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PubMed2006

Invertebrate predation selects for the loss of a morphological antipredator trait.

Antagonistic selection by different predators has been suggested to underlie variation in morphological antipredator traits among and within species. Direct empirical proof is equivocal, however, given the potential interrelationships of morphological and behavioral traits. Here, we tested whether spines in larvae of the dragonfly Leucorrhinia caudalis, which are selected for by fish predators, are selected against by invertebrate aeshnid predators. Using a manipulative approach by cutting spines instead of making comparisons among species or inducing spines, we were able to decouple the presence of spines from other potentially covarying morphological antipredator traits. Results showed survival selection for the loss of spines imposed by invertebrate predation. Moreover, spined and nonspined larval L. caudalis did not differ in the key antipredator behaviors, activity level, and escape burst swimming speed. The observed higher mortality of spined larvae can therefore be directly linked to selection by aeshnid predation against spines.

Animals↗
PubMed2006

[Predation of Orius minutus on Odontothrips loti].

In this paper, a laboratory study was made on the predation of Orius minutus on the 3rd to approximately 4th instar nymphs of Odontothrips loti, and the intraspecific interference within O. minutus. The results showed that the functional responses of adult O. minutus to O. loti nymphs fitted Holling II type equation, i. e., Na = 1.0113N/(1 + 0.04149N) in test tubes, Na = 0. 6777N/(1 + 0.03395N) in Petri dishes, and Na = 0.6417N/(1 + 0.03934N) in enveloped pots. The predation of O. minutus had strong intraspecific interference, and the relationship between predation efficiency and individual interference fitted Hassell model. Under the same spatial conditions, the predation rate of O. minutus was positively related, while its searching efficiency was negatively associated with the prey density. With the increase of the space, the attack rate (a') and maximum predation (Na) of O. minutus decreased, its handling time (Th) increased, while the type of its functional responses to the densities of 3rd to approximately 4th instar O. loti, still fitted Holling II model.

Animals↗
PubMed2006

[Predation of Axinoscymnus cardilobus to Bemisia tabaci].

The laboratory study on the predation of Axinoscymnus cardilobus to Bemisia tabaci showed that the functional response of A. cardilobus to B. tabaci was of Holling' s type II. With the increasing age of B. tabaci, the searching rate of A. cardilobus adult decreased, and its handling time became longer. The searching rate of A. cardilobus larva was increased with its age, and the handling time became shorter. The mutual interference in individual predator could be described by Hassell and Varley equation, and the relationship between predation ratio (E) and natural enemies density (P) was E =0. 5205P(-0 6631.) The predation efficiency (E) of predator varied with environmental temperature, and the effects of the temperature on search rate (a) and handling time ( T ) could be described by a = -0. 0002T(3)+ 0. 0166T(2) - 0. 3492T + 3. 2329 and Th = 4 x 10 (-7) T-( 3) x 10(-5) T(2) + 0.0006T 0.0009, respectively.

Animals↗
PubMed1985

The impact of the exotic fish Gambusia affinis (Baird and Girard) on some natural predators of immature mosquitoes.

The effects of Gambusia affinis on some suspected predators of mosquitoes were studied for a period of 12 months. A list of such predators was given. The most abundant invertebrate predators were Odonata, followed by Hemiptera and Ephemeroptera and the least common were Coleoptera. The population density of mosquito predators, with exception of Notonectidae and the fish Oreochromis niloticus, was markedly reduced in the presence of G. affinis. Application of aerial pesticides reduced the population of both G. affinis and O. niloticus fish. However it had no effect on the numbers of all invertebrate predators.

Agriculture↗
PubMedDate not supplied

[The behaviour of Lymnaea (Galba) truncatula Müler non- or infested ny Fasciola hepatica L. in the presence of predators (author's transl)].

