Animals experience varying levels of predation risk as they navigate heterogeneous landscapes, and behavioral responses to perceived risk can structure ecosystems. The concept of the landscape of fear has recently become central to describing this spatial variation in risk, perception, and response. We present a framework linking the landscape of fear, defined as spatial variation in prey perception of risk, to the underlying physical landscape and predation risk, and to resulting patterns of prey distribution and antipredator behavior. By disambiguating the mechanisms through which prey perceive risk and incorporate fear into decision making, we can better quantify the nonlinear relationship between risk and response and evaluate the relative importance of the landscape of fear across taxa and ecosystems.

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Landscapes of Fear: Spatial Patterns of Risk Perception and Response

A mechanistic understanding of seed movement and survival is important both for the development of theoretical models of plant population dynamics, spatial spread, and community assembly, and for the conservation and management of plant communities under global change. While models of wind-borne seed dispersal have advanced rapidly over the past two decades, models for animal-mediated dispersal have failed to make similar progress due to their dependence on interspecific interactions and complex, context-dependent behaviours. In this review, we synthesize the literature on seed dispersal and consumption by scatter-hoarding, granivorous rodents and outline a strategy for development of a general mechanistic seed-fate model in these systems. Our review decomposes seed dispersal and survival into six distinct sub-processes (exposure, harvest, allocation, preparation, placement, and recovery), and identifies nine intermediate (latent) variables that link physical state variables (e.g. seed and animal traits, habitat structure) to decisions regarding seed allocation to hoarding or consumption, cache placement and management, and deployment of radicle-pruning or embryo excision behaviours. We also highlight specific areas where research on these intermediate relationships is needed to improve our mechanistic understanding of scatter-hoarder behaviour. Finally, we outline a strategy to combine detailed studies on individual functional relationships with seed-tracking experiments in an iterative, hierarchical Bayesian framework to construct, refine, and test mechanistic models for context-dependent, scatter-hoarder-mediated seed fate.

Seed fate and decision‐making processes in scatter‐hoarding rodents

Fear of predation can have major impacts on the behaviour of prey species. Recently the concept of the ecology of fear has been defined and formalised; yet there has been relatively little focus on how these ideas apply to large carnivore species which, although not prey sensu stricto, also experience fear as a result of threats from humans. Large carnivores are likely also subject to a Landscape of Fear similar to that described for prey species. We argue that although fear is generic, ‘human-caused mortality’ represents a distinct and very important cause of fear for large carnivores, particularly terrestrial large carnivores as their activities overlap with those of humans to a greater degree. We introduce the idea of a ‘Landscape of Coexistence’ for large carnivores to denote a subset of the Landscape of Fear where sufficient areas of low human-caused mortality risk are present in the landscape for long term coexistence of large carnivores and humans. We then explore aspects of terrestrial large carnivore behavioural ecology that may be best explained by risk of human-caused mortality, and how the nature of a Landscape of Coexistence for these large carnivores is likely to be shaped by specific factors such as habitat structure, wild and domestic prey base, and human distribution and behaviour. The human characteristics of this Landscape of Coexistence may be as important in determining large carnivore distribution and behavioural ecology as the distribution of resources. Understanding the Landscape of Coexistence for terrestrial large carnivores is therefore important for their biology and conservation throughout large parts of their remaining ranges.




Synthesis



The Landscape of Fear concept describing the relationship between predator and prey also applies to the relationship between humans and top carnivores. We synthesise current research to introduce the Landscape of Coexistence concept, arguing that top predators respond to the risks of human-caused mortality through spatiotemporal partitioning of activities to reduce contact with people. The character of the Landscape of Coexistence may be more important than the distribution of resources in determining large carnivore distribution and behavioural ecology in human dominated landscapes. Understanding their behavioural responses to human threats is crucial to successful conservation of large carnivores.

Landscapes of Coexistence for terrestrial carnivores: the ecological consequences of being downgraded from ultimate to penultimate predator by humans

Novel perspectives on bat insectivory highlight the value of this ecosystem service in farmland: Research frontiers and management implications

Summary


Herbivores frequently have to make trade-offs between two basic needs: the need to acquire forage and the need to avoid predation. One manifestation of this trade-off is the ‘landscape of fear’ phenomenon – wherein herbivores avoid areas of high perceived predation risk even if forage is abundant or of high quality in those areas. Although this phenomenon is well established among invertebrates, its applicability to terrestrial large herbivores remains debated, in part because experimental evidence is scarce.
This study was designed to (i) experimentally test the effects of tree density – a key landscape feature associated with predation risk for African ungulates – on herbivore habitat use and (ii) establish whether habitat use patterns could be explained by trade-offs between foraging opportunities and predation risk avoidance.
In a Kenyan savanna system, replicate plots dominated by the tree Acacia drepanolobium were cleared, thinned or left intact. Ungulate responses were measured over four years, which included years of moderate rainfall as well as a severe drought.
Under average rainfall conditions, most herbivores (primarily plains zebra, Grant's gazelle and hartebeest) favoured sites with fewer trees and higher visibility – regardless of grass production – while elephants (too large to be vulnerable to predation) favoured sites with many trees. During the drought, however, herbivores favoured sites that had high grass biomass, but not high visibility. Thus, during the drought, herbivores sought areas where food was more abundant, despite probable higher risk of predation.
These results illustrate that the ‘landscape of fear’, and the associated interactions between top-down and bottom-up effects, is not static, but rather shifts markedly under different conditions. Climate thus has the potential to alter the strength and spatial dynamics of behaviourally mediated cascades in large herbivore systems.

https://besjournals.onlinelibrary.wiley.com/doi/epdf/10.1111/1365-2656.12262

Climate and the landscape of fear in an African savanna.

Identifying factors that may be responsible for regulating the size of animal populations is a cornerstone in understanding population ecology. The main factors that are thought to influence population size are either resources (bottom-up), or predation (top-down), or interspecific competition (parallel). However, there are highly variable and often contradictory results regarding their relative strengths and influence. These varied results are often interpreted as indicating "shifting control" among the three main factors, or a complex, nonlinear relationship among environmental variables, resource availability, predation, and competition. We argue here that there is a "missing link" in our understanding of predator-prey dynamics. We explore whether the landscape-of-fear model can help us clarify the inconsistencies and increase our understanding of the roles, extent, and possible interactions of top-down, bottom-up, and parallel factors on prey population abundance. We propose two main predictions derived from the landscape-of-fear model: (1) for a single species, we suggest that as the makeup of the landscape of fear changes from relatively safe to relatively risky, bottom-up impacts switch from strong to weak as top-down impacts go from weak to strong; (2) for two or more species, interspecific competitive interactions produce various combinations of bottom-up, top-down, and parallel impacts depending on the dominant competing species and whether the landscapes of fear are shared or distinctive among competing species. We contend that these predictions could successfully explain many of the complex and contradictory results of current research. We test some of these predictions based on long-term data for small mammals from the Chihuahuan Desert in the United States, and Mexico. We conclude that the landscape-of-fear model does provide reasonable explanations for many of the reported studies and should be tested further to better understand the effects of bottom-up, top-down, and parallel factors on population dynamics.

Perla López Medina

Papers

The landscape of fear: the missing link to understand top-down and bottom-up controls of prey abundance?