Brian E. McLaren

Plant-Specific Response to Herbivory: Simulated Browsing of Suppressed Balsam Fir on Isle Royale

Balsam fir (Abies balsamea) is a shade-tolerant conifer that experiences striking growth suppression from browsing of the understory of mixed, boreal-type forests of Isle Royale, Michigan, where it forms an important component of moose (Alces alces) diet in winter. Suppression increases with increasing canopy cover and forest age. However, response to an individual, severe browsing episode cannot be generalized in terms of suppression. Such shorter-term responses are best investigated by experimentation. Artificial removal of foliage from understory balsam fir in two sites on Isle Royale and one mainland site showed that damage such as reduced terminal growth and complete mortality was actually highest among least suppressed trees. Canopy cover produced a secondary effect, in which trees experiencing >60% cover were unable to compensate for removal by clipping. Among less suppressed trees, competition for limited light produced an apically oriented morphology that countered the laterally oriented morphology associated with suppression. Higher vulnerability to the artificial browsing occurred because trees were no longer protected by snow cover. By the second growing season following clipping, surviving clipped trees even in the most damaged sites resumed the same growth as controls. Over the long term, suppression may be a means by which fir remains alive when subjected to continuous browsing. Over the shorter term, delayed growth recovery following severe browsing in an unsuppressed understory may also contribute to sustainability in Isle Royales plant-herbivore system.

Effects of Mine Development on Woodland Caribou Rangifer Tarandus Distribution

Abstract Knowledge of the effect of mining developments on caribou Rangifer tarandus is fragmentary. We examined the impact of the Hope Brook gold mine, southwestern Newfoundland, on the La Poile woodland caribou herd on a section of their year-round range. We examined the impact of the mine on caribou distribution during three phases of mine activity (pre-disturbance, construction and open-pit mining and underground mine and mill operation) in five seasons (winter, late winter, pre-calving, calving and autumn). Aerial surveys were conducted on a monthly basis from September 1985 to July 1991. Following initiation of the mine construction, caribou abundance increased with distance from the mine site in all seasons, and caribou avoided areas within 4 km of the site in most seasons. Within 6 km of the mine centre, group size and the number of caribou decreased as mine activity progressed in late winter, pre-calving and calving seasons. Although the impact of the mine was most prominent in the pre-calving and calving seasons, caribou responded to mine disturbance in all seasons. This highlights the importance of evaluating the year-round impact of human-induced environmental change.

Can rare positive interactions become common when large carnivores consume livestock

Livestock populations in protected areas are viewed negatively because of their interaction with native ungulates through direct competition for food resources. However, livestock and native prey can also interact indirectly through their shared predator. Indirect interactions between two prey species occur when one prey modifies either the functional or numerical responses of a shared predator. This interaction is often manifested as negative effects (apparent competition) on one or both prey species through increased predation risk. But indirect interactions can also yield positive effects on a focal prey if the shared predator modifies its functional response toward increased consumption of an abundant and higher-quality alternative prey. Such a phenomenon between two prey species is underappreciated and overlooked in nature. Positive indirect effects can be expected to occur in livestock-dominated wildlife reserves containing large carnivores. We searched for such positive effects in Acacia-Zizhypus forests of Indias Gir sanctuary where livestock (Bubalus bubalis and Bos indicus) and a coexisting native prey (chital deer, Axis axis) are consumed by Asiatic lions (Panthera leo persica). Chital vigilance was higher in areas with low livestock density than in areas with high livestock density. This positive indirect effect occurred because lion predation rates on livestock were twice as great where livestock were abundant than where livestock density was low. Positive indirect interactions mediated by shared predators may be more common than generally thought with rather major consequences for ecological understanding and conservation. We encourage further studies to understand outcomes of indirect interactions on long-term predator-prey dynamics in livestock-dominated protected areas.

Youth Views on Environmental Changes, the Future of the Environment, and Stewardship: The Case of a Canadian Coastal Community

This article discusses and provides insights concerning rural youths perceptions of their natural environment and the future role of rural youths in environmental stewardship. Insights are based on two focus groups with youths 17–24 years of age living in an isolated coastal Canadian community. The youths expressed a strong attachment to place, as well as a concern for local, natural resources. However, because of the economic instability of their local community, many youths are planning a future in places far away with more lucrative employment and education opportunities. We suggest that strategies need to be developed that allow youths to engage in environmental stewardship activities “from away.” Some suggestions for “virtual stewardship” are discussed.

Losing the Predator—Prey Space Race Leads to Extirpation of Woodland Caribou from Pukaskwa National Park

Abstract: Persistence for woodland caribou (Rangifer tarandus) in Pukaskwa National Park (PNP, Ontario, Canada; 1878 km2) was tied to females finding safe calving areas on offshore islands with a water barrier created by Lake Superior. During 1975–1988, PNP caribou fluctuated around a carrying capacity of 24, but after 1988 the population declined, falling to 5 individuals by 2009. Caribou are now likely extirpated from PNP, even in the absence of any local or increased anthropogenic disturbance since the protected area was created in 1978. As moose (Alces alces) in the region declined concurrently, their relative density remained higher along the Lake Superior coastal strip than further inland, the reverse of the situation during 1975–1988; moose especially held to the coast during heavy snow years. Wolves (Canis lupus) accordingly shifted more of their hunting effort to the coast, likely encountering both moose and caribou with increasing search efficiency. These behaviours are described as a predator—prey “space race” that wolves eventually won.

Domestic ungulates in protected areas and the potential for indirect interactions via shared predation

Abstract In many parts of the world, protected areas harbour permanent livestock that range freely with native herbivores. These domestic animals are typically an undesirable ecosystem component because they pose a challenge to park managers and biologists who wish to maintain ‘natural’ species interactions and diversity. Studies dealing with livestock in protected areas have primarily focussed on interactions such as competition for food resources with native herbivores, habitat degradation, and human-carnivore conflicts caused by livestock depredation. The negative effects of such interactions are a major threat to the survival of many mammalian prey and predator species. However, the role of indirect interactions between native herbivores and domestic prey, via their common enemy, has received comparatively little attention and poses a significant knowledge gap in understanding the net impacts of domestic prey on native herbivores. We present our perspectives on ignored or missed indirect interactions in livestock–native ungulate systems, and suggest some management actions for understanding these systems and minimising conflicts. A broader understanding of indirect interactions among livestock, native herbivores and their predators will aid in more informed protected-area management.

Characteristics of the Boreal Mixedwood Forest Associated with the use of Subnivean Access Points by American Martens

Abstract: Habitat for American martens (Martes americana) is associated with forest types that offer fine-scale structural complexity in part used to access the winter subnivean environment, which is used for food procurement, predator avoidance, and rest. We assessed habitat characteristics associated with points of subnivean access by martens from winter tracking in a boreal mixedwood forest in northern Ontario. We then assessed areas designated as reserved marten habitat according to Forest Management Guidelines for the Provision of Marten Habitat in Ontario with respect to these characteristics. Coarse woody debris counts were positively associated with subnivean access. We found some evidence that subnivean access points differed in a transition from patches of coniferous to mixedwood forest, defined by tree basal area. Especially in mixedwood patches, deciduous shrub density may also facilitate subnivean access. Development of guidelines to protect features associated with fine-scale structural complexity important in winter to martens should be a research priority. Nomenclature: Flora of North America Editorial Committee, 1993; Wilson & Reeder, 1993.