Daniel T. Blumstein

Fear in animals: a meta-analysis and review of risk assessment

The amount of risk animals perceive in a given circumstance (i.e. their degree of ‘fear’) is a difficult motivational state to study. While many studies have used flight initiation distance as a proxy for fearfulness and examined the factors influencing the decision to flee, there is no general understanding of the relative importance of these factors. By identifying factors with large effect sizes, we can determine whether anti-predator strategies reduce fear, and we gain a unique perspective on the coevolution of predator and anti-predator behaviour. Based on an extensive review and formal meta-analysis, we found that predator traits that were associated with greater risk (speed, size, directness of approach), increased prey distance to refuge and experience with predators consistently amplified the perception of risk (in terms of flight initiation distance). While fish tolerated closer approach when in larger schools, other taxa had greater flight initiation distances when in larger groups. The presence of armoured and cryptic morphologies decreased perception of risk, but body temperature in lizards had no robust effect on flight initiation distance. We find that selection generally acts on prey to be sensitive to predator behaviour, as well as on prey to modify their behaviour and morphology.

Coupled dynamics of body mass and population growth in response to environmental change

Environmental change has altered the phenology, morphological traits and population dynamics of many species. However, the links underlying these joint responses remain largely unknown owing to a paucity of long-term data and the lack of an appropriate analytical framework. Here we investigate the link between phenotypic and demographic responses to environmental change using a new methodology and a long-term (1976–2008) data set from a hibernating mammal (the yellow-bellied marmot) inhabiting a dynamic subalpine habitat. We demonstrate how earlier emergence from hibernation and earlier weaning of young has led to a longer growing season and larger body masses before hibernation. The resulting shift in both the phenotype and the relationship between phenotype and fitness components led to a decline in adult mortality, which in turn triggered an abrupt increase in population size in recent years. Direct and trait-mediated effects of environmental change made comparable contributions to the observed marked increase in population growth. Our results help explain how a shift in phenology can cause simultaneous phenotypic and demographic changes, and highlight the need for a theory integrating ecological and evolutionary dynamics in stochastic environments.

Flight-initiation distance in birds is dependent on intruder starting distance

The distance at which animals move away from approaching threats (often quantified as flight-initiation distance [FID], or flush distance) has been used by behavioral ecologists to understand the economics of antipredator behavior. Wildlife managers often use FID when seeking to develop set-back distances to reduce human impacts on wildlife. Economic models of escape behavior predict that escape decisions will be dynamic and will be influenced by both the costs and benefits of remaining. In contrast, wildlife managers often aim to generate a single set-back distance for each species. While a number of factors are acknowledged to influence FID, the starting distance between the observer and the animal is typically ignored in FID studies. For 64 of 68 species of Australian birds, I found a significant positive relationship between starting distance and FID. This demonstrates that, as predicted by economic models, species generally assess risk dynamically and flush at a greater distance as starting distances increase. My finding is consistent with the idea that animals accrue an attentional cost for continued monitoring of an approaching predator. Researchers or managers aiming to quantify human impact using FID should use starting distance as a covariate.

