Predator Avoidance Responses Research Articles

ORIENTATION OF THE HERMIT CRAB CLIBANARIUS ANTILLENSIS: EFFECTS OF VISUAL AND CHEMICAL CUES

Orientation of the hermit crabs Clibanarius antillensis to solid and striped targets of different visual angles was tested in a circular arena upon exposure to background sea water, calcium concentrations, gastropod odor, predatory fish odor, and seagrass odor. The test hypotheses were that (1) this hermit crab has the capacity to use visual cues for orientation and (2) it discriminates between objects on the basis of visual and chemical information. Adult crabs were tested during the day without their gastropod shells, and orientation varied with concentration and chemical cue. In general, orientation increased as concentration increased up to a maximum orientation response and then declined at higher concentrations. Solid targets representing gastropod shells attracted crabs in the presence of calcium and gastropod odor. Orientation toward striped targets representing seagrass increased in the presence of seagrass odor. Finally, orientation directly away from a target (predator avoidance response) was only observed in the presence of predator odor. Thus, both hypotheses were supported.

Differential use of visual and chemical cues in predator recognition and threat-sensitive predator-avoidance responses by larval newts (Notophthalmus viridescens)

For prey under the threat of predation, the ability to distinguish between different levels of danger can have important fitness consequences. Larval central newts, Notophthalmus viridescens louisianensis, distinguished between predatory (Ambystoma tigrinum tigrinum larvae) and nonpredatory (Hyla chrysoscelis/versicolor complex tadpoles) heterospecifics, but only when chemical cues were available. When only visual cues were present, larvae responded to both predatory and nonpredatory stimuli by reducing activity (fright response), but did not distinguish between the two types. Fine-scale discrimination of visual stimuli may have failed to develop because larval newts typically live in aquatic habitats in which chemical cues may be more reliable than visual cues, owing to large amounts of sediments and vegetation or possibly to myopia. Late-stage newt larvae that were approaching metamorphosis were unpalatable to A. t. tigrinum, and histological examination of the skin revealed that granular (poison) glands were present in the skin of late-stage but not early-stage larvae. Late-stage larvae did not distinguish between chemical stimuli from predators and nonpredators, which suggests that fright responses of larval newts are plastic and can be modified according to the level of perceived threat.

Differential use of visual and chemical cues in predator recognition and threat-sensitive predator-avoidance responses by larval newts (<i>Notophthalmus viridescens</i>)

Differential use of visual and chemical cues in predator recognition and threat-sensitive predator-avoidance responses by larval newts (<i>Notophthalmus viridescens</i>)

Hiding responses of locusts to approaching objects

Locusts, Locusta migratoria, sitting on a plant stem hide from dark moving or expanding shapes in their environment. The fore- and middle legs perform this avoidance response by making lateral tilting movements, while the hindlegs slide laterally and guide rotation of the posterior body over the stem. During larger turns, the legs take lateral steps when lateral tilting is limited by the joints. Slow hiding movements of less than 300 degrees s-1 of angular velocity are induced by slowly changing (looming) shapes, and interposed stops or slowing of the movement can delay the progress of this hiding manoeuvre. Fast hiding movements with angular velocities between 120 degrees s-1 and 860 degrees s-1 proceed continuously and rapidly in response to rapidly expanding stimuli. Hiding responses to expanding shapes occur only after the expanding image has exceeded a threshold visual angle of 8-9.5 degrees. Hiding response latencies range between 220 ms and 1.2 s for fast hiding and are approximately 1.2 s for most slow hiding responses. Predator-avoidance responses such as freezing, jerking, crouching, walking backwards, dropping or jumping can be used instead of or in conjunction with hiding behaviour. We conclude that the fast hiding behaviour of locusts is a specific goal-directed type of optomotor behaviour requiring positional information from small-field detectors of shape expansion in the interneurone layers of the locust eye.

Orientation of blue crab, Callinectes sapidus (Rathbun), Megalopae: Responses to visual and chemical cues

Post-larvae (megalopae) of the blue crab Callinectes sapidus are transported from offshore areas into estuaries where they settle and metamorphose in specific areas, such as seagrass beds. The present study tested the hypothesis that intermolt and premolt megalopae had different behavioral responses to visual and chemical cues that are associated with predator avoidance and settlement. Visually directed movements to solid and striped rectangular targets subtending different visual angles (5–350°) were tested in an arena in the presence of either Offshore Water, Seagrass ( Zostera marina) Odor Water or Predator ( Fundulus heteroclitus) Odor Water. Intermolt megalopae generally swam away from 10° to 180° targets in all water types which was interpreted as a predator avoidance response. Premolt megalopae had similar behavior in Offshore and Seagrass Odor Water. However in Predator Odor water, they displayed different predator avoidance behavior. When presented with a solid target, premolt megalopae either remained motionless or swam directly away from the target. If presented with targets resembling stalks of seagrass (vertical stripes), they swam in all directions which was interpreted as a startle response. In a chemical choice chamber, both molt stages were not attracted to Seagrass Odor Water but avoided Predator Odor Water. There was no evidence that megalopae used chemical cues for orientation toward settlement sites. Thus, the hypothesis was supported and the results suggest that behavioral responses to the test chemical and visual cues are involved in predator avoidance.

