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PubMed2005

Coping with predator stress: interclonal differences in induction of heat-shock proteins in the water flea Daphnia magna.

Although predation is a strong selection pressure, little is known about the molecular mechanisms to cope with predator stress. This is crucial to understanding of the mechanisms and constraints involved in the evolution of antipredator traits. We quantified the expression of heat-shock protein 60 (Hsp60), a potential marker for predator stress, in four clones of the water flea Daphnia magna, when exposed to fish kairomones. Expression of Hsp60 induction increased after 6 h and returned to base levels after 24 h of predator stress. This suggests that it is a costly transient mechanism to temporarily cope with novel predator stress, before other defences are induced. We found genetic variation in the fixed levels and in the fish-induced levels of Hsp60, which seemed to be linked to each clone's history of fish predation. Our data suggest that Hsp60 can be considered part of a multiple-trait antipredator defence strategy of Daphnia clones to cope with predator stress.

Adaptation, Physiological↗
PubMed2006

Evolution of handling time can destroy the coexistence of cycling predators.

Several consumers (predators) with Holling type II functional response may robustly coexist even if they utilize the same resource (prey), provided that the population exhibits nonequilibrium dynamics and the handling time of predators is sufficiently different. We investigate the evolution of handling time and, in particular, its effect on coexistence. Longer handling time is costly in terms of lost foraging time, but allows more nutrients to be extracted from a captured prey individual. Assuming a hyperbolically saturating relationship between handling time and the number of new predators produced per prey consumed, we obtain three results: (i) There is a globally evolutionarily stable handling time; (ii) At most two predator strategies can coexist in this model; (iii) When two predators coexist, a mutant with intermediate handling time can always invade. This implies that there is no evolutionarily stable coexistence, and the evolution of handling time eventually leads to a single evolutionarily stable predator. These results are proven analytically and are valid for arbitrary (not only small) mutations; they however depend on the relationship between handling time and offspring production and on the assumption that predators differ only in their prey handling strategy.

Animals↗
PubMed2006

Predator diversity strengthens trophic cascades in kelp forests by modifying herbivore behaviour.

Although human-mediated extinctions disproportionately affect higher trophic levels, the ecosystem consequences of declining diversity are best known for plants and herbivores. We combined field surveys and experimental manipulations to examine the consequences of changing predator diversity for trophic cascades in kelp forests. In field surveys we found that predator diversity was negatively correlated with herbivore abundance and positively correlated with kelp abundance. To assess whether this relationship was causal, we manipulated predator richness in kelp mesocosms, and found that decreasing predator richness increased herbivore grazing, leading to a decrease in the biomass of the giant kelp Macrocystis. The presence of different predators caused different herbivores to alter their behaviour by reducing grazing, such that total grazing was lowest at highest predator diversity. Our results suggest that declining predator diversity can have cascading effects on community structure by reducing the abundance of key habitat-providing species.

Animals↗
PubMed2006

Parent birds assess nest predation risk and adjust their reproductive strategies.

Avian life history theory has long assumed that nest predation plays a minor role in shaping reproductive strategies. Yet, this assumption remains conspicuously untested by broad experiments that alter environmental risk of nest predation, despite the fact that nest predation is a major source of reproductive failure. Here, we examined whether parents can assess experimentally reduced nest predation risk and alter their reproductive strategies. We experimentally reduced nest predation risk and show that in safer environments parents increased investment in young through increased egg size, clutch mass, and the rate they fed nestlings. Parents also increased investment in female condition by increasing the rates that males fed incubating females at the nest, and decreasing the time that females spent incubating. These results demonstrate that birds can assess nest predation risk at large and that nest predation plays a key role in the expression of avian reproductive strategies.

Adaptation, Physiological↗
PubMed2006

Predators accelerate nutrient cycling in a bromeliad ecosystem.

