The Role of Vertebrate and Invertebrate Predators in a Grasshopper Community

Belovsky, Gary E.; Slade, Jennifer B.

doi:10.2307/3544830

Cited by 117 publications

(101 citation statements)

References 26 publications

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“…Crypsis is determined by complex interactive effects of animal pigmentation pattern, background coloration, ambient light conditions and the visual perceptive abilities of the beholder (e.g., Endler, 1978Endler, , 1990. Birds, which may constitute a selective force on these grasshoppers (Belowsky and Slade, 1993;Forsman and Appelquist, 1999), have a visual spectrum beyond that of humans, including wavelengths within the UV-spectrum (Vorobjev et al, 2001). Although human vision thus may confound our assessment of crypsis, the fact that the gray morph spent most time on the dark brown and least time on the gray background is difficult to reconcile with a pure background matching strategy.…”

Section: Discussionmentioning

confidence: 99%

Differential Habitat Selection by Pygmy Grasshopper Color Morphs; Interactive Effects of Temperature and Predator Avoidance

2006

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Habitat selection behavior is affected by complex interplays between competing requirements. Here we combine field observations with laboratory experiments to examine how thermal benefits and predator avoidance influences habitat selection by different color morphs of the pygmy grasshopper Tetrix undulata. The composition of substrate types and surface temperatures in areas selected by free-ranging individuals did not reflect relative availability, and varied among morphs and sexes. Surface temperatures of selected habitats deviated less from the range of preferred body temperatures than would result from a random utilization of surface temperatures, suggesting that grasshoppers selected habitats with thermal properties which were suitable for maintaining preferred body temperatures. The thermal property of habitats occupied by different color morphs suggests that darker morphs (which absorb more solar radiation) selected cooler habitats to avoid overheating. Dissimilarities in substrate use among color morphs in the field and laboratory emphasize a role also of predator avoidance by background matching for habitat choice. The degree of habitat selectivity was lowest in the striped morph, supporting the notion that a disruptive color pattern may constitute a solution to the trade-off between relative crypsis in different visual backgrounds. Finally, individuals modified their habitat use when subjected to elevated risk of predation, showing that habitat choice is governed by conflicting priorities. Collectively, our findings suggest that, as a result of direct and indirect effects of coloration on performance, alternative color morphs use different solutions to the trade-off between competing requirements. Our results also lend support to the notion that relative fitness of alternative color morphs and sexes may be dependent on microhabitat selection, as predicted by the theory of multiple niche polymorphisms.

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Section: Discussionmentioning

confidence: 99%

Differential Habitat Selection by Pygmy Grasshopper Color Morphs; Interactive Effects of Temperature and Predator Avoidance

2006

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“…However, although density effects are also important in aquatic systems (2, 33, 34), we found little indication that density-mediated effects were important in our experimental study system. This may be the result of our focus on the adult life stage when direct predation may be more prevalent in juvenile stages (17,35,36). Our study nevertheless represents one step toward an integrated evaluation of the food web implications of ontogenetic responses, via behavior-and density-mediated mechanisms, to predation in terrestrial food webs.…”

Section: Discussionmentioning

confidence: 99%

Experimental evidence for a behavior-mediated trophic cascade in a terrestrial food chain

Beckerman

Uriarte

Schmitz

1997

Proc. Natl. Acad. Sci. U.S.A.

