Changes In Predator Behavior Research Articles

High resolution temporal data shows how increasing prey availability reduces early season intraguild predation and pest spread in cereal crops

Intraguild predation is an extreme form of competition, that depends on resource availability, niche overlap, behaviour and diversity. However, despite modelling and mesocosm experiments, field studies are scarce, and we know nothing of its temporal dynamics within real-world food webs, particularly in the context of biological control. To address this, we added manure to cereal fields to increase decomposer prey, and analysed the diet of over 6000 predators over the entire cropping season during two consecutive years. Our results show that manure increased available prey temporarily and reduced intraguild predation. With this organic fertilization, a reduction in pest spread between tillers within fields correlated with lower intraguild predation, while pest density remained unchanged across treatments, making the net effect on biological control unclear. We hypothesize that the mechanism responsible for why lowering intraguild predation reduces pest spread are changes in predator behaviour, that allow predators to exert more pressure on pests. Conversely, the absence of an effect on pest density may be linked to other effects of fertilization, such as increased pest and plant growth counteracting any increase in predation pressure. The high temporal resolution of our data showed how dynamic IGP is throughout the season, which stresses the importance of studying food webs over time, to generate a mechanistic understanding of biological control.

Behavioral responses of the lady beetles Cryptolaemus montrouzieri and Tenuisvalvae notata to specific mealybug prey

AbstractLady beetles (Coleoptera: Coccinellidae) are important biocontrol agents that are considered generalist predators, although some tribes, such as Scymnini, are specialized in predation of sucking pests, such as mealybugs, aphids, and whiteflies. However, prey preference or pre‐imaginal conditioning may occur as coccinellids are subjected to large‐scale rearing. Thus, predator–prey interaction may be an outcome of conditioning to prey stimuli. To evaluate possible pre‐imaginal conditioning, population lines were created for the lady beetles Cryptolaemus montrouzieri Mulsant and Tenuisvalvae notata (Mulsant), each fed for at least eight generations the mealybugs Ferrisia dasylirii (Cockrell) or Planococcus citri Risso (Hemiptera: Pseudococcidae). Next, the behavioral response of these coccinellids was measured in arenas treated with prey volatiles or footprints, regarding walking time, walking speed, walking distance, and residence time. Finally, food preference between prey species was measured in laboratory and semi‐field conditions on infested cotton plants. Conditioned coccinellids responded similarly to volatiles released by either prey species offered. Furthermore, there were no changes in predator behavior towards footprints of either prey species. Both predator species consumed more P. citri in all tests, regardless of rearing prey indicating no pre‐imaginal conditioning. These results suggest that rearing prey may not affect the predator behavior, and both coccinellid species are effective in the biological control of mealybugs.

Interactions between temperature and predation impact insect emergence in alpine lakes

AbstractWhile insect populations are simultaneously threatened by many local‐ and global‐scale stressors, the interacting effects of these factors remain poorly understood. These interactions between stressors, whether additive or antagonistic, may have profound effects on our assumptions about and predictions for any given system. Here we address this gap by exploring the interactive effects of introduced predators and elevated temperatures on emerging aquatic insects across alpine lakes. Using a crossed factorial field survey, we examine whether warmer temperatures either directly affect the magnitude or diversity of insect emergence, or mediate the impacts of predation via interactions with predator presence. Based on data from more than 11,000 insects collected across a two‐year period, we find a 71% reduction in insect emergence associated with an additional 3.6°C of water temperature in oligotrophic alpine lakes. While our work confirms prior findings that predator presence drives strong reductions in insect emergence, we find that the effects of predation are significantly weaker in warmer lakes (2% reduction in warmest lakes studied vs. 75% reduction in coldest). Combining our results with regional studies of predator communities to identify mechanisms suggests that the interaction effects between temperature and predator presence are likely due to changes in predator behavior across temperatures. Critically, to fully understand the multiple stressors that impact insect populations and predict their future effects, we must consider the interactions between stressors across spatial scales.

