Anti-predator Strategies Research Articles

Dynamics of Predator-prey Interactions in Sharp Tooth Catfish (Clarias gariepinus; Burchell, 1822) and Carp Fingerlings (Labeo bata; Hamilton, 1822) with Special Reference to the Development of Anti-Predatory Strategies

This study explores the dynamics of predator-prey interactions and functional response of Clarias gariepinus (African Magur/Sharptooth Catfish - predator) and of Labeo bata (Carp fingerlings - prey). Author investigated the behavioral patterns of both species in isolation and during encounters, exploring the impacts of predator size, prey-predator ratio, encounter duration and placement of separators on anti-predatory strategies. Results indicated that prey behavior is influenced by predator presence, with crowding, hiding, and inspection emerging as key anti-predatory strategies. The development and intensity of these strategies are intricately linked to prey-predator ratio, size difference, and encounter duration. Notably, larger predators trigger more pronounced anti-predatory responses in preys, while high prey composition motivates individuals to inspect predators, conveying fearlessness and fitness. Findings provide valuable insights into the evolution of predator-avoidance behaviors in prey species, sheds light on the complex dynamics governing predator-prey interactions in aquatic ecosystems.

Aposematism vs. scavenging? camera trapping unveils low and seasonal-dependent consumption of toxic salamander carcasses by wild boars

Abstract Aposematic species rely on primary and secondary antipredator strategies. Yet, some opportunistic and generalist species may consume them, although this has been largely supported by indirect evidence such as dietary analyses or clay model experiments. Here, we studied the role of the wild boar, Sus scrofa, as a consumer and possible predator of an aposematic and toxic salamander, Salamandra salamandra gallaica. We investigated this behaviour using camera traps and salamander carcasses on a small island where both species co-occur. Our results show a very low proportion of salamanders consumed by wild boars (3.8%), which indicates that fire salamanders might not completely rely on their aposematic strategy to avoid being consumed by this generalist species. The number of predation events does not differ between wild boar age classes, but it does between seasons, with a higher consumption in spring, which can be associated with an increase in animal consumption when fruits (e.g., acorns) are no longer available on this island. We also highlight the need for temporal studies targeting predator-prey interactions through behavioural data and complementary approaches to better understand the possible impact of opportunistic and generalist species in the ecosystem. This is particularly important in management plans involving the control of generalist species such as the wild boar, which is considered one of the most invasive species globally and a threat to countless species worldwide.

The importance of color and body size for reproductive decision making by males and females of the giant river prawn, Macrobrachium rosenbergii (de Man, 1879) (Decapoda, Caridea, Palaemonidae).

The selection and expression of conspicuous colorations in animals is often related to anti-predation strategies and sociosexual communication. The giant river prawn, Macrobrachium rosenbergii (de Man, 1879) is a species with three male morphotypes that vary in claws' coloration and the size of the animals. It has been suggested that male reproductive quality might be associated to their coloration, but evidence is still conflicting. In addition, a possible communication function of orange patches, that occupies a large portion of egg-bearing females' cephalothorax, has never been investigated before. For that matter, in this study, we evaluated the importance of visual cues for reproductive decision making by males and females of the giant river prawn. Through two-choice discrimination experiments, we verified whether: 1) females would be equally attracted to the presence of males expressing different claw colorations and body sizes; 2) female reproductive status and body size would influence males' decision making. Under the tested experimental conditions, females predominantly chose larger over smaller males, while males showed no significant preference for any kind of female. It is possible that body size is one of the cues that females use to identify males' morphotype. The choice of larger males could provide greater protection for females against harassment by other males. Further studies should employ visual cues in combination with chemical ones for a better understanding of mate choice in this species.

