Effects of environmental conditions in the period of early ontogenesis on the formation of defensive behavior in juvenile roach Rutilus rutilus (Cyprinidae)

The feeding and defensive behavior of juvenile roach Rutilus rutilus (offspring of one pair of spawners) that were held at early stages of ontogenesis under conditions of differently enriched environments was studied. After the beginning of active swimming (the 12th day upon hatching), roach were reared for 95 days under different environmental conditions (feeding on active or immobilized organisms, the presence or absence of constant water flow, and the presence or absence of a predator), after which comparison of the efficiency of feeding behavior in the presence of a predator in juveniles of different groups was performed. It was established that the degree of environmental richness at early stages of ontogenesis exerts a determining effect on the formation of habits of defensive and feeding behavior. The most efficient behavior was observed in individuals that were held together with the predator during rearing.     

Is mating of copepods associated with increased risk of predation?

In laboratory experiments, we tested whether the cyclopoid copepodCyclops vicinus is more vulnerable to predation by juvenile(young-of-the-year) roach (Rutilus rutilus) and/or larvae ofthe phantom midge Chaoborus flavicans during mating than individualadult copepods of the same species. We also tested whether C.vicinusavoided mating, displayed shorter mating times and/or loweractivity when a predator (Chaoborus) was present, or when exposedto water in which predators (Chaoborus) were previously held.Fish ate the same quantity of pairs in copulation and individualegg-bearing females but significantly fewer females withouteggs. Chaoborus ate similar quantities of pairs and femalesbut fewer males. Pairs in copulation and egg-bearing femaleswere detected earlier by fish than individual non-ovigerousfemales or males, and pairs in copulation were captured mosteasily by fish. Cyclops vicinus mated less often when Chaoboruslarvae were present than in water in which Chaoborus was previouslyheld, or in pure tap water. However, predator presence or exposureto predator-treated water had no effect on (i.e. did not reduce)mating duration. Activity of C.vicinus pairs during copulationwas significantly lower when a predator was present, or in predator-treatedwater, than in pure tap water, and activity of pairs decreasedwith increasing activity of the predator. Although our experimentswere carried out under artificial conditions which cannot betransferred to the complex conditions in the field, they suggestthat mating in copepods is dangerous and that copepods haveevolved particular strategies to reduce the risk of predationduring mating.     

Effects of brown and turbid water on piscivore–prey fish interactions along a visibility gradient

1. Environmental changes such as eutrophication and increasing inputs of humic matter (brownification) may have strong effects on predator–prey interactions in lakes through a reduction in the visual conditions affecting foraging behaviour of visually oriented predators. 2. In this experiment, we studied the effects of visual range (25–200 cm) in combination with optically deteriorating treatments (algae, clay or brown humic water) on predator–prey interactions between pike (Esox lucius) and roach (Rutilus rutilus). We measured effects on reaction distance and strike distance for pike and escape distance for roach, when pike individuals were exposed to free‐swimming roach as well as to roach held in a glass cylinder. 3. We found that reaction distance decreased with decreasing visual range caused by increasing levels of algae, clay or humic matter. The effect of reaction distance was stronger in turbid water (clay, algae) than in the brown water treatment. 4. Strike distance was neither affected by visual range nor by optical treatment, but we found shorter strike distances when pike attacked roach using visual cues only (roach held in a cylinder) compared to when pike could use multiple senses (free‐swimming roach). Escape distance for roach was longer in turbid than in brown water treatments. 5. Changes in environmental drivers, such as eutrophication and brownification, affecting the optical climate should thus have consequences for the strength of predator–prey interactions through changes in piscivore foraging efficiency and prey escape behaviour. This in turn may affect lake ecosystems through higher‐order interactions.     

