There has been an increase in the cougar population in the state in recent years, and a corresponding increase in sightings by people. Fortunately, however, there have been no confirmed attacks on humans during this period. Nonetheless, officials in one state park are concerned about the safety of their visitors. A national forest is about a mile and a half from the park, and many visitors hike from the park on trails or old logging roads that continue into the national forest. If there are potentially cougars in the park or forest, or in between, the officials want to make sure visitors to the park are aware of the danger. On the other hand, they don't want to alarm potential visitors; a drop in visitation would mean reduced funding for the park in next year's state budget.
The officials decide to undertake a study of cougar populations in and around the park. The first phase of the study will be to map potential cougar habitat. In the interest of interagency cooperation, and cost sharing, the officials approach the administrators at the nearby national forest about collaborating on the study. The national forest officials are interested—the Forest Service has several cougar habitat mapping projects in progress in other parts of the state, in conjunction with the state's Department of Fish and Wildlife (DFW). They see an opportunity to get additional funding from the state and suggest bringing the Department of Fish and Wildlife into the project. The state park officials agree.
Once the division of labor and funding details are worked out, a technical committee is set up, with wildlife experts from all three agencies.
Defining the project boundary
The committee's first task is to define the project study area. The Department of Fish and Wildlife has been mapping wildlife habitat watershed-by-watershed throughout the state. They suggest the major watershed that includes the park and the western portions of the forest as the study area. For their part, the state park staff are mainly concerned with the area in and around the park where visitors might encounter a cougar. Their surveys have found that many people hike, at most, about three miles from the park (a six-mile round trip), an area that encompasses the trails leading into the national forest. Using ArcGIS they create a three-mile buffer around the park and present the map to the committee as their proposed study area boundary. The Forest Service staff, naturally, want the study area to include the entire national forest, along with the area included in the state park buffer.
DFW, which is providing most of the data for the study, points out that the level of detail in the data does not support working at the scale of the area covered by the buffer, which comprises a small area. The results of the analysis will define generalized habitat for a relatively larger area, such as several subwatersheds, and not specific, localized habitat.
As a compromise between the three proposed study areas, and given the available funding, the committee members decide to limit the study area to three subwatersheds in the southeast portion of the major watershed. This area encompasses the state park and a portion of the national forest.
DFW and the national forest staff will use this study as a pilot project for this part of the state in their ongoing cougar habitat mapping efforts.
What is suitable cougar habitat?
Having agreed on the study area boundary, the committee members next turn to the analysis itself.
The method that DFW has been using for its other habitat studies is suitability analysis, and, for consistency, the committee members decide to stick with this approach for the current study. In suitability analysis, criteria are specified for what makes an area suitable for a particular use such as a housing subdivision, a wind farm, or cougar habitat. The criteria are often based on firsthand experience, expert knowledge (including published studies), or industry standards. Map layers representing the various criteria are overlaid to create a new layer containing areas that meet the criteria.
DFW has been basing its analysis on studies that link known cougar populations with various factors such as terrain, vegetation, proximity to water, and presence of prey. As a starting point for discussion, they present the criteria they have been using:
- Steep slopes
- Near streams
- Away from highways and major roads
- Presence of prey (primarily deer or elk)
The wildlife experts on the committee will define the specific criteria for the study area, for example, the distance that constitutes being near a stream. While the experts from DFW have general knowledge of cougar habitat across the state, the park and forest staff have knowledge of the local terrain and forest types. The local experts also know that prey are plentiful throughout the study area and therefore not a limiting factor. Hence the committee members decide that presence of prey does not need to be included as a criterion in this case.
To facilitate the discussions, the experts will view maps of the layers representing each of the criteria. An analyst with the national forest is tasked with assembling the data and doing the GIS analysis (once the criteria are defined). DFW provides the subwatershed boundaries, along with layers of streams, vegetation, and steep slopes clipped to the subwatersheds. The analyst downloads highways from the statewide GIS data clearinghouse. She then creates the study area outline from the subwatershed layer and uses it to clip the highways to create a layer of the highway within the study area.
Once the analyst has all the layers for the study area, she publishes them to a set of web maps for the experts to view before and during their discussions.
The first criterion for discussion is terrain. The earlier DFW study defined steep slopes as those greater than 18 degrees. All the participants are willing to accept this definition as suitable cougar habitat. However, they decide to include a caveat in the documentation for the study stating that cougars may also be found on gentler slopes, and even flatlands, but that steep slopes are preferred habitat. The committee members are off to a good start.