De-hooking depredation: Exploring multiple fisher perceptions about marine depredation in Florida

Marine depredation involves the removal of or damage to captured fish by predators, and recent evidence suggests it is increasing globally likely due to increasing fishing effort and changes in predator behavior. Anecdotal reports indicate that marine depredation in Florida may be especially severe, given the high number of fishers and predator species. However, the magnitude of marine depredation in Florida and fisher perceptions of these events are poorly understood. We employed a survey of commercial, private recreational, and for-hire saltwater license holders to explore the extent and magnitude of fishing experiences and perceptions related to marine depredation across Florida, highlighting differences among fisher groups using closed- and open-ended survey questions. We found few to no significant differences between fishing sector groups, meaning depredation was prevalent across all locations, gear types, and target species. Most user groups experienced depredation by more than one predator, but sharks and dolphins were reported as the most common predators. Commercial and for-hire operators were more likely to have very negative and negative sentiments toward predators, while private recreational fishers were more likely to view their depredation experiences as neutral. The need for improved management of predators and other fish stocks was expressed across all sectors, especially among commercial fishers. Our results support the growing literature on increased depredation experiences statewide and the need to devise a solution for all marine fisheries users in Florida. We anticipate our exploratory findings to be used as a starting point for researchers and fisheries management agencies to understand fishing sector perceptions and attempt to mitigate negative depredation experiences.

The effects of landscape complexity and local management on a generalist predator in Kenyan maize push‐pull systems

AbstractFarmers looking to maximize ecosystem services often use diversification practices on their fields to increase abundance and diversity of insect natural enemies. These practices affect functional traits of natural enemies such as body size that can play an important role in their effectiveness as biological control agents. However, landscape features out of the control of farmers might also affect functional traits of natural enemies and their herbivores, including land use surrounding farms. There have been few studies elucidating how landscape complexity and local diversity interact to affect functional traits, and ultimately ecosystem services such as predation on herbivore pests. We examined combined effects of landscape complexity and a local management practice (push‐pull) on lady beetle size, and its consequences for egg predation of lepidopteran pests in Kenyan smallholder maize farms. Cheilomenes sulphurea (Olivier) (Coleoptera: Coccinellidae), a potential predator of the invasive fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), was collected in push‐pull and control fields along a landscape gradient. We measured beetle size and conducted feeding assays with fall armyworm eggs. We found that female beetles had larger bodies in landscapes with greater complexity. Predation rates not only increased as a response to beetle size but also in response to landscape complexity, suggesting it is not just size that determines predation. Surprisingly, we did not find any effect of the local management practice or its interaction on functional traits or predation rates. Our study suggests that landscape complexity could benefit pest control through two mechanisms: (1) increase in predator body size, leading to higher predation rates; and (2) changes in predator behavior as a function of landscape characteristics – increasing egg predation. Further studies on these mechanisms would allow deeper understanding of landscape simplification's effect on ecosystem services, as mediated by morphological and behavioral traits, and help us harness these traits to increase biological control.

Feeding History Affects Intraguild Interactions between Harmonia axyridis (Coleoptera: Coccinellidae) and Episyrphus balteatus (Diptera: Syrphidae).

While the effect of several factors such as predator and prey size, morphology and developmental stage on intraguild predation (IGP) is widely investigated, little is known about the influence of diet on the occurrence and outcome of IGP. In the present study, the effect of the diet experienced during larval development on IGP between the ladybird Harmonia axyridis and the syrphid Episyrphus balteatus is investigated. Four diets were tested for H. axyridis: eggs of the Mediterranean flour moth Ephestia kuehniella, pea aphids, Acyrthosiphon pisum, in an ad libitum amount, pea aphids in a limited amount, and honey bee pollen. For E. balteatus only the two aphid diets were tested. First, experiments were performed to determine the quality of the various diets for development of both predators. Second, IGP experiments between H. axyridis and E. balteatus were performed both in Petri dishes and on potted pepper plants. The diet of both species influenced the incidence of IGP between H. axyridis and E. balteatus both in Petri dishes and on potted plants. In general, smaller larvae of H. axyridis (those fed on poor or restricted diet) fed more on hoverflies than large (well-nourished) ladybird larvae. Further, poorly nourished (smaller) larvae of E. balteatus were more susceptible to predation than well-fed (larger) hoverfly larvae. The observed effects were not only due to the lower fitness of larvae of both predators reared on an inferior quality diet but also to changes in predator behaviour. The results from this study show that IGP interactions are influenced by a multitude of factors, including feeding history of the organisms involved, and emphasize the importance of taking these factors into account in order to fully understand the ecological relevance of IGP.

