Antipredator Behavior In Response Research Articles

Beyond ungulate density: Prey switching and selection by the wolf in a recolonised area

The analysis of mechanisms underlying prey use and selection is crucial for understanding the potential for apex predators to shape ecological processes across trophic levels. Significant implications for the conservation and management of ecosystems can ensue, especially in human-modified landscapes characterised by the recent recovery of apex predators, such as those of Europe. Generalist predators may show frequency-dependent prey selection, leading to prey switching; however, there is no ubiquitous support for positive relationships between prey abundance and prey selection. In a protected area recently recolonised by the wolf Canis lupus and hosting abundant wild prey (>20 individuals/km2), we assessed prey use and selection (>3000 wolf scats analysed) throughout 7 years since wolf settlement (April 2016-to-March 2023), during which prey density was relatively stable. Wolf diet was dominated by wild boar Sus scrofa and fallow deer Dama dama (>70 % of occurrences and volume); the roe deer Capreolus capreolus and coypu Myocastor coypus represented main secondary prey. The wolf showed a clear prey switching throughout the study. In the first two years, the fallow deer was the main prey and was positively selected. Then, wild boar replaced fallow deer as main prey, and was positively selected, with a progressive decrease in the use of fallow deer throughout the years. Selection indices of wild boar were negatively associated with those of fallow deer. The relationship between selection indices and population density was inconsistent across species, being negative for the wild boar and weakly positive for the fallow deer, although the latter showed no sharp decline in the area. Concurrent studies showed increased diurnal activity of fallow deer and a consequent reduced temporal overlap with the wolf throughout years since the settlement of this predator, suggesting temporal avoidance. By supporting a minor role of prey density in mediating prey switching, our results suggest a major role of other factors (e.g., antipredator behavioural responses). Alternative substantial prey are important to buffer apex predators not only towards changes in the abundance of main prey, but also towards the effects of other factors potentially reducing prey detectability, e.g., antipredator behaviour.

Influence of social and physical environmental variation on antipredator behavior in mixed-species parid flocks.

Carolina chickadees (Poecile carolinensis) and tufted titmice (Baeolophus bicolor) regularly form flocks with multiple species through the winter months, including white-breasted nuthatches (Sitta carolinensis). Earlier studies found that behavior of both chickadees and titmice was sensitive to mixed-species flock composition. Little is known about the influence of background noise level and vegetation density on the antipredator behaviors of individuals within these flocks, however. We tested for the effects of vegetation density, traffic noise, and flock composition (conspecific number, flock diversity, and flock size) on antipredator behavioral responses following an alarm call playback (Study 1) and an owl model presentation (Study 2) at feeders. We recorded background traffic noise and performed lidar scans to quantify vegetation density at each site. After a feeder had been stocked with seed and a flock was present, we recorded calls produced, and we identified flock composition metrics. We coded seed-taking latency, call latency, mob latency, and mob duration following the respective stimulus presentation and tested for effects of flock composition metrics, vegetation density, and background noise on these responses. For the alarm call playback study, flock composition drove behaviors in chickadees and titmice, and vegetation density drove behaviors in chickadees and nuthatches. For the owl model study, conspecific number predicted behavior in chickadees, and mob duration was predicted by nuthatch number. The results reveal individual sensitivity to group composition in anti-predatory and foraging behavior in simulated risky contexts. Additionally, our data suggest that the modality of perceived simulated risk (acoustic vs. visual) and the density of vegetation influence behavior in these groups.

Phenotypic response to different predator strategies can be mediated by temperature.

