龟纹瓢虫对棉蚜的捕食行为

为探讨天敌对害虫的捕食作用机制,充分发挥生物防治的作用,本文从捕食能学角度,系统地观测了龟纹瓢虫Propylea japonica (Thunberg)对棉蚜Aphis gossypii Glover的捕食行为及影响的因素。结果表明：龟纹瓢虫对棉蚜的捕食行为依棉蚜的密度变化而逐渐转变;它在棉蚜密度高时,搜索活动下降;而在棉蚜密度低时,则搜索活动增加。产生这种行为是由于肠胃量与棉蚜遭遇率变化的综合作用结果。因此,将瓢蚜比调控在一定水平上,可以更有效地发挥以瓢治蚜的生物防治作用。     

An Adaptive Difference in the Relationship between Foraging Mode and Responses to Prey Chemicals in two Congeneric Scincid Lizards

Sensory abilities must allow efficient detection of prey, but the senses used and their relative importance may vary with hunting methods. In lizards, ambush foragers locate prey visually and active foragers use a combination of vision and vomerolfaction, the chemical sense associated with the vomeronasal system. Active foragers, but not ambush foragers, discriminate between prey chemicals and other chemical stimuli sampled by tongue-flicking. In active foragers, features of the tongue that may improve chemical sampling, such as elongation and forking are more pronounced and density of vomeronasal chemoreceptors is greater, than in ambush foragers. Foraging mode is fixed in most lizard families, and correlated evolution has been demonstrated among foraging mode, discrimination of prey chemicals, and lingual-vomeronasal morphology by interfamilial comparisons. Here I present information on a rare case of an intrageneric difference in foraging mode in the genus Mabuya . Laboratory experiments on the discrimination of prey chemicals showed that the active forager M . striata sparsa exhibits prey chemical discrimination, but the ambush forager M . acutilabris does not. The active forager also has a slightly more elongated tongue with deeper notching at the tip than the ambush forager, which might be a response to a change in foraging behavior or a reflection of unrelated differences in head shape. These findings confirm predictions based on correlated evolution between the hunting method and use of the chemical sense to locate food. They further show that chemosensory behavior is adjusted to change in foraging mode more rapidly than was previously known and suggest that behavioral changes may occur more rapidly than associated modifications of chemosensory morphology.     

Absence of Prey Chemical Discrimination by Tongue-flicking in an Ambush-foraging Lizard Having Actively Foraging Ancestors

Lingually mediated detection of prey chemicals is widespread in one major clade of lizards, Scleroglossa, but rare in the other, Iguania. It is absent in all ambush-foraging families tested and present in all actively foraging families. In Iguania, prey chemical discrimination is known only in the herbivorous Iguanidae; in Scleroglossa, it was heretofore known to be absent only in ambush-foraging gekkonids. Because ambush foraging precludes lingual sampling of a wide area and tongue-flicking would disrupt the crypticity ambushers maintain by immobility, we predicted that prey chemical discrimination would be absent in scleroglossans that have secondarily adopted ambush foraging. The Cape girdled lizard, Cordylus cordylus, is member of Cordylidae, a family of ambush foragers considered derived from active foragers in the Autarchoglossa, a group of scleroglossan families having highly developed lingual chemosensory behaviours. As predicted, this species did not discriminate surface chemicals of three prey species from control substances in a series of standardized experiments in which prey chemicals were presented on cotton-tipped applicators. Thus, even in taxa having highly developed prey chemical discrimination, adoption of ambush foraging may induce loss of prey chemical discrimination, providing further and stronger evidence that prey chemical discrimination is adaptively adjusted to foraging mode.     

Does body size influence thermal biology and diet of a python (Morelia spilota imbricata)?

