Fleshy scoli removed without detriment: structure and potential anti-predation function in a slug caterpillar (Limacodidae)

Anti-predator outgrowths are found prevalent in animals such as stinging spines of caterpillars. However, an encounter with a predator is usually fatal as caterpillars would die easily even if just small body parts were taken. Here, we showed the larvae of Phrixolepia sp. did not get injured when the fleshy but not urticating scoli were removed. By showing the morphologic traits, we assume these particular scoli function as enlarged warning signals and substitute to be attacked so that caterpillars can warn multiple predators, with a lower chance of getting injured when encountering natural enemies, such as birds and carabid beetles.

Warming decreases host survival with multiple parasitoids, but parasitoid performance also decreases

Current global changes are reshaping ecological communities and modifying environmental conditions. We need to recognize the combined impact of these biotic and abiotic factors on species interactions, community dynamics and ecosystem functioning. Specifically, the strength of predator-prey interactions often depends on the presence of other natural enemies: it weakens with competition and interference, or strengthens with facilitation. Such effects of multiple predators on prey are likely to be affected by changes in the abiotic environment, altering top-down control, a key structuring force in both natural and agricultural ecosystems. Here, we investigated how warming alters the effects of multiple predators on prey suppression using a dynamic model coupled with empirical laboratory experiments with Drosophila-parasitoid communities. While the effects of multiple parasitoids on host suppression were the average of the effects of individual parasitoid at ambient temperature, host suppression with multiple parasitoids was higher than expected under warming. Multiple parasitoid species had equivalent effect to multiple individuals of a same species. While multiple parasitoids enhanced top-down control under warming, parasitoid performance generally declined when another parasitoid was present due to competitive interactions, which could reduce top-down control in the long-term. Our study highlights the importance of accounting for interactive effects between abiotic and biotic factors to better predict community dynamics in a rapidly changing world, and better preserve ecosystem functioning and services such as biological control.

Temporal niche partitioning as a novel mechanism promoting co-existence of sympatric predators in marine systems

Niche partitioning of time, space or resources is considered the key to allowing the coexistence of competitor species, and particularly guilds of predators. However, the extent to which these processes occur in marine systems is poorly understood due to the difficulty in studying fine-scale movements and activity patterns in mobile underwater species. Here, we used acceleration data-loggers to investigate temporal partitioning in a guild of marine predators. Six species of co-occurring large coastal sharks demonstrated distinct diel patterns of activity, providing evidence of strong temporal partitioning of foraging times. This is the first instance of diel temporal niche partitioning described in a marine predator guild, and is probably driven by a combination of physiological constraints in diel timing of activity (e.g. sensory adaptations) and interference competition (hierarchical predation within the guild), which may force less dominant predators to suboptimal foraging times to avoid agonistic interactions. Temporal partitioning is often thought to be rare compared to other partitioning mechanisms, but the occurrence of temporal partitioning here and similar characteristics in many other marine ecosystems (multiple predators simultaneously present in the same space with dietary overlap) introduces the question of whether this is a common mechanism of resource division in marine systems.

Inducible responses to antagonistic predation risks are not in a dilemma: Evidences from multi-traits and transcriptome of Ceriodaphnia

Inducible defenses of prey are evolved under diverse and variable predation risks. In the co-evolution of prey and multiple predators with antagonistic selection pressures, whether inducible defense responses of prey will fall into a dilemma and its underlying mechanism are still unclear. Based on the antagonistic predation pressure from invertebrate predator Chaoborus larvae and vertebrate predator fish, we studied multi-traits and transcriptome of the freshwater crustacean Ceriodaphnia cornuta under multiple predation risks. Our results showed that Chaoborus larvae predation risks altered the expression of genes encoding cuticle protein and changed the biosynthesis of steroid hormone, cutin, suberine, and wax, promoting Ceriodaphnia to express horns and grow larger at a late development stage, whereas fish predation risks mainly triggered responses in genes encoding ribosome and pathways of unsaturated fatty acids biosynthesis, cysteine and methionine metabolism, resulting in a smaller individual size and earlier reproduction. The inducible responses on transcription and individual traits both revealed that predator unique responses are dominant and the antagonistic responses are the least. Besides, Pearson correlations between different predator unique responses are extremely weak. Furthermore, the unique individual traits triggered by different predators can be expressed simultaneously. These results indicated that Ceriodaphnia can avoid the dilemma by performing predator unique responses and diverse inducible responses are favored in the co-evolution of zooplankton and multiple predators.

Predicting multi-predator risk to elk (Cervus canadensis) using scats: Are migrant elk exposed to different predation risk?