Temperature change affects biological systems in multifaceted ways, including the alteration of species interaction strengths, with implications for the stability of populations and communities. Temperature-dependent changes to antipredatory responses are an emerging mechanism of destabilization and thus there is a need to understand how prey species respond to predation pressures in the face of changing temperatures. Here, using ciliate protozoans, we assess whether temperature can alter the strength of phenotypic antipredator responses in a prey species and whether this relationship depends on the predator's hunting behavior. We exposed populations of the ciliate Paramecium caudatum to either (i) a sit-and-wait generalist predator (Homalozoon vermiculare) or (ii) a specialized active swimmer predator (Didinium nasutum) across two different temperature regimes (15 and 25°C) to quantify the temperature dependence of antipredator responses over a 24-h period. We utilized a novel high-throughput automated robotic monitoring system to track changes in the behavior (swimming speed) and morphology (cell size) of P. caudatum at frequencies and resolutions previously unachievable by manual sampling. The change in swimming speed through the 24 h differed between the two temperatures but was not altered by the presence of the predators. In contrast, P. caudatum showed a substantial temperature-dependent morphological response to the presence of D. nasutum (but not H. vermiculare), changing cell shape toward a more elongated morph at 15°C (but not at 25°C). Our findings suggest that temperature can have strong effects on prey morphological responses to predator presence, but that this response is potentially dependent on the predator's feeding strategy. This suggests that greater consideration of synergistic antipredator behavioral and physiological responses is required in species and communities subject to environmental changes.

Exploratory individuals are bolder in Great Tit: Correlation between personality and antipredator behavior

AbstractConsistent individual behavioral differences from other members of local populations are called animal personality, and a suite of these correlated behaviors generates a behavioral syndrome. Differential selection patterns among personality types can be largely influenced by predatory behavior. Prey has a large arsenal of antipredator behaviors at their disposal; However, how closely these behaviors are linked to personality is almost unknown. Using a social model species, the Great Tit, Parus major, we investigated whether antipredator behavior in response to predators is correlated with personality. First, we determined if individual differences in exploratory behavior were consistent across trials, that is, whether they were repeatable. Second, we looked into how antipredator behavior was correlated to personality. Individuals were subjected to two repeated trials of standard personality assays followed by an alternative control (Rock Pigeon, Columba livia domestica) and predator display (Eurasian Sparrowhawk, Accipiter nisus) treatment. We found that exploratory behavior was repeatable across trials and had a greater tendency for positive correlation with antipredator behavior when a predator model was displayed. Individuals that swiftly explored novel environments were slower to react to predators than those who explored the novel room slowly. As a result, our findings provide some of the first experimental evidence for a link between exploratory and antipredator behavior, suggesting that personality traits may impact individual fitness.

Behavioral responses of tadpoles of Clinotarsus curtipes (Anura: Ranidae) to odor cues of dragonfly larvae


 
 
 
 In aquatic environments, many prey animals, including anuran larvae, predominantly use chemical cues to assess predation risk. In such systems, a variety of chemical cues (e.g., kairomones, alarm, dietary) affect the behavioral responses of the prey tadpoles. Many anuran tadpoles are able to discriminate different chemical cues and exhibit differential antipredator behavioral responses according to the perceived risk. The behavioral responses of tadpoles of Clinotarsus curtipes to predatory larvae of the dragonfly Pantala flavescens were studied in the laboratory. The predator’s kairomones (water conditioned by a starved predator) or its diet-derived metabolites released in excreta of a predator after consumption of conspecific (C. curtipes) or heterogeneric (Indosylvirana temporalis) prey tadpoles were used to simulate predation threat. The tadpoles of C. curtipes had no behavioral response to predator kairomones. However, the tadpoles showed antipredator behavioral responses i.e., reduced swimming movements and overall time spent swimming, and had a higher burst speed in response to water-borne cues released from the excreta of predators fed both conspecific and heterogeneric prey. The antipredator behavioral responses of tadpoles were most intense in response to cues of predators fed on conspecific prey. The findings of the present study show that tadpoles of C. curtipes are capable of assessing levels of predation threat and modulating the intensity of their defense behavior in accordance with the perceived threat.
 