Effects of environmental history, sibship, and age on predator-avoidance responses of tadpoles

Gray treefrog (Hyla chrysoscelis) tadpoles exhibit predator-avoidance behaviors, such as increased refugium use, in the presence of predators. We presented tadpoles with waterborne chemical cues from predators and with epidermal extracts of conspecifics. We also examined whether responses of tadpoles are affected by the presence of a predator in the environment in which they were reared, by their developmental stage, or by genetic (family) effects. Predator cues significantly increased the tadpoles' use of a refugium. Although there was no effect due to age alone, there was a significant interaction between predator cues and age, indicating that tadpoles may exhibit predator avoidance at most vulnerable sizes. The degree of expression of this behavior is also dependent upon the environmental history of the organism (i.e., rearing condition), indicating that this response can interact with environmental conditions (i.e., composition of the predator community). Additionally, we found no differences among full-sib families, suggesting that predator avoidance in this species may be influenced more by the environment than by genes.

Predator-induced diel vertical migration inDaphnia: Enrichment and preliminary chemical characterization of a kairomone exuded by fish

Planktivorous fish release a cue of an unknown chemical nature into the water that induces diel vertical migration inDaphnia as predator avoidance response. We used a bioassay to obtain information about the chemical nature of the kairomone. We present a method to enrich the cue from holding water of fish by sorbent extraction. The kairomone exuded byLeucaspius delineatus can be characterized as a nonolefinic low-molecular-weight anion of intermediate lipophilicity. The presence of amino groups in the molecule can be excluded, whereas hydroxy groups are essential for activity. Separation by HPLC yielded only one active fraction. The kairomones released byCarassius carassius andRutilus rutilus showed the same chemical characteristics, suggesting that the kairomones from different species of fish, sensed byDaphia, are very similar, if not identical.

Freshwater snails alter habitat use in response to predation

This study compared snail habitat use in Michigan lakes that contain a predator, the molluscivorous pumpkinseed sunfish, Lepomis gibbosus, with snail habitat use in adjacent lakes lacking pumpkinseeds. Snails in lakes with pumpkinseeds used the covered portion of standardized substrates more often than did snails in lakes lacking pumpkinseeds. The hypothesis that covered habitats provide a refuge from fish predation was experimentally tested by stocking Physellainto artificial pools and manipulating the presence of cover and pumpkinseeds. After 3 days, survivorship of Physellawas 15-fold higher in pools containing a covered habitat. To test for the existence of chemically mediated predator avoidance behaviours in Physella, they were exposed to water that had been in contact with (1) pumpkinseeds and (2) crushed conspecifics. Physelladid not change their habitat use when exposed to water that had been in contact with pumpkinseeds, but increased their refuge use two-fold over controls when exposed to water that had been in contact with crushed conspecifics. The effects of habitat structure on the type of predator avoidance response used by Physellawas tested by exposing them to mortality risk in wading pools with and without covered habitats. Physelladid not move to the surface in response to mortality risk if a covered habitat was available, but in the absence of a covered habitat they responded to mortality risk by moving to the water's surface. Possible consequences of flexible behavioural choices by snails for population and community-level processes are discussed.

Microhabitat and Activity Periodicity of Predatory Stoneflies and Their Mayfly Prey in a Western Colorado Stream