No evidence of quantitative honest signaling in aposematic traits of the green and black dendrobatid frog Dendrobates auratus in Costa Rica

Abstract Aposematism is an antipredator strategy in which conspicuous coloration acts as a warning of chemical defenses to potential predators. Evidence suggests that aposematism largely functions under positive frequency-dependent selection, which is thought to maintain uniformity of aposematic signals. Many studies of aposematic organisms have found evidence that color signals and defenses are positively correlated, indicating a quantitatively honest aposematic signal. Dendrobatid poison frogs represent a well-studied group of aposematic organisms that in addition to exhibiting a diversity of color signals also display unique defensive behaviors. Few studies have examined if both behavior and coloration act as quantitative honest signals of alkaloid defenses in poison frogs. We aimed to determine if coloration and behavior are quantitatively honest signals in the green and black poison frog (Dendrobates auratus) among six populations from Costa Rica. We (1) evaluated antipredator displays by using behavioral assays in the field, (2) assessed frog conspicuousness and pattern using digital images, and (3) quantified alkaloid profiles from frog skin secretions. We found that Pacific populations are less conspicuous in coloration, had greater quantities of alkaloids, and more frequently performed body-raising defensive behaviors when compared to Caribbean populations. Our results do not support the hypothesis that aposematic traits in D. auratus are quantitatively honest. Rather, our results suggest that phenotypic differences among populations may represent different phenotypic optima for advertising unprofitability to predators based on local environmental conditions, leading to the diversification of aposematic signals in this species.

Recognition of Predator Type and Risk Level in Azure-Winged Magpies (Cyanopica cyanus) Through Visual and Auditory Cues.

Predation events are an important key factor determining the survival and reproduction of prey species. To cope, prey species have evolved various anti-predator strategies, including mechanisms for accurate predator identification and distinguishing predator types and risk levels. Birds rely on visual, auditory, and olfactory cues to perceive and categorize predators. However, previous studies have focused on single sensory modalities and have largely been conducted during breeding seasons. Thus, analyses of the accuracy and differences in predator recognition cues, especially during non-breeding periods, are needed. In this study, predator recognition in Azure-winged Magpies (Cyanopica cyanus) was evaluated during the non-breeding season. We examined responses to two predators, Common Kestrel (Falco tinnunculus) and Domestic Cat (Felis catus), and two non-predators, Oriental Magpie (Pica serica) and Oriental Turtle Dove (Streptopelia orientalis). Using specimens and playback experiment, the ability of Azure-winged magpies to identify threats through both visual and auditory cues was evaluated. The results showed that Azure-winged Magpies can identify predator types through both visual and auditory cues, accurately distinguish threat levels, and adjust their foraging behavior accordingly. Notably, they exhibited the strongest anti-predator response to Domestic Cats (frequently encountered under natural conditions), as evidenced by longer observation times, shorter foraging duration, and quicker flight responses. The results indicate that Azure-winged Magpies can correctly identify predator types and threat levels through both visual and auditory cues and exhibit stronger anti-predator behaviors with increasing apparent threat levels.

Moulting stage is not defenceless: antipredator strategy of gregarious locusts during moulting

Moulting stage is not defenceless: antipredator strategy of gregarious locusts during moulting

Neighbor Density and Post‐Contact Immobility Duration as Antipredator Behavior: Antlion Larvae Do Not Fit the Selfish Prey Hypothesis

ABSTRACTRemaining immobile for an unpredictable period after being touched by a potential predator (post‐contact immobility, PCI) may favor survival. However, the factors that determine variation in PCI duration are poorly understood. We tested whether PCI duration depends on the surrounding conspecific density (the selfish prey hypothesis) in the tropical antlion larvae Myrmeleon crudelis. These insects avoid predation by being immobile or burying themselves. The selfish prey hypothesis predicts a reduction in the PCI duration as conspecific density increases because this high density of conspecifics around can stimulate the redirection of the predator's interest in other nearby potential prey. In the field, we measured PCI and found that its duration was independent of the conspecific density. In the lab, we also measured the PCI of a subset of the same larvae in the absence of neighbors. Using a paired design, we found that PCI duration was lower in the lab in the absence of neighbors than in the field. Our results suggest that the antlion larvae did not follow the selfish prey hypothesis. We propose two alternative explanations. First, the larvae have a limited ability to detect neighbors in the field and keep up with the changing number of surrounding active pits. Second, burying may be more important than PCI as an antipredator strategy. In our lab experiment, larvae had a more accurate idea of the conspecific density around their pit because they explored the area. We propose that knowing the absence of conspecifics triggered a shorter PCI duration. Under a high predation risk (i.e., no other prey to which the predator would redirect its attention), the larvae select the unequivocal antipredator behavior of burying. This work illustrates the relevance of accurate information in deciding how to avoid predation, especially when prey can prioritize between alternative behaviors, with success varying between the contexts.