Conventional ecological theory predicts that predators affect nutrient cycling by decreasing the abundance or activity of prey. By using a predator-detritivore-detritus food chain in bromeliads, we show that predators can increase nutrient cycling by a previously undescribed, but broadly applicable, mechanism: reducing nutrient export by prey emigration. Contrary to expectations, predation on detritivores increases detrital nitrogen uptake by bromeliads. Predation reduces detritivore emergence and hence export of nitrogen from the system. Detritivores therefore benefit their host plant, but only when predators are present. More generally, our results show that predator loss or extinction can dramatically and unexpectedly affect ecosystem functioning.

Animals↗
PubMed2006

Bdellovibrio predation in the presence of decoys: Three-way bacterial interactions revealed by mathematical and experimental analyses.

Bdellovibrio bacteriovorus is a small, gram-negative, motile bacterium that preys upon other gram-negative bacteria, including several known human pathogens. Its predation efficiency is usually studied in pure cultures containing solely B. bacteriovorus and a suitable prey. However, in natural environments, as well as in any possible biomedical uses as an antimicrobial, Bdellovibrio is predatory in the presence of diverse decoys, including live nonsusceptible bacteria, eukaryotic cells, and cell debris. Here we gathered and mathematically modeled data from three-member cultures containing predator, prey, and nonsusceptible bacterial decoys. Specifically, we studied the rate of predation of planktonic late-log-phase Escherichia coli S17-1 prey by B. bacteriovorus HD100, both in the presence and in the absence of Bacillus subtilis nonsporulating strain 671, which acted as a live bacterial decoy. Interestingly, we found that although addition of the live Bacillus decoy did decrease the rate of Bdellovibrio predation in liquid cultures, this addition also resulted in a partially compensatory enhancement of the availability of prey for predation. This effect resulted in a higher final yield of Bdellovibrio than would be predicted for a simple inert decoy. Our mathematical model accounts for both negative and positive effects of predator-prey-decoy interactions in the closed batch environment. In addition, it informs considerations for predator dosing in any future therapeutic applications and sheds some light on considerations for modeling the massively complex interactions of real mixed bacterial populations in nature.

Bacillus subtilis↗
PubMed1998

Higher-order predators and the regulation of insect herbivore populations.

Empirical research has not supported the prediction that populations of terrestrial herbivorous arthropods are regulated solely by their natural enemies. Instead, both natural enemies (top-down effects) and resources (bottom-up effects) may play important regulatory roles. This review evaluates the hypothesis that higher-order predators may constrain the top-down control of herbivore populations. Natural enemies of herbivorous arthropods generally are not top predators within terrestrial food webs. Insect pathogens and entomopathogenic nematodes inhabiting the soil may be attacked by diverse micro- and mesofauna. Predatory and parasitic insects are attacked by their own suite of predators, parasitoids, and pathogens. The view of natural enemy ecology that has emerged from laboratory studies, where natural enemies are often isolated from all elements of the biotic community except for their hosts or prey, may be an unreliable guide to field dynamics. Experimental work suggests that interactions of biological control agents with their own natural enemies can disrupt the effective control of herbivore populations. Disruption has been observed experimentally in interactions of bacteria with bacteriophages, nematodes with nematophagous fungi, parasitoids with predators, parasitoids with hyperparasitoids, and predators with other predators. Higher-order predators have been little studied; manipulative field experiments will be especially valuable in furthering our understanding of their roles in arthropod communities.

Animals↗
PubMed1993

Anti-predation benefits in a mixed-species group of Amazonian tamarins.

Because of their small body size, tamarins are potentially vulnerable to a wide range of predator species. This paper examines the general patterns of predator avoidance of the Avila-Pires saddle-back tamarin (Saguinus fuscicollis avilapiresi) and the red-cap moustached tamarin (Saguinus mystax pileatus) in the upper Urucu river, Amazonas, Brazil. One highly stable mixed-species group of these species suffered an average of 1 attack by carnivorous raptors every 8.8 days of activity. Although none of these attacks was successful tamarins occasionally fall prey to raptors or terrestrial predators. The two tamarin species exhibited a high degree of coordination in their anti-predation tactics. Saddle-back tamarins accounted for most of the vigilance and detection of terrestrial and scansorial threats, whereas moustached tamarins scanned for and detected most aerial and arboreal threats. Of the two species, however, moustached tamarins contributed a significantly greater proportion of scanning time after predation attempts, during pre-retirement periods and at other times. Moreover, their substantially larger groups (1.6 times larger than those of saddle-back tamarins) accounted for a further increase in their effective vigilance effort. The anti-predation benefits gained by saddle-back tamarins from joining mixed-species groups with moustached tamarins thus appeared to be greater than the reverse, because the latter provide greater protection to the group, particularly against aerial sources of threat. However, the greater vigilance of saddle-back tamarins towards potential terrestrial predators cannot be discounted, because these may on rarer occasions pose a real threat to either species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Response of predators to loss and fragmentation of prey habitat: a review of theory.