Experiments were conducted to determine whether overlap between microhabitat preferences and activity periodicities of four mayfly species and their stonefly predators could explain species-specific differences in predator-prey encounter frequencies. Preferences for rock type (slate or granite), flow microhabitat (high or low), rock surface (top, bottom, upstream or downstream sides), and periodicity of drift and the use of rock tops were measured in a stream-side system of flow-through circular Plexiglas chambers receiving natural stream water and light levels. These parameters were compared among the predatory stoneflies, Megarcys signata or Kogotus modestus, and four species of mayflies that vary in their encounter rates with the stoneflies. Based on predator-prey encounter rates previously observed in similar chambers, we expected greater overlap between Megarcys and Ephemerella infrequens and the overwintering generation of the bivoltine mayfly, Baetis bicaudatus than with Cinygmula sp. Likewise, we expected Kogotus microhabitat use to overlap more strongly with that of summer generation Baetis than with later instars of Cinygmula and Epeorus deceptivus. Results ran counter to our predictions, indicating that microhabitats of the prey species with high predator encounter rates did not overlap more strongly with the stoneflies than did mayflies with low predator encounter rates. Most mayflies and stoneflies preferred the bottom surfaces of granite rocks, and showed few flow preferences. Most were nocturnal in their use of top rock surfaces, in drift and feeding activity periodicity. Therefore, nocturnal activity periodicities of both mayflies and stoneflies confirm that mayflies have not evolved feeding periodicity to avoid encounters with foraging stonefly predators. We conclude therefore, that neither temporal nor spatial microhabitat overlap is a reasonable explanation of differential encounter rates between predatory stoneflies and their mayfly prey. Alternative explanations for differential encounter rates are that more abundant or more mobile mayflies have higher encounter rates with predators, and effective pre-contact predator avoidance responses of other mayflies reduce their encounter rates with stoneflies.

No Evidence for Kin-Preferential Swarming in a Daphnia magna Population Coexisting with Fish

In a recent paper, Young et al. (1994) proposed a graphical model indicating that under certain conditions (a dome-shaped functional response of the predator) prey swarming may entail not only benefits for the individual (Hamilton 1971), but also for the swarm as a whole (group level benefit). They argue that, in organisms that partially reproduce by apomictic parthenogenesis such as Daphnia, any grouprelated benefits may favour the formation of swarms among clone-mates. Young et al. (1994) then present field and laboratory observations on D. longispina that support the above notion, by showing that electrophoretically defined uniclonal populations often show a higher cohesion than multiclonal assemblages in a laboratory set-up, and that a swarm of D. longispina in a garden pond apparently mainly consisted of members of a single 'electrophoretic clone' (sensu Carvalho & Crisp 1987). The authors themselves point to the fact that this latter result needs to be interpreted with caution due to the fact that only one enzyme system (esterase), with an uncertain number of loci, was screened. We here present data that show for a population that coexists with fishes, where swarming is most probably a predator-avoidance strategy, that Daphnia swarms are no less genetically diverse than non-swarming individuals. The present data were collected during a survey of spatial genetic heterogeneity in Daphnia magna Straus populations, and in our opinion provide a more robust test of the above hypothesis than that presented by Young et al. (1994), since more samples (individuals and swarms/non-swarms) were analysed at four loci per individual. Our findings do not support the generality of kin-preferential swarming behaviour in Daphnia as a predator avoidance response.

Diel foraging periodicity of lotic mayfly (Ephemeroptera) nymphs during the subarctic summer

We used a combination of gut content analysis and direct behavioural observations to examine the diel periodicity of lotic mayfly nymphs. In early July, close to the summer solstice, feeding of Heptagenia sulphurea was aperiodic. Baetis rhodani fed most actively during the day, yet drift of large nymphs peaked sharply during the short period of dusk around midnight. In August, Heptagenia dalecarlica was strongly nocturnal, whereas only a slight tendency towards nocturnality was observed in baetid nymphs. All aspects of Baetis feeding behaviour indicated night-time activity in September. There were some differences between Baetis size-classes, small nymphs being less constrained to feed at night. Activity of heptageniid nymphs was low in September, but diel variation in gut fullness implied primarily nocturnal feeding. Diel variation in water temperature was not closely associated with mayfly periodicity, and we suggest that the tendency to night-time activity is best explained by fish predation risk. Although the presence of fish was not manipulated in this study, nymphs may have perceived chemical fish signals from the water used in the laboratory trials. Some behavioural patterns, e.g. strong nocturnality of Heptagenia nymphs in August, may be fixed predator avoidance responses of highly vulnerable prey. We emphasize the importance of considering predation risk and prey size in studies of lotic mayfly periodicity. In high northern areas, the role of these factors in affecting the foraging periodicity of aquatic insects may vary seasonally in concert with varying day-length.