Exploratory behavior of juvenile roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.) (Teleostei: Cyprinidae) in a maze after different magnetic impacts on embryos

We have investigated a sequence of visits to arms in a cross maze in juvenile (1-year-old) roach Rutilus rutilus (L.). Fish embryos of one group are raised under a natural geomagnetic field. The embryos of another group are exposed to the main phase of a simulated geomagnetic storm (changes in geomagnetic field up to 100 nT for each component). It turns out that the sequence of visits does not differ from random in both groups. Thus, the exploratory behavior in juvenile roach differs from other animal taxa investigated earlier. In the latter taxa a spontaneous alternation was observed: a tendency to visit the arm which was visited least recently.     

Sex‐Specific Response of Pardosa milvina (Araneae: Lycosidae) to Experience with a Chemotactile Predation Cue

Predators frequently leave behind chemical information (i.e., semiochemicals such as pheromones or kairomones) that can be detected by their prey and used to avoid areas where predators are likely present. Prey that have interacted indirectly with predators via chemical information thus may gain insight into their risk of being consumed that naïve individuals lack. Pardosa milvina (Araneae: Lycosidae) is a chemosensitive wolf spider that shows adaptive responses to chemotactile cues deposited by the larger wolf spider Tigrosa helluo. We raised offspring from P. milvina to examine the effect of experience with a predation cue on activity, foraging, and antipredator behavior. Spiders differed in activity and foraging behavior across ontogeny and between sexes, but there was no effect of experience with a predation cue. However, a sex‐specific effect of experience was found in antipredator behavior. Male spiders, but not females, used experience with a predator cue to increase their survival in the presence of a live predator. Specifically, naïve males were attacked sooner than experienced males, indicating that prior exposure to predator cues can modify Pardosa antipredator behavior. Intersexual differences in how spiders respond to experience with a predation cue likely reflect the risk of predation faced by males and females in nature.     

Behavior of juveniles of roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (cyprinidae), produced by breeders from a tributary of the Rybinsk Reservoir and from a nonfreezing area of the Moskva River at variable temperatures

The study has revealed differences in search behavior among juvenile individuals of the roach Rutilus rutilus produced by breeders from a tributary of the Rybinsk Reservoir and from nonfreezing areas of the Moskva River. It has been shown that differences in behavioral responses of juveniles are minimal at a stable temperature (approximately 20°C). Gradually rising or falling temperatures lead to an increase in the variation of behavioral parameters. Response to rising temperature is more pronounced in juvenile roach individuals produced by breeders from the Rybinsk Reservoir tributary, while response to decreasing temperature is, on the contrary, more pronounced in individuals produced by breeders from the nonfreezing Moskva River area. Year-round occurrence in zones with heated water in the nonfreezing Moskva River area has probably contributed to a change in the roach population’s adaptation to cold, consolidated by selection at the genetic level over several generations.     

Influence of Predator Presence and Prey Density on Behavior and Growth of Damselfly Larvae (Ischnura elegans) (Odonata: Zygoptera)

Foraging behavior is often determined by the conflicting benefits of energy gain and the risk of mortality from predation or other causes. Theory predicts that animals should have lower activity levels when either the risk of predation or the availability of resources in the environment is high. We investigated the adjustment of the behavior of I. elegans larvae to predator presence (Anax imperator) and prey density (Daphnia sp.) and their interaction in a completely crossed factorial experiment in the lab and the effect of behavior on growth. The foraging activity of the I. elegans larvae was significantly reduced in the presence of a free-swimming predator but not a caged predator. Abdominal movements were significantly reduced at a low prey density. Growth was significantly reduced by the presence of a free swimming predator and low prey densities. These results provide evidence that these damselfly larvae adjust their behavior to the presence of predators to increase their survival at the expense of reduced growth and development.     