 
 

Behavioral responses of laboratory-reared and wild-caught Polypedates maculatus (Anura: Rhacophoridae) tadpoles to dietary cues from the carnivorous tadpoles of Hoplobatrachus tigerinus (Anura: Dicroglossidae)


 
 
 
 The behavioral responses of laboratory-reared and wild-caught tadpoles of Polypedates maculatus to predatory tadpoles of Hoplobatrachus tigerinus were studied in the laboratory. The predator’s diet-derived metabolites released in excreta of predator after consumption of P. maculatus tadpoles were used to simulate predation threat. Both laboratory-reared and wild-caught tadpoles of P. maculatus showed antipredator behavioral responses i.e., reduced swimming movements and overall time spent in swimming and had a higher burst speed in response to water borne dietary cues of predators. Further, the antipredator responses of wild-caught tadpoles were significantly higher than those exhibited by laboratory-reared tadpoles. The studythus shows that antipredator behavior in these tadpoles is innate. Further, an enhanced antipredator behavior of wild-caught tadpoles may suggest their prior experience with predators in natural waters.
 
 
 

Consistent Antipredator Behavioral Responses among Populations of Red River Pupfish with Disparate Predator Communities

Many desert fishes, which evolved in isolated aquatic “islands” with limited predation pressure, have been severely impacted by non-native predators. These impacts have been attributed to the evolutionary loss of antipredator competence, known as the predator naiveté hypothesis. Recent work provided support for this hypothesis for one desert fish species. We sought to examine the generality of the predator naiveté hypothesis by evaluating antipredator competence in five populations of Red River pupfish (Cyprinodon rubrofluviatilis), a species that occupies habitats that vary in the degree of isolation and levels of fish species richness. Fish were exposed to a conspecific chemical alarm cue released from damaged epidermal tissue as a general assay of antipredator response. We found that pupfish from all five populations exhibited antipredator behavior in response to the alarm cue, regardless of the exposure to predation risk. These data provide evidence that antipredator responses to alarm cues are conserved in Red River pupfish, even in populations isolated from piscivorous species.

Effects of human and nonhuman predation risk on antipredator movement behaviors of an upland game bird

AbstractPredators elicit antipredator behaviors such as proactive and reactive movements in prey, but both are rarely investigated simultaneously. Impacts of human predation risk on antipredator behaviors can be greater than those of nonhuman predators, resulting in increased effects on populations and community structure. We compared the influence of human and nonhuman predation risk on proactive and reactive antipredator movement behaviors of male Eastern wild turkeys (Meleagris gallopavo, hereafter turkey). We used simultaneously collected GPS locations from 31 turkeys and 36 coyotes (Canis latrans) to investigate the antipredator behavior of turkeys to coyotes. To assess antipredator behaviors of turkeys to hunters, we used 1661 hunting tracks collected while monitoring 109 turkeys. For proactive movements, we quantified how predation risk influenced resource selection. To investigate reactive movements, we quantified changes in movement behavior of turkeys after encountering hunters and coyotes. Coyote and turkey home range overlap was high, but lack of core area overlap, encounters, and similar resource selection suggested the use of different areas on the landscape. Turkeys selected areas associated with decreased coyote risk and closer to hardwoods. Coyotes preferred shrubs and open areas, suggesting turkeys avoided coyote risk and the habitats coyotes preferred. We detected 17 coyote and turkey contacts, and the probability of contact decreased by 16.6% for every 100 m farther from a forest edge. Turkeys did not display reactive movement behaviors after a direct encounter with coyotes, as step lengths were similar prior to and after encounters, which did not differ from random step lengths. After hunting, turkeys selected areas farther from public access points and closer to private property, suggesting proactive avoidance of hunter risk. We detected 31 hunter and turkey contacts; increased step lengths after hunter contacts suggested fleeing behavior. The probability of a hunter–turkey contact decreased by 5.5% for every 100 m farther from a secondary road. Antipredator movement behaviors by turkeys suggest coyote risk to be low over a broad temporal window, while hunter risk is high for a narrow temporal window. We provide insight into how human‐induced fear can cause antipredator behavioral responses greater than nonhuman fear, potentially causing changes in species distribution and community structure.