Experimental study of behavior of Lymnaea truncatula in the presence of terrestrial or aquatic predators. The presence of predators disturbes the daily rhythm connected with amphibious conditions of non-infested snails. In half-immersed habitats, Zonitoides nitidus, terrestrial predator, produces a progressive immersion of surviving snails; but the latter run away to dry zones in drying habitats or with aquatic predators. The infested snails (phasis E 1) present the same reactions of behaviour in presence of predators, but the reactions are more limited.

Animals↗
PubMed1996

Evaluation of Mesocyclops aspericornis (Cyclopoida:Cyclopidae) and Toxorhynchites speciosus as integrated predators of mosquitoes in tire habitats in Queensland.

This study addressed biological control of peridomestic Aedes notoscriptus, known to be a highly effective colonizer of tire habitats and a possible vector of Ross River virus. A laboratory trial of the compatibility of the predators Mesocyclops aspericornis and Toxorhynchites speciosus in small container habitats showed that 4th-instar Tx. speciosus did not significantly affect M. aspericornis mortality. Introduced M. aspericornis and naturally occurring Tx. speciosus were found to form a compatible predator pair for reduction of larval Ae. notoscriptus and Culex quinquefasciatus populations in tire habitats. Over 22 months of field survey, 97% of tires without predators contained mosquito larvae, at a median density of 43 larvae/liter. By comparison, 51% of tires containing both predator species held mosquito larvae at a median density of 4 larvae/liter. Predation by Tx. speciosus persisted for the duration of the study. The inability of the Lake Kurwongbah strain of M. aspericornis to tolerate temperatures of < or = 10 degrees C, which are prevalent in Brisbane during winter, resulted in a failure to deliver persistent reduction of mosquitoes in tires. The temperature-dependent population characteristics of M. aspericornis emphasize the long-recognized importance of matching a biological control candidate's physiological requirements to the environment in which control is sought.

Aedes↗
PubMed2004

Daphnia response to predation threat involves heat-shock proteins and the actin and tubulin cytoskeleton.

Of all the environmental pressures that all organisms across all kingdoms must face, one of the greatest is the risk of predation. The unpredictability of predation events from the perspective of a single individual is one of the major components of a changing, unstable environment (Gliwicz and Pijanowska, 1989; Lampert, 1987). The panoply of antipredator defenses among terrestrial and aquatic organisms involves a variety of morphological, behavioral, and life-history adaptations that even if they are not life-saving, may enable organisms to complete reproduction before predation occurs. Most of these phenotypic changes are directly induced by cues associated with the biotic agent, in the case of aquatic organisms, the chemical compounds (kairomones) released by a predator into the water. Herein we show that exposure of Daphnia to invertebrate and vertebrate kairomones results in changes in motion, behavior, and life history and at the molecular level involves changes in heat-shock proteins (HSPs) level and the actin and tubulin cytoskeleton. In addition, some of these effects are transgenerational, i.e., they are passed on from the mother to her offspring.

Actins↗
PubMed2003

Influence of a short exposure to teflubenzuron residues on the predation of thrips by Iphiseius degenerans (Acari: Phytoseiidae) and Orius laevigatus (Hemiptera: Anthocoridae).

A short duration (24h) leaf-disc bioassay was used to determine the effects of teflubenzuron residues on the predation levels of two predators, Iphiseius degenerans (Berlese) and Orius laevigatus (Fieber), foraging on nymphs of two species of thrips, Frankliniella occidentalis (Pergande) and Heliothrips haemorrhoidalis (Bouche), on a range of different species of plant. Teflubenzuron did cause thrips mortality during the 24-h bioassay; it was more active against H haemorrhoidalis than F occidentalis. Teflubenzuron did not cause significant mortality to either species of predator, although on some plants the effectiveness of both predators was reduced in the presence of teflubenzuron.