Current theory predicts that larger‐bodied snakes not only consume larger prey (compared with smaller individuals), but may also have a different range of prey available to them due to their thermal biology. It has been argued that smaller individuals, with lower thermal inertia (i.e. faster cooling rates at nightfall when air temperature falls and basking opportunities are limited), may be thermally restricted to foraging and hunting during the day on diurnally active prey, and have reduced capacity to hunt crepuscular and nocturnal prey species. This predictive theory was investigated by way of dietary analysis, assessment of thermal biology and thermoregulation behaviour in an ambush forager, the south‐west carpet python (Morelia spilota imbricata, Pythonidae). Eighty‐seven scats were collected from 34 individual pythons over a 3‐year radiotelemetry monitoring study. As predicted by gape size limitation, larger pythons took larger prey; however, 65% of prey items of small pythons were represented by nocturnally active, small mammals, a larger proportion than present in larger snakes. Several measures of thermal biology (absolute body temperature, thermal differential of body temperature to air temperature, maximum hourly heating and cooling rates) were not strongly affected by python body mass. Additionally, body temperature was only influenced by the behavioural choice of microhabitat selection and was not affected by python body size or position, suggesting that these behavioural choices do not allow smaller pythons to vastly increase their temporal foraging window. By coupling dietary analysis, measures of body temperature and behavioural observations of free‐ranging animals, we conclude that, contrary to theoretical predictions, a small body size does not thermally restrict the temporal window for ambush foraging in M. s. imbricata. An ontogenetic or size‐determined switch from ambush feeding to actively foraging on slower prey would account for the differences in prey taken by these animals. The concept of altered foraging behaviour warrants further investigation in this species.     

Foraging strategy of a mantid,Paratenodera angustipennis S.: Mechanisms of switching tactics between ambush and active search

Summary Foraging strategies of a mantid, Paratenodera angustipennis de Saussure were investigated both in the laboratory and in the field to determine how mantids assess the profitability of their location, and based on it, how they switch their tactics. Although mantids are often considered to be ambush predators, nymphs and adult females changed their tactics from ambushing to active searching when they did not capture any prey for more than about 2 days (nymphs) and 3 days (adult females). Switching between the two tactics was such that the females and nymphs spent more searching effort in sites with higher prey density. As opposed to the females and nymphs, male mantids did not change their tactics according to their hunger level (in our definition, and the prey density in the hunting site. The males moved around more than twice as much as did the females. In the field, female mantids moved less frequently at higher female densities.     

Foraging Behavior in the Arboreal Boid Corallus grenadensis

Corallus grenadensis is an arboreal boa endemic to the Grenada Bank. Thirty-five encounters with boas resulted in 17.65 hours of observations, including 6.3 hours of video-tape (which included two acts of predation). Boas under 100 cm are largely active foragers that move slowly through bushes and trees and tongue-flick leaf and branch surfaces apparently seeking chemosensory evidence of nocturnally quiescent lizard (Anolis) prey. Significantly more search time was directed to branches below the snake rather than to either the branches supporting the snake or to those above the snake, and tongue-flick rates were significantly higher for moving snakes than for those that were stationary. Smaller snakes prey on nocturnally quiescent lizards and they spent more time moving than did large snakes that feed on nocturnally active rodents and often employ an ambush foraging strategy. Once visual and, presumably, thermal information was received from a sleeping anole, C. grenadensis adopted a lengthy stalking process devoid of tongue-flicks. Snakes approached inactive lizards from adjacent branches with great stealth, moving at a rate of about 1 cm/min. The strike was made from close range (within 3 cm), and the prey was never released once contact was made. We conclude that, if chemosensory cues successfully lead a treeboa to a visual encounter with a sleeping lizard, subsequent behavior ensures a high rate of predation success.     

Foraging habitat determines predator–prey size relationships in marine fishes

Predator–prey size (PPS) relationships are determined by predator behaviour, with the likelihood of prey being eaten dependent on their size relative to that of the consumer. Published PPS relationships for 30 pelagic or benthic marine fish species were analysed using quantile regression to determine how median, lower and upper prey sizes varied with predator size and habitat. Habitat effects on predator foraging activity/mode, morphology, growth and natural mortality are quantified and the effects on PPS relationships explored. Pelagic species are more active, more likely to move by caudal fin propulsion and grow more rapidly but have higher mortality rates than benthic species, where the need for greater manoeuvrability when foraging in more physically complex habitats favours ambush predators using pectoral fin propulsion. Prey size increased with predator size in most species, but pelagic species ate relatively smaller prey than benthic predators. As pelagic predators grew, lower prey size limits changed little, and prey size range increased but median relative prey size declined, whereas the lower limit increased and median relative prey size was constant or increased in benthic species.     