Diet niche relationships among predator and prey fish species in their early life stages in Lake Võrtsjärv (Estonia)

In Lake Võrtsjärv pikeperch was observed not to shift to piscivory in their first autumn of life, although juvenile stages of a variety of fish species were abundant in the lake. It was hypothesized that the diets of predator and prey fish fry overlap and that coarse fish species are important food competitors for juvenile piscivores and thus, pikeperch and perch fry do not shift to piscivory during their first growing season. To discover the possible linkages in this pattern, in 2009 the feeding relationships of pikeperch, perch, ruffe and roach fry were analysed. The stomach content analyses showed that in the summer period, Mesocyclops leuckarti was the most frequent prey for perch and ruffe, pikeperch consumed Leptodora kindti in large quantities, and roach ate mostly plant material. Towards autumn, M. leuckarti was the most abundant prey for all percids. However, average stomach content weight and the number of prey items eaten by ruffe were considerably higher than for other fish fry. Since the feeding opportunities of fish fry are considered poor in the examined lake, the prey has the potential to restrict the recruitment to piscivory of their predators, as prey fish seem to have better abilities to persist in this ecosystem. Furthermore, supposed competition in the juvenile stage may result in a reduced top‐down effect on coarse fish.     

Larval behavioral syndrome does not affect emergence behavior in a damselfly (<Emphasis Type="Italic">Lestes congener</Emphasis>)

Activity is a key behavioral trait that often mediates a trade-off between finding food for growth and evading predation. We investigated how activity of the damselfly Lestes congener is affected by larval state and predator presence and if larval behavioral type (BT) can be used to predict larval emergence behavior. Activity level of individual larvae was studied without predators at two different physiological states (hungry, fed) and in two predator treatments (familiar or unfamiliar predator cues). Larvae did not adjust their activity depending on state or when subjected to unfamiliar predator cues but a general reduction in activity was seen in the familiar predator treatment. Hence, active individuals remained active compared to their conspecifics, independent of state or predator treatment illustrating the presence of a behavioral syndrome. However, we found no correlation between larval BT and emergence behavior. Active individuals did not differ from less active individuals in any emergence characteristics. The results illustrate that the larval BT occurs in many situations keeping active larvae active even in maladaptive situations. Furthermore, we show that damselfly emergence behavior can be completely decoupled from larval BT, indicating a loss of stability in individual BT during critical stages in ontogeny.     

Effect of environment on the adaptive abilities of fry roach Rutilus rutilus (L.) (Cyprinidae) during early ontogenesis

In recent years a considerable decrease in the abundance of predatory fishes has been observed in spawning tributaries of the Rybinsk Reservoir caused by their intensive catching. The lack of encounters with predators before the downstream migration of young fish hampers the development of necessary skills of defensive behavior in the absence of predation experience. As a result, after downstream migration, the juveniles are incapable of adapting to the predation pressure in the reservoir and are subjected to intensive elimination. The adaptive potential of the roach Rutilus rutilus L. was experimentally studied in siblings raised from the larvae to the late fry stage both in the presence and absence of a predator. It has been found that the fry that was raised under different conditions differed in their adaptive potential in new environment conditions.     

Habitat shift in roach (Rutilus rutilus) induced by pikeperch (Stizostedion lucioperca) introduction: predation risk versus pelagic behaviour

Changes in the fish community structure and habitat use were followed after the introduction of pikeperch (Stizostedion lucioperca) to the roach-dominated Lake Gjersjøen. Quantitative echosounding showed that the density of juvenile roach (Rutilus rutilus) was dramatically reduced in pelagic areas, from 12 000–15 000 fish/ha to 250 fish/ha, while total fish density remained unchanged in littoral areas. At the same time, the habitat segregation between different size groups of roach was altered as larger roach utilized the pelagic zone after pikeperch introduction. The loss of the pelagic refuge for juvenile roach increased the availability of juvenile roach to littoral predators, notably perch. In littoral areas, the fish community changed from one dominated by roach (> 95%) to one dominated by perch (> 50%).     