Acari↗
PubMed1997

Refuge use and predation risk in a desert baboon population

Baboons face a serious threat of predation from leopards, Panthera pardusand lions, Panthera leoSince trees and cliff faces provide safety from these predators, baboons might use such refuges in order to reduce predation risk. This hypothesis was explored in a study of four groups of chacma baboons, Papio cynocephalus ursinusin a desert population in Namibia (groups ranged between 22 and 55 individuals with one to six adult males). All baboons spent most of their time close by refuges and little time distant from them. This pattern was most accentuated among females in smaller groups. These females spent more time on refuges primarily as a result of greater refuge use during resting and grooming. This pattern was less clear during feeding and travelling, apparently owing to the constraints on refuge use imposed by the nature of these activities. A comparison of refuge use in high-risk and low-risk habitats (after the confounding effects of habitat-specific refuge availability had been removed) suggests that baboons might adopt one of two strategies in high-risk areas; if refuges are widespread they will use refuges more intensively, but if refuges are scarce they will adopt a time-minimizing strategy to leave the area as rapidly as possible. The baboons also increased their vigilance when refuges were distant. These results are consistent with the hypothesis that baboons use refuges to reduce predation risk.

Journal Article↗
PubMed1997

Red colobus and Diana monkeys provide mutual protection against predators.

We tested the hypothesis that red colobus monkeys, Procolobus badius and Diana monkeys, Cercopithecus diana in Taï National Park, Ivory Coast, associate to increase safety from predation. We recorded stratum use, exposure and vigilance of each species in the presence and in the absence of the partner species. In the presence of Diana monkeys, red colobus used lower strata more often, were more exposed to the forest floor and looked down less often while foraging. This suggests that red colobus reduce predation pressure from ground predators by associating with Diana. There are several indications that both species are less vulnerable to birds of prey when associated: red colobus looked sideways less often and were more exposed to the front, Diana monkeys used greater heights and were more exposed to the front, to the rear and from above. We also asked whether specific sentinel qualities of Diana monkeys might explain why other sympatric monkey species additionally seek their presence. When groups of various species compositions were approached by an observer, or confronted with an eagle model, Diana monkeys raised the alarm in most cases. Since neither monkey species improves its foraging success when associated, this study shows that predation can both maintain and be the ultimate cause of interspecific associations.Copyright 1997 The Association for the Study of Animal Behaviour

Journal Article↗
PubMed1998

Predator discrimination error and the benefits of Müllerian mimicry.

Müllerian mimicry has traditionally been thought to benefit both unpalatable mimic and model species but recently its existence has been questioned. Even if both mimic and model species are unpalatable, they are unlikely to be equally unpalatable. It has been argued that the more unpalatable species will suffer a cost of increased predation because the presence of the more palatable mimic will increase its perceived palatability (by the predator), similar to that experienced by a model in Batesian mimicry. Yet, previous models of Müllerian mimicry have assumed that a predator can discriminate perfectly between available prey. We argue that this is not the case and that discrimination error is an important factor in determining the nature of mimetic relationships. Using computer simulations we show that the nature of a mimetic relationship will depend on the trade-off between the cost of an increase in perceived palatability and the benefits of a reduction in predator discrimination error. We show that mimicry can be unequivocally Müllerian, with both species benefiting, and propose that palatability should no longer be used as the sole defining characteristic of a mimetic relationship. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Yellowhammers get fatter in the presence of a predator.

According to predictions from theoretical models, body mass and the daily foraging pattern of small birds in winter should be sensitive to predation risk. With increased risk of predation birds are expected to lower their body mass and shift their foraging to the afternoons. I studied the effect of predator presence on daily mass gain in captive yellowhammers, Emberiza citrinella. The birds were tested in unisex pairs, one bird being dominant over the other. In the first treatment the amount of food was restricted, and the daily pattern of mass gain was recorded. The second treatment was identical to the first, but, in addition, a stuffed sparrowhawk, Accipiter nisus, was displayed to the birds in the morning. Contrary to predictions from some theoretical models and other studies, the birds gained weight on days when the hawk was shown. Furthermore, the increased foraging happened mainly in the first half of the day, which also contradicts predictions from models. These results could be explained as a response to interrupted foraging, decreasing the probability of the birds acquiring the critical evening body mass. Alternatively, the birds increased their body reserves in preparation to leave a dangerous situation. Both dominance classes showed a similar response. The results suggest that the effects of predators on foraging interruptions should be included in models of daily routines of reserve accumulation. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Light-induced migration behaviour of Daphnia modified by food and predator kairomones.

