridors consist of naturally vegetated areas, often forested land, that run through more developed and open landscapes. They connect the remaining natural areas within and beyond the municipality. Other potentially significant corridors include forested river valleys, shrubby riparian vegetation along smaller watercourses such as creeks, and undeveloped lake shorelines. Sparsely vegetated areas can also function as corridors provided they link relatively natural areas. Many wildlife species move freely through agricultural land to reach natural areas.

It is seldom possible to observe wildlife species using corridors. Some species pass through corridors quickly whereas others may reside there for some time. Often animal movement corridors can be determined accurately using maps, aerial photographs, and a sound knowledge of species’ habitat requirements. The following guidelines are presented to help identify potentially significant animal movement corridors.

  • Identify animal movement corridors only after other natural heritage features, including significant wildlife habitats have been located and mapped.
  • Contact OMNR for their suggestions on the locations of corridors and restorable corridors. Knowledgeable local residents may be aware of locations of some corridors, especially for large, visible species.
  • Use knowledge of habitat requirements and behaviour of key species to help identify potential corridors for them.
  • Use the most recent aerial photographs and maps (topographical, FRI, wetland, ANSI, land use) to help to identify potentially significant corridors. Use them to locate:
    • the largest natural areas within the municipality and adjacent municipalities that should be linked by existing or restorable inter-regional movement corridors. These inter-regional corridors will be visible on aerial photographs and topographical maps as mostly naturally-vegetated links.
    • the largest and oldest forest stands in and adjacent to the planning area. These areas are likely to support high species diversity. Use the FRI maps to determine the age and composition of the forest stands in the region. Examination of aerial photographs will help to verify the accuracy of FRI maps.
    • the largest and most diverse wetlands. Examination of aerial photographs and topographical maps of wetlands will reveal their configurations and spatial relationship to other natural heritage areas, as well as help to indicate important linkages among them.
    • relatively steep and undeveloped river valleys and riparian zones along lakes, rivers and streams. Although it is easy to identify these areas by using aerial photographs and topographical maps, an evaluation of at least some of them is recommended. In some of the most densely populated municipalities of southern Ontario, these riparian areas may be the most important remaining animal movement corridors.
    • the most probable linkages to and from known significant wildlife habitat such as winter deer yards and amphibian breeding ponds.
    • unopened road and rail allowances, and utility corridors that are potential animal movement corridors.
    • hedgerows, windbreaks, and old fields that could function as animal movement corridors. Examination of aerial photographs can help to identify these smaller linkages. In densely populated and heavily developed parts of some municipalities, these small corridors may be the only remaining natural areas that allow animal movement from one area to another.

Identifying the most important corridors that provide connectivity across the landscape is challenging because of a lack of specific information concerning animal movements. There is also some uncertainty about the optimum width and mortality risks of corridors. Furthermore, a corridor may be beneficial for some species but detrimental to others. For example, narrow linear corridors may concentrate breeding species. Raccoons, cats, and other predators can quickly decimate these populations. Also, narrow corridors dominated by edge habitat may encourage invasion by weedy generalist plants and opportunistic species of birds and mammals. Despite the difficulty of identifying exact movement corridors for all species, these landscape features are important to the long-term viability of certain wildlife populations.

7.3.1 Recommendations

The following recommendations are based on widely accepted principles of corridor identification and design.

  • All potentially significant corridors should allow safe movement of animals and provide safe dwelling habitat for resident wildlife populations. Corridors should protect moving animals from predators and road mortality.
  • Emphasis should be on retaining connections among the most significant and similar natural areas at the larger scale (inter-regional) and within the municipality as well as habitats of species most in need of conservation.
  • Maintain corridors that provide several benefits. For example, riparian corridors permit animal movement and help to ensure stable soils, necessary inputs of organic matter, and good water quality. Often these corridors are diverse natural areas because of fertile soils, a variety of habitat structure, a dependable source of water, abundant insect and plant foods, and several different microclimates.
  • Corridors should be as continuous and unfragmented as possible. However, some gaps in a potential corridor should not preclude it from consideration.
  • There should be no barriers to animal movement within designated corridors.
  • Wherever possible, select corridors in regions of the landscape with the lowest road density. Roads can be a serious cause of mortality for species such as nesting and migrating turtles, basking snakes, and frogs, as well as mammals and birds that feed near roadsides.
  • Generally, corridor habitat should be as similar as possible to the habitat in which the target species lives.
  • Incorporate known animal migration routes into corridors.
  • Shorter corridors are preferred since the longer the corridor, the greater the likelihood of increased mortality, barriers to movement, and unsuccessful dispersal attempts. Longer corridors may also need to be wider.
  • Generally, the widest possible corridors are best for linking patches of a species’ habitat that are farther apart than normal juvenile dispersal distances. Wider corridors minimise edge effects. However, for some small animals at least, corridor width may not be as important as corridor presence. Even small fencerow corridors may be beneficial to the movement of small mammals such as chipmunks.
  • Corridors surrounded by inhospitable habitat need to be as wide as possible.
  • Corridors should have a good diversity of vegetation structure and composition.
  • Consider restoring corridors that link important natural areas or wildlife habitats when and where restoration activities such as reforestation, stream rehabilitation, and regulation of land uses are feasible.
  • Natural areas that have been historically isolated should not be connected as they are unique and have evolved to their existing condition.