C. Cormack Gates

Differentiation of tundra/taiga and boreal coniferous forest wolves: genetics, coat colour and association with migratory caribou

The grey wolf has one of the largest historic distributions of any terrestrial mammal and can disperse over great distances across imposing topographic barriers. As a result, geographical distance and physical obstacles to dispersal may not be consequential factors in the evolutionary divergence of wolf populations. However, recent studies suggest ecological features can constrain gene flow. We tested whether wolf–prey associations in uninterrupted tundra and forested regions of Canada explained differences in migratory behaviour, genetics, and coat colour of wolves. Satellite‐telemetry data demonstrated that tundra wolves (n = 19) migrate annually with caribou (n = 19) from denning areas in the tundra to wintering areas south of the treeline. In contrast, nearby boreal coniferous forest wolves are territorial and associated year round with resident prey. Spatially explicit analysis of 14 autosomal microsatellite loci (n = 404 individuals) found two genetic clusters corresponding to tundra vs. boreal coniferous forest wolves. A sex bias in gene flow was inferred based on higher levels of mtDNA divergence (FST = 0.282, 0.028 and 0.033; P < 0.0001 for mitochondrial, nuclear autosomal and Y‐chromosome markers, respectively). Phenotypic differentiation was substantial as 93% of wolves from tundra populations exhibited light colouration whereas only 38% of boreal coniferous forest wolves did (χ2 = 64.52, P < 0.0001). The sharp boundary representing this discontinuity was the southern limit of the caribou migration. These findings show that substantial genetic and phenotypic differentiation in highly mobile mammals can be caused by prey–habitat specialization rather than distance or topographic barriers. The presence of a distinct wolf ecotype in the tundra of North America highlights the need to preserve migratory populations.

Seasonality and reoccurrence of depredation and wolf control in western North America

Abstract Due primarily to wolf (Canis lupus) predation on livestock (depredation), some livestock producers and other interest groups oppose wolf conservation, which is an important objective for large sectors of the public. Predicting depredation occurrence is difficult, yet necessary to prevent it. Better prediction of wolf depredation also would facilitate application of sound depredation management actions. In this paper we analyze temporal trends in wolf depredation occurrence and wolf control, which is employed as a depredation management action. We gathered data from wolf depredation investigations for Alberta, Canada, from 1982–1996 and for Idaho, Montana, and Wyoming, USA, from 1987–2003. We showed that wolf attacks occurred with a seasonal pattern, reflecting the seasonality of livestock calving, grazing practices, and seasonal variation in energetic requirements of wolf packs. Seasonal wolf attacks were auto-correlated with lags of one year, indicating annual reoccurrence. Cross-correlation analyses indicated that limited wolf control was rapidly employed as a short-term response to depredation, and was not designed to decrease wolf depredation at a regional scale or in the long-term. We therefore discovered a reoccurring seasonal-annual pattern for wolf depredation and wolf control in western North America. Ranchers and managers could use our data for focusing investment of resources to prevent wolf depredation increases during high-depredation seasons.

Restoration of foothills rough fescue grassland following pipeline disturbance in southwestern Alberta.

The effects of pipeline construction and reclamation techniques on the restoration of rough fescue plant communities following pipeline construction in southwestern Alberta, Canada were evaluated after 7-40 years. The pipeline construction right-of-way (ROW) sites varied from no recovery of rough fescue grassland to moderate recovery. The ROW sites had a higher proportion of introduced grasses and forbs, less topsoil, and poorer rangeland health than the adjacent undisturbed grassland. Within the ROW sites, less topsoil was present on those with larger diameter pipe and which had topsoil fully stripped from the ROW during construction. Introduced grasses, Festuca ovina (sheep fescue) and Poa compressa (Canada bluegrass), succeeded in establishment following seeding and persisted for at least 40 years. Poa pratensis (Kentucky bluegrass) dominated many of the ROW sites. Contributing factors to moderate recovery of rough fescue grassland were related to post-growing season pipeline construction, ideally, between August and March, summer or fall seeding, and minimum disturbance trench-only stripping. Reclamation practices appeared more important than time since restoration in the restoration of rough fescue grassland.

