Predator Attack Research Articles

Collective Predator Perception Advertisement in Fish

The idea that prey might advertise their perception of predators to avoid attacks has received considerable attention in the literature. However, evidence for reduced attack frequencies or attack success in predators as a result of perception advertisement in prey is limited or indirect. Here we present a field study which investigated the benefits of waves produced by fish at the water surface when diving down collectively in response to attacks of avian predators. Instead of merely escaping, fish engaged in surface waves that were highly conspicuous, repetitive and rhythmic involving many thousands of individuals for up to 2 min. Experimentally-induced fish waves doubled the time birds waited until their next attack therefore substantially reducing attack frequency. In one avian predator, capture probability, too, decreased with wave number and birds switched perches in response to wave displays more often than in control treatments suggesting that they directed their attacks elsewhere. Taken together these results support fish waves’ function of perception advertisement. A predator confusion effect is also possible but so far is not known to be associated with waving behaviour especially given that rhythmic waving could make prey more predictable. Collectively produced perception advertisements raise some intriguing questions of how fish synchronise to produce such signals and which pathway has led to their evolution.

Something Scary is Out There II: the Interplay of Childhood Experiences, Relict Sexual Dinichism, and Cross-cultural Differences in Spatial Fears

Children’s nighttime fear is hypothesized as a cognitive relict reflecting a long history of natural selection for anticipating the direction of nighttime predatory attacks on the presumed human ancestor, Australopithecus afarensis, whose small-bodied females nesting in trees would have anticipated predatory attacks from below. Heavier males nesting on the ground would have anticipated nighttime predatory attacks from their sides. Previous research on preschool children and adults supports this cognitive-relict hypothesis by showing developmental consistencies in their remembrances of the location of a “scary thing” relative to their beds. The current study expands this research by investigating whether nighttime fear in childhood, including the effect of parental threats to behave, influenced adult spatial fears in different biotic and abiotic situations. A 25-item questionnaire employing ordinal scales was given to 474 foreign-born Vietnamese and ethnic Chinese adults living in the USA. Univariate analyses of adult remembrances of childhood indicated that females were more fearful of something scary below their beds than males. To examine the influence of childhood nighttime fear on adult fears, exploratory factor analyses supported three factors: (1) indeterminate agents, indicated something scary under the bed, the difficulty locating unspecific threats, and the brief appearances of large apparitions; (2) environmental uncertainty, indicated by potential encounters with unseen animate threats; (3) predictable animals, as the relative comfort of viewing animals in zoo exhibits. Using structural equation modeling, the results suggest that childhood nighttime fear influenced only the latent variable, indeterminate agents, in both groups via the mediating variable, parental threats.

Collective behaviour: Movement rules under imminent threat

Evading predator attacks requires making rapid decisions. A new study has found that instead of moving towards others, as predicted by classical models of anti-predator behaviour, homing pigeons move away from their flock when faced with an imminent attack.

The evolutionary origin of near-death experiences: a systematic investigation.

Near-death experiences are known from all parts of the world, various times and numerous cultural backgrounds. This universality suggests that near-death experiences may have a biological origin and purpose. Adhering to a preregistered protocol, we investigate the hypothesis that thanatosis, aka death-feigning, a last-resort defense mechanism in animals, is the evolutionary origin of near-death experiences. We first show that thanatosis is a highly preserved survival strategy occurring at all major nodes in a cladogram ranging from insects to humans. We then show that humans under attack by animal, human and ‘modern’ predators can experience both thanatosis and near-death experiences, and we further show that the phenomenology and the effects of the two overlap. In summary, we build a line of evidence suggesting that thanatosis is the evolutionary foundation of near-death experiences and that their shared biological purpose is the benefit of survival. We propose that the acquisition of language enabled humans to transform these events from relatively stereotyped death-feigning under predatory attacks into the rich perceptions that form near-death experiences and extend to non-predatory situations.

Fish Scales and Their Biomimetic Applications

Biomaterials are evolving quite rapidly over the last decade. Many applications have been considered toward their involvement in saving lives in the line of duty for law enforcement agencies and military operations. This article discusses recent work on the role of biomaterials that can be considered as a competitive alternative to composites, being used against ballistic impacts. The fish-scaled biomaterials are focused on in this paper, highlighting their excellent mechanical properties and structural configurations. In its natural environment, the scale provides fishes with an armor plating, which is significantly effective in their survival against attacks of predator and the impact inflicted from sharp teeth. These bioinspired materials, if engineered properly, can provide an excellent alternative to current Kevlar® type armors, which are significantly heavier and can cause fatigue to the human body over long-term usage. The investigated materials can provide effective alternatives to heavier and expensive materials currently used in different industrial applications. Additionally, some recent development in the usage of fish scales as a biomaterial and its applications in rapid prototyping techniques are presented. Finally, this review provides useful information to researchers in developing and processing cost-effective biomaterials.

Thick cuticles as an anti-predator defence in nematodes

Summary Although some anti-predator defences have been documented in nematodes, the role of the cuticle in defending against predator attacks remains unclear. Microscopical observations have suggested that certain Poikilolaimus species, including P. oxycercus and P. regenfussi, have thick cuticles relative to their congeners, which may represent an anti-predator defence, but the role of the cuticle in reducing predation has not been examined. To address this knowledge gap, we first quantified cuticle structure using transmission electron microscopy among four Poikilolaimus species (P. oxycercus, P. regenfussi, P. floridensis and P. carsiops). We then examined their survival rates following exposure to the predