Predation has long been implicated as a major selective force in the evolution of several morphological and behavioral characteristics of animals. The importance of predation during evolutionary ti...

Behavioral decisions made under the risk of predation: a review and prospectus

1. Introduction and Overview. 2. Detecting Influential Observations and Outliers. 3. Detecting and Assessing Collinearity. 4. Applications and Remedies. 5. Research Issues and Directions for Extensions. Bibliography. Author Index. Subject Index.

Regression Diagnostics: Identifying Influential Data and Sources of Collinearity

Agricultural intensification has led to a widespread decline in farmland biodiversity measured across many different taxa. The changes in agricultural practices affect many different aspects of the farmland habitat, but agricultural industry, policy and much previous research has tended to be concerned with specific sectors or practices (e.g. pesticide use or cereal husbandry). Here, we review the empirical literature to synthesize the research effort that has been directed to investigate specific practices or goals to make general statements regarding the causes and consequences of farmland biodiversity decline. We argue that the loss of ecological heterogeneity at multiple spatial and temporal scales is a universal consequence of multivariate agricultural intensification and, therefore, that future research should develop cross-cutting policy frameworks and management solutions that recreate that heterogeneity as the key to restoring and sustaining biodiversity in temperate agricultural systems.

https://www.cell.com/trends/ecology-evolution/pdf/S0169-5347(03)00011-9.pdf

Farmland biodiversity: is habitat heterogeneity the key?

Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.

Citation classic - optimal foraging - a selective review of theory and tests

In the Hamadryas baboon, males are substantially larger than females. A troop of baboons is subdivided into a number of ‘one-male groups’, consisting of one adult male and one or more females with their young. The male prevents any of ‘his’ females from moving too far from him. Kummer (1971) performed the following experiment. Two males, A and B, previously unknown to each other, were placed in a large enclosure. Male A was free to move about the enclosure, but male B was shut in a small cage, from which he could observe A but not interfere. A female, unknown to both males, was then placed in the enclosure. Within 20 minutes male A had persuaded the female to accept his ownership. Male B was then released into the open enclosure. Instead of challenging male A , B avoided any contact, accepting A’s ownership.

Evolution and the Theory of Games

A growing number of studies quantify the impact of nonlethal human disturbance on the behavior and reproductive success of animals. Athough many are well designed and analytically sophisticated, most lack a theoretical framework for making predictions and for understanding why particular responses occur. Behavioral ecologists have recently begun to fill this theoretical vacuum by applying economic models of antipredator behavior to disturbance studies. In this emerging paradigm, predation and nonlethal disturbance stimuli create similar trade-offs between avoiding perceived risk and other fitness-enhancing activities, such as feeding, parental care, or mating. A vast literature supports the hypothesis that antipredator behavior has a cost to other activities, and that this trade-off is optimized when investment in antipredator behavior tracks short-term changes in predation risk. Prey have evolved antipredator responses to generalized threatening stimuli, such as loud noises and rapidly approaching objects. Thus, when encountering disturbance stimuli ranging from the dramatic, lowflying helicopter to the quiet wildlife photographer, animal responses are likely to follow the same economic principles used by prey encountering predators. Some authors have argued that, similar to predation risk, disturbance stimuli can indirectly affect fitness and population dynamics via the energetic and lost opportunity costs of risk avoidance. We elaborate on this argument by discussing why, from an evolutionary perspective, disturbance stimuli should be analogous to predation risk. We then consider disturbance effects on the behavior of individuals—vigilance, fleeing, habitat selection, mating displays, and parental investment—as well as indirect effects on populations and communities. A wider application of predation risk theory to disturbance studies should increase the generality of predictions and make mitigation more effective without over-regulating human activities.

/pdf/human-caused-disturbance-stimuli-as-a-form-of-predation-risk-ro9mekfw7k.pdf

Human-caused Disturbance Stimuli as a Form of Predation Risk

It is well documented that animals take risk of predation into account when making decisions about how to behave in particular situations, often trading-off risk against opportunities for mating or acquiring energy. Such an ability implies that animals have reliable information about the risk of predation at a given place and time. Chemosensory cues are an important source of such information. They reliably reveal the presence of predators (or their presence in the immediate past) and may also provide information on predator activity level and diet. In certain circumstances (e.g., in the dark, for animals in hiding) they may be the only cues available. Although a vast literature exists on the responses of prey to predator chemosensory cues (or odours), these studies are widely scattered, from marine biology to biological control, and not well known or appreciated by behavioural ecologists. In this paper, we provide an exhaustive review of this literature, primarily in tabular form. We highlight so...

The scent of death: Chemosensory assessment of predation risk by prey animals

Publisher Summary The chapter describes a simple economic model that predicts in a qualitative way on how costs (lost feeding opportunity and risk) interact to produce an optimal flight distance from approaching predators. Animals often defer the decision to flee from an approaching predator and continue with their ongoing activities. The view is that, a profitable approach to the problem of why such decisions are deferred, and how they are eventually made, is to view the process as an economic, one in which the relative costs of fleeing and staying change as a predator approaches. It is suggested that the economic approach will prove useful in analyzing many aspects of predator-prey interactions.

The Economics of Fleeing from Predators

Although both food availability and predation risk have been hypothesized to affect dolphin habitat use and group size, no study has measured both factors concurrently to determine their relative influences. From 1997 to 1999, we investigated the effect of food availability and tiger shark (Galeocerdo cuvier) predation risk on bottlenose dolphin (Tursiops aduncus) habitat use and group size in Shark Bay, Western Australia. Food availability was measured by fish trapping, while predation risk was assessed by shark catch rates, acoustic tracks, and Crittercam deployments. Dolphin habitat use was deter- mined using belt transects. The biomass of dolphin prey did not vary seasonally and was significantly greater in shallow habitats than in deeper ones. Tiger sharks were virtually absent during cold months of 1997 and 1998, abundant in warm months of all years, and found at an intermediate density during cold months of 1999. When present, shark density was highest in shallow habitats. Decreased echolocation efficiency in very shallow water and poor visual detection of tiger sharks (camouflaged over seagrass) probably further enhance the riskiness of such habitats, and the relative riskiness of shallow habitats is supported by the observation that dolphins select deep waters in which to rest. The observed dolphin group sizes were consistent with a food-safety trade-off. Groups were larger in more dangerous shallow habitats and larger during resting than during foraging. Foraging dolphins matched the distribution of their food when sharks were absent. However, during warm months, the distribution of foraging dolphins significantly deviated from that of their food, with fewer dolphins foraging in the productive (but dangerous) shallow habitats than expected on the basis of food alone. When shark density was intermediate, habitat use by foraging dolphins was more similar to the high-shark-density seasons than periods of low shark density. These results suggest that foraging dolphin distributions reflect a trade-off between predation risk and food availability. Because the distribution and abundance of tiger sharks are influenced by species other than dolphins, the distribution of the tiger sharks' primary prey may indirectly influence dolphin habitat use, suggesting that it is important to consider the community context in studies of habitat use.

/pdf/food-availability-and-tiger-shark-predation-risk-influence-224h5oxoz4.pdf

Lawrence M. Dill

Papers

Behavioral decisions made under the risk of predation: a review and prospectus

Human-caused Disturbance Stimuli as a Form of Predation Risk

The scent of death: Chemosensory assessment of predation risk by prey animals

The Economics of Fleeing from Predators

Food availability and tiger shark predation risk influence bottlenose dolphin habitat use