Behaviour and conservation

Part I. Introduction: 1. Advances in the study of behaviour and their role in conservation William J. Sutherland and L. Morris Gosling Part II. Conservation Impact of People: 2. The evolutionary ecology of human population growth Ruth Mace 3. Grassland conservation and the pastoralist commons Monique Borgerhoff Mulder and Lore M. Ruttan 4. Predicting the consequences of human disturbance from behavioral decisions Jennifer A. Gill and William J. Sutherland 5. The role of behavioural models in predicting the ecological impact of harvesting John D. Goss-Custard, Richard Stillman, Andrew D. West, Selwyn McGrorty, Sarah E. A. le V. dit Durell and Richard W. C. Caldow Part III. Habitat Loss and Fragmentation: 6. Butterfly movement and conservation in patchy landscapes Chris D. Thomas, Michel Baguette and Owen T. Lewis 7. Life history characteristics and the conservation of migratory shorebirds Theunis Piersma and Alan J. Baker 8. Ranging behaviour and vulnerability to extinction in carnivores Rosie Woodroffe and Joshua R. Ginsburg 9. Habitat fragmentation and swarm raiding army ants Graeme P. Boswell, Nigel R. Franks and Nick F. Britton Part IV. Sexual Selection, Threats and Population Viability: 10. Sexual selection and conservation Anders Pape Moller 11. Dispersal patterns, social organisation and population viability Sarah Durant 12. Incorporating behaviour in predictive models for conservation Richard A. Pettifor, Ken J. Norris and J. Marcus Rowcliffe 13. Controversy over behaviour and genetics in cheetah conservation Tim Caro 14. The role of animal behaviour in marine conservation John D. Reynolds and Simon Jennings Part V. Conservation Applications of Behaviour: 15. Communication behaviour and conservation Peter K. McGregor, Thomas M. Peake and Gillian Gilbert 16. Reducing predation through conditioned taste aversion David P. Cowan, Jonathon C. Reynolds and Elaine L. Gill 17. Retaining natural behaviour in captivity and in reintroduction programmes Michael P. Wallace 18. Consequences of social perturbation for wildlife management and conservation Frank A. M. Tuyttens and David W. Macdonald 19. Animal welfare and wildlife conservation Elizabeth L. Bradshaw and Patrick Bateson Bibliography Index.

Rules of Thumb for Predation Hazard Assessment: Predictions from a Dynamic Model

Before an animal can evaluate the benefits and costs associated with a particular behavior, it must first assess them. Since perfect information is impossible to acquire, it has been suggested that animals use simple rules of thumb to acquire information. The use of rules, however, may lead to substantially inaccurate perceptions. In this article, we present the results of a dynamic optimization model developed to study the opportunity for the evolution of rules of thumb for predation hazard assessment. There are four main conclusions from this model. First, selection will not always favor perfect estimates, if one assumes there is some cost in acquiring accurate information. There is a zone of tolerance where inaccurate perceptions perform just as well as perfect knowledge of predation hazard. This implies that animals need not have perfect, only sufficient, information in order to behave optimally. Second, this zone of tolerance is generally shifted toward overestimating predation hazard: animals that overestimate hazard will have a lower mortality than animals that underestimate hazard. Third, animals should attempt to track fluctuating predation hazard rather than act on the average predation hazard. Finally, the model is robust: several simplying assumptions can be relaxed, and the same general conclusions are reached. We suggest instances where animals are using simple rules to assess predation hazard and outline an experimental protocol to study the use of rules of thumb for predation hazard assessment.

Alarm calling in yellow-bellied marmots: I. The meaning of situationally variable alarm calls

Abstract Yellow-bellied marmots, Marmota flaviventris were reported to produce qualitatively different alarm calls in response to different predators. To test this claim rigorously, yellow-bellied marmot alarm communication was studied at two study sites in Colorado and at one site in Utah. Natural alarm calls were observed and alarm calls were artificially elicited with trained dogs, a model badger, a radiocontrolled glider and by walking towards marmots. Marmots ‘whistled’, ‘chucked’ and ‘trilled’ in response to alarming stimuli. There was no evidence that either of the three call types, or the acoustic structure of whistles, the most common alarm call, uniquely covaried with predator type. Marmots primarily varied the rate, and potentially a few frequency characteristics, as a function of the risk the caller experienced. Playback experiments were conducted to determine the effects of call type (chucks versus whistles), whistle rate and whistle volume on marmot responsiveness. Playback results suggested that variation in whistle number/rate could communicate variation in risk. No evidence was found of intraspecific variation in the mechanism used to communicate risk: marmots at all study sites produced the same vocalizations and appeared to vary call rate as a function of risk. There was significant individual variation in call structure, but acoustic parameters that were individually variable were not used to communicate variation in risk.