Olfactory sensitivity and threat-sensitive responses to alarm cue in an invasive fish

Establishing how invasive animals perceive and manage the threat of predation improves our understanding of why certain species rapidly invade unfamiliar environs where others do not. The threat-sensitive response hypothesis predicts that prey that modulate their antipredator behavior in response to the perceived intensity of the threat will have a selective advantage. We investigated the behavioral and olfactory antipredator responses of migrating invasive sea lamprey to varying concentrations of a conspecific alarm cue in the laboratory and field. We hypothesized the odor indicates the presence and location of predation risk on river shorelines, allowing sea lamprey to either alter their migratory path and/or movement timing to reduce exposure to the predator. Migratory sea lampreys exhibited threat-sensitivity in space-use both in the laboratory and nature by increasingly avoiding areas as the concentration of alarm cue increased when safe space was available (areas without the alarm cue). The intensity of the avoidance at higher concentrations was greater in the field. Electrophysiological recordings from the olfactory organ confirmed a concomitant increase in signal output to the olfactory bulb of the brain when exposed to increased alarm cue concentrations. However, increasing the alarm cue concentration did not alter the animal’s motivation to move upstream in either avoidable risk or unavoidable risk scenarios. Exposure to alarm cue affected decisions regarding how to move, but not whether to move. Knowledge of how the animal uses the cue in nature reveals ways to use the cue to manipulate movement and achieve conservation goals.

Adaptive echolocation behavior of bats and toothed whales in dynamic soundscapes.

Journal of Experimental Biology has a long history of reporting research discoveries on animal echolocation, the subject of this Centenary Review. Echolocating animals emit intense sound pulses and process echoes to localize objects in dynamic soundscapes. More than 1100 species of bats and 70 species of toothed whales rely on echolocation to operate in aerial and aquatic environments, respectively. The need to mitigate acoustic clutter and ambient noise is common to both aerial and aquatic echolocating animals, resulting in convergence of many echolocation features, such as directional sound emission and hearing, and decreased pulse intervals and sound intensity during target approach. The physics of sound transmission in air and underwater constrains the production, detection and localization of sonar signals, resulting in differences in response times to initiate prey interception by aerial and aquatic echolocating animals. Anti-predator behavioral responses of prey pursued by echolocating animals affect behavioral foraging strategies in air and underwater. For example, many insect prey can detect and react to bat echolocation sounds, whereas most fish and squid are unresponsive to toothed whale signals, but can instead sense water movements generated by an approaching predator. These differences have implications for how bats and toothed whales hunt using echolocation. Here, we consider the behaviors used by echolocating mammals to (1) track and intercept moving prey equipped with predator detectors, (2) interrogate dynamic sonar scenes and (3) exploit visual and passive acoustic stimuli. Similarities and differences in animal sonar behaviors underwater and in air point to open research questions that are ripe for exploration.

Intensive hunting changes human-wildlife relationships.

Wildlife alter their behaviors in a trade-off between consuming food and fear of becoming food themselves. The risk allocation hypothesis posits that variation in the scale, intensity and longevity of predation threats can influence the magnitude of antipredator behavioral responses. Hunting by humans represents a threat thought to be perceived by wildlife similar to how they perceive a top predator, although hunting intensity and duration varys widely around the world. Here we evaluate the effects of hunting pressure on wildlife by comparing how two communities of mammals under different management schemes differ in their relative abundance and response to humans. Using camera traps to survey wildlife across disturbance levels (yards, farms, forests) in similar landscapes in southern Germany and southeastern USA, we tested the prediction of the risk allocation hypothesis: that the higher intensity and longevity of hunting in Germany (year round vs 3 months, 4x higher harvest/km2/year) would reduce relative abundance of hunted species and result in a larger fear-based response to humans (i.e., more spatial and temporal avoidance). We further evaluated how changes in animal abundance and behavior would result in potential changes to ecological impacts (i.e., herbivory and predation). We found that hunted species were relatively less abundant in Germany and less associated with humans on the landscape (i.e., yards and urban areas), but did not avoid humans temporally in hunted areas while hunted species in the USA showed the opposite pattern. These results are consistent with the risk allocation hypothesis where we would expect more spatial avoidance in response to threats of longer duration (i.e., year-round hunting in Germany vs. 3-month duration in USA) and less spatial avoidance but more temporal avoidance for threats of shorter duration. The expected ecological impacts of mammals in all three habitats were quite different between countries, most strikingly due to the decreases in the relative abundance of hunted species in Germany, particularly deer, with no proportional increase in unhunted species, resulting in American yards facing the potential for 25x more herbivory than German yards. Our results suggest that the duration and intensity of managed hunting can have strong and predictable effects on animal abundance and behavior, with the potential for corresponding changes in the ecological impacts of wildlife. Hunting can be an effective tool for reducing wildlife conflict due to overabundance but may require more intensive harvest than is seen in much of North America.