Landscape structure influences the use of social information in an insectivorous bat

In anthropogenic landscapes, aerial insectivores are often confronted with variable habitat complexity, which may influence the distribution of prey. Yet, high mobility may allow aerial insectivores to adjust their foraging strategy to different prey distributions. We investigated whether aerial-hunting common noctules Nyctalus noctula adjust their foraging strategy to landscapes with different habitat complexity and assumingly different prey distribution. We hypothesized that the movement behaviour of hunting common noctules and changes of movement behaviour in reaction towards conspecifics would depend on whether they hunt in a structurally poor cropland dominated landscape or a structurally rich forest dominated landscape. We tracked flight paths of common noctules in northeastern Germany using GPS loggers equipped with an ultrasonic microphone that recorded foraging events and presence of conspecifics. Above cropland, common noctules hunted mainly during bouts of highly tortuous and area restricted movements (ARM). Bats switched from straight flight to ARM after encountering conspecifics. In the forested landscape, common noctules hunted both during ARM and during straight flights. The onset of ARM did not correlate with the presence of conspecifics. Common noctules showed a lower feeding rate and encountered more conspecifics above the forested than above the cropland dominated landscape. We conjecture that prey distribution above cropland was patchy and unpredictable, thus making eavesdropping on hunting conspecifics crucial for bats during search for prey patches. In contrast, small scale structural diversity of the forested landscape possibly led to a more homogeneous prey distribution at the landscape scale, thus enabling bats to find sufficient food independent of conspecific presence. This suggests that predators depending on ephemeral prey can increase their foraging success in structurally poor landscapes by using social information provided by conspecifics. Hence, a minimum population density might be obligatory to enable successful foraging in simplified landscapes.     

Ambush or active life: foraging mode influences haematocrit levels in snakes

The rate at which organisms acquire resources is a critical trait and foraging mode can vary from sit‐and‐wait tactics to being highly mobile and active. Snakes provide a robust opportunity to examine the physiological correlates of contrasted foraging strategies. In this context, haematocrit (Hct), a proxy of blood oxygen carrying capacity, should be a reliable indicator of aerobic activity levels. We used phylogenetically informed models to examine the relationship between foraging mode and Hct in 80 snake species. After accounting for clade and habitat effects, we found a significant relationship of Hct with foraging mode; Hct is lower in snakes that ambush prey compared to active foragers across habitats. Species using both foraging tactics had marginally lower Hct than active foragers. Ambush foraging tactics are widespread in snakes, notably among low‐energy specialists that usually display low feeding frequency, as well as limited activity and daily movements. Because Hct influences blood viscosity, low levels may thus be advantageous by reducing maintenance and locomotory costs. Further studies are required to better understand the implication of foraging mode on blood characteristics and other aspects of snake physiology. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 636–645.     

Foraging modes of stream benthic fishes in relation to their predation effects on local prey density

Habitat use and foraging behavior of two benthic insectivorous gobies, Rhinogobius sp. CO (cobalt type) and Rhinogobius sp. DA (dark type), were examined in relation to their predation effects on local prey density in a small coastal stream in southwestern Shikoku, Japan. Correlations among the foraging range, frequency of foraging attempts and current velocity indicated that individuals using fast-current habitats had small foraging ranges and infrequently made foraging attempts while those in slow currents frequently foraged over large areas. The former and the latter were recognized as ambush and wandering foragers, respectively. Interspecific comparisons of habitat use, foraging behavior and prey preference suggested that Rhinogobius sp. CO selectively forage mobile prey by ambushing in fast currents, whereas Rhinogobius sp. DA randomly forage available prey by wandering in slow-current habitats. A cage experiment was conducted to assess prey immigration rate and the degree of predation effects on local prey density in relation to current velocity. The results of the experiment support, at least in part, our initial predictions: (1) prey immigration rates increase with current velocity and (2) the effects of fish predation on local prey density are reduced as current velocity increases. Overall results illustrated a link between the foraging modes of the stream gobies and their predation effects on local prey density: fish adopt ambush foraging in fast currents, where the decrease in prey density tends to be less, whereas fish actively forage over large areas in slow currents, where the decrease in prey is relatively large.     

