Stan Boutin

Predator‐mediated Allee effects in multi‐prey systems

Allee effects can have significant consequences for small populations and understanding the causal mechanisms for such effects is important for guiding conservation actions. One proposed mechanism is through predation, in which a type II functional response leads to increasing predation rates as prey numbers decline. However, models to support this mechanism have incorporated only a single declining prey species in the functional response, which is probably an oversimplification. We reevaluated the potential for predator-mediated Allee effects in a multi-prey system using Hollings disc equation. We also used empirical data on a large herbivore to examine how grouping behavior may influence the potential for predation-mediated Allee effects. Results based on a multi-prey expression of the functional response predict that Allee effects caused by predation on relatively rare secondary prey may not occur because handling time of the abundant prey dominates the functional response such that secondary prey are largely bycatch. However, a predator-mediated Allee effect can occur if secondary prey live in groups and if, as the population declines, their average group size declines (a relationship seen in several species). In such a case, the rate at which the number of groups declines is less than the rate at which the population declines. Thus the rate at which a predator encounters a group remains relatively stable, but when a predator kills one animal from smaller groups, the predation rate increases. These results highlight the need to evaluate risks associated with potential changes in group size as populations decline.

Modeling and field-testing of Ovenbird (Seiurus aurocapillus) responses to boreal forest dissection by energy sector development at multiple spatial scales

Although the area disturbed by linear features in forested systems is small relative to many other human disturbances, linear features create significantly more amounts of edge per unit area. In the boreal plains of Alberta, Canada, energy sector exploration has resulted in extensive dissection of the landscape through 8xa0m wide seismic lines. A spatially explicit model was developed to test how bird abundance might change in response to increasing seismic line density if individuals use seismic lines as territory boundaries or actively avoid these edges. Assuming birds had fixed territory shape and size, increasing seismic line density from 0 to 8xa0km/km2 resulted in a 38% decline and an 82% decline in bird abundance when individuals used lines as territory boundaries or avoided edges by 50xa0m, respectively. We tested the assumptions of our model using the Ovenbird (Seiurus aurocapillus). Based on radio-telemetry (nxa0=xa012), all Ovenbirds crossed seismic lines at some point during the breeding season. However, male Ovenbirds showed a distinct use of one side of the seismic line, suggesting lines acted as territory boundaries. In 12.25xa0ha plots (nxa0=xa024) spot-mapping detected no change in Ovenbird density as linear feature density increased from 0 to 8.6xa0km/km2. In 4xa0km2 landscapes (nxa0=xa062) sampled using a grid of nine point-counts, we also detected no changes in Ovenbird numbers across the same range of seismic line densities. Ovenbirds declined with seismic line density at the level of the individual point-count station (12xa0ha scale), but only when a threshold seismic line density of 8.5xa0km/km2 was reached. Above the threshold, Ovenbirds declined 19% for each 1xa0km/km2 increase in seismic line density. While relatively few places in Alberta’s boreal forest have local seismic line densities of 8.5xa0km/km2, forest dissection could increasingly become an issue if current energy exploration practices continue.

Functional and numerical responses of ovenbirds (Seiurus aurocapilla) to changing seismic exploration practices in Alberta's boreal forest

ABSTRACT Rapid development of energy reserves in the boreal forest of western Canada has raised concerns about the potential impacts of forest fragmentation caused by seismic lines. Seismic lines are narrow linear corridors cut by the energy sector to access remote areas. Traditionally, seismic lines were cut using a bulldozer and averaged about 8 m in width. In response to concerns about conventional seismic line impacts, some energy companies have turned to new “best practices” that use lower-impact techniques to reduce their footprint (2- to 3-m-wide lines). Crucial to assessing the efficacy of this change in seismic policy for maintenance of biodiversity is determining how conventional and low-impact seismic lines are perceived by wildlife. We assessed the functional and numerical response of male ovenbirds (Seiurus aurocapilla) to conventional and low-impact seismic lines in mature aspen forest in northeastern Alberta. Based on radio-telemetry, ovenbirds perceived conventional seismic lines as creating a gap in the forest and used it as a territory boundary. In contrast, ovenbirds incorporated low-impact seismic lines within their territories. Spot-mapping data suggested no differences in ovenbird density in stands with a single conventional seismic line, multiple low-impact lines, or reference plots with no seismic lines. Despite the lack of numerical response to any seismic practice, we believe it is prudent to recommend that energy companies consider using new low-impact approaches in their seismic operations to minimize the ecological risks of energy sector activity for forest birds.

Achieving Conservation when Opportunity Costs Are High: Optimizing Reserve Design in Alberta’s Oil Sands Region

Recent studies have shown that conservation gains can be achieved when the spatial distributions of biological benefits and economic costs are incorporated in the conservation planning process. Using Alberta, Canada, as a case study we apply these techniques in the context of coarse-filter reserve design. Because targets for ecosystem representation and other coarse-filter design elements are difficult to define objectively we use a trade-off analysis to systematically explore the relationship between conservation targets and economic opportunity costs. We use the Marxan conservation planning software to generate reserve designs at each level of conservation target to ensure that our quantification of conservation and economic outcomes represents the optimal allocation of resources in each case. Opportunity cost is most affected by the ecological representation target and this relationship is nonlinear. Although petroleum resources are present throughout most of Alberta, and include highly valuable oil sands deposits, our analysis indicates that over 30% of public lands could be protected while maintaining access to more than 97% of the value of the regions resources. Our case study demonstrates that optimal resource allocation can be usefully employed to support strategic decision making in the context of land-use planning, even when conservation targets are not well defined.

Effects of a Severe Mountain Pine Beetle Epidemic in Western Alberta, Canada under Two Forest Management Scenarios

We used a simulation model to investigate possible effects of a severe mountain pine beetle (Dendroctonus ponderosae Hopkins) epidemic under two management scenarios in Alberta, Canada. Our simulated outbreak was based on the current epidemic in British Columbia, which may kill close to 80% of the provinces pine volume. Our two management scenarios were conventional harvest and a pine-reduction strategy modeled on a component of Albertas Mountain Pine Beetle Management Strategy. The pine strategy seeks to reduce the number of susceptible pine stands by 75% over the next 20 years through targeted harvesting by the forest industry. Our simulations showed that the pine strategy could not be effectively implemented, even if the onset of the beetle outbreak was delayed for 20 years. Even though we increased mill capacity by 20% and directed all harvesting to high volume pine stands during the pine strategys surge cut, the amount of highly susceptible pine was reduced by only 43%. Additional pine volume remained within mixed stands that were not targeted by the pine strategy. When the outbreak occurred in each scenario, sufficient pine remained on the landscape for the beetle to cause the timber supply to collapse. Alternative management approaches and avenues for future research are discussed.