Landscape use by prey: Bottom‐up regulation prevails under reduced predation risk

AbstractResource specialist herbivores may suppress antipredator strategies to access scarcely available key resources, while proactive antipredator behaviors should be favored by generalists or when resources are abundant. We quantified the relative effects of predation‐ (top‐down) and resource‐driven (bottom‐up) constraints on spatiotemporal patterns of landscape use by a prey community in a dynamic system under low predator abundance, and investigated how prey manage the risk posed by predators with different hunting strategies. We fitted Royle–Nichols co‐abundance models to camera‐trapping data collected between 2017 and 2019 in Bicuar National Park (Angola), to assess spatial association/segregation across predator–prey dyads, while accounting for the effects of water and food availability during dry and wet seasons. We further estimated pairwise seasonal differences in diel activity overlap between predator and prey. We failed to detect spatiotemporal proactive antipredator responses either toward the cursorial or ambush predator. The community‐wide predator–prey association patterns we found support that predation pressure is insufficient to displace prey from their preferred habitats or to adjust their endogenous clock, and support predominantly bottom‐up regulated behaviors. We suggest that, in landscapes where predator density is low, limited perception of risk may prevent the employment of proactive antipredator behavior.

Individual consistency of hissing displays across night and day in a free-living female songbird

Birds have evolved a variety of antipredator strategies, which have been extensively studied during day-time. Yet, how diurnal birds directly respond to nocturnal predation threats remains largely elusive, despite that predation risk can be high during both night- and day-time. One form of antipredator behaviour found in several tit species when confronted with a predator at the nest is the hissing display. As for many forms of antipredator behaviour, studies on hissing displays have so far focussed on the day-time. Here, we exposed cavity-nesting free-living female great tits (Parus major) to simulated predator intrusions inside their nest box during both night- and day-time. We showed that 28 % of females uttered at least one hissing call during night-time, while the occurrence of hissing calls was higher during day-time (84 %). Hissing females at night, compared to non-hissing females, produced more hissing calls during day-time, providing evidence for individual cross-context consistency. Night-time hissing behaviour did not predict lay date, clutch size, breeding or nest success, indicating the absence of consequences in terms of current reproduction. Together, we reveal the hitherto undescribed occurrence of hissing displays at night in a cavity-nesting bird, while simultaneously strengthening the evidence for the existence of hissing behavioural types.

What determines the antipredator strategy in antlion larvae? Burrowing ability decreases the duration of post‐contact immobility

Abstract For prey exhibiting alternative antipredator strategies, selecting the most effective one is critical for survival. However, what determines such selection remains an open question. We hypothesised that this selection depends on prey skill. We test this idea in Myrmeleon immaculatus De Geer, 1773 (Neuroptera: Myrmeleontidae) antlion larvae that exhibit two alternative antipredator behaviours: post‐contact immobility (PCI) and burying. As the larvae live under sandy soils, PCI is only a temporary strategy, and eventually, all larvae will burrow. However, deciding how long to remain immobile before burying may depend on how fast larvae bury themselves (i.e., how quickly the individual can camouflage itself in the substrate). In a tropical forest from the Yucatan peninsula, Mexico, we measured the PCI duration, bury time and body size of 45 larvae in a fine‐grained experimental substrate. We also measured the mandible length to assess their effects on burying skills. The PCI duration was consistently shorter in larvae that took less time to bury but was longer and more variable in larvae that took more time to bury. This effect was independent of larvae body size. Mandible length did not affect burial time. Our findings suggest that when a given prey should select between two mutually excluding antipredator strategies, the intrinsic skill to perform the most relevant one (how fast burying themselves, in this case) may modulate the duration of the other (PCI, in this case). This reinforces the role of predation as a selective force that modulates prey behaviours.