Predator Avoidance and Alarm‐response Behaviour in Kin‐discriminating Tadpoles (Rana cascadae)

AbstractWhen captured by predators, the tadpoles of some species of frogs and toads may release an alarm substance that alters the behaviour of conspecifics. Such ‘alarm response’ behaviour has been proposed as a potential mechanism whereby related conspecifics may ‘warn’ relatives of a predator's presence and thus, improve their inclusive fitness. We examined predator avoidance and alarm response behaviour in tadpoles of the Cascades frog (Rana cascadae) and tested whether such behaviour is influenced by kinship factors. Tadpoles reduced activity when in the presence of a predatory newt (Taricha granulosa). Individuals in sibling groups were more active than both solitary tadpoles and individuals in mixed groups of siblings and nonsiblings. However, we found no evidence of an alarm response in R. cascadae. Behaviour of tadpoles in groups exposed only to predators was not different from that of tadpoles in groups exposed to predators plus crushed conspecifics. Tadpoles in groups exposed to crushed tadpoles were as active as tadpoles in groups exposed to water controls, and some test individuals fed upon the dead tadpoles. Thus, while R. cascadae tadpoles reduce activity in response to newt predators, crushed tadpoles appear to initiate a feeding response rather than an alarm response as has been previously proposed.

Predator-Avoidance Responses in Freshwater Decapod-Gastropod Interactions Mediated by Chemical Stimuli

Previous studies on single species of snails reached conflicting conclusions regarding the importance of chemical cues in predator-avoidance behavior. We performed laboratory experiments to determine if chemically mediated, predator-avoidance behavior, such as crawling out of the water by freshwater gastropods, occurred among prey of different species from several geographic sources: Oklahoma, Oregon, and Wisconsin. We compared responses of eight gastropod populations when they were exposed to predation by three species of crayfish. We observed no crawl-out from two prosobranch species. Individuals from four of six populations of pulmonates responded to crayfish predators; physid and lymnaeid populations consistently responded whereas some planorbid populations did not respond. We also examined individual variation in response to predators and the proximate costs and benefits to prey associated with crawling out of the water. Trade-offs between risks of immediate, direct mortality from aquatic, amphibious...

Use of terrestrial arthropod prey by a stream-dwelling cyprinid fish

The spatio-temporal availability to, and use of terrestrial (allochthonous) prey by, a subset of the fish assemblage of a Virginia piedmont stream were investigated during spring and summer. Terrestrial invertebrates were most abundant in drift nets, but least common in fish stomachs, during April. In contrast, during August, terrestrial prey dominated the diet of the major cyprinid fish,Notropis ardens, even though terrestrial prey availability in the stream declined by an order of magnitude. Several other co-occurring fishes only rarely consumed prey of terrestrial origin. Drifting terrestrial invertebrates, were concentrated at the surface near the thalweg, compared to stream margin or substrate locations. This study suggests that morphologial and behavioral constraints of individual fish taxa, including predator avoidance responses, regulate the use of terrestrial prey within a given fish assemblage.

Regional distribution of glucose utilization in the telencephalon of toads in response to configurational visual stimuli: a14C-2DG study

The regional glucose utilization in the telencephalon of toadsBufo bufo during stimulation with different visual key stimuli was quantitatively mapped by means of the14C-2DG autoradiographic method: (i) a 4×28 mm2 worm-like stripe (W) eliciting prey catching responses, (ii) a 84×84 mm2 square (S) releasing predator avoidance responses, and (iii) a 28×4 mm2 antiwormlike stripe (A) eliciting no motor response. Various telencephalic structures changed14C- 2DG uptake statistical significantly during stimulation with the above visual objects in comparison with binocular enucleated animals (brain-to-brain comparison) and in comparison between both hemispheres in monocular animals (interhemispherical comparison): (1) The ventral two-thirds of the posterior half of the medial palliumdecreased 14C-2DG uptake during W- and S-experiments, particularly in response to W. (2) In the posterior two-thirds of the lateral pallium,14C- 2DG uptake wasdecreased in response to the worm-, andincreased in response to the square (S) and antiworm stimuli (A). (3) The ventral striatumincreased uptake of14C-2DG during the animal's response to W- and S-stimuli significantly stronger than in the A-experiment. (4) The dorsal striatum also showed a significant change in14C-2DG uptake which, on a lower level, was not correlated with the type of stimulation experiment. Various prosencephalic structures are involved in circuitries related to attentional phenomena and the gating of prey catching and predator avoidance behavior. The different functions of these structures are discussed.