Anti-predator behavioral responses of Italian agile frog tadpoles (Rana latastei) exposed to microplastics

Microplastics (MPs) are nowadays abundant, persistent, and ubiquitous in the environment, representing a new threat for terrestrial, marine, and freshwater ecosystems. Although anuran populations and species are globally declining, the effect of MP exposure on this taxon has been poorly investigated. With the aim of assessing the effects of microplastic exposure on the defensive responses of Italian agile frog (Rana latastei) tadpoles, we exposed them to three different concentrations (1, 7, and 50 mg L−1) of a mixture of plastic polymers (HPDE, PVC, PS, and PES) for 2 weeks. Then, we measured the total distance covered by individual tadpoles before and after exposure to tadpole-fed dragonfly larvae (Aeshna cyanea) cues. As expected, predation risk sharply lowered the total distance travelled by tadpoles; however, MP concentration did not affect their defensive performances. We also collected data on tadpole development, activity, and mortality. In contrast with previous experiments, neither tadpole growth nor mortality varied with MP concentration. Our results indicate that the intensity of MP effects on growth and development may depend on tadpole size, with large tadpoles being less susceptible to the negative effects of MP exposure.

Hierarchy of fear: experimentally testing ungulate reactions to lion, African wild dog and cheetah

AbstractExperiments have begun demonstrating that the fear (antipredator behavioral responses) large carnivores inspire in ungulates can shape ecosystem structure and function. Most such experiments have focused on the impacts of either just one large carnivore, or all as a whole, rather than the different impacts different large carnivores may have in intact multi-predator-prey systems. Experimentally testing the relative fearfulness ungulates demonstrate toward different large carnivores is a necessary first step in addressing these likely differing impacts. We tested the fearfulness ungulates demonstrated to playbacks of lion (Panthera leo), African wild dog (Lycaon pictus), cheetah (Acinonyx jubatus) or non-predator control (bird) vocalizations, in Greater Kruger National Park, South Africa. Ungulates ran most to lions, then wild dogs, and then cheetahs, demonstrating a very clear hierarchy of fear. Those that did not run looked toward the sound more on hearing large carnivores than controls, looking most on hearing lions. Notably, prey species-specific population level kill rates by each predator did not predict the patterns observed. Our results demonstrate that different large carnivores inspire different levels of fear in their ungulate prey, pointing to differing community-level impacts, which we discuss in relation to the ongoing worldwide decline and loss of large carnivores.

The functional basis for variable antipredatory behavioral strategies in the chameleon Chamaeleo calyptratus.

ABSTRACTTo counterbalance demands of different selective pressures, many species possess morphological, physiological and behavioral specializations that increase survival in their environments. Predation is one such pressure that can elicit multiple adaptive responses, and the effectiveness of antipredator behaviors likely vary both by environment and individual across time. Chameleons use multiple antipredator strategies, many of which vary with body size and habitat type. Although their unique morphological and physiological traits produce relatively slow locomotion, which is poorly suited for fleeing, chameleons can also use crypsis or aggression to avoid predation. To examine the functional basis for variable antipredator behavioral responses, we subjected chameleons to a series of mock predation trials and determined how often individuals adopted each antipredator strategy, and then quantified the performance capacities underlying each strategy. In particular, we measured bite force as a determinant for aggression, sprint velocity for fleeing, and degree of color change for crypsis. We found that aggression was predicted by traits associated with higher absolute and relative bite force, as well as habitat type; fleeing was predicted by higher normalized sprint velocity and habitat type; and crypsis was predicted by habitat type, color change capacity in bird color space and the interaction between the two. These results illustrate the importance of considering both functional capacity and environmental context in antipredator behavior decision-making.