Efficiency evaluation of two competing foraging modes under different conditions

Various foraging modes are employed by predators in nature, ranging from ambush to active predation. Although the foraging mode may be limited by physiological constraints, other factors, such as prey behavior and distribution, may come into play. Using a simulation model, we tested to what extent the relative success of an ambush and an active predator changes as a function of the relative velocity and movement directionality of prey and active predator. In accordance with previous studies, we found that when both active predator and prey use nondirectional movement, the active mode is advantageous. However, as movement becomes more directional, this advantage diminishes gradually to 0. Previous theoretical studies assumed that animal movement is nondirectional; however, recent field observations show that in fact animal movement usually has some component of directionality. We therefore suggest that our simulation is a better predictor of encounter rates than previous studies. Furthermore, we show that as long as the active predator cannot move faster than its prey, it has little or no advantage over the ambush predator. However, as the active predator's velocity increases, its advantage increases sharply.     

Prey‐specific foraging tactics in a web‐building spider

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The effect of prey density on foraging mode selection in juvenile lumpfish: balancing food intake with the metabolic cost of foraging

1. In many species, individuals will alter their foraging strategy in response to changes in prey density. However, previous work has shown that prey density has differing effects on the foraging mode decisions of ectotherms as compared with endotherms. This is likely due to differences in metabolic demand; however, the relationship between metabolism and foraging mode choice in ectotherms has not been thoroughly studied. 2. Juvenile lumpfish Cyclopterus lumpus forage using one of two modes: they can actively search for prey while swimming, or they can 'sit-and-wait' for prey while clinging to the substrate using a ventral adhesive disk. The presence of these easily distinguishable foraging modes makes juvenile lumpfish ideal for the study of foraging mode choice in ectotherms. 3. Behavioural observations conducted during laboratory experiments showed that juvenile lumpfish predominantly use the 'cling' foraging mode when prey is abundant, but resort to the more costly 'swim' mode to seek out food when prey is scarce. The metabolic cost of active foraging was also quantified for juvenile lumpfish using swim-tunnel respirometry, and a model was devised to predict the prey density at which lumpfish should switch between the swim and cling foraging modes to maximize energy intake. 4. The results of this model do not agree with previous observations of lumpfish behaviour, and thus it appears that juvenile lumpfish do not try to maximize their net energetic gain. Instead, our data suggest that juvenile lumpfish forage in a manner that reduces activity and conserves space in their limited aerobic scope. This behavioural flexibility is of great benefit to this species, as it allows young individuals to divert energy towards growth as opposed to activity. In a broader context, our results support previous speculation that ectotherms often forage in a manner that maintains a minimum prey encounter rate, but does not necessarily maximize net energy gain.     

How phylogeny and foraging ecology drive the level of chemosensory exploration in lizards and snakes

The chemical senses are crucial for squamates (lizards and snakes). The extent to which squamates utilize their chemosensory system, however, varies greatly among taxa and species’ foraging strategies, and played an influential role in squamate evolution. In lizards, ‘Scleroglossa’ evolved a state where species use chemical cues to search for food (active foragers), whereas ‘Iguania’ retained the use of vision to hunt prey (ambush foragers). However, such strict dichotomy is flawed as shifts in foraging modes have occurred in all clades. Here, we attempted to disentangle effects of foraging ecology from phylogenetic trait conservatism as leading cause of the disparity in chemosensory investment among squamates. To do so, we used species’ tongue‐flick rate (TFR) in the absence of ecological relevant chemical stimuli as a proxy for its fundamental level of chemosensory investigation, that is baseline TFR. Based on literature data of nearly 100 species and using phylogenetic comparative methods, we tested whether and how foraging mode and diet affect baseline TFR. Our results show that baseline TFR is higher in active than ambush foragers. Although baseline TFRs appear phylogenetically stable in some lizard taxa, that is a consequence of concordant stability of foraging mode: when foraging mode shifts within taxa, so does baseline TFR. Also, baseline TFR is a good predictor of prey chemical discriminatory ability, as we established a strong positive relationship between baseline TFR and TFR in response to prey. Baseline TFR is unrelated to diet. Essentially, foraging mode, not phylogenetic relatedness, drives convergent evolution of similar levels of squamate chemosensory investigation.     

