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Data from: Vertebrate scavenging dynamics differ between carnivore and herbivore carcasses in the northern boreal forest
Peers, Michael; Konkolics, Sean; Majchrzak, Yasmine; Menzies, Allyson; Studd, Emily; Boonstra, Rudy; Boutin, Stan; Lamb, Clayton — 2021-07-23 <p>Vertebrate scavenging can impact food web dynamics, but our understanding of this process stems predominantly from monitoring herbivore carrion and extrapolating results across carcass types. Recent evidence suggests carnivores may avoid intraguild scavenging to reduce parasite transmission. If this behavior is widespread across diverse ecosystems, estimation of nutrient cycling and community scavenging rates are likely biased to a currently unknown degree. We examined whether the time to initiate scavenging, carcass persistence, or the richness of species scavenging in the boreal forest of Yukon, Canada, differed between carnivore and herbivore carcasses. Vertebrates took longer to initiate scavenging on carnivore carcasses (3.2 days) relative to herbivore carcasses (1.1 days), and carnivore carcasses persisted on the landscape for over a month longer (48.4 days and 5.5 days, respectively). The longer persistence times were due to the reduction in scavenging by carnivores such as Canada lynx (<i>Lynx canadensis</i>). Decreased scavenging was caused by changes in the propensity to consume carnivore carrion, as the number of species detecting a carcass within the first week did not differ between carnivore and herbivore carcasses. These results have ramifications for our understanding of nutrient cycling and food web dynamics in the boreal forest, and provide further support that carcass type should be included in future studies.</p>
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Data from: Effects of habitat quality and access management on the density of a recovering grizzly bear population
Lamb, Clayton; Mowat, Garth; Reid, Aaron; Smit, Laura; Proctor, Michael; McLellan, Bruce N.; Nielsen, Scott E.; Boutin, Stan — 2020-04-06 Human activities have dramatic effects on the distribution and abundance of wildlife. Increased road densities and human presence in wilderness areas have elevated human-caused mortality of grizzly bears and reduced bears' use. Management agencies frequently attempt to reduce human-caused mortality by managing road density and thus human access, but the effectiveness of these actions is rarely assessed. We combined systematic, DNA-based mark–recapture techniques with spatially explicit capture–recapture models to estimate population size of a threatened grizzly bear population (Kettle–Granby), following management actions to recover this population. We tested the effects of habitat and road density on grizzly bear population density. We tested both a linear and threshold-based road density metric and investigated the effect of current access management (closing roads to the public). We documented an c. 50% increase in bear density since 1997 suggesting increased landscape and species conservation from management agencies played a significant role in that increase. However, bear density was lower where road densities exceeded 0.6 km/km2 and higher where motorised vehicle access had been restricted. The highest bear densities were in areas with large tracts of few or no roads and high habitat quality. Access management bolstered bear density in small areas by 27%. Synthesis and applications. Our spatially explicit capture–recapture analysis demonstrates that population recovery is possible in a multi-use landscape when management actions target priority areas. We suggest that road density is a useful surrogate for the negative effects of human land use on grizzly bear populations, but spatial configuration of roads must still be considered. Reducing roads will increase grizzly bear density, but restricting vehicle access can also achieve this goal. We demonstrate that a policy target of reducing human access by managing road density below 0.6 km/km2, while ensuring areas of high habitat quality have no roads, is a reasonable compromise between the need for road access and population recovery goals. Targeting closures to areas of highest habitat quality would benefit grizzly bear population recovery the most.
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Data from: Prey availability and ambient temperature influence carrion persistence in the boreal forest
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Peers, Michael; Konkolics, Sean; Lamb, Clayton; Majchrzak, Yasmine; Menzies, Allyson; Studd, Emily; Boonstra, Rudy; Kenney, Alice; Krebs, Charles; Martinig, April Robin; McCulloch, Baily; Silva, Joseph; Garland, Laura; Boutin, Stan — 2020-10-09 <p>1. Scavenging by vertebrates can have important impacts on food web stability and persistence, and can alter the distribution of nutrients throughout the landscape. However, scavenging communities have been understudied in most regions around the globe, and we lack understanding of the biotic drivers of vertebrate scavenging dynamics.</p> <p>2. In this paper, we examined how changes in prey density and carrion biomass caused by population cycles of a primary prey species, the snowshoe hare (<i>Lepus americanus</i>), influence scavenging communities in the northern boreal forest. We further examined the impact of habitat and temperature on scavenging dynamics.</p> <p>3. We monitored the persistence time, time until first scavenger, and number of species scavenging experimentally-placed hare carcasses over four consecutive years in the southwestern Yukon. We simultaneously monitored hare density and carrion biomass to examine their influence relative to temperature, habitat, and seasonal effects. For the primary scavengers, we developed species-specific scavenging models to determine variation on the effects of these factors across species, and determine which species may be driving temporal patterns in the entire community.</p> <p>4. We found that the efficiency of the scavenging community was affected by hare density, with carcass persistence decreasing when snowshoe hare densities declined, mainly due to increased scavenging rates by Canada lynx (<i>Lynx canadensis</i>). However, prey density did not influence the number of species scavenging a given carcass, suggesting prey abundance affects carrion recycling but not necessarily the number of connections in the food web. In addition, scavenging rates increased in warmer temperatures, and there were strong seasonal effects on the richness of the vertebrate scavenging community.</p> <p>5. Our results demonstrate that vertebrate scavenging communities are sensitive to changes in species’ demography and environmental change, and that future assessments of food web dynamics should consider links established through scavenging.</p>

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(Author: Lamb, Clayton)

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