Early life sensory ability—ventilatory responses of thornback ray embryos (Raja clavata) to predator‐type electric fields

Predator avoidance is fundamental for survival and it can be particularly challenging for prey animals if physical movement away from a predatory threat is restricted. Many sharks and rays begin life within an egg capsule that is attached to the sea bed. The vulnerability of this sedentary life stage is exacerbated in skates (Rajidae) as the compulsory ventilatory activity of embryos makes them conspicuous to potential predators. Embryos can reduce this risk by mediating ventilatory activity if they detect the presence of a predator using an acute electrosense. To determine how early in embryonic life predator elicited behavioral responses can occur, the reactions of three different age groups (1/3 developed, 2/3 developed, and near hatching) of embryonic thornback rays Raja clavata were tested using predator‐type electric field stimuli. Egg capsules were exposed to continuous or intermittent stimuli in order to assess varying predator‐type encounter scenarios on the ventilatory behavior of different developmental stages. All embryos reacted with a “freeze response” following initial electric field (E‐field) exposure, ceasing ventilatory behavior in response to predator presence, demonstrating electroreceptive functionality for the first time at the earliest possible stage in ontogeny. This ability coincided with the onset of egg ventilatory behavior and may represent an effective means to enhance survival. A continuous application of stimuli over time revealed that embryos can adapt their behavior and resume normal activity, whereas when presented intermittently, the E‐field resulted in a significant reduction in overall ventilatory activity across all ages. Recovery from stimuli was significantly quicker in older embryos, potentially indicative of the trade‐off between avoiding predation and adequate respiration. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 721–729, 2016     

The influence of predator presence on utilization of artificial seagrass habitats by juvenile walleye pollock,Theragra chalcogramma

Synopsis Behavioral preference for a structured habitat (artificial seagrass) by juvenile walleye pollock,Theragra chalcogramma, was tested in controlled laboratory experiments. We monitored position of fish in 2000 1 tanks with and without artificial seagrass present in one half of the tank. In addition, we exposed walleye pollock to a predator model, assessing their response when a grass plot was available or unavailable as a potential refuge. In the absence of predators, the fish avoided the artificial seagrass, displaying a preference for the open water side of the experimental tanks. In the presence of a predator model, however, juvenile walleye pollock readily entered the artificial seagrass plots. In addition, they often remained in the grass canopy in proximity to the predator instead of moving out of the grass to avoid the predator (when no grass was present they consistently moved to the opposite side of the tank from the predator). The behavioral choices exhibited in this study suggest that juvenile walleye pollock modify habitat selection in response to perceived predation risk, and recognize the structure provided by artificial seagrass as a potential refuge.     

Fishing spiders, green sunfish, and a stream-dwelling water strider: male-female conflict and prey responses to single versus multiple predator environments

Many studies have experimentally addressed the effects of a particular predator species on prey behavior. In nature, however, prey frequently face multiple species of predators that often vary in their predatory mode and in their level of predation risk. Relatively few studies have considered prey responses under these complex conditions. In Kentucky, the stream-dwelling water strider (Aquariusremigis) coexists with many potentially dangerous predators, two of which are the green sunfish (Lepomiscyanellus) and the fishing spider (Dolomedesvittatus). Green sunfish occupy stream pools and attack water striders from below. In contrast, fishing spiders hunt along stream shorelines where they perch on overhanging vegetation or rocks and attack water striders near shore. We compared how A. remigis individuals respond to these two very different predators in pools with one or both predators. The presence of sunfish in pools had strong effects on male water strider behavior, including increased use of three types of refuge from sunfish (riffles, climbing out of the water, sitting on the water but at the edges of pools), decreased activity and a decreased number of aggressive males on the water. Spiders also influenced water strider behavior; male water striders avoided spiders by shifting away from the edges of pools. Comparisons of the effects of the two predator species showed that in general, antipredator responses by male water striders were stronger in pools with fish alone than in those with spiders alone. In the presence of both predators, male water strider behavior (microhabitat use and activity) was generally similar to behavior in the presence of fish alone. In contrast, female water striders showed no significant response to the presence of sunfish, and little response to the presence of spiders. This lack of response could be because females spent much of their time in refuges even in the absence of predators (apparently hiding from harassment by males). Both spiders and fish caused decreases in water strider mating activity. The presence of fish reduced both the number of matings per pool (mating frequency), and mean mating durations. Spiders induced a decrease in mean mating duration, but not in mating frequency. The largest reductions in mating activity occurred in pools with both predators present. Pools with either spiders or fish alone suffered 15–20% water strider mortality during our experiment (versus no mortality in predator-free pools). Extant theory suggests that when prey face conflicting microhabitat responses to two predators (as in this study), the predators should have facilitative effects on predation rates (i.e., prey that avoid one predator are often killed by the other and vice versa). Mortality rates in pools with both predators present, however, were not significantly different from that predicted by a null model of multiple predator effects. The lack of predator facilitation can be explained by the compensatory reductions in water strider activity and mating activity in the presence of both predators. Received: 26 August 1996 / Accepted: 12 June 1998     