Despite extensive empirical research and previous reviews, no clear patterns regarding the effects of habitat loss and fragmentation on predator-prey interactions have emerged. We suggest that this is because empirical researchers do not design their studies to test specific hypotheses arising from the theoretical literature. In fact, theoretical work is almost completely ignored by empirical researchers, perhaps because it may be inaccessible to them. The purpose of this paper is to review theoretical work on the effects of habitat loss and fragmentation on predator-prey interactions. We provide a summary of clear, testable theoretical predictions for empirical researchers. To test one or more of these predictions, an empiricist will need certain information on the predator and prey species of interest. This includes: (1) whether the predator is a specialist on one prey species or feeds on many kinds of prey (omnivore and generalist); (2) whether the predator is restricted to the same habitat type as the focal prey (specialist), can use a variety of habitats but has higher survival in the prey habitat (omnivore), or lives primarily outside of the focal prey's habitat (generalist); (3) whether prey-only patches have lower prey extinction rates than predator-prey patches; and (4) whether the prey emigrate at higher rates from predator-prey patches than from prey-only patches. Empiricists also need to be clear on whether they are testing a prediction about habitat loss or habitat fragmentation and need to conduct empirical studies at spatial scales appropriate for testing the theoretical prediction(s). We suggest that appropriate use of the theoretical predictions in future empirical research will resolve the apparent inconsistencies in the empirical literature on this topic.

Animals↗
PubMed2006

Diverse trait-mediated interactions in a multi-predator, multi-prey community.

Trait-mediated interactions (TMII) can alter the outcome or magnitude of species interactions. We examined how the interaction between a guild of ground and rove beetles and their fly egg prey was altered by a larger predator, the ground beetle Pterostichus melanarius, and an additional prey, aphids. In field and laboratory experiments, we manipulated the presence or absence of P. melanarius and aphids and recorded the impact of these manipulations on beetle activity and fly egg predation. Individually, aphids, by serving as preferred prey, and P. melanarius, by reducing focal beetle activity, weakened egg predation. However, egg predation was restored when both aphids and P. melanarius were present together, because aphids triggered greater foraging activity, and thus increased incidental predation of fly eggs, by P. melanarius. Thus, TMII among subsets of the community that were disruptive to predation on fly eggs could not be summed to predict the dominant, positive TMII within a more diverse community. Future TMII studies should include more realistic representations of species diversity, and should not ignore the influence of prey on predator behavior.

Animals↗
PubMed2006

Predators have large effects on ecosystem properties by changing plant diversity, not plant biomass.

Cascading effects of predators on total plant trophic-level biomass tend to be weaker in terrestrial than in aquatic systems. Accordingly, it is hypothesized that top predator effects on terrestrial plant diversity and on ecosystem function should likewise be weak or unimportant. This report presents a test of this hypothesis using data from a long-term field experiment. The five-year experiment manipulated the trophic structure of an old field ecosystem by excluding either predators or predators and herbivores relative to an unmanipulated, natural control. Long-term manipulations led to systematic treatment effects on community properties (plant trophic-level biomass, plant species biomass, plant species evenness) and on ecosystem properties (supply rate of solar radiation, N mineralization rate). The strengths of top predator effects on community properties were modest compared with nonterrestrial systems. But, predator-caused changes in plant community structure via alteration of plant dominance, and hence plant species evenness, strengthened effects on ecosystem properties. Counter to the hypothesis, weak trophic cascades do not necessarily lead to weak indirect effects of predators on ecosystem properties.

