Prey habitat selection under shared predation: tradeoffs between risk and competition?

Vijayan, Sundararaj; Morris, Douglas W.; McLaren, Brian

doi:10.1111/j.1600-0706.2011.19906.x

Cited by 15 publications

(16 citation statements)

References 38 publications

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“…This is consistent with previous research in a variety of animal taxa (Roberts 1996, Fortin et al 2004, Pays et al 2012, Sorato et al 2012, Vijayan et al 2012, Olson et al 2015. With respect to small-to medium-sized groups, higher rates of foraging with increasing group size could have been a consequence of reduced vigilance, which thereby enabled fish to devote more time to feeding.…”

Section: Discussionsupporting

confidence: 91%

“…With respect to small-to medium-sized groups, higher rates of foraging with increasing group size could have been a consequence of reduced vigilance, which thereby enabled fish to devote more time to feeding. responsible for diminished foraging returns (Moody and Ruxton 1996, Bednekoff and Lima 2004, Vijayan et al 2012. Larger group sizes (those with lower foraging returns), food scarcity, and competition (exploitative or interference) may have been Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Among the benefits of grouping behavior are minimizing energy expenditure in the search for food (Pitcher et al 1982), reducing predation risk in high-risk habitats (Lima and Dill 1990, Wrona and Dixon 1991, Cresswell 1994, Lima et al 1999, Cresswell and Quinn 2011, Creel et al 2014, and enabling predators to capture large prey that would otherwise be difficult to secure by any one individual Creel 1995, Courchamp andMacdonald 2001). Costs to individuals in groups may include lower reproductive and developmental rates (Borries et al 2008), reduced food availability (Vijayan et al 2012), and more intense competition between conspecifics leading to a reduction in per capita consumption (Moody andRuxton 1996, Beauchamp 1998).…”

Section: Introductionmentioning

confidence: 99%

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Maximizing foraging success: the roles of group size, predation risk, competition, and ontogeny

Hintz

Lonzarich

2018

Ecosphere

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Grouping is an evolutionary strategy that allows individuals to optimize foraging success in habitats of varying quality and when under the risk of predation, but group foraging can lead to competition between group members. The effects of group size, habitat, predation, and competition on foraging success also can change as animals grow. Our study explored how these concurrent factors influenced the foraging success of group members at two different life stages. In a wild population of coho salmon (Oncorhynchus kisutch), we first tested four hypotheses concerning the effects of group size on foraging success. We then analyzed our field observations with structural equation modeling to test causal relationships between group size, habitat, predation risk, competition, and the foraging success of individuals during two periods of development. We found support for the hypothesis that the relationship between group size and foraging success was parabolic during both study periods, revealing an optimal range of group sizes that maximized individual foraging success, which was conserved as fish aged. Predation risk had a positive effect on group size, particularly for older fish, and distance to cover and water depth were indicators of risk for both age groups. As group size increased, so did competition, but only for young fish; competition only had a weak positive effect on foraging success for older fish. Our results reveal that the relative direct effects of predation risk and competition on foraging success were weak compared with the direct effect of group size. Our study provides new insights and theoretical implications for understanding how selective forces-that is, group size, predation risk, competition, habitat, and ontogeny-act concurrently to affect foraging success in wild populations.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Maximizing foraging success: the roles of group size, predation risk, competition, and ontogeny

Hintz

Lonzarich

2018

Ecosphere

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“…Presence of livestock did not reduce the time vicuñas spent vigilant at any density, unlike the conclusion of Vijayan et al. () for spotted deer. In fact, in the RW region of the CFPR, vigilance was more frequent and flight occurred with longer approach distances where livestock were present.…”

