Human Activity Helps Prey Win the Predator-Prey Space Race

Predator-prey interactions, including between large mammalian wildlife species, can be represented as a “space race”, where prey try to minimize and predators maximize spatial overlap. Human activity can also influence the distribution of wildlife species. In particular, high-human disturbance can displace large carnivore predators, a trait-mediated direct effect. Predator displacement by humans could then indirectly benefit prey species by reducing predation risk, a trait-mediated indirect effect of humans that spatially decouples predators from prey. The purpose of this research was to test the hypothesis that high-human activity was displacing predators and thus indirectly creating spatial refuge for prey species, helping prey win the “space race”. We measured the occurrence of eleven large mammal species (including humans and cattle) at 43 camera traps deployed on roads and trails in southwest Alberta, Canada. We tested species co-occurrence at camera sites using hierarchical cluster and nonmetric multidimensional scaling (NMS) analyses; and tested whether human activity, food and/or habitat influenced predator and prey species counts at camera sites using regression tree analysis. Cluster and NMS analysis indicated that at camera sites humans co-occurred with prey species more than predator species and predator species had relatively low co-occurrence with prey species. Regression tree analysis indicated that prey species were three times more abundant on roads and trails with >32 humans/day. However, predators were less abundant on roads and trails that exceeded 18 humans/day. Our results support the hypothesis that high-human activity displaced predators but not prey species, creating spatial refuge from predation. High-human activity on roads and trails (i.e., >18 humans/day) has the potential to interfere with predator-prey interactions via trait-mediated direct and indirect effects. We urge scientist and managers to carefully consider and quantify the trait-mediated indirect effects of humans, in addition to direct effects, when assessing human impacts on wildlife and ecosystems

Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web

Ongoing debate about whether food webs are primarily regulated by predators or by primary plant productivity, cast as top-down and bottom-up effects, respectively, may becoming superfluous. Given that most of the world\u27s ecosystems are human dominated we broadened this dichotomy by considering human effects in a terrestrial food-web. We studied a multiple human-use landscape in southwest Alberta, Canada, as opposed to protected areas where previous terrestrial food-web studies have been conducted. We used structural equation models (SEMs) to assess the strength and direction of relationships between the density and distribution of: (1) humans, measured using a density index; (2) wolves (Canis lupus), elk (Cervus elpahus) and domestic cattle (Bos taurus), measured using resource selection functions, and; (3) forage quality, quantity and utilization (measured at vegetation sampling plots). Relationships were evaluated by taking advantage of temporal and spatial variation in human density, including day versus night, and two landscapes with the highest and lowest human density in the study area. Here we show that forage-mediated effects of humans had primacy over predator-mediated effects in the food web. In our parsimonious SEM, occurrence of humans was most correlated with occurrence of forage (beta = 0.637, p \u3c 0.0001). Elk and cattle distribution were correlated with forage (elk day: beta = 0.400, p \u3c 0.0001; elk night: beta = 0.369, p \u3c 0.0001; cattle day: beta = 0.403, p \u3c 0.0001; cattle, night: beta = 0.436, p \u3c 0.0001), and the distribution of elk or cattle and wolves were positively correlated during daytime (elk: beta = 0.293, p \u3c 0.0001, cattle: beta = 0.303, p \u3c 0.0001) and night-time (elk: beta = 0.460, p \u3c 0.0001, cattle: beta = 0.482, p \u3c 0.0001). Our results contrast with research conducted in protected areas that suggested human effects in the food web are primarily predator-mediated. Instead, human influence on vegetation may strengthen bottom-up predominance and weaken top-down trophic cascades in ecosystems. We suggest that human influences on ecosystems may usurp top-down and bottom-up effects

Effects of Wolves on Elk and Cattle Behaviors: Implications for Livestock Production and Wolf Conservation

BACKGROUND: In many areas, livestock are grazed within wolf (Canis lupus) range. Predation and harassment of livestock by wolves creates conflict and is a significant challenge for wolf conservation. Wild prey, such as elk (Cervus elaphus), perform anti-predator behaviors. Artificial selection of cattle (Bos taurus) might have resulted in attenuation or absence of anti-predator responses, or in erratic and inconsistent responses. Regardless, such responses might have implications on stress and fitness. METHODOLOGY/PRINCIPAL FINDINGS: We compared elk and cattle anti-predator responses to wolves in southwest Alberta, Canada within home ranges and livestock pastures, respectively. We deployed satellite- and GPS-telemetry collars on wolves, elk, and cattle (n = 16, 10 and 78, respectively) and measured seven prey response variables during periods of wolf presence and absence (speed, path sinuosity, time spent head-up, distance to neighboring animals, terrain ruggedness, slope and distance to forest). During independent periods of wolf presence (n = 72), individual elk increased path sinuosity (Z = -2.720, P = 0.007) and used more rugged terrain (Z = -2.856, P = 0.004) and steeper slopes (Z = -3.065, P = 0.002). For cattle, individual as well as group behavioral analyses were feasible and these indicated increased path sinuosity (Z = -2.720, P = 0.007) and decreased distance to neighbors (Z = -2.551, P = 0.011). In addition, cattle groups showed a number of behavioral changes concomitant to wolf visits, with variable direction in changes. CONCLUSIONS/SIGNIFICANCE: Our results suggest both elk and cattle modify their behavior in relation to wolf presence, with potential energetic costs. Our study does not allow evaluating the efficacy of anti-predator behaviors, but indicates that artificial selection did not result in their absence in cattle. The costs of wolf predation on livestock are often compensated considering just the market value of the animal killed. However, society might consider refunding some additional costs (e.g., weight loss and reduced reproduction) that might be associated with the changes in cattle behaviors that we documented

