@article{EccardMendesFerreiraPeredoArceetal.2022,
  author    = {Eccard, Jana and Mendes Ferreira, Clara and Peredo Arce, Andres and Dammhahn, Melanie},
  title     = {Top-down effects of foraging decisions on local, landscape and regional biodiversity of resources (DivGUD)},
  series = {Ecology letters},
  volume    = {25},
  journal   = {Ecology letters},
  number    = {1},
  publisher = {Wiley-Blackwell},
  address   = {Oxford [u.a.]},
  issn      = {1461-0248},
  doi       = {10.1111/ele.13901},
  pages     = {3 -- 16},
  year      = {2022},
  abstract  = {Foraging by consumers acts as a biotic filtering mechanism for biodiversity at the trophic level of resources. Variation in foraging behaviour has cascading effects on abundance, diversity, and functional trait composition of the community of resource species. Here we propose diversity at giving-up density (DivGUD), i.e. when foragers quit exploiting a patch, as a novel concept and simple measure quantifying cascading effects at multiple spatial scales. In experimental landscapes with an assemblage of plant seeds, patch residency of wild rodents decreased local alpha-DivGUD (via elevated mortality of species with large seeds) and regional gamma-DivGUD, while dissimilarity among patches in a landscape (beta-DivGUD) increased. By linking theories of adaptive foraging behaviour with community ecology, DivGUD allows to investigate cascading indirect predation effects, e.g. the ecology-of-fear framework, feedbacks between functional trait composition of resource species and consumer communities, and effects of inter-individual differences among foragers on the biodiversity of resource communities.},
  language  = {en}
}
@article{SchlaegelMerrillLewis2017,
  author    = {Schl{\"a}gel, Ulrike E. and Merrill, Evelyn H. and Lewis, Mark A.},
  title     = {Territory surveillance and prey management: Wolves keep track of space and time},
  series = {Ecology and evolution},
  volume    = {7},
  journal   = {Ecology and evolution},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {2045-7758},
  doi       = {10.1002/ece3.3176},
  pages     = {8388 -- 8405},
  year      = {2017},
  abstract  = {Identifying behavioral mechanisms that underlie observed movement patterns is difficult when animals employ sophisticated cognitive\&\#8208;based strategies. Such strategies may arise when timing of return visits is important, for instance to allow for resource renewal or territorial patrolling. We fitted spatially explicit random\&\#8208;walk models to GPS movement data of six wolves (Canis lupus; Linnaeus, 1758) from Alberta, Canada to investigate the importance of the following: (1) territorial surveillance likely related to renewal of scent marks along territorial edges, to reduce intraspecific risk among packs, and (2) delay in return to recently hunted areas, which may be related to anti\&\#8208;predator responses of prey under varying prey densities. The movement models incorporated the spatiotemporal variable "time since last visit," which acts as a wolf's memory index of its travel history and is integrated into the movement decision along with its position in relation to territory boundaries and information on local prey densities. We used a model selection framework to test hypotheses about the combined importance of these variables in wolf movement strategies. Time\&\#8208;dependent movement for territory surveillance was supported by all wolf movement tracks. Wolves generally avoided territory edges, but this avoidance was reduced as time since last visit increased. Time\&\#8208;dependent prey management was weak except in one wolf. This wolf selected locations with longer time since last visit and lower prey density, which led to a longer delay in revisiting high prey density sites. Our study shows that we can use spatially explicit random walks to identify behavioral strategies that merge environmental information and explicit spatiotemporal information on past movements (i.e., "when" and "where") to make movement decisions. The approach allows us to better understand cognition\&\#8208;based movement in relation to dynamic environments and resources.},
  language  = {en}
}
@article{SteinhoffWarfenVoigtetal.2020,
  author    = {Steinhoff, Philip O. M. and Warfen, Bennet and Voigt, Sissy and Uhl, Gabriele and Dammhahn, Melanie},
  title     = {Individual differences in risk-taking affect foraging across different landscapes of fear},
  series = {Oikos},
  volume    = {129},
  journal   = {Oikos},
  number    = {12},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0030-1299},
  doi       = {10.1111/oik.07508},
  pages     = {1891 -- 1902},
  year      = {2020},
  abstract  = {One of the strongest determinants of behavioural variation is the tradeoff between resource gain and safety. Although classical theory predicts optimal foraging under risk, empirical studies report large unexplained variation in behaviour. Intrinsic individual differences in risk-taking behaviour might contribute to this variation. By repeatedly exposing individuals of a small mesopredator to different experimental landscapes of risks and resources, we tested 1) whether individuals adjust their foraging behaviour according to predictions of the general tradeoff between energy gain and predation avoidance and 2) whether individuals differ consistently and predictably from each other in how they solve this tradeoff. Wild-caught individuals (n = 42) of the jumping spiderMarpissa muscosa, were subjected to repeated release and open-field tests to quantify among-individual variation in boldness and activity. Subsequently, individuals were tested in four foraging tests that differed in risk level (white/dark background colour) and risk variation (constant risk/variable risk simulated by bird dummy overflights) and contained inaccessible but visually