Friends because of foes: synchronous movement within predator-prey domains.

For prey, movement synchrony represents a potent antipredator strategy. Prey, however, must balance the costs and benefits of using conspecifics to mediate risk. Thus, the emergent patterns of risk-driven sociality depend on variation in space and in the predators and prey themselves. We applied the concept of predator-prey habitat domain, the space in which animals acquire food resources, to test the conditions under which individuals synchronize their movements relative to predator and prey habitat domains. We tested the response of movement synchrony of prey to predator-prey domains in two populations of ungulates that vary in their gregariousness and predator community: (i) elk, which are preyed on by wolves; and (ii) caribou, which are preyed on by coyotes and black bears. Prey in both communities responded to cursorial predators by increasing synchrony during seasons of greater predation pressure. Elk moved more synchronously in the wolf habitat domain during winter and caribou moved more synchronously in the coyote habitat domains during spring. In the winter, caribou increased movement synchrony when coyote and caribou domains overlapped. By integrating habitat domains with movement ecology, we provide a compelling argument for social behaviours and collective movement as an antipredator response. This article is part of the theme issue 'The spatial-social interface: A theoretical and empirical integration'.

Effects of Starve and Shelter Availability on the Group Behavior of Two Freshwater Fish Species (Chindongo demasoni and Spinibarbus sinensis).

In complex environments, fish often suffer from reduced physiological functioning due to starvation, which may have a significant effect on their behavioral adaptive strategies to predator attacks. We selected qingbo (Spinibarbus sinensis, which prefers flowing water habitats) and demasone cichlid (Chindongo demasoni, which prefers still water habitats), to investigate the differences in group distribution and dynamics between the two species when faced with a simulated predation attack under different trophic states (fasted for 2 weeks or fed). We chose to conduct our experiments in a six-arm maze that included a central area and six arms of equal length and width and to obtain evidence of how the fish used the various areas of the maze to respond to simulated predation attacks. We found that the two fish species differed in their responses to simulated predation attacks under different trophic states. The group structure of the two species was relatively stable, and the effect of fasting on the qingbo group was not significant, whereas the demasone cichlid group was more susceptible to the effects of fasting, shelter and a simulated predation attack. In an environment with shelter, both species had the same anti-predator strategy and tended to enter the shelter arm to hide after encountering a simulated predation attack. However, differences in the anti-predator strategies of the two species emerged in the no-shelter environment, with the qingbo tending to enter the arm to hide, whereas the demasone cichlid group chose to enter the central area to congregate, and this phenomenon was more pronounced in the fasted group. In conclusion, our research shows that even group-stable fish may shift their anti-predation strategies (i.e., entering a shelter to hide shifts to aggregating in situ into a shoal) when starved and that the worse the swimming ability of the fish, the more affected they are by starvation.

Disguise or surprise: spider antipredator adaptations as a function of the architecture of their webs

Abstract Animals exhibit a variety of strategies to avoid predation; spiders are no exception. We explored whether web-building spiders that differ in the architecture of their webs exhibit morphologies or behaviors suggestive of antipredator strategies that trade-off with the degree of protection offered by their webs. Spiders build webs of 3 types: the more protected tangles and sheet-and-tangles, which are three-dimensional (3D), and the more exposed orbs, which are two-dimensional (2D), both with or without a refuge. We hypothesize that spiders whose webs offer greater protection—a 3D architecture or a refuge—will be less likely to be armored or brightly colored when compared to spiders without these protections. We collected data on 446 spiders and their webs in 2 lowland tropical rainforest sites. We show that 2D web builders with no refuges tended to be brightly colored (background contrasting) and spiny (spiky), whereas those with refuges tended to blend against the background of their refuges. 3D web builders, on the other hand, were neither cryptic nor brightly colored nor armored but were more likely to drop out of the web upon simulated predator contact. These results support the hypothesis that web-building spiders tend to be protected either through the architecture of their webs or their morphology and behavior, suggesting a trade-off between different types of antipredator strategies.