Animals↗
PubMed2003

Response in nematocyst uptake by the nudibranch Flabellina verrucosa to the presence of various predators in the Southern Gulf of Maine.

Aeolid nudibranchs maintain nematocysts sequestered from their cnidarian prey for protection against predators. Selection for nematocyst incorporation is a function of diet and prey choice, but ratios vary among nudibranchs feeding on a given diet, indicating that other factors may be involved. It is proposed that the presence of predators influences nematocyst incorporation. Nematocyst uptake in the nudibranch Flabellina verrucosa collected from the southern Gulf of Maine was examined in response to various potential predators, including Crossaster papposus, Tautogolabrus adspersus, and Carcinus maenas. Nudibranchs in individual flow-through containers feeding on a diet of the hydroids Tubularia spp. and Obelia geniculata were subjected to tanks containing a predator, then their nematocyst distribution was examined. Although most of the changes over the experimental period were attributable to diet, F. verrucosa responded to both T. adspersus and C. papposus by significantly increasing microbasic mastigophore incorporation. No differential uptake was seen with C. maenas. Response was evident in the nudibranchs both for predators present in the collection area and for those with which they had no previous exposure, indicating that F. verrucosa modulates nematocyst incorporation in response to the presence of predators as well as to diet. A coevolution of nudibranchs and potential predators may govern changes in nematocyst uptake.

Animal Structures↗
PubMed2000

[Predation on Myzus persicae by Propylaea japonica adults with different extents of starvation].

The study showed that the functional response of predation on M. persicae by the female and male adults of P. japonica with different extents of starvation belonged to the type of Holling II. Female adults had a larger attacking rate than male adults, but the predacious amount of M. persicae by female and male adult predators of different extent of starvation within 24 hrs had no significant difference. The predacious amount by female adult was larger than that of male. The significant difference of predacious amount between female and male adults increased with the time of their starvation and the prey density. The predation by unstarved female and male adult predators on M. persicae in 24 hours was concentrated at 6:00-18:00 and the predation rate (V) between female and male adults had no significant difference. The predation by starved female and male adults for 48 h on the prey in 24 hours was at 0-4 hours after the experiment started, and the predation rate(V) between female and male starved adults had no significant difference either.

Animals↗
PubMedDate not supplied

[Explicit model for searching behavior of predator].

The authors present an approach for explicit modeling of spatio-temporal dynamics of predator-prey community. This approach is based on a reaction-diffusion-adjection PD (prey dependent) system. Local kinetics of population is determined by logistic reproduction function of prey, constant natural mortality of predator and Holling type 2 trophic function. Searching behavior of predator is described by the advective term in predator balance equation assuming the predator acceleration to be proportional to the prey density gradient. The model was studied with zero-flux boundary conditions. The influence of predator searching activity on the community dynamics, in particular, on the emergence of spatial heterogeneity, has been investigated by linear analysis and numerical simulations. It has been shown how searching activity may effect the persistence of species, stabilizing predator-prey interactions at very low level of pest density. It has been demonstrated that obtaining of such dynamic regimes does not require the use of complex trophic functions.

Animals↗
PubMed2004

Effects of interspecific competition, predation, and their interaction on survival and development time of immature Anopheles quadrimaculatus.

We examined the effect of predation by the backswimmer (Notonecta undulata; Hemiptera: Notonectidae), competition by zooplankton and snails, and both predation and competition on the survival and development time of larval Anopheles quadrimaculatus mosquitoes in experimental mesocosms. We found that both predation and interspecific competition greatly reduced the survivorship of larvae and the number of larvae emerging into adulthood. Treatments with both predators and competitors had fewer larvae transitioning among instars and into adulthood but not in an additive way. In addition, mosquito larvae in the presence of predators and competitors took two days longer to emerge than where predators and competitions were absent. Our work provides evidence that biotic interactions, such as predation and competition, can strongly regulate the number of mosquito larvae by reducing the number of larvae that survive through instars and to emergence and by increasing the generation time.