Responses of Acilius sulcatus (Coleoptera: Dytiscidae) to chemical cues from perch (Perca fluviatilis)

In this study we tested the hypothesis that the presence of chemical stimuli from a hungry predator would initiate anti-predator responses, while stimuli from a satiated predator would not. We used chemical stimuli released from starved perch (Perca fluviatilis) and from satiated perch (predator). As prey we used adult Acilius sulcatus (Coleoptera: Dytiscidae). The reaction of the beetles to different predator conditions was tested during daytime. We also tested the reaction to starved perch during the night. A. sulcatus activity decreased when it was exposed to stimuli released from starved perch during daytime when visibility was poor, due to the presence of artificial vegetation. There was, however, no reaction to satiated perch under the same experimental conditions. These results indicate that A. sulcatus can discriminate between chemical cues from hungry and satiated fish predators. When visibility was good and the concentration of chemical cues was constant, the beetles did not react to starved perch in the daytime, but their activity decreased at night in response to stimuli released from starved perch. Visual as well as chemical cues seem to be important for detecting a potential predator. When visibility is good, beetles seem to rely on visual stimuli, while in darkness they seem to use chemical stimuli to detect the presence of predators. Received: 4 October 1996 / Accepted: 7 February 1997     

Temporary intermissions in capturing prey (<Emphasis Type="Italic">Daphnia</Emphasis>) by planktivorous fish (<Emphasis Type="Italic">Rutilus</Emphasis><Emphasis Type="Italic">rutilus</Emphasis>): Are they due to scramble competition or the need for antipredation vigilance?

Capture rates in planktivorous fish may differ in individuals foraging alone or in a group, and this may result either from the altered risk of predation due to vigilance sharing in the group, or from a difference in the intensity of scramble competition for encountered prey items. Changes in capture frequency and the feeding pattern observed in young roach (Rutilus rutilus) feeding alone and in a group of three on a high density prey (Daphnia), in the presence and in the absence of predator odor, were used to determine which of these two alternate explanations is more likely. Earlier studies revealed that a foraging roach captures Daphnia prey in uninterrupted sequences of captures occurring every 1–3 s. Such multiple captures are separated by intermissions of 10–20 s, with their duration being likely to determine the overall capture rate. An experiment was performed to examine whether feeding in a group of three permits higher capture rates (hypothesis 1), and whether the intermittent foraging pattern is due to the need to invest more time for vigilance when foraging alone (hypothesis 2). Video recordings were made of many series of subsequent prey captures by roach feeding on high Daphnia densities, alone or in a group, and in the presence or absence of predator odor. Analysis of these data revealed that the mean duration of intermissions between bursts of feeding activity was significantly greater in the presence of predator odor, which resulted in a significant decrease in the capture rate. Furthermore, when the roach were feeding in a group, these intermissions were reduced to a greater extent in the presence of predator odor than in its absence, implying that the intermission intervals represent an investment for vigilance as an effective antipredation defense that permits increased food intake regardless of whether or not it is enhanced by the resource or the interference competition.     