Neurochemical exposure disrupts sex-specific trade-offs between body length and behaviour in a freshwater crustacean.

Ongoing pollution of aquatic ecosystems with neurochemical compounds warrants an improved understanding of how this affects key organisms. Neurochemicals are shown to alter the behaviour of common study species but it remains difficult to translate these results to biologically meaningful predictions across taxa. This is partly because studies on species with non-generic life-history strategies such as many freshwater crustaceans are currently underrepresented. Here, we use a laboratory experiment to assess baseline behavioural variation (spontaneous activity level and geotaxic behaviour) in the freshwater fairy shrimp Branchipodopsis wolfi and how this is affected by chronic exposure to an environmentally-relevant concentration of the anxiolytic pharmaceutical fluoxetine. The more conspicuously coloured and larger females of the species were overall less active and more benthic than males. Moreover, amongst females, vertical activity was negatively associated with size, while an opposite relationship was found for males. These trade-offs are likely part of an antipredator strategy to reduce the probability of being detected by visual hunters, but disappeared after exposure to fluoxetine. This is of particular interest since it is an effective proof of principle that neurochemicals may impact ecologically-relevant trade-offs between conspicuous morphology and antipredator behaviour. In natural ecosystems, such disturbed antipredator behavioural responses could have far-reaching fitness consequences.

Stability switching and chaos in a multiple delayed prey–predator model with fear effect and anti-predator behavior

Recent studies demonstrate that the density of prey population is not only affected by direct killing by the predator, but the fear in prey caused by predator also reduces it by cutting down the reproduction rate of prey community, and prey shows anti-predator behavior in response to this fear. In this study, we propose a prey–predator model with fear in prey due to predator and anti-predator behavior by prey against the predator with fear response delay and gestation delay. It is assumed that the predator consumes prey via simplified Holling Type-IV functional response. We evaluate the equilibrium points and study the local and global stability behavior of the system around them. It is observed that our system undergoes Hopf-bifurcation with respect to the fear parameter. Moreover, the system shows the attribute of bi-stability involving two stable equilibriums. Further, we study the dynamics of the delayed system by incorporating fear response delay and gestation delay. We observe that the delayed system suffers Hopf-bifurcation with respect to both delays. Using the normal form method and center manifold theory, the direction and stability of Hopf-bifurcation are studied. Chaotic behavior for delayed system is observed for large values of fear response delay. All these findings are supported by numerical simulation.

Divergence in foraging and predator avoidance behavior across the geographic range of native and non-native crayfish

There is growing evidence that species’ traits may diverge during biological invasions; however, we still lack a general understanding of how the invasion process affects behavior. We used a biogeographic approach to compare foraging and antipredator behavior across a reciprocal invasion (in which each species invaded the native range of the other) of virile (Faxonius virilis) and rusty crayfish (F. rusticus). We hypothesized that the invasion process would select for individuals that invest more in foraging and less in defense than their native counterparts. We used laboratory experiments to examine crayfish boldness, activity, and foraging voracity and mesocosm experiments to examine antipredator behavior in response to fish. Non-native virile crayfish (Indiana, USA) were less bold, active and voracious than native virile crayfish (Wisconsin, USA), and they exhibited more antipredator behavior. Non-native rusty crayfish (Wisconsin) were more active in mesocosms and exhibited less antipredator behavior than native rusty crayfish (Indiana). Combined, these findings suggest a growth/mortality trade-off. Counter to our hypothesis, relative investment in foraging versus predator avoidance differed across regions and was not consistently associated with native or invasive populations. Thus, the substantial divergence in behavior we observed may by driven by local adaptation.

Do predictive environmentally relevant concentrations of ZnO nanoparticles induce antipredator behavioral response deficit in Swiss mice?