Social risk to infant: The role of kin for maternal visual monitoring in Tibetan macaques.

Maternal monitoring of conspecifics is a crucial anti-predator strategy that also protects infants against risks within the social group. This study examines how maternal characteristics, infant characteristics, mother-infant distance, and the social environment affect maternal monitoring behaviors in free-ranging Tibetan macaques (Macaca thibetana). We observed 12 females with infants and analyzed their visual monitoring patterns. Our findings indicate that maternal rank significantly influences the time allocated to maternal visual monitoring, higher-ranking mothers spending less time than lower-ranking mothers. Maternal experience also played a role in monitoring strategies. Differences in monitoring strategies were observed based on maternal experience: first-time mothers (primiparity) engaged in longer but less frequent monitoring sessions compared to experienced mothers (multiparity). The time and frequency of maternal monitoring decreased as infants aged, and mothers with male infants showed higher levels of monitoring than those with female infants. The distance between mother and infant also affected visual monitoring behavior, with mothers increasing their monitoring levels when infants were nearby (1-5 m), rather than within reach (0-1 m) or beyond nearby (>5 m). Additionally, the presence of kin and non-kin influenced monitoring: as the number of nearby kin increased, monitoring levels decreased, while the presence of more non-kin males led to an increase in monitoring time, and higher-ranking non-kin neighbors increased the frequency of monitoring. These results suggest that Tibetan macaque mothers can adapt their visual monitoring to the social risks faced by their infants, adjusting their strategies to their status and the needs of their offspring.

Role of body size and shape in animal camouflage.

Animal camouflage serves a dual purpose in that it enhances both predation efficiency and anti-predation strategies, such as background matching, disruptive coloration, countershading, and masquerade, for predators and prey, respectively. Although body size and shape determine the appearance of animals, potentially affecting their camouflage effectiveness, research over the past two centuries has primarily focused on animal coloration. Over the past two decades, attention has gradually shifted to the impact of body size and shape on camouflage. In this review, we discuss the impact of animal body size and shape on camouflage and identify research issues and challenges. A negative correlation between background matching effectiveness and an animal's body size has been reported, whereas flatter body shapes enhance background matching. The effectiveness of disruptive coloration is also negatively correlated with body size, whereas irregular body shapes physically disrupt the body outline, reducing the visibility of true edges and making it challenging for predators to identify prey. Countershading is most likely in larger mammals with smaller individuals, whereas body size is unrelated to countershading in small-bodied taxa. Body shape influences a body reflectance, affecting the form of countershading coloration exhibited by animals. Animals employing masquerade achieve camouflage by resembling inanimate objects in their habitats in terms of body size and shape. Empirical and theoretical research has found that body size affects camouflage strategies by determining key aspects of an animal's appearance and predation risk and that body shape plays a role in the form and effectiveness of camouflage coloration. However, the mechanisms underlying these adaptations remain elusive, and a relative dearth of research on other camouflage strategies. We underscore the necessity for additional research to investigate the interplay between animal morphology and camouflage strategies and their coevolutionary development, and we recommend directions for future research.

STABILITY AND BIFURCATION OF A PREDATOR–PREY SYSTEM WITH MULTIPLE ANTI-PREDATOR BEHAVIORS

In this paper, a predator–prey system with multiple anti-predator behaviors is developed and studied, where not only the prey may spread between patches but also the fear effect and counter-attack behavior of the prey are taken into account. First, the stability and existence of coexistence equilibria are presented. The unique positive equilibrium may be a saddle-node or a cusp of codimension 2. Then, various transversality conditions of bifurcations such as saddle-node bifurcation, transcritical bifurcation, Hopf bifurcation and Bogdanov–Takens bifurcation are obtained. Moreover, compared with a single strategy, the multiple anti-predator strategies are more beneficial to the persistence and the population density of prey.