Next up is vegetation. The committee members can see that there are a number of vegetation and land-cover types in the study area and they must decide which ones constitute preferred cougar habitat.
Three land-cover types within the study area are quickly eliminated as habitat: urban, agriculture, and open water. And there is general agreement among the experts that cougars are likely to be found in forested areas that provide cover for hunting. Three forest types within the study area clearly constitute suitable habitat, they decide: True Fir-Hemlock Montane Forest (code 34), Douglas Fir-Western Hemlock-Red Cedar Forest (code 49), and Mixed Conifer/Mixed Deciduous Forest (code 67). However, there is some debate over a fourth vegetation type: code 121. While described in the dataset as Grass-shrub-sapling or Regenerating young forest, the experts from the state park and national forest know that, at least within the study area, these are primarily areas that were recently harvested for timber and provide little cover. The experts from DFW contend that, while not providing the same amount of cover as nearby forest, these areas are likely to be frequently crossed by cougars moving between forest patches and, as such, should be included as cougar habitat. The experts from the national forest tend to agree, but the experts from the state park dissent. The committee members decide to move on to the next criterion—streams—and come back to vegetation later.
The DFW experts present research showing that cougars have a wide home area and can fairly easily find water, although the presence of streams might provide better habitat. The research has found that the area within 2,500 feet of a stream can be considered preferred habitat. The experts from the state park counter with a study by a local college showing that cougars often use streams and riparian areas as corridors to move around their territory. They believe preferred habitat should be limited to areas within 500 feet of a stream.
Meanwhile, the discussion continues on the remaining criteria. The experts from DFW and the national forest cite research showing that in areas where there are many roads there may be fewer prey (deer and elk), which can make the area less desirable habitat for cougars. But there is only one major road in the study area. They believe that cougars might stay at most 500 feet away from the highway, but even then they would likely approach or cross the highway in search of prey. The experts from the state park believe that the presence of cars and people on the roads within the park would tend to make the immediate area less desirable for cougars. They suggest excluding as habitat the area within 1,500 feet of the highway, which would cover the roads inside the park.
In the course of the discussion, it's become apparent that DFW's definition of cougar habitat is fairly broad compared to the definition favored by the state park officials. Both DFW and the national forest staff need to identify large habitat areas for various management goals—conservation, management of wildlife, recreation, and so on. The state park officials are mainly interested in identifying cougar habitat in the vicinity of the park, to ensure the safety of their visitors. Hence they tend to favor a narrower definition of habitat, identifying areas where people and cougars are most likely to meet face-to-face.
Recognizing these divergent interests, the decision is made to create two models of cougar habitat: one based on a narrower definition, using the criteria preferred by the experts from the state park, and another based on a broader definition, using the criteria preferred by the experts at DFW and the national forest. Since the analysis is being done using GIS, it's relatively easy to model the habitat using several different sets of criteria.
The GIS analyst lists the general criteria and specific values for both approaches and has the committee review it before she undertakes the analysis.
Two views of cougar habitat
With the data ready to go and the criteria defined, the analyst combines the layers, specifying the parameters for the criteria as part of the process. First the analyst runs the analysis using the criteria preferred by the experts at the state park. The resulting layer shows all the areas that meet the criteria.
The analyst then runs the analysis again using the criteria favored by the experts from DFW and the national forest.
It's clear that using the narrower criteria favored by the state park experts results in a layer with much less potential habitat than the layer created using the DFW criteria.
The analyst publishes the results of the analysis as web maps so the committee members, along with administrators at the three agencies, can review the results.
The next phase
The state park officials can see that their criteria resulted in a very limited cougar habitat area. The staff from DFW and the national forest, however, are confident that the results created using their criteria are a good first attempt at identifying potential cougar habitat.
After reviewing the preliminary results of the study, administrators at the agencies agree to fund the next phase. To start, the results will be made available to a wider range of wildlife experts for review, including university researchers and conservation groups. To facilitate this, the GIS analyst creates a story map showing the results of the two models along with the criteria that were used for each.
In addition, scientists from DFW and the national forest will work together to field check the results, looking for evidence of cougars inside, as well as outside, the potential habitat areas. The analysis process highlighted several specific issues to focus on, such as the extent to which cougars frequent stream corridors and timber harvest areas. For her part, the GIS analyst will continue to monitor current GIS-based studies on cougar habitat and movement, such as Cougar Corridors of Southern California. The information the researchers gather will be used to refine their analysis.
Workflow using ArcGIS Online
View the story map for the workflow in ArcGIS Online.
Workflow using ArcGIS Desktop
View the story map for the workflow in ArcGIS Desktop.