Wolves, Elk, Bison, and Secondary Trophic Cascades in Yellowstone National Park

Wolves were reintroduced into Yellowstone National Park in 1995/96, likely reestablishing a trophic cascade involving wolves, elk, and woody browse species. The return of wolves may have also triggered a secondary trophic cascade involving bison, which are generally a minor prey species for wolves in northern Yellowstone. We hypothesize a sequence of events in northern Yellowstone where: 1) wolves prey on elk, changing elk behavior and reducing elk numbers, 2) causing reduced elk herbivory and more forage available to bison, and 3) allowing higher bison densities and additional bison effects on the ecosystem. This secondary trophic cascade, whereby wolf predation may have indirectly allowed bison numbers to increase through a reduction in inter-specific competition with elk, may represent an example of an alternative top-down pathway by which predators can influence multiple trophic levels through mediating the competitive interaction between two prey species. Both wolves and bison can have important effects on ecosystems, and there is growing interest in restoring these animals to wider portions of their former range. However, there are many potential routes for interactions between species and it is important to consider the conservation implications of other cascading effects when reintroducing such ecologically influential species into wild landscapes. The potential benefits of bison to their native ecosystems may not be realized in situations with low predation pressure, high bison densities, and constraints on bison movement and migration, thus likely contributing to impairment of resources.

The Influence of Land Use and Fences on Habitat Effectiveness, Movements and Distribution of Pronghorn in the Grasslands of North America

The pronghorn Antilocapra americana is a grassland and shrub-steppe obligate unique to North America. The species was driven to low abundance during agricultural settlement in the West. Extensive conversion of grasslands to crop production early in the twentieth century severely reduced the availability of native habitat. Populations have partially recovered with protective legislation and the species is common again in many areas of its original range. Pronghorn are most abundant in large open native grassland landscapes. Driven by harsh winter conditions (storms and deep snow), large herds in the grasslands of the Canadian Provinces and north-western United Sates may undertake opportunistic long-distance migration to seek forage in favourable areas. In Alberta the largest recorded return movement of a doe in spring was 445 km. Cumulative changes from several types of land use continue to reduce the effectiveness of remaining habitat. Expansion of the transportation network, poorly designed fences, urban expansion, exurban development, water development and energy development are reducing the effectiveness and area of native habitat. In particular, roads combined with fences can impede or block pronghorn movements. Plans that focus on maintaining the ecological coherence of landscapes for common species like the pronghorn should benefit the conservation of other species too. We suggest that the status of pronghorn, including its abundance and distribution and relevant landscape metrics (composition, configuration and connectivity) could serve as indicators for land use and conservation planning at landscape and regional scales.

Climate and vegetation change during the twentieth century in the lower Peace River district, northern Alberta, Canada.

A 96-yr climate record (1908—2004), historical descriptions, multiyear (1950, 1964, 1978, 1994) lake-surface area measurements, and 1950 and 2004 physiognomically based vegetation maps were compiled to assess vegetation change in the Fox Lake area (4248 ha) within the lower Peace River district of northern Alberta. A climatic warming trend (r = 0.615, P < 0.001; 0.35°C/decade) was evident during the twentieth century, with peak precipitation occurring from 1970 to 1990. Five major wet—dry cycles, based on net water balance values (precipitation minus potential evaporation), were evident with peaks occurring at about 17(±3) year intervals. Each cycle became slightly less arid than the previous until the mid-1990s. Deciduous forests dominated upland sites in 2004, whereas deciduous shrub and juvenile tree stands comprised 78% in 1950. Total wetland area remained relatively constant between 1950 and 2004, but less meadow and more standing water were present in 2004. Lake-surface area changes suggested that wetlands were recharged by precipitation rather than floodwaters from the nearby Peace River. Low water availability and historical descriptions suggest grassland-dominated parkland-like vegetation occurred in the study area during the early part of the twentieth century, with upland shrubs replacing grasslands by 1950. Increased atmospheric water availability rather than cessation of aboriginal burning or natural fires was considered responsible for increased forest abundance after 1945. Greater aridity in response to future global warming could reduce the abundance of forests in the lower Peace River district, and shift the regional climate from a boreal to a grassland-dominated parkland climatic regime.

Wood bison population recovery and forage availability in northwestern Canada

Forage availability was assessed to determine sustainable stocking rates for eight broadly defined vegetation types (Treed Uplands, Treed Lowlands, Mixed Tall Shrub/Sedge, Closed-canopied Willow, and Open-canopied Willow, Meadow, Wetland Grass, Wetland Sedge) for use by wood bison (Bison bison athabascae), a threatened subspecies, in the Canadian boreal forest of northern Alberta. Clip plots (n=108) were used to sample peak availability of herbs and current annual growth of Salix spp. in late summer. Graminoid wetlands dominated by Carex atherodes, Carex aquatilis, Carex utriculata, Scolochloa festucacea, or Calamagrostis stricta produced 1975-4575 kg ha(-1) of fair to good quality forage, whereas treed stands produced < 250 kg ha(-1) of forb-dominated forage (>85% content), which was below a published 25% foraging efficiency threshold of 263 kg ha(-1) for bison. Upland forests that dominate the region produced < or = 1 animal unit day (AUD) of forage per hectare in summer. Most forest understory plants were of poor forage value, suggesting the potential sustainable stocking rate of such areas was actually < or = 0.3 AUD ha(-1), with even lower rates during winter due to snow cover. Herbaceous wetlands contained approximately 78 AUD ha(-1) of forage, but were considered largely unavailable in summer because of flooding and soft organic soils that make access difficult. Conversion of prime foraging habitat to agricultural land, forest expansion due to fire control, and a warmer and wetter climatic regime after the mid-1900s likely contributed to a regional reduction in carrying capacity. It is hypothesized that substantial recovery of the wood bison population toward historical levels will be constrained in northern Alberta by the availability of summer forage, and the limited extent of graminoid wetlands that provide winter foraging habitat.