Justin Schmidt’s originality

The research career of Justin O. Schmidt (1947–2023) is reviewed and assessed. The pioneering nature of his research lay in treating the defensive means and tactics of aculeate hymenoptera and some arachnids as features of their overall anti-predator strategies. He devised methods for comparing the effects of hymenopteran venoms and stings that challenged the assumed correlation between venom potency and the pain that it induces.

Behavioral and physiological responses of nocturnal marine shellfish to predation pressure

Predator-prey interactions are critical in ecological communities. As the wild resources of Pacific abalone are on the verge of exhaustion, efforts to reveal the effects of predation by hostile organisms on the efficiency of its bottom sowing and proliferation are crucial for the success of resource restoration. In this study, abalone and its predator, starfish Asterias amurensis, were placed in a customized monitoring unit. Through continuous infrared video monitoring, predation pressure was found to cause a significant decrease in the distance moved, duration of movement, cumulative feeding duration and orexin levels in hemolymph (P < 0.01). It also caused a significant increase in the average velocity of movement, group cohesion, coordination and cholecystokinin levels in hemolymph (P < 0.01). Surprisingly, when a shelter was set up in the environment, the cumulative feeding duration of abalone was significantly extended in the presence of the predator (P < 0.001), whereas when the predator was removed, the distance moved, duration of movement, and cumulative feeding duration of abalone were found to significantly increase during continuous 24 h monitoring (P < 0.01). These results first identified the anti-predation strategy by nocturnal marine organisms when exposed to predation risk, and supported the pivotal role of shelter in helping abalone make a trade-off between predation pressure and survival needs, which not only provides a new insight to optimizing the strategy for prevention and control of marine ecological disasters and strengthening the protection of marine endangered species, but also results in a productive attempt to restore the marine benthic ecosystem.

Response of diademed sifaka (Propithecus diadema) to fosa (Cryptoprocta ferox) predation in the Betampona Strict Nature Reserve, Madagascar.

Large-bodied mammals living in fragmented habitats are at higher risk of extinction, and such risk can be influenced by ecological factors such as predator-prey system dynamics. These dynamics can be particularly complex for conservation management when one endangered species preys on another endangered species in an isolated or poor-quality habitat. Here we describe predation events observed over 19 months that involved two threatened species: the largest carnivore in Madagascar, the fosa (Cryptoprocta ferox), and three groups of diademed sifaka (Propithecus diadema) in the Betampona Strict Nature Reserve. This site is a 22 km2 low-altitude rainforest that is surrounded by agricultural land and isolated from larger forest corridors. We aim to (1) assess the behavioral changes of P. diadema in response to fosa attacks and identify any antipredator strategies that they adopted, and (2) quantify the frequency of fosa attacks and the predation impact on the sifaka population. We report five direct observations of fosa predation attempts (one successful), the discovery of a dead sifaka with evidence of fosa predation, and the disappearance of three individuals. We describe the observed attacks and compare the sifaka activity budgets and movement patterns before and after the events. To escape the predator, sifakas fled short distances, hid, and remained vigilant. The impact of predation, combined with low reproductive rates and potentially high inbreeding of this isolated diademed sifaka population, could affect the survival of this species in Betampona.Given the compounding effects of habitat isolation and high hunting pressure, community-specific conservation strategies should incorporate predator-prey dynamics via longitudinal monitoring of predator and prey population densities and quantifying the predation pressure between them.

Selective use of forest habitat by Biłgoraj horses

Primitive horses are quite often kept in nature reserves with access to the forest, which they sometimes penetrate to use the vegetation. Horses, as grazers, use specific foraging and anti-predator strategies that differ from typical browsers. The aim of the study was to assess the factors influencing the pattern of forest use by Bilgoraj horses. We hypothesized that the essential factors influencing their pattern of foraging are: browse abundance, distance to pasture, and openness of the habitat. Data were collected at the Biłgoraj Horse-Breeding Centre near Janów Lubelski, Poland. The horses browsed significantly more on woody vegetation in parts of the forest more exposed to sunlight and more abundant in browse material (especially containing preferred species). Distance to the main pasture had a significant effect upon browsing intensity only when an interaction with the abundance of preferred browse was considered.