The toxicity of zinc oxide nanoparticles (ZnO NPs) has been addressed in several studies; however, their effect on the mammalian group, even at environmentally relevant concentrations, remains poorly understood. The aims of the present study are to expose female Swiss mice to ZnO NP concentrations commonly faced by mammals who enter aquatic systems to perform different ecological functions and to assess the possible effects of such particles on their behavior. The test animals were placed in water added with ZnO NPs for 3 min, 2 times/day, for 21 days. Two experimental groups were set, NP1x, composed of animals subjected to ZnO NP concentration of 760 μg/L; and NP50x (control), which encompassed animals subjected to 38,000 μg/L. Based on field test results (OF), the contact with NPs did not induce locomotor deficits or anxiogenic and anxiolytic effect on the animal models. However, models exposed to NPs were not able to recognize the predatory threat posed by the presence of Pantherophis guttatus and Arapaima gigas; on the other hand, animals in the control group, who were not exposed to ZnO NPs, did not present antipredator behavioral response deficit. Furthermore, mice exposed to NPs were unable to distinguish real predators from plastic copies, and it suggests antipredator behavioral response deficit. High Zn concentrations in blood, liver, brain and skin samples are associated with deficit caused by the exposure to ZnO NPs. To the best of our knowledge, the current study is in the first to evidence that ZnO NPs induce changes in antipredator behavioral responses, even under ephemeral conditions and at low concentrations. However, the exposure to ZnO NPs can be a risk to the health of the assessed individuals and to the dynamics of their populations if the present antipredator behavioral response test results are extrapolated to the ecological context.

A meta‐analysis of fish behavioural reaction to underwater human presence

AbstractIn an increasingly anthropic world, humans have profound impacts on the distribution and behaviour of marine fishes. The increased human presence has modified fishes’ antipredator behavioural responses, and consequently flight decisions, as a function of their changed perceptions of risk. Understanding how fish react to human presence can help identify the most vulnerable functional groups/species and estimate impacts caused by human disturbance. Shoal and body size are known to influence fish flight initiation distance (FID; the distance between the predator and prey when the prey begins to escape); however, few studies attempt to test the moderators of these relationships. Here, we present a comprehensive meta‐analysis evaluating FID of fish in response to human presence. Specifically, we investigated six candidate moderators that could influence the relationship between FID with shoal and body size. Our results showed that individual fish size was strongly and positively correlated with FID and the most important moderator that explained the variance in individual body size‐FID relationship was shoaling behaviour. However, and somehow surprisingly, we detected no significant relationship between shoal size and FID. We discuss how these results can inform the development of fish conservation strategies and ultimately assist in the management of marine protected areas.

Anti-predator responses in the Chilean Swallow Tachycineta leucopyga breeding in northwest Patagonia

ABSTRACTCapsuleBreeding Chilean Swallows Tachycineta leucopyga in Argentina use visual and acoustic signals in response to potential threats from a predator, but these did not vary with brood age.AimsTo study anti-predator behavioural responses in breeding Chilean Swallows from North Patagonia, Argentina, by using a nest-box experiment.MethodsAt days eight and 14 after the first nestlings hatched, Chilean Swallow breeding adults were exposed to a stuffed decoys of either a natural local predator, the Austral Pygmy-Owl Glaucidium nana, or a neutral decoy, a stuffed Rufous-Collared Sparrow Zonotrichia capensis.ResultsAnti-predator behavioural responses consisted of displaying dives, circling flights and group mobbing around the predator decoy, together with the emission of several vocalizations, among which a mobbing alarm call was the most frequent. We did not find significant differences in the intensity of parental nest defence behaviours at different nestling ages (8 and 14 days old).ConclusionAnti-predator behaviour of breeding Chilean Swallows consists of visual and acoustic signals, involving swallows other than the nest owners, and without variation during the nestling period. Our exploratory assessment on the anti-predator behaviour of Chilean Swallows is the first description of the southernmost Neotropical swallow defence behaviour and will therefore help delineate future research.