Presence Of Predation Risk Research Articles

Differential Behavioral Responses to Water-Borne Cues to Predation in Two Container-Dwelling Mosquitoes.

Larvae of the mosquito Toxorhynchites rutilus (Coquillett) prey upon other container-dwelling insects, including larvae of Aedes albopictus (Skuse), which is native to Asia but was introduced into the United States, and on the native tree hole mosquito Ochlerotatus triseriatus (Say). Previous work has established that O. triseriatus adopts low-risk behaviors in the presence of predation risk from T. rutilus. It is unknown whether introduced A. albopictus show a similar response to this predator. Behavior of fourth instars of A. albopictus or O. triseriatus was recorded in water that had held either A. albopictus or O. triseriatus larvae alone (control) and in water that had held T. rutilus larvae feeding on either A. albopictus or O. triseriatus (predation). Activity and position of larvae were recorded in 30-min instantaneous scan censuses. In response to water-borne cues to predation, O. triseriatus adopted low-risk behaviors (more resting, less feeding and movement), but A. albopictus did not change its behavior. We also tested the species specificity of the cues by recording the behavior of A. albopictus in water prepared using O. triseriatus and vice versa. O. triseriatus adopted low-risk behaviors even in predation water prepared by feeding T. rutilus with A. albopictus, but A. albopictus did not alter its behavior significantly between predation and control treatments prepared using O. triseriatus. Thus, A. albopictus does not seem to respond behaviorally to cues produced by this predator and may be more vulnerable to predation than is O. triseriatus.

Survival strategies and growth of krill: avoiding predators in space and time

Although Antarctic krill live in a relatively harsh and variable environment, they are extremely abundant and occur across a wide geographic range. Krill are also the dominant prey item for a variety of predators ranging from fish to whales. Thus, krill life histories and survival strategies represent an interesting and biologically relevant theoretical question: How do krill survive and what makes them so successful? The factors that influence krill size and spatial distributions and life- history patterns are not generally understood. We present a conceptual framework for studying krill life histories and patterns of distribution. This approach uses what is known about krill physiology and environmental conditions within an evolutionary framework to increase our understanding of krill distributions and abundance. Using a dynamic state-variable model, we determined the factors predicted to affect the distribution of krill among habitats and feeding behavior of krill. Habitats vary in their associated survival, predation risk, food availability, and metabolic costs. Existing data on variation in temperature, phytoplankton abundance, metabolic costs, growth rates and predator behavior are used to parameterize the model. The model predicts that krill will shrink when experi- encing extreme temperatures or food deprivation (under negative energy budgets), but we also pre- dict that krill may shrink due to predation risk (under positive energy budgets). Furthermore, preda- tion patterns are predicted to strongly influence krill size and spatial distributions. If predation risk is size-dependent, krill are predicted to shrink between reproductive events which reduces predation. Differences between habitats in predation risk may cause krill to shift away from risky habitats even if this slows growth. In the presence of predation risk when feeding, krill are predicted to experience a tradeoff between growth and survival and shift their feeding behavior and habitat distribution accordingly. Differences between habitats in water temperature and travel costs are also predicted to cause size-dependent shifts in habitat use and migration behavior. Our results reinforce the impor- tance of predator behavior on krill life histories, growth, and distributions. Patterns of predation risk may be the key to understanding krill distribution in space, time and size.

Effects of stoat's presence and auditory cues indicating its presence on tree seedling predation by meadow voles

Predators may control the impact of herbivores on their plant resources by 1) decreasing herbivore numbers, 2) imposing predation risk affecting foraging behavior. The goal of the present study was to examine the effects of a predator and auditory cues indicating its presence on the rate of tree seedling (Acer rubrum, Betula lenta) consumption by meadow voles (Microtus pennsylvanicus). The first of our experiments involved introduction of a stoat (Mustela erminea) into an enclosed vole population and the second a playback of recordings of vole distress calls, movements of a stoat and its vocalizations. In both experiments we manipulated vegetation cover and the availability of food next to the experimental seedlings to assess the effects of microhabitat under the different risk situations. The results of the first unreplicated experiment suggested an increased rate of seedling predation in the presence of the stoat. Consistent with these results, the playback of predator sounds in the second replicated experiment caused an increased rate of seedling predation compared to control plots with no recordings. A mowed circle around a seedling station, representing increased risk of predation on the voles, decreased seedling consumption. This effect was modest in the playback treatment. We suggest the results to be due to displacement behavior by the voles exposed to prolonged risk and conflicting demands of foraging and avoiding predators. Alternatively, as suggested by the model of Lima and Bednekoff, prolonged risk of predation forced the voles to decrease their levels of vigilance during low‐risk playback breaks. The modest inhibitory effect of cover removal on seedling predation in the playback treatment is consistent with this interpretation. The results confirm recent evidence for trophic cascades mediated by behavioral interactions between predator and prey. They are novel in suggesting that the presence of predation risk can increase the inhibitory effects of consumers on their resources.