Survival and recovery estimates of male elk in a harvested inter-jurisdictional population

Demographic rates are critical pieces of information for understanding ungulate population dynamics and effectively managing populations. In harvested elk Cervus elaphus canadensis populations, human harvest is often the greatest source of adult male mortality. In the Cypress Hills of southeast Alberta and southwest Saskatchewan, Canada, hunting is a tool to mitigate conflicts between elk and agricultural producers in the area. We estimated survival (S) and animal recovery (f) rates based on individually marked male elk (n = 47) using hunter-returned ear tags from 1998–2001. Recovery rate differed between jurisdictions and was substantially lower in Saskatchewan (f = 0.16, SE = 0.05) compared to Alberta (f = 0.31, SE = 0.08). A constant survival rate (S = 0.61, SE = 0.15) was most supported. The average longevity for male elk in the Cypress Hills was 2.02 (SE = 0.51) years after surviving their first year of life. This research highlights the importance of considering regulatory regimes and requirements when investigating and interpreting demographic and population dynamics of populations managed across jurisdictions.

Effects of disturbance on silver sagebrush communities in dry mixed-grass prairie.

Restoration specialists are increasingly interested in re-establishing silver sagebrush (Artemisia cana) communities due to the large number of wildlife species that are partial sagebrush obligates. Energy development within native grasslands can contribute to habitat loss through introduction of invasive species. In this study, pipeline and reclaimed well site footprints were assessed relative to undisturbed sample units to identify management practices that achieve effective restoration of silver sagebrush communities on disturbed sites. Our objectives were to compare silver sagebrush communities on energy disturbances with undisturbed areas in two ecological range sites in dry mixed-grass prairie: blowouts (hard-packed bare ground) and overflows (mesic sedimentation). Our hypothesis was that moisture, greater nutrient values, and potential seed banks found in overflows may benefit silver sagebrush growth. We were also interested in plant communities resulting from of various seeding treatments, hypothesizing that silver sagebrush may be negatively impacted by some seeding treatments. We used a paired transect design to measure variations in plant species cover in each ecological range type. We found similar silver sagebrush cover values to adjacent undisturbed areas following disturbances on both overflow and blowout ecological range types; however, silver sagebrush was significantly reduced in disturbed areas that were seeded with grass species compared to sites that were allowed to recover naturally. We recommend minimum disturbance practices with natural recovery, avoidance of seeding agronomic cultivars, and in particular preventing introduction of invasive species such as crested wheatgrass.

Index measurements of carcass composition for Coats Island caribou

D u r i n g a 2-year study of the ecology of barren-ground car ibou (Rangifer tarandus groenlandicus) on Coats Island, N o r t h w e s t Territories , Canada , 27 side dissections were conducted; bone, muscle, and fat were separated and weighed. Mature female caribou made up 17 of the 27 dissections and the remaining 10 were calves ranging i n age f r o m 1 week to 11 months. The extreme cycle of body condi t ion in Coats Island car ibou permitted the study to span the range f rom fat fall animals to emaciated spring animals near starvation. Weight of the gastrocnemius muscle (a small , readily identifiable muscle in the h i n d quarter) was an accurate predictor of total muscle weight ( In (total muscle in kg) = —2.791 + 1.071 In (gastrocnemius weight in g); r = 0.98). The regression was not affected by age or cond i t ion , and muscle compos i t ion varied little w i t h season except in very lean animals, in w h i c h intramuscular fat decreased. Weight of the femur was an equally useful predictor of total bone weight (In (total bone in kg) = —4.878 41.137 In (femur weight in g); r = 0.98). This regression was also unaffected by age or cond i t ion . Three carcass fat depots — subcutaneous, intermuscular, and pelvic — and two internal depots — omental and perirenal — were graphed against the total fat in these depots for each animal. Age and body condi t ion again had little effect on the curves for each depot. Subcutaneous fat was the latest maturing but the earliest depleted. A multiple Rangifer, Special Issue N o . 1, 1986: 353