Comparison of fish and phantom midge influence on cladocerans diel vertical migration in a dual basin lake

Diurnal vertical migrations (DVM) behaviour of cladocerans was investigated in two mesotrophic Irish lakes connected by a canal, characterised by interesting differences in the presence of zooplanktivorous predators. In Doon Upper, fish (mostly juvenile perch and roach) and a little-studied phantom midge Mochlonyx fuliginosus (Chaoboridae) were found, but Doon Lower was solely inhabited by fish. As the presence of diverse predators may alter spatial avoidance behaviour of zooplankton prey in different ways, the aim of this study was to determine whether and how two predator types, fish and phantom midge larvae, have changed DVM pattern of cladocerans during day and night in Doon lakes. Two sampling series of phytoplankton, zooplankton, fish, and water physical analyses were conducted on 09–10 June and 19–20 September 2007 in both lakes. In the study conducted in June, under a similar distribution of M. fuliginosus and juvenile fish in Doon Upper, a reverse migration of Daphnia galeata was observed as a strategy allowing them to avoid both types of predators. However, in September, when M. fuliginosus lived in a 24 h refugium below the oxycline as a response to increasing predation risk posed by YOY fish penetrated the upper strata of water during day and night, reverse migrations of D. galeata were not clear. In Doon Lower, normal migration was observed as an advantageous behavioural response against visual predators (fish), in both large and small Cladocera species: D. galeata, Diaphanosoma branchyurum and Bosmina sp. Thus, our results indicate dissimilar migration patterns of D. galeata depending on the presence of one (Doon Lower) or two predators with different predation behaviour (Doon Upper).     

Foraging under the risk of predation in desert grassland whiptail lizards (<Emphasis Type="Italic">Aspidoscelis uniparens</Emphasis>)

The whiptail lizard Aspidoscelis uniparens searches for fossorial prey using a series of moves and pauses punctuated by bouts of digging. We examined the effect of predation risk on foraging A. uniparens in outdoor enclosures, observing their behavior in the presence and absence of the predatory lizard Gambelia wislizenii. Predator presence led to changes in activity patterns and foraging behavior. When predators were present, A. uniparens reduced both the proportion of time active and time moving, shifted activity periods, reduced their movement rate, and changed the duration of moves. There were no apparent changes in digging effort, but the likelihood of successfully digging for food decreased when a predator was present.     

The role of thyroid hormones in the formation of behavioral responses in juvenile roach (<Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.) (Cyprinidae)

The effect of thyroid hormones (THs) on the formation of behavioral responses in juvenile roach was studied. Eggs taken from one pair of spawners were split into three groups and kept in different environments: a clean water control, with the addition of a hormone, and with the addition of a substance blocking thyroid-gland synthetic activity. It was revealed that control fish and those with an enhanced hormonal status manifest more mature behavior than the fish with a lowered hormonal status.     

Trait‐mediated effects of predation across life‐history stages in container mosquitoes

1. It was determined if the predatory midge Corethrella appendiculata Grabham imposes a fitness cost in a native mosquito, Ochlerotatus triseriatus Say, and an invasive mosquito, Aedes albopictus Skuse. The hypothesis that decreased activity of immature prey in the presence of predator cues is associated with life history costs through all life cycle stages was tested. 2. In experiment 1, individual larvae of O. triseriatus or A. albopictus were raised in the presence or absence of predation cues at two resource levels. Prey were video recorded to detect behavioural responses and to measure development time, size at emergence, and adult longevity. In experiment 2, prey populations were reared in similar environments and the frequency of predator cue additions was varied. 3. Only O. triseriatus reduced its activity in the presence of predation cues. Predation cues were associated with longer immature development times and shorter adult life spans in O. triseriatus, whereas in A. albopictus, the cues were associated with a larger size of emerging adults. 4. In the present study, it was found that behavioural modifications during the larval stage can affect mosquitoes through multiple stages of their complex life cycle. The species‐specific behavioural differences are probably attributable to the longer evolutionary history O. triseriatus has with predators, relative to the invasive A. albopictus.