Paul C. Paquet

Human predators outpace other agents of trait change in the wild

The observable traits of wild populations are continually shaped and reshaped by the environment and numerous agents of natural selection, including predators. In stark contrast with most predators, humans now typically exploit high proportions of prey populations and target large, reproductive-aged adults. Consequently, organisms subject to consistent and strong ‘harvest selection’ by fishers, hunters, and plant harvesters may be expected to show particularly rapid and dramatic changes in phenotype. However, a comparison of the rate at which phenotypic changes in exploited taxa occurs relative to other systems has never been undertaken. Here, we show that average phenotypic changes in 40 human-harvested systems are much more rapid than changes reported in studies examining not only natural (n = 20 systems) but also other human-driven (n = 25 systems) perturbations in the wild, outpacing them by >300% and 50%, respectively. Accordingly, harvested organisms show some of the most abrupt trait changes ever observed in wild populations, providing a new appreciation for how fast phenotypes are capable of changing. These changes, which include average declines of almost 20% in size-related traits and shifts in life history traits of nearly 25%, are most rapid in commercially exploited systems and, thus, have profound conservation and economic implications. Specifically, the widespread potential for transitively rapid and large effects on size- or life history-mediated ecological dynamics might imperil populations, industries, and ecosystems.

HUMAN ACTIVITY MEDIATES A TROPHIC CASCADE CAUSED BY WOLVES

Experimental evidence of trophic cascades initiated by large vertebrate predators is rare in terrestrial ecosystems. A serendipitous natural experiment provided an opportunity to test the trophic cascade hypothesis for wolves (Canis lupus) in Banff National Park, Canada. The first wolf pack recolonized the Bow Valley of Banff National Park in 1986. High human activity partially excluded wolves from one area of the Bow Valley (low-wolf area), whereas wolves made full use of an adjacent area (high-wolf area). We investigated the effects of differential wolf predation between these two areas on elk (Cervus elaphus) population density, adult female survival, and calf recruitment; aspen (Populus tremuloides) recruitment and browse intensity; willow (Salix spp.) production, browsing intensity, and net growth; beaver (Castor canadensis) density; and riparian songbird diversity, evenness, and abundance. We compared effects of recolonizing wolves on these response variables using the log response ratio between the low-wolf and high-wolf treatments. Elk population density diverged over time in the two treatments, such that elk were an order of magnitude more numerous in the low-wolf area compared to the high-wolf area at the end of the study. Annual survival of adult female elk was 62% in the high-wolf area vs. 89% in the low-wolf area. Annual recruitment of calves was 15% in the high-wolf area vs. 27% without wolves. Wolf exclusion decreased aspen recruitment, willow production, and increased willow and aspen browsing intensity. Beaver lodge density was negatively correlated to elk density, and elk herbivory had an indirect negative effect on riparian songbird diversity and abundance. These alternating patterns across trophic levels support the wolf-caused trophic cascade hypothesis. Human activity strongly mediated these cascade effects, through a depressing effect on habitat use by wolves. Thus, conservation strategies based on the trophic importance of large carnivores have increased support in terrestrial ecosystems.

CARNIVORES AS FOCAL SPECIES FOR CONSERVATION PLANNING IN THE ROCKY MOUNTAIN REGION

Viability analysis of well-selected focal species can complement ecosystem-level conservation planning by revealing thresholds in habitat area and landscape connectivity. Mammalian carnivores are good candidates for focal species because their distributional patterns often strongly reflect regional-scale population processes. We incorporated focal species analysis of four carnivore species, fisher (Martes pennanti), lynx (Lynx canadensis), wolverine (Gulo gulo), and grizzly bear (Ursus arctos), into a regional conservation plan for the Rocky Mountains of the United States and Canada. We developed empirical habitat models for fisher, lynx, and wolverine based on a geographically extensive data set of trapping and sighting records. Predictor variables derived directly from satellite imagery were significantly correlated with carnivore distribution and allowed us to predict distribution in areas lacking detailed vegetation data. Although we lacked similar distributional data for grizzly bear, we predicted be...

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.

USE OF POPULATION VIABILITY ANALYSIS AND RESERVE SELECTION ALGORITHMS IN REGIONAL CONSERVATION PLANS

Current reserve selection algorithms have difficulty evaluating connectivity and other factors necessary to conserve wide-ranging species in developing landscapes. Conversely, population viability analyses may incorporate detailed demographic data, but often lack sufficient spatial detail or are limited to too few taxa to be relevant to regional conservation plans. We developed a regional conservation plan for mammalian carnivores in the Rocky Mountain region using both a reserve selection algorithm (SITES) and a spatially explicit population model (PATCH). The spatially explicit population model informed reserve selection and network design by producing data on the locations of population sources, the degree of threat to those areas from landscape change, the existence of thresholds to population viability as the size of the reserve network increased, and the effect of linkage areas on population persistence. A 15% regional decline in carrying capacity for large carnivores was predicted within 25 years i...

