Predation Risk

Every studied animal engages in sleep, and many animals spend much of their lives in this vulnerable behavioural state. We believe that an explicit description of this vulnerability will provide many insights into both the function and architecture (or organization) of sleep. Early studies of sleep recognized this idea, but it has been largely overlooked during the last 20 years. We critically evaluate early models that suggested that the function of sleep is antipredator in nature, and outline a new model in which we argue that whole-brain or ‘blackout’ sleep may be the safest way to sleep given a functionally interconnected brain. Early comparative work also suggested that the predatory environment is an important determinant of sleep architecture. For example, species that sleep in risky environments spend less time in the relatively vulnerable states of sleep. Recent experimental work suggests that mammals and birds shift to relatively vigilant (lighter) states of sleep in response to an increase in perceived risk; these results mirror the influence of stress on sleep in humans and rats. We also outline a conceptual model of sleep architecture in which dynamic changes in sleep states reflect a trade-off between the benefits of reducing a sleep debt and the cost of predation. Overall, many aspects of plasticity in sleep related to predation risk require further study, as do the ways in which sleeping animals monitor predatory threats. More work outside of the dominant mammalian paradigm in sleep is also needed. An ecologically based view of sleeping under the risk of predation will provide an important complement to the traditional physiological and neurological approaches to studying sleep and its functions.

Vertical migration of Daphnia represents the best-studied predator-avoidance behaviour known; yet the mechanisms underlying the choice to migrate require further investigation to understand the role of environmental context. To investigate the optimal habitat choice of Daphnia ...

The role of abiotic and biotic factors in determining the distribution and movement patterns of five species of coarse fish in a shallow eutrophic lake were examined between 1987 and 1990. Early chemical analyses revealed that the lake was mildly eutrophic.

Routine fish sampling showed that although bream, rudd, perch and pike were present, the fish community was numerically dominated by a stunted roach population.

Intraspecific and interspecific variations in habitat use were observed using a combination of radio telemetry, tagging techniques and C.P.U.E. data. Roach, perch and bream displayed flexible patterns of habitat use when compared to rudd and pike. Both rudd and pike showed strong preferences for littoral vegetated habitats, although older individuals of both species were occasionally recovered from open habitats. Juvenile
roach, bream, rudd and perch all occupied the littoral zone during the summer months but only rudd were totally restricted to this habitat. Association and dietary overlap indices revealed that both spatial and diet overlap differs seasonally and within/between species groups. The influence of competitive and predatory interactions on observed
patterns of resource utilization are discussed.

Both temporal and spatial aspects of spawning behaviour were elucidated using C.P.U.E. data for mature fish and radio tracking techniques (for pike only). All species utilized shallow vegetated areas for spawning, however no large scale movements to recognised spawning areas were observed.

Seasonal activity patterns were strongly influenced by temperature, whereas diel activity patterns were largely governed by ambient illumination levels. An analysis of diel temporal activity and foraging patterns revealed that although the feeding activity of visually oriented predators (perch and pike) was restricted to diurnal and crepuscular periods, cyprinids continued to forage at low light levels. Diel horizontal migrations were not observed. Interpecific and Intraspecific variations in the vertical distribution of all species in relation to temperature, oxygen and light levels were also examined.

Laboratory experiments showed that predation risk by piscivorous pike influenced habitat choice and activity levels of potential prey species. The role of abiotic factors/habitat structural complexity and the importance of competitive/predatory interactions in the movement and distribution of fish populations in eutrophic lakes is discussed in relation to the 'trophic cascade' theory and biomanipulation.

This study investigates differences in the δ13Ccol, δ15N, δ13Csc, δ18Osc, Sr/Ca, and Ba/Ca values of juvenile and adult woolly mammoths (Mammuthus primigenius) from Old Crow, Yukon, Canada. The data indicate that nursing in woolly mammoths lasted at least three years, and was associated with minimal decreases in δ13Ccol (~0.2‰), large decreases in δ13Csc (~1.5‰), and large increases in δ15N (~2‰) and δ18Osc (~2‰) values. Sr/Ca and Ba/Ca ratios suggest that woolly mammoth juveniles began consuming plant foods between 2 and 3 “African Elephant Years” of age, much later than the initiation of weaning in modern elephants. We hypothesize that delayed weaning was an adaptation to increased predation risk and decreased food quality/quantity during the extended hours of darkness that occur in winter at high latitudes. Prolonged nursing and delayed weaning may have made mammoths particularly vulnerable to climatic stressors or human hunting.

Aim: Predation on livestock is one of the primary concerns for Mexican wolf (Canis lupus baileyi) recovery because it causes economic losses and negative attitudes toward wolves. Our objectives were to develop a spatial risk model of cattle depredation by Mexican wolves in the USA portion of their recovery area to help reduce the potential for future depredations. Location: Arizona and New Mexico, USA. Methods: We used a presence-only maximum entropy modeling approach (Maxent) to develop a risk model based on confirmed depredation incidents on public lands. In addition to landscape and human variables, we developed a model for annual livestock density using linear regression analysis of Animal Unit Month (AUM), and models for abundance of elk (Cervus canadensis), mule deer (Odocoileus hemionus) and white-tailed deer (Odocoileus virginiana) using Maxent, to include them as biotic variables in the risk model. We followed current recommendations for controlling model complexity and other sources of bias. Results: The primary factors associated with increased risk of depredation by Mexican wolf were higher canopy cover variation and higher relative abundance of elk. Additional factors with increased risk but smaller effect were gentle and open terrain, and greater distances from roads and developed areas. Main conclusions: The risk map revealed areas with relatively high potential for cattle depredations that can inform future expansion of Mexican wolf distribution (e.g., by avoiding hotspots) and prioritize areas for de-predation risk mitigation including the implementation of active non-lethal methods in depredation hotspots. We suggest that livestock be better protected in or moved from potential hotspots, especially during periods when they are vulnerable to depredation (e.g. calving season). Our approach to create natural prey and livestock abundance variables can facilitate the process of spatial risk modeling when limitations in availability of abundance data are a challenge, especially in large-scale studies.

Artificial macrophytes were experimentally deployed in Boadella Reservoir (NE Spain) and assessed for fish use throughout the first 3 months of the 2007 summer drawdown. In total, 1,832 individuals of seven fish species were recorded through visual censuses, with introduced perch Perca fluviatilis being the prevalent species. Fish richness and abundance were significantly higher in artificial macrophytes than in rocky shores and sandy beaches, displaying a unimodal variation through time. P. fluviatilis, Rutilus rutilus and Abramis brama were significantly more abundant in artificial macrophytes than in the other two naturally submersed habitats, where no individuals of these species were recorded. The abundances of Squalius laietanus, Lepomis gibbosus, Micropterus salmoides and Cyprinus carpio were overall greater in artificial macrophytes than in rocky shores but displayed significant habitat × time interactions. A decrease in predation risk was apparently the key-factor of the intensive use of artificial macrophytes by small fish (≤100 mm TL) in Boadella Reservoir, since most species reduced drastically or completely the use of submerged structures when body size increased. This study demonstrates that adding artificial structures mimicking aquatic macrophytes can be an interesting tool to mitigate the adverse effects of water level fluctuations on fish assemblages in structure-less and homogeneous ecosystems, and to understand the mechanisms affecting habitat use and species replacement.

In this study we asked whether, in the context of a trap crop system, differential predation risks among plants influence host choice patterns of adult whiteflies, Bemisia argentifolii. We investigated whether adult whiteflies avoid natural enemies inhabiting poinsettia (a cash crop) and whether this behavior can be used to increase the movement of whiteflies to cucumber (a trap crop). The