Population regulation of epibenthic species in coastal ecosystems, with implications for latitudinal patterns

The effect of predation on population regulation among (epi)benthic communities along the Atlantic coasts is reviewed. Population regulation requires density-dependent mortality at some phase in the life cycle, which can occur through predation under certain functional (Type III) and numerical feeding responses. Although the potential to induce regulation has been suggested for some epibenthic predators in the coastal zone, studies linking direct observations of predator–prey responses to observed regulation of the prey population are scarce. The identification of Type III functional response curves is mainly restricted to laboratory or cage studies, and the effect is confined to a limited range of prey densities. Numerical responses, especially predator aggregations, may be more common in the natural environment. The response type seems to be affected not only by habitat structure but also by water temperature. Prevailing temperature conditions can affect the functional response type possibly through changes in predator behavior. The effect of temperature on the response curve appears to be species-specific and hence, predator–prey specific. Therefore, no general effect of latitude on population regulation can be expected. Most likely there is a mosaic of predator–prey interactions that depend on local habitat, temperature conditions, multiple species interactions and predator and prey species types. We surmise that any latitudinal pattern in the overall recruitment variability along species distributional range is more likely to result from a trend in controlling rather than regulating factors.

Dynamic Risk Assessment: Prey Rapidly Adjust Flight Initiation Distance to Changes in Predator Approach Speed

AbstractThe pre‐eminent model of flight initiation distance assumes that the function relating predation risk to distance between predator and prey is constant. However, the risk–distance function can change dramatically during approaches by predators. Changes in predator behavior during approach and in availability of benefits (e.g. food or potential mates) may alter risks and/or costs during encounters. Thus, prey should be able to respond appropriately to changes in cues to risk, such as predator approach speed. Under the assumption that prey assess risk in real time, it was predicted that flight initiation distance (distance between predator and prey when escape begins) decreases when approach speed increases and increases when approach speed decreases during an encounter. Effects of single, abrupt changes from slower to faster approach or the reverse were studied in a lizard,Anolis lineatopus. Flight initiation distances were determined solely by final approach speed, being nearly identical for: (1) continuously fast approaches and approaches initially at the slower and finally at the faster speed and (2) for continuously slower approaches and approaches initially at faster and finally at slower speed. Escape should be adjusted to match changes in risk and cost caused by changes in predator behavior, ability to escape, and costs of escape as attacks unfold. A recent model by Broom and Ruxton [Behavioural Ecology(2004) vol. 16, pp. 534—540] predicts that cryptic prey should stay motionless until detected, then flee immediately. Our results suggest that current escape models can be applied to prey escape strategies when cues to risk change, by assuming that prey base decisions on the current relationship between risk and distance. Empirical studies are needed to test predictions concerning continuous risk assessment.

A multi-nutrient model for the description of stoichiometric modulation of predation in micro- and mesozooplankton

Changes in predator behaviour when confronted with prey of disadvantageous composition have been termed stoichiometric modulation of predation (SMP; Mitra and Flynn, 2005; J. Plankton Res. 27, 393–399). Through SMP, a predator may compensate for (positive SMP) or compound (negative SMP) dietary deficiencies. While these responses are documented in experiments, albeit typically with poor parameterization, previous zooplankton models contain no explicit description of these events. A new multi-nutrient biomass-based generic zooplankton model is described, capable of handling SMP at the levels of ingestion and assimilation, for the exploration of zooplankton growth dynamics in situations where prey quality and quantity changes over time. SMP is enabled by configuring ingestion rate and assimilation efficiency descriptors as functions of food quality (indexed here to prey N:C). Sensitivity analysis of the new model shows the structure to be robust against variation in parameter (constant) values. The form of the model enables its use in population dynamic studies of different zooplankton groups; here, the model has been configured to represent micro- and mesozooplankton. It is shown that in the absence of inclusion of SMP, fits of the model to experimental data can be poor with potential for significant misrepresentation of trophic dynamics.