Section: Discussioncontrasting

confidence: 68%

Livestock and the functional habitat of vicuñas in Ecuador: a new puzzle

2018

Self Cite

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Abstract. Whether interactions between wildlife and livestock are competitive or facilitative is context dependent. Intermediary factors that explain how context (seasonal or regional characteristics of the ecological community) affects these interactions are rarely reported. We compared activity time and density in vicuñas (Vicugna vicugna) introduced into the Chimborazo Faunal Production Reserve (CFPR), Ecuador, to describe how they interact with livestock. We compared vicuña density in wetlands and uplands (two landscape structures) with and without livestock (two conditions) using an isodar approach. We measured, over two seasons, vicuña forage abundance, composition, preference and accessibility, time vicuñas spent vigilant, and their flight distances on approach. We tested optimal foraging theory relating to the hypothesis that time mediates behavior, and found that vicuñas were no less frequently vigilant, nor were flight distances greater, during a wet season or in habitats of greater forage abundance and accessibility. We also found no evidence that vicuña behavior was density dependent; instead, we found that more time was spent vigilant by vicuñas when they foraged near livestock in rainy regions during the dry season. Although forage abundance was similar throughout CFPR during a dry season, better forage quality in areas occupied by livestock may constitute an effect of their facilitating vicuñas. A puzzling finding, because it was not explained by any of the other variables we measured, was that at low densities vicuñas selected habitat irrespective of livestock, and where their density was higher, it was doubly so adjacent to livestock. We conclude that in the CFPR, spatial heterogeneity in habitat quality determines the interactions between livestock and vicuñas. To support recommendations that minimize competition between wildlife and livestock, and to expand on descriptions of the contexts that determine the direction of species interactions, future study may require a wider sampling of the densities of sympatric large herbivores in general, and, in the CFPR, a closer resolution of spatial heterogeneity in forage plant quality.

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“…Other potential explanations are available, but less likely to be the main drivers of the whole process. Prey animals under nutritional limitation, especially when living in herds, have been shown to strongly reduce their response to predators , Winnie and Creel 2007, Vijayan et al 2012, but moose in our study area are not likely to experience significant nutritional constraints (Sand et al 2012) or density dependence (Sand et al 2006, Grøtan et al 2009). …”

Section: Discussionmentioning

confidence: 97%

Decomposing risk: Landscape structure and wolf behavior generate different predation patterns in two sympatric ungulates

Gervasi

Sand

Zimmermann³

et al. 2013

Ecological Applications

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Abstract. Recolonizing carnivores can have a large impact on the status of wild ungulates, which have often modified their behavior in the absence of predation. Therefore, understanding the dynamics of reestablished predator-prey systems is crucial to predict their potential ecosystem effects. We decomposed the spatial structure of predation by recolonizing wolves (Canis lupus) on two sympatric ungulates, moose (Alces alces) and roe deer (Capreolus capreolus), in Scandinavia during a 10-year study. We monitored 18 wolves with GPS collars, distributed over 12 territories, and collected records from predation events. By using conditional logistic regression, we assessed the contributions of three main factors, the utilization patterns of each wolf territory, the spatial distribution of both prey species, and fine-scale landscape structure, in determining the spatial structure of moose and roe deer predation risk. The reestablished predator-prey system showed a remarkable spatial variation in kill occurrence at the intra-territorial level, with kill probabilities varying by several orders of magnitude inside the same territory. Variation in predation risk was evident also when a spatially homogeneous probability for a wolf to encounter a prey was simulated. Even inside the same territory, with the same landscape structure, and when exposed to predation by the same wolves, the two prey species experienced an opposite spatial distribution of predation risk. In particular, increased predation risk for moose was associated with open areas, especially clearcuts and young forest stands, whereas risk was lowered for roe deer in the same habitat types. Thus, fine-scale landscape structure can generate contrasting predation risk patterns in sympatric ungulates, so that they can experience large differences in the spatial distribution of risk and refuge areas when exposed to predation by a recolonizing predator. Territories with an earlier recolonization were not associated with a lower hunting success for wolves. Such constant efficiency in wolf predation during the recolonization process is in line with previous findings about the naı¨ve nature of Scandinavian moose to wolf predation. This, together with the human-dominated nature of the Scandinavian ecosystem, seems to limit the possibility for wolves to have large ecosystem effects and to establish a behaviorally mediated trophic cascade in Scandinavia.

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Prey habitat selection under shared predation: tradeoffs between risk and competition?

Cited by 15 publications

References 38 publications

Maximizing foraging success: the roles of group size, predation risk, competition, and ontogeny

Maximizing foraging success: the roles of group size, predation risk, competition, and ontogeny

Livestock and the functional habitat of vicuñas in Ecuador: a new puzzle

Decomposing risk: Landscape structure and wolf behavior generate different predation patterns in two sympatric ungulates

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