Prey Use Strategies of Sympatric Wolves and Coyotes in Riding Mountain National Park, Manitoba

Allopatric distribution of wolves ( Canis lupus ) and coyotes ( C. latrans ) in some areas of North America can be explained by competitive exclusion of coyotes by wolves. However, in Riding Mountain National Park, Manitoba, the potential for competition between the two species was minimized by differential use of nonlimiting food resources. Wolves primarily preyed on elk ( Cervus elaphus ) and white-tailed deer ( Odocoileus virginianus ), and secondarily on moose ( Alces alces ). Coyotes preyed on deer and rarely, young elk. Although wolves occasionally killed coyotes, coyotes followed wolves and scavenged at their kills. The benefits accrued from scavenging apparently compensated for the associated risk of being killed by wolves.

Landscape heterogeneity and marine subsidy generate extensive intrapopulation niche diversity in a large terrestrial vertebrate

1. Inquiries into niche variation within populations typically focus on proximate ecological causes such as competition. Here we examine how landscape heterogeneity and allochthonous (marine) subsidy might ultimately generate intrapopulation niche diversity. 2. Using stable isotope analysis, we detected extensive terrestrial-marine isotopic niche variation among subpopulations, social groups, and individual grey wolves (Canis lupus) that occupy a spatially heterogeneous landscape in coastal British Columbia comprising a mainland area and adjacent archipelago. 3. The inner island subpopulation exhibited the widest isotopic niche in the population, consuming extensive terrestrial and marine resources. Mainland and outer island subpopulations occupied comparatively narrow and primarily terrestrial, and primarily marine, niches respectively. Within these biogeographical subpopulations, social groups also diverged in niche. 4. To support examination at the individual level, we used an isotopic approach to test Van Valens (1965) niche variation hypothesis. Consistent with the hypothesis, we observed that among-individual variation increased with subpopulation niche width. 5. Patterns at all levels related to how a spatially heterogeneous coastal landscape structured the competitive environment, which in turn mediated the availability and use of terrestrial and marine resources. Broadly, our results suggest that spatial heterogeneity and allochthonous subsidy--both widespread but commonly subject to contemporary anthropogenic change--might provide novel opportunities for examination and conservation of ecological variation within populations.

The Practices of Wolf Persecution, Protection, and Restoration in Canada and the United States

Abstract Wolf management can be controversial, reflecting a wide range of public attitudes. We analyzed wolf management case histories representing a spectrum of approaches in Canada and the United States. During the early 20th century, wolves were considered undesirable. They were subject to persecution and were extirpated from large areas of their original range. With increased environmental awareness in the 1970s, attitudes toward wolves began to change. Wolf conservation became a focus of public interest, providing conditions that favored regional wolf recovery. However, in regions where livestock production or big-game hunting is valued, wolves have continued to be controlled by management authorities or through the actions of individual citizens. With US wolf populations recovering in the conterminous states, a rule was approved to delist the species from endangered to threatened status under the Endangered Species Act. Notwithstanding the intent of legal instruments, history has demonstrated that societal values ultimately determine the survival of species such as the wolf.

MOVEMENT PATTERNS OF BARREN-GROUND WOLVES IN THE CENTRAL CANADIAN ARCTIC

Abstract We collected information on the movement patterns of wolves (Canis lupus) captured within a 30,000-km2 area in the Northwest Territories and western Nunavut. Currently, diamond mining and road construction are occurring in the area used by these migratory wolves for denning. During summers of 1997 and 1998, 23 wolves in 19 different packs were captured and fitted with collar-mounted satellite transmitters. Areas used by these wolves varied seasonally and seemed to correspond to movements of migratory caribou (Rangifer tarandus). Annual home-range sizes (95% minimum convex polygon), averaged 63,058 km2 ± 12,836 SE for males and 44,936 ± 7,564 km2 for females. Wolves began to restrict movements around a den site on the tundra by late April. They did not depart from their summer ranges until late October, after which they followed caribou to their wintering grounds. Straight-line distances from the most distant location on the winter range to the den site averaged 508 ± 26 km during 1997–1998 and 265 ± 15 km in 1998–1999 (P < 0.01). Home range in summer averaged 2,022 ± 659 km2 for males and 1,130 ± 251 km2 for females. No difference was detected between sexes or years. All but 2 of 15 wolves returned to <25 km of a previous den, and 2 wolves returned to the same den site. We believe that human activities that disturb or displace denning wolves, or that alter the distribution or timing of caribou movements, will have negative affects on reproductive success of wolves.

HIERARCHICAL HABITAT SELECTION BY TUNDRA WOLVES

Abstract Using resource selection functions, we examined habitat selection patterns of tundra wolves (Canis lupus) in the central Canadian Arctic at the level of the home range and within the home range. Esker habitat was relatively preferred by wolves at the home range level of selection, possibly indicating the importance of denning habitat as a limiting factor for tundra wolves. We failed to conclusively tie vegetation communities to movements of wolves within the home range. Eskers make up only about 1–2% of the landscape; hence, a potential conflict between wolf conservation and industrial development in the region may occur as eskers are targeted as a source of granular material for road construction. Results of this study underline the importance of scale dependence in habitat selection. Failure to view habitat selection as a hierarchical process may result in a narrow and possibly misleading notion of the value of habitats to animals.