There is evidence that prey can perceive the risk of predation and alter their behaviour in response, resulting in changes in spatial distribution and potential fitness consequences. Previous approaches to mapping predation risk quantify predator space use to estimate potential predator-prey encounters, yet this approach does not account for successful predator attacks resulting in prey mortality. An exception is a prey kill-site, which reflects an encounter resulting in mortality, but obtaining these data can be expensive and requires time to accumulate adequate sample sizes. We illustrate an alternative approach using predator scat locations and their contents to quantify spatial predation risk for elk (Cervus canadensis) from multiple predators in Alberta, Canada. We combined predictions of scat-based resource selection functions for bears (Ursus arctos/U. americanus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus) based on scat-detection dog surveys with predictions for the probability that a predator-specific scat in a location contained elk. We evaluated our approach by comparing predictions to a predation risk model developed from elk kill sites and applied it to describing spatial patterns in predation risk that were consistent with changes in the distribution of elk over the past decade. We found a strong correlation between risk predicted by kill sites and risk predicted by our approach (r = 0.98, P < 0.001). There was a spatial pattern to predation risk, where elk that migrated east of their winter range were exposed to highest risk from cougars, non-migratory elk were exposed to high risk from wolves and bears, and risk to elk that migrated west of their winter range into protected areas was high only from bears. The patterns in predator risk were consistent with changes in the migratory tactics in this population. The scat-based approach we present permits broad-scale inferences on predation risk for prey.

Predator-specific responses and emergent multi-predator effects on oviposition site choice in grey treefrogs, Hyla chrysoscelis

Predators affect prey through both consumptive and non-consumptive effects (NCEs), and prey typically face threats from multiple simultaneous predators. While different predators have a variety of NCEs on prey, little is known regarding effects of simultaneous multiple predators on demographic habitat selection. Demographic habitat selection is unique among NCEs, especially in discrete habitat patches; decisions directly affect both distribution and abundance of species across habitat patches, rather than simply abundance and performance within patches. Our goal was to determine strength of avoidance responses to multiple species/species combinations of predatory fish, and responses to predator richness. We assessed responses of ovipositing grey treefrogs ( Hyla chrysoscelis ) to three predatory fish species and substitutive combination of species. In single-species treatments, treefrogs avoided only one species, Notemigonus crysoleucas . All two-species combinations, and the three-species combination, were avoided, including the Fundulus chrysotus × Noturus phaeus combination, of which neither were avoided alone. This suggests emergent properties of multiple predators, with potential interactive effects among cues themselves or in the perception of cues by treefrogs. Our results indicate effects of multiple predators are not predictable based on individual effects, and illustrate the importance and complexity of effects of demographic habitat selection on distribution and abundance.

Predicting multi-predator risk to elk (Cervus canadensis) using scats: Are migrant elk exposed to different predation risk?

There is evidence that prey can perceive the risk of predation and alter their behaviour in response, resulting in changes in spatial distribution and potential fitness consequences. Previous approaches to mapping predation risk quantify predator space use to estimate potential predator-prey encounters, yet this approach does not account for successful predator attacks resulting in prey mortality. An exception is a prey kill-site, which reflects an encounter resulting in mortality, but obtaining these data can be expensive and requires time to accumulate adequate sample sizes. We illustrate an alternative approach using predator scat locations and their contents to quantify spatial predation risk for elk (Cervus canadensis) from multiple predators in Alberta, Canada. We combined predictions of scat-based resource selection functions for bears (Ursus arctos/U. americanus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus) based on scat-detection dog surveys with predictions for the probability that a predator-specific scat in a location contained elk. We evaluated our approach by comparing predictions to a predation risk model developed from elk kill sites and applied it to describing spatial patterns in predation risk that were consistent with changes in the distribution of elk over the past decade. We found a strong correlation between risk predicted by kill sites and risk predicted by our approach (r = 0.98, P < 0.001). There was a spatial pattern to predation risk, where elk that migrated east of their winter range were exposed to highest risk from cougars, non-migratory elk were exposed to high risk from wolves and bears, and risk to elk that migrated west of their winter range into protected areas was high only from bears. The patterns in predator risk were consistent with changes in the migratory tactics in this population. The scat-based approach we present permits broad-scale inferences on predation risk for prey.

Effect of fear on two predator-one prey model in deterministic and fluctuating environment

Recent ecological studies on predator-prey interactions has concentrated on determining the impacts of antipredator behavior due to fear of predators. These studies are mainly confined into one predator-one prey system. But in case of multiple predator attack on single prey species, fear mechanism is still unknown. The combined impact of multiple predator often cannot be anticipated from their independent effects. So coexistence of multiple predators and prey’s fitness becomes an important issue from an ecological point of view. Based on the above observations, we proposed and analyzed a model consisting of two competing predator sharing a common prey where prey’s reproduction rate is affected due to fear generated by the predators. We first study the boundedness, uniform persistence, stability and Hopf bifurcation of the deterministic model. Thereafter, we have investigated the existence and uniqueness of the global positive solution, boundedness, asymptotic stability of the stochastic model. Numerical examples are provided to support our obtained results.