Lake-dwelling waterfleas, Daphnia, often face a dilemma. Food availability is highest, near the water surface, but predation by visually hunting predators is also most severe. Swimming downward at dawn reduces predation risk, but food availability and temperature also decrease with depth. We tested whether Daphnia process information derived from food and predator presence to estimate the costs and benefits of migration, and to determine when it pays to swim down. We studied downward swimming of D. galeataxhyalina in response to stepwise accelerations of relative increases in the intensity of light at several food and fish kairomone concentrations. Both had a modifying, additive, although independent effect. We studied in six clones the clonal differences of this environmentally induced plasticity of photobehaviour. These clones were caught at two depths at noon during a period of vertical migration in Lake Maarsseveen (the Netherlands), and so presumably differed in vertical migration behaviour. Two clones, one from the epilimnion and one from the hypolimnion, showed a particularly significant difference in migration behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

The effect of predation on begging-call evolution in nestling wood warblers.

I combined a comparative study of begging in ground- and tree-nesting wood warblers (Parulidae) with experimental measures of the predation costs of warbler begging calls. Throughout their development, ground-nesting warbler nestlings had significantly higher-frequency begging calls than did tree-nesting warblers. There was also a trend for ground-nesting birds to have less rapidly modulated calls. There were no consistent associations between nesting site and the amplitude of the calls. Using miniature walkie-talkies hidden inside artificial nests, I reciprocally transplanted the begging calls of 5- and 8-day-old black-throated blue warblers, Dendroica caerulescens (tree-nesting) and ovenbirds, Seiurus aurocapillus (ground-nesting) and measured the corresponding changes in rates of nest predation. For the begging calls of 8-day-old nestlings, but not those of 5-day-olds, the calls of the tree-nesting species coming from ground nests incurred greater costs than did the calls of ground nesters. The reciprocal transplant had little effect on the rate of predation. Tooth imprints on clay eggs placed in artificial nests indicated that eastern chipmunks, Tamias striatus, were responsible for the increased cost of begging for black-throated blue calls coming from the ground. These data suggest that nest predation may be responsible for maintaining some of the interspecific differences in the acoustic structure of begging calls. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Water temperature influences the shoaling decisions of guppies, Poecilia reticulata, under predation threat.

In previous experiments, we found antipredator behaviours in female Trinidadian guppies to be influenced by water temperature. To distinguish between hypotheses suggested to explain these observations, we examined the effect of an increase in water temperature on the choice of shoal size of individual female guppies, in the absence and presence of predation threat from a confined cichlid. At 22 degrees C, guppies showed no significant preference for either of two shoal sizes of female guppies, although other responses indicated a reaction to the threat. At 26 degrees C, females chose to shoal with the smaller group when the predator was absent, but, once threatened, switched to a strong preference for the larger group. Variation in preference between individuals was quite high in all treatments, and was somewhat lower for guppies under threat in warmer water, although not significantly so. Our evidence indicates that guppies in warmer water behave as if they are at greater risk of predation, but only when under threat. Temperature-dependent increases in predation risk from ectothermic piscivores could result from less efficient escape responses and from greater vulnerability because of increased foraging activity. We suggest that selection favouring guppies displaying an optimal balance between foraging and antipredator behaviours should act more strongly at higher temperature. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Lack of preference for low-predation-risk habitats in larval damselflies explained by costs of intraspecific interactions.