Ecosystem consequences of wolf behavioural response to climate

Because apex predators exert considerable influence on the structure and function of top-down ecosystems1,2,3, their responses to climate may shape responses at lower trophic levels4. Previous reports of trophic cascades and ecosystem dynamics induced by predators have focused on changes in their abundance5,6,7,8, whereas we investigated whether changes in predator behaviour could precipitate cascades of similar ecological scale. Here we report the ecological consequences of predator behavioural response to global climatic variation using 40 years of data on wolf predation from Isle Royale, USA, where wolves limit abundance of moose9, which limit productivity of fir trees10. In response to increases in winter snow related to the North Atlantic Oscillation, wolves hunted in larger packs and, consequently, tripled the number of moose killed per day compared with less snowy years when they hunted in smaller packs. Following increased predation rates, moose abundance declined, and, following release from heavy browsing, growth of understory fir increased. Hence, cascading behavioural responses of apex predators may be a substantial link in the pathway from climatic change to ecosystem function.

Sub‐lethal effects of deltamethrin residues on the within‐crop behaviour and distribution of Coccinella septempunctata

AbstractThe behaviour and distribution of adult Coccinella septempunctata L. (Coleoptera: Coccinellidae) were recorded in two plots of winter wheat infested with the cereal aphids Sitobion avenae (F.) and Metopolophium dirhodum (Walk.) (Homoptera: Aphididae). One plot was sprayed with the pyrethroid insecticide deltamethrin at a rate of 6.25 g a.i./ha and the other was left unsprayed. Single ladybird beetles were released sequentially on the ground at the centre of the sprayed and unsprayed plots and their behaviour and position in the crop canopy were recorded at 30 second intervals for a total of 15 min per beetle. Assessments, with fresh beetles, continued for four days after spray application with a total of eighty ladybird beetles observed. The 15 min period was selected to avoid lethal effects and no ladybird beetles were killed or knocked down as a result of exposure to deltamethrin residues during this period. Significant differences were found between the overall behaviour patterns of C. septempunctata in the untreated and deltamethrin treated plots up to three days after the spray application. Ladybird beetles exposed to deltamethrin residues were observed to walk and groom significantly more frequently and to rest significantly less frequently than those in the unsprayed plot. Significant differences were also found between the observed distribution of ladybird beetles in the sprayed and unsprayed crop canopies, with higher numbers of observations towards the bottom of the crop canopy and on the ground in the deltamethrin treated plot than in the untreated plot during the first two days after deltamethrin application. Upon the foliage itself, ladybird beetles were observed significantly more frequently on the abaxial leaf surface in the deltamethrin treated crop compared with the untreated crop. The results are discussed in terms of possible evidence for the repellency of deltamethrin to C. septempunctata and also the implications for integrated pest management of changes in predator behaviour and crop distribution resulting from sub‐lethal uptake of insecticides.

The Kinetics of Functional Response

Holling's Type II functional-response relationship is presented, and the formulations expressing the underlying organismal interactions which might generate such a relation arc generalized into the Type III response typical of predators showing learning behavior. An equation derived through an analogy with allosteric enzyme kinetics is given which will account for both Type II and Type III responses. The response behavior can be explained by three parameters: maximal feeding rate (F); an affinity constant (G) related to handling times, capture efficiencies, etc.; and the number of encounters (n) a predator must have with a prey item before becoming maximally efficient at utilizing the prey item as a resource. A discussion follows on the biological processes which result in shifts from Type II to Type III functional responses. Most of the learning processes involve changes in predator behavior associated with increasing encounters with prey, thus supporting parameter n as a major determinant in shifting thc functional response. Three hypotheses concerning the values parameters F, G, and n will assume under different ecological situations are posited: (l) food preferences will be reflected in an increase in resource-utilization efficiency (F) and affinity (G) and a decrease in values of n encounters; (2) a size ordering of the predators will result in shifts up in the resource-utilization efficiency (F) and affinity (G); while (3) increasing habitat complexity will generate decreases in n and F.