Animals↗
PubMed1994

Is the testing of TFT strategy during predator inspections possible by use of mirror image? A review and some controls of recent studies.

In order to answer some of the questions concerning the "inadequacies" of mirror-images in experiments examining co-operative behaviour during predator inspection, several control experiments were carried out. The average positions (distance from predator's tank) of guppies was influenced by the presence of a preadator, but the effect of previous experience with a predator was manifestated only in the presence of predator. The average position of guppies also depended on the mirror-treatment (changing the length and position) but it was influenced only by the length but not the angle of mirror. The relative independence of the position of the mirror observed in the guppies' behaviour challenges the basic assumption (i.e. closer to the predator by long parallel than short angled mirror) is indeed the result of TFT as interpreted earlier. Instead, the effect of mirror treatment appears superpositioned on the predator inspection as an independent variable. In light of these results we discuss the usefulness of mirror systems in testing predator inspection as TFT-like behaviour.

Animals↗
PubMed2026

A predator-derived odor specifically triggers avoidance in gregarious mated female Locusta migratoria.

BACKGROUND: Insects possess a highly specialized olfactory system. The migratory locust (Locusta migratoria), a major agricultural pest, is thought to emit odors that serve as aposematic signals to protect gregarious individuals from predation. However, whether locusts can detect the odors of their natural enemies to preemptively avoid predation remains unclear. RESULTS: Here, we show that gregarious mated female locusts exhibit strong avoidance behavior toward the odors of two avian predators, Numida meleagris and Anas platyrhynchos. Through volatile compound profiling, we identified 1-octen-3-ol, a key predator-released odor, which elicited significant aversive responses specifically in gregarious mated females; notably, virgin females showed no behavioral response to this odor. Through screening 82 olfactory receptors in L. migratoria, we identified two receptors, LmOR1 and LmOR17, that detect 1-octen-3-ol. A temporal expression study of LmOR1 and LmOR17 across different developmental stages of two locust phases using quantitative real-time polymerase chain reaction (qRT-PCR) showed that both genes are significantly more highly expressed in the gregarious mated females. Genome editing of these receptors revealed that knockout of LmOR1 significantly reduced both the electrophysiological response and the behavioral avoidance of 1-octen-3-ol, whereas knockout of LmOR17 had no effect. In our results we thus uncover a striking mating-state dependence of an innate avoidance behavior to a predator-derived odor, and further we identify LmOR1 as the major receptor mediating this olfactory-driven defense. CONCLUSION: Our findings provide crucial insights into the behavioral and olfactory mechanisms underlying insect-predator interactions, as well as the role of mating status in modulating defensive responses, offering potential olfactory targets for locust management. © 2026 Society of Chemical Industry.

Animals↗
PubMed1998

Fighting behaviour, vigilance and predation risk in the cichlid fish Nannacara anomala.

I studied the fighting behaviour of a small South American cichlid fish, Nannacara anomala, in relation to predation risk. In this species, which reduces vigilance during escalated fighting, differences in fighting ability are most accurately assessed during mouth wrestling. Thus, there is a potential trade-off between agonistic behaviours that are effective for assessing differences in fighting ability between contestants and agonistic behaviours that minimize the risk of being killed by predators. I investigated whether breaks between bouts of mouth wrestling improved the contestants' ability to flee from an approaching model fish predator. During the breaks between mouth wrestling the contestants had a significantly longer escape distance than males that were actively mouth wrestling. Fighting males also changed their fighting behaviour after the introduction of the model predator compared with males that were not exposed to it. Low-intensity behaviours such as lateral display and tail beating were preferred to mouth wrestling. In addition, both the number and duration of bouts of active mouth wrestling decreased significantly after the introduction of the model predator while the duration of the breaks between bouts of active mouth wrestling increased significantly compared with the control. Including predation risk in the costs of intense fighting may increase our understanding of both the temporal structuring of fighting behaviour and the evolution of fighting behaviour in general.1998 The Association for the Study of Animal Behaviour

Journal Article↗