The adaptive significance of behavioural ontogeny in some. centrarchid fishes

Studies on the ontogeny of behaviour in fish have seldom considered the adaptive significance of the order of appearance of the behaviours. Results of laboratory studies and field observations on the ontogeny of feeding, predator-avoidance, and agonistic behaviour in largemouth bass, Micropterus salmoides, rock bass, Ambloplites rupestris, and pumpkinseed, Lepomis gibbosus, young indicate that the order of appearance of the various behavioural systems enhances the survival of the young. In the laboratory, all species spend significantly more time feeding during the first weeks of free-swimming than the later weeks. During a corresponding period in the field the young are either occupying an offshore area low in predators (rock bass, pumpkinseed) or are being guarded by a parent (largemouth bass); thus the risk of predation is low. When the young are in a predator-rich environment (inshore) both the predator-avoidance response and agonistic behaviour are well developed. Agonistic behaviour is the last to appear and may serve to disperse the young. Dispersal may relate to the feeding mode of the various species and may also reduce the probability of predation. It is apparent that the sequential onsets of the behavioural systems are in concert with ecological events and selective pressures confronting centarchid young.

Mapping of brain activity in mesencephalic and diencephalic structures of toads during presentation of visual key stimuli: a computer assisted analysis of (14C)2DG autoradiographs

The (14C)2DG autoradiographic technique has been employed to quantitatively map glucose utilization in the mesencephalon, the diencephalon and the cerebellum, of toads in response to configurational moving visual stimuli: (i) a 0.4 cm × 2.8 cm worm-like stripe (W) which elicited prey catching responses, (ii) a 8.4 cm × 8.4 cm square (S) that released predator avoidance responses, and (iii) a 2.8 cm × 0.4 cm antiworm-like stripe (A) which elicited no motor activity.

Parental care and the ontogeny of predator-avoidance in two species of centrarchid fish

Stamps (1978) suggested that the type and extent of parental care can influence the behavioural ontogeny of the offspring. Largemouth bass ( Micropterus salmoides) males guard the fry for up to a month after they leave the nest while rock bass ( Ambloplites rupestris) males guard the fry only until they leave the nest. In laboratory experiments, naive largemouth fry displayed reduced predator-avoidance responses to large and small predators during their first 3 weeks of free-swimming. Rock bass fry, on the other hand, avoided predators throughout the study period. From 6 weeks (largemouth) and 5 weeks (rock bass) of age the fry showed a significantly greater response to the large predator than the small predator. The responses of laboratory-reared largemouth bass fry to the small predator changed from avoidance to association as the fry grew. The size of the fry relative to predator size was found to be important.

SELECTION FOR HOST MODIFICATION BY INSECT PARASITOIDS.

The ability of parasites to influence the behavior of their hosts is an important aspect of parasite-host biology (Price, 1980). Holmes and Bethel (1972) review an extensive literature that documents the influence of parasites on the behavior of their intermediate hosts. They argue that these effects by parasites on their hosts are adaptations of the parasites to increase transmission to subsequent hosts. Holmes and Bethel suggest that parasites affect intermediate host behavior by reducing stamina, increasing conspicuousness, causing disorientation, and altering responses so that hosts are more susceptible to predation by the definitive host of their parasites. Modification of insect hosts by their parasitoids, however, has received little attention. Insect parasitoids, unlike parasites, are of relatively large size, they possess a freeliving stage, and their development kills the hosts; therefore their effect on host population dynamics resembles that of predators (Doutt, 1959). Parasitoids, other than insects, and parasitic castrators show similar characteristics (Kuris, 1974; Trail, 1980). Most insect species are attacked by one or more parasitoid species during their development. The growth, development, and survival of parasitized hosts are of direct consequence to the parasitoids; if the host dies before the parasitoid emerges, so does the parasitoid. Vinson (1975) developed the concept that host regulation is necessary for the parasitoid's success. He stated that growth and development of parasitoids were enhanced by physiological regulation of the host through venoms, hormones and parasitoid feeding. Parasitized hosts may behave differently from unparasitized hosts in predator avoidance responses, microhabitat selection, and developmental and growth rates. Some of these modifications may be adaptively significant, and promote the coevolution between the host and its parasitoid. Here I propose a hypothesis that extends Vinson's host regulation concept to explain the evolution of host modification by insect parasitoids. This hypothesis leads to predictions of the characteristics of hosts that should influence how parasitoids should modify their hosts.

HALOGENATION IN THE RHODOPHYTA1,2 A REVIEW

SUMMARYThe halogens—chlorine, bromine and iodine—play an important, role in the biochemical processes of marine red algae. Recent studies show that various species from at least 5 orders of the Rhodophyta possess the unique ability to synthesize organic halogen‐containing compounds which are derived from seawater components. A variety of substances have been reported, with various structures from simple aliphatic halo‐ketones and brominated phenols to more sophisticated mono‐, sesqui‐ and diterpenes. While the biological functions of these compounds are not clearly understood, they appear to provide environmental advantage, probably involving predator avoidance responses and microflora antibiosis.