Learning specificity in acquired predator recognition

Predator recognition is often dependent upon experience. This behavioural plasticity can potentially be exploited to enhance the antipredator behaviour of captive-bred animals, but it is first necessary to understand the specificity of learning. We enhanced the responses of tammar wallabies, Macropus eugenii, to a model fox, Vulpes vulpes, by presenting this novel predator in conjunction with a human simulating a capture procedure. A control group had identical total exposure to fox and human, but with no such predictive relationship between these two events. Animals that experienced paired presentations of fox and human behaved more cautiously towards the fox after training than controls. To assess whether this learnt response was specific to the fox, we presented the animals with an array of visual stimuli both before and after training. The tammars generalized their acquired response from the predator with which they were trained to a predator with which they were not trained (cat, Felis catus), but not to a nonpredator (goat, Capra hircus). Tammars also exhibited a transient increase in response to a model wallaby after training. We suggest that this effect is more likely to reflect social behaviour than generalization of the learnt response from predator to conspecific. Two additional controls revealed that changes in behaviour after training were not attributable to the presentation device and were not caused by a general decrease in response threshold associated with training. Our results suggest that tammar wallabies perceive predators as a natural category.

Does sociality drive the evolution of communicative complexity? A comparative test with ground-dwelling sciurid alarm calls

While sociality has been hypothesized to drive the evolution of communicative complexity, the relationship remains to be formally tested. We derive a continuous measure of social complexity from demographic data and use this variable to explain variation in alarm repertoire size in ground‐dwelling sciurid rodents (marmots, Marmota spp.; prairie dogs, Cynomys spp.; and ground squirrels, Spermophilus spp.). About 40% of the variation in alarm call repertoire size was explained by social complexity in the raw data set. To determine the degree to which this relationship may have been influenced by historical relationships between species, we used five different phylogenetic hypotheses to calculate phylogenetically independent contrasts. Less variation was significantly explained in contrast‐based analyses, but a general positive relationship remained. Social complexity explained more variation in alarm call repertoire size in marmots, while sociality explained no variation in repertoire size in prairie dogs and no variation in phylogenetically based analyses of squirrels. In most cases, substantial variation remained unexplained by social complexity. We acknowledge that factors other than social complexity, per se, may contribute to the evolution of alarm call repertoire size in sciurid rodents, and we discuss alternative hypotheses. Our measure of social complexity could be used by other researchers to test explicit evolutionary hypotheses that involve social complexity.

Testing a key assumption of wildlife buffer zones: is flight initiation distance a species-specific trait?

Abstract The distance at which animals flee an approaching predator is known as the ‘flight initiation distance’ (FID). Wildlife managers use FID to develop buffer zones to reduce human impacts on wildlife. Many variables have been demonstrated to influence FID leading one to question whether it can be viewed as a species-specific trait. We tested this critical assumption for developing buffer zones by experimentally approaching eight species of shorebirds found at six sites around Botany Bay, 15 km south of Sydney, Australia. Botany Bay encompasses a range of human impacted areas, from urban developments with high levels of human presence, through to National Parks and wildlife protection areas where human presence is significantly lower. We found that both species and site influenced the distance birds flew away from an approaching human. Importantly, however, there was no significant statistical interaction between site and species demonstrating that ‘flighty’ species were consistently flighty while more tolerant species were consistently tolerant. Taken together, these results suggest that FID can therefore be viewed as a species-specific trait for these shorebirds. The great variability in FID suggests that wildlife managers should be somewhat conservative in developing buffer zones, but they can use previously published FID data for a given species as guidelines for setting buffer zones.

The loss of anti-predator behaviour following isolation on islands.

When isolated from predators, costly and no longer functional anti-predator behaviour should be selected against. Predator naiveté is often pronounced on islands, where species are found with few or no predators. However, isolation on islands involves other processes, such as founder effects, that might be responsible for naiveté or reduced anti-predator behaviour. We report the first comparative evidence that, in macropodid marsupials, isolation on islands may lead to a systematic loss of ‘group size effects’—a behaviour whereby individuals reduce anti-predator vigilance and allocate more time to foraging as group size increases. Moreover, insular animals forage more, and are less vigilant, than mainland ones. However, we found no evidence that animals on the mainland are ‘flightier’ than those on islands. Remarkably, we also found no evidence that isolation from all predators per se is responsible for these effects. Together, these results demonstrate that anti-predator behaviour may indeed be lost or modified when animals are isolated on islands, but it is premature to assume that all such behaviour is affected.