334

268

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Predators of herbivorous animals can affect plant populations by altering herbivore density, behavior, or both. To test whether the indirect effect of predators on plants arises from density or behavioral responses in a herbivore population, we experimentally examined the dynamics of terrestrial food chains comprised of old field plants, leafchewing grasshoppers, and spider predators in Northeast Connecticut. To separate the effects of predators on herbivore density from the effects on herbivore behavior, we created two classes of spiders: (i) risk spiders that had their feeding mouth parts glued to render them incapable of killing prey and (ii) predator spiders that remained unmanipulated. We found that the effect of predators on plants resulted from predatorinduced changes in herbivore behavior (shifts in activity time and diet selection) rather than from predator-induced changes in grasshopper density. Neither predator nor risk spiders had a significant effect on grasshopper density relative to a control. This demonstrates that the behavioral response of prey to predators can have a strong impact on the dynamics of terrestrial food chains. The results make a compelling case to examine behavioral as well as density effects in theoretical and empirical research on food chain dynamics.The ecological literature contains numerous examples of the influence of predators on natural communities. A trophic cascade, the indirect interaction between predators and the resources consumed by the predators' prey, has been the focus of much of this attention. In a three-trophic level system comprised of carnivores, herbivores, and plants, a trophic cascade describes an increase in plant abundance that results from carnivore effects on herbivore populations (1-3).Carnivores can affect the impact that herbivores have on plants in two ways (4). They may cause changes in herbivore density through direct consumption of herbivores. This density-mediated effect between predators and plants results from a reduction in the number of herbivores feeding on plants (5-7). Alternatively, the presence of predators in itself represents a risk of predation to herbivores that can mediate predator-plant interactions by altering herbivore prey foraging behavior (4,(8)(9)(10). This behavioral mediation results from reduced feeding time and shifts in diet selection, both of which can cause a decrease in herbivore impact on plants.Increasing evidence suggests that density-and behaviormediated effects may be important causes of trophic cascades (4,(8)(9)(10)(11). Although the existence of prey behavioral responses to predators is well established (4, 12), especially in aquatic systems, there is still little evidence for their effects and importance in terrestrial food web dynamics (4,13). Few studies have even tested for trophic cascades in terrestrial systems (7,(13)(14)(15)(16)(17)(18)(19)(20), in contrast to the multitude of studies in aquatic systems (21).We report on a field study that provides considerable evidence that a trophic casca...

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“…Both forms generate significantly decreased roosting possibilities, which increase the predation risk, while motor mowing also threatens with the direct killing of individuals (Humbert et al 2009(Humbert et al , 2010. Moreover, insects or their eggs are carried off with the mowed grass and the then bared soil is overheated and dried out (Belovsky & Slade 1993;Konvička et al 2005). Our discoveries agree with the situation in regularly mown alpine meadows where only several grasshopper species dominated (e.g., C. parallelus), while bush-crickets had very low individual densities (Marini et al 2008).…”

Section: Discussionmentioning

confidence: 99%

Response of Orthoptera assemblages to management of montane grasslands in the Western Carpathians

2011

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Montane grassy habitats in the Western Carpathians are relatively well preserved, maintain high species richness and are often important in accordance to the nature conservation policy in Europe. However, knowledge about the impact of farming on the habitat quality there is rather poor. The influence of various management types (permanent sheep pen, irregular grazing, mowing) on Orthoptera diversity and species determining assemblages of these habitats were analysed on 72 plots in Poľana Mts Biosphere Reserve. Altogether, 36 Orthoptera species (15 Ensifera, 21 Caelifera) were found, whereas the highest number of species was found on plots with irregular grazing (28 species), followed by plots with mown grass (17) and permanent sheep pens (14). All four measures of the assemblages' diversity confirmed significant differences. Using Discriminant Function Analysis, correct classification rate of Orthoptera assemblages was unambiguous according to the type of management. Each form of the management harboured several characteristic species. Thus implications regarding the biodiversity conservation and grassland management were given.

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The Role of Vertebrate and Invertebrate Predators in a Grasshopper Community

Cited by 117 publications

References 26 publications

Differential Habitat Selection by Pygmy Grasshopper Color Morphs; Interactive Effects of Temperature and Predator Avoidance

Differential Habitat Selection by Pygmy Grasshopper Color Morphs; Interactive Effects of Temperature and Predator Avoidance

Experimental evidence for a behavior-mediated trophic cascade in a terrestrial food chain

Response of Orthoptera assemblages to management of montane grasslands in the Western Carpathians

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