Many studies indicate prey organisms select microhabitats with high structural complexity as a way of reducing risk of predation. We used laboratory experiments to show that damselfly larvae, Ischnura verticalis, suffer higher predation rates from pumpkinseed sunfish in low-density vegetation. However, larvae do not preferentially occupy microhabitats with high vegetation density in either the presence or absence of sunfish; when given a choice, the number of larvae per stem of vegetation was equal across all densities of vegetation. That larvae do not congregate in dense vegetation may reflect costs of aggressive interactions. Results from laboratory experiments indicated larval interactions increase conspicuous behaviours (most notably swimming) and consequently increase fish predation. A subsequent experiment indicated that frequency of larval interactions increases with increased vegetation density when number of larvae/stem is constant. Thus, larval microhabitat selection may reflect a trade-off between reduced risk of predation in areas of high vegetation density, caused by reduced fish foraging ability, and increased aggressive larval interactions, due to decreased proximity of larvae. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1996

A probabilistic model for deriving soil quality criteria based on secondary poisoning of top predators. I. Model description and uncertainty analysis.

In previous studies, the risk of toxicant accumulation in food chains was used to calculate quality criteria for surface water and soil. A simple algorithm was used to calculate maximum permissable concentrations [MPC = no-observed-effect concentration/bioconcentration factor(NOEC/BCF)]. These studies were limited to simple food chains. This study presents a method to calculate MPCs for more complex food webs of predators. The previous method is expanded. First, toxicity data (NOECs) for several compounds were corrected for differences between laboratory animals and animals in the wild. Second, for each compound, it was assumed these NOECs were a sample of a log-logistic distribution of mammalian and avian NOECs. Third, bioaccumulation factors (BAFs) for major food items of predators were collected and were assumed to derive from different log-logistic distributions of BAFs. Fourth, MPCs for each compound were calculated using Monte Carlo sampling from NOEC and BAF distributions. An uncertainty analysis for cadmium was performed to identify the most uncertain parameters of the model. Model analysis indicated that most of the prediction uncertainty of the model can be ascribed to uncertainty of species sensitivity as expressed by NOECs. A very small proportion of model uncertainty is contributed by BAFs from food webs. Correction factors for the conversion of NOECs from laboratory conditions to the field have some influence on the final value of MPC5, but the total prediction uncertainty of the MPC is quite large. It is concluded that the uncertainty in species sensitivity is quite large. To avoid unethical toxicity testing with mammalian or avian predators, it cannot be avoided to use this uncertainty in the method proposed to calculate MPC distributions. The fifth percentile of the MPC is suggested as a safe value for top predators.

Algorithms↗
PubMed1998

Effects of habitat destruction in a prey-predator metapopulation model

A mean field, metapopulation model of a predator-prey interaction is developed in order to understand the consequences of habitate destruction at different trophic levels. Such a model allows is to explore different ecological scenarios (donor control vs. top-down control) by changing a single parameter. The response to habitat destruction is qualitatively the same for both predator and prey, although there are interesting differences linked to the trophic position. A similar decrease in the colonization rates affects the two species quite differently. Predators diminish faster than prey, and furthermore, the fraction of occupied sites decreases more sharply as colonization rates are lowered, i.e. there is a nonlinear relationship between regional abundance and colonization rate. There is a well-defined threshold in the colonization rate below which the predator becomes extinct. Thus, dispersal rate is critical for predicting the consequences of habitat destruction. Finally, these results are compared with the behavior of a spatially explicit simulation. The only difference between the analytical model and the simulation is that colonization is no longer a global phenomenon in the latter, but it is a local process, constrained to the nearest patches. The bulk of the results are similar to the mean field behavior, and we comment on some differences related with non-homogeneity and real space. Some general implications for conservation biology and biological control are outlined. Copyright 1998 Academic Press

Journal Article↗