Livestock depredation by wolves and the ranching economy in the Northwestern U.S.

Due primarily to wolf predation on livestock (depredation), some groups oppose wolf (Canis lupus) conservation in the Northwestern U.S., which is an objective for large sectors of the public. Livestock depredation by wolves is a cost of wolf conservation borne by livestock producers, which creates conflict between producers, wolves and organizations involved in wolf conservation and management. Compensation is the main tool used to mitigate the costs of depredation, but this tool may be limited at improving tolerance for wolves. Furthermore, livestock production may in fact provide indirectly an important benefit for wolf conservation - i.e. a positive externality, by maintaining relatively intact habitat on private lands. We analyzed some of the costs of livestock depredation by wolves to livestock producers relative to recent economic trends in the livestock production industry, specifically income generated from livestock production and trends in land and livestock value. Data were gathered from depredation investigations, from the livestock compensation program and on land and livestock price in Idaho, Montana and Wyoming, U.S.A. from 1987 to 2003 - a period during which wolves had endangered species status. We found that instigation of attacks on livestock by wolves was determined by need for food, but wolves may kill sheep in excess of food needs. Excessive killing of livestock may contribute significantly to intolerance for wolves. Livestock killed by wolves cost producers approximately $11,076.49 per year between 1987 and 2003, although costs were increasing linearly (R2 = 0.789, P Livestock production Canis lupus conservation Damage compensation Depredation Economic externality Northwestern U.S.

Data from: Influence of in-situ oil sands development on caribou (Rangifer tarandus) movement

In-situ oil sands development (ISD) involves a network of facilities, wells, roads and pipelines to extract and transport subsurface bitumen. This technology is rapidly expanding and there is uncertainty whether ISDs restrict animal movement, leading to increased extinction probabilities for some wide-ranging species. Here we test for effects of simulated future (i.e., 50 years from now) and current ISDs on simulated movements of woodland caribou (Rangifer tarandus), a threatened species across North America. In simulations of future scenarios, we varied the spacing and permeability of ISDs and the presence/absence of protected areas. Permeability was measured as the number of times simulated caribou crossed ISDs with different levels of modelled permeability. We estimated the effects of these factors on caribou step length and annual home range size, key metrics of small and large spatiotemporal scales of movement, respectively. Current caribou crossings of above-ground pipeline features of ISDs were measured using camera traps and compared to expected caribou crossing rates based on present-day caribou movement simulations. Current crossing rates were evaluated within the context of predicted future crossing success rates necessary to maintain caribou step lengths and home ranges. With few exceptions, permeability across ISDs was the main factor affecting caribou movement, more so than spacing between developments or the presence of protected areas. However, minimal permeability (crossing rates of c. 15% to 60%, relative to an undisturbed site was needed to maintain existing home range size and step lengths. The effect of permeability on home range size and step length was non-linear, suggesting that small increases in permeability would provide a disproportionately greater benefit to caribou movement. Our predictions demonstrate that maintaining permeability across ISDs is more important than spacing between leases or including protected areas, and thus provides clear direction for mitigation efforts for features that will exist on the landscape for decades to come

caribou_movement_simulation_20140810

Simulated caribou movement location output for each scenario

Co-occurrence of species at camera sites as determined by non-metric multidimensional scaling (NMS) ordination of species counts at camera sites in southwest Alberta, Canada during the summer of 2008.

<p>Ordinations along axis one are indicated. Location along axis one where the NMS score equals zero is indicated by a vertical dashed line.</p

Regression tree analysis of large mammalian prey counts at camera sites in southwest Alberta, Canada during the summer of 2008.

<p>For each partition of the tree (indicated by arrows), the explanatory variable is shown with the value that best determines the partition (i.e., the cut-off point that maximizes homogeneity within a group). Indicated at each node are the number of cameras in the group and the mean number of prey photographs per 100 days (with standard deviation in parentheses).</p

Dendrogram of the hierarchical cluster analysis of species presence/absence data that illustrates co-occurrence of species at camera sites in southwest Alberta, Canada during the summer of 2008.

<p>The dendrogram is scaled with the percentage of information remaining in the analysis, where less information remaining indicates a weaker association between species.</p