Adaptive variation in the foraging behaviour of Grey Plover Pluvialis squatarola and Whimbrel Numenius phaeopus

Between-site variation in the diet and foraging behaviour of a fixed-method forager, the Grey Plover Pluvialis squatarola , and a versatile forager, the Whimbrel Numenius phaeopus , was examined and compared at nine tropical and south temperate sites. Grey Plover always foraged in a run-stop-search manner but changed the emphasis of components of this behaviour in response to prey type. Whimbrel foraged tactilely or visually and readily changed foraging speed and habitat. Both species ate a variety of prey species depending on their availability. The diet of Grey Plover was dominated by small prey, polychaetes and crabs, and Whimbrel ate mostly crabs, with Whimbrel being the more specialized in prey choice. The broader diversity of prey types consumed by Grey Plover was attributed to limitations imposed by obligate visual foraging, whereas the flexible foraging behaviour of Whimbrel allowed the latter to concentrate their efforts on the most profitable prey. Grey Plover appeared to have a density upper limit, determined by their stereotyped foraging behaviour. Whimbrel densities varied greatly in response to prey type and foraging method. Foraging effort could not be predicted from measurements of instantaneous daytime energy intake rates, and reasons for the lack of this relationship are discussed.     

The Relationship Between Foraging Ecology and Lizard Chemoreception: Can a Snake Analogue (Burton’s Legless Lizard,Lialis burtonis) Detect Prey Scent?

In lizards and snakes, foraging mode (active vs. ambush) is highly correlated with the ability to detect prey chemical cues, and the way in which such cues are utilized. Ambush-foraging lizards tend not to recognize prey scent, whereas active foragers do. Prey scent often elicits strikes in actively-foraging snakes, while ambushers use it to select profitable foraging sites. We tested the influence of foraging ecology on the evolution of squamate chemoreception by gauging the response of Burton's legless lizard ( Lialis burtonis Gray, Pygopodidae) to prey chemical cues. Lialis burtonis is the ecological equivalent of an ambush-foraging snake, feeding at infrequent intervals on relatively large prey, which are swallowed whole. Captive L. burtonis did not respond to prey odour in any manner: prey chemical cues did not elicit elevated tongue-flick rates or feeding strikes, nor were they utilized in the selection of ambush sites. Like other ambushing lizards, L. burtonis appears to be a visually oriented predator. In contrast, an active forager in the same family, the common scaly-foot ( Pygopus lepidopodus ), did tongue-flick in response to odours of its preferred prey. These results extend the correlation between lizard foraging mode and chemosensory abilities to a heretofore-unstudied family, the Pygopodidae.     

Feeding Experience Modifies the Assessment of Ambush Sites by the Timber Rattlesnake, a Sit-and-Wait Predator

To effectively ambush prey, sit‐and‐wait predators must locate sites where profitable prey are likely to return. One means by which predators evaluate potential ambush sites is by recognizing high‐use areas through chemical cues deposited inadvertently by their prey. However, it is unknown whether ambush predators can use chemical cues associated with past prey items in the assessment of potential ambush sites. I examined selection of ambush sites by timber rattlesnakes (Crotalus horridus) exposed to trails made from chemical extracts of the integument of various prey species. I evaluated the role of feeding experience in ambush site selection by comparing the behavior of timber rattlesnakes before and after feeding experience with different sized prey items. Timber rattlesnakes are more likely to select ambush sites adjacent to chemical trails from prey with which they have had feeding experience, but only those fed relatively large prey showed an increase in responsiveness. Increased responsiveness after feeding experience was exhibited in experiments using integumentary extracts of mammals (the natural prey of timber rattlesnakes), but not in those using extracts of fish. These results indicate that ambush predators may learn to recognize chemicals on the integument of profitable food items, and use that experience when subsequently selecting ambush sites. Additionally, these findings provide evidence that size‐dependent predation by snakes may be, in some species, a result of active prey selection.     