perceivable food patches. When exposed to a white background, individuals reduced some aspects of movement and foraging intensity, suggesting that the degree of camouflage serves as a proxy of perceived risk in these predators. Short pulses of acute predation risk, simulated by bird overflights, had only small effects on aspects of foraging behaviour. Notably, a significant part of variation in foraging was due to among-individual differences across risk landscapes that are linked to consistent individual variation in activity, forming a behavioural syndrome. Our results demonstrate the importance of among-individual differences in behaviour of animals that forage under different levels of perceived risk. Since these differences likely affect food-web dynamics and have fitness consequences, future studies should explore the mechanisms that maintain the observed variation in natural populations.},
  language  = {en}
}
@article{MendesFerreiraDammhahnEccard2022,
  author    = {Mendes Ferreira, Clara and Dammhahn, Melanie and Eccard, Jana},
  title     = {Forager-mediated cascading effects on food resource species diversity},
  series = {Ecology and Evolution},
  volume    = {12},
  journal   = {Ecology and Evolution},
  number    = {11},
  publisher = {John Wiley \& Sons},
  issn      = {2045-7758},
  doi       = {10.1002/ece3.9523},
  pages     = {13},
  year      = {2022},
  abstract  = {Perceived predation risk varies in space and time. Foraging in this landscape of fear alters forager-resource interactions via cascading nonconsumptive effects. Estimating these indirect effects is difficult in natural systems. Here, we applied a novel measure to quantify the diversity at giving-up density that allows to test how spatial variation in perceived predation risk modifies the diversity of multispecies resources at local and regional spatial levels. Furthermore, we evaluated whether the nonconsumptive effects on resource species diversity can be explained by the preferences of foragers for specific functional traits and by the forager species richness. We exposed rodents of a natural community to artificial food patches, each containing an initial multispecies resource community of eight species (10 items each) mixed in sand. We sampled 35 landscapes, each containing seven patches in a spatial array, to disentangle effects at local (patch) and landscape levels. We used vegetation height as a proxy for perceived predation risk. After a period of three nights, we counted how many and which resource species were left in each patch to measure giving-up density and resource diversity at the local level (alpha diversity) and the regional level (gamma diversity and beta diversity). Furthermore, we used wildlife cameras to identify foragers and assess their species richness. With increasing vegetation height, i.e., decreasing perceived predation risk, giving-up density, and local alpha and regional gamma diversity decreased, and patches became less similar within a landscape (beta diversity increased). Foragers consumed more of the bigger and most caloric resources. The higher the forager species richness, the lower the giving-up density, and alpha and gamma diversity. Overall, spatial variation of perceived predation risk of foragers had measurable cascading effects on local and regional resource species biodiversity, independent of the forager species. Thus, nonconsumptive predation effects modify forager-resource interactions and might act as an equalizing mechanism for species coexistence.},
  language  = {en}
}
@article{EccardLiesenjohannDammhahn2020,
  author    = {Eccard, Jana and Liesenjohann, Thilo and Dammhahn, Melanie},
  title     = {Among-individual differences in foraging modulate resource exploitation under perceived predation risk},
  series = {Oecologia},
  volume    = {194},
  journal   = {Oecologia},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {0029-8549},
  doi       = {10.1007/s00442-020-04773-y},
  pages     = {621 -- 634},
  year      = {2020},
  abstract  = {Foraging is risky and involves balancing the benefits of resource acquisition with costs of predation. Optimal foraging theory predicts where, when and how long to forage in a given spatiotemporal distribution of risks and resources. However, significant variation in foraging behaviour and resource exploitation remain unexplained. Using single foragers in artificial landscapes of perceived risks and resources with diminishing returns, we aimed to test whether foraging behaviour and resource exploitation are adjusted to risk level, vary with risk during different components of foraging, and (co)vary among individuals. We quantified foraging behaviour and resource exploitation for 21 common voles (Microtus arvalis). By manipulating ground cover, we created simple landscapes of two food patches varying in perceived risk during feeding in a patch and/or while travelling between patches. Foraging of individuals was variable and adjusted to risk level and type. High risk during feeding reduced feeding duration and food consumption more strongly than risk while travelling. Risk during travelling modified the risk effects of feeding for changes between patches and resulting evenness of resource exploitation. Across risk conditions individuals differed consistently in when and how long they exploited resources and exposed themselves to risk. These among-individual differences in foraging behaviour were associated with consistent patterns of resource exploitation. Thus, different strategies in foraging-under-risk ultimately lead to unequal payoffs and might affect lower trophic levels in food webs. Inter-individual differences in foraging behaviour, i.e. foraging personalities, are an integral part of foraging behaviour and need to be fully integrated into optimal foraging theory.},
  language  = {en}
}