Pikeperch Sander lucioperca trapped between niches: foraging performance and prey selection in a piscivore on a planktivore diet

The foraging behaviour of planktivorous pikeperch Sander lucioperca during their first growing season was analysed. Field data showed that S. lucioperca feed on extremely rare prey at the end of the summer, suggesting the presence of a bottleneck. In experiments, foraging ability of planktivorous S. lucioperca was determined when fish were feeding on different prey types (Daphnia magna or Chaoborus spp.) and sizes (D. magna of lengths 1 or 2·5 mm) when they occurred alone. From these results, the minimum density requirement of each prey type was analysed. The energy gain for three different foraging strategies was estimated; a specialized diet based on either large D. magna or Chaoborus spp. or a generalist diet combining both prey types. Prey value estimates showed that Chaoborus spp. should be the preferred prey, assuming an energy maximizing principle. In prey choice experiments, S. lucioperca largely followed this principle, including D. magna in the diet only when the density of the Chaoborus spp. was below a threshold value. Splitting the foraging bout into different sequences, however, resulted in a somewhat different pattern. During an initial phase, S. lucioperca captured both prey as encountered and then switched to Chaoborus spp. if prey density was above the threshold level. The prey selection observed was mainly explained by sampling behaviour and incomplete information about environmental quality, whereas satiation only had marginal effects. It was concluded that the observed diet based on rare prey items was in accordance with an optimal foraging strategy and may generate positive growth in the absence of prey fish in suitable sizes.     

Short‐term prey field lability constrains individual specialisation in resource selection and foraging site fidelity in a marine predator

Spatio‐temporally stable prey distributions coupled with individual foraging site fidelity are predicted to favour individual resource specialisation. Conversely, predators coping with dynamic prey distributions should diversify their individual diet and/or shift foraging areas to increase net intake. We studied individual specialisation in Scopoli's shearwaters (Calonectris diomedea) from the highly dynamic Western Mediterranean, using daily prey distributions together with resource selection, site fidelity and trophic‐level analyses. As hypothesised, we found dietary diversification, low foraging site fidelity and almost no individual specialisation in resource selection. Crucially, shearwaters switched daily foraging tactics, selecting areas with contrasting prey of varying trophic levels. Overall, information use and plastic resource selection of individuals with reduced short‐term foraging site fidelity allow predators to overcome prey field lability. Our study is an essential step towards a better understanding of individual responses to enhanced environmental stochasticity driven by global changes, and of pathways favouring population persistence.     

A Comparison of the Seasonal Movements of Tiger Sharks and Green Turtles Provides Insight into Their Predator-Prey Relationship

During the reproductive season, sea turtles use a restricted area in the vicinity of their nesting beaches, making them vulnerable to predation. At Raine Island (Australia), the highest density green turtle Chelonia mydas rookery in the world, tiger sharks Galeocerdo cuvier have been observed to feed on green turtles, and it has been suggested that they may specialise on such air-breathing prey. However there is little information with which to examine this hypothesis. We compared the spatial and temporal components of movement behaviour of these two potentially interacting species in order to provide insight into the predator-prey relationship. Specifically, we tested the hypothesis that tiger shark movements are more concentrated at Raine Island during the green turtle nesting season than outside the turtle nesting season when turtles are not concentrated at Raine Island. Turtles showed area-restricted search behaviour around Raine Island for ∼3–4 months during the nesting period (November–February). This was followed by direct movement (transit) to putative foraging grounds mostly in the Torres Straight where they switched to area-restricted search mode again, and remained resident for the remainder of the deployment (53–304 days). In contrast, tiger sharks displayed high spatial and temporal variation in movement behaviour which was not closely linked to the movement behaviour of green turtles or recognised turtle foraging grounds. On average, tiger sharks were concentrated around Raine Island throughout the year. While information on diet is required to determine whether tiger sharks are turtle specialists our results support the hypothesis that they target this predictable and plentiful prey during turtle nesting season, but they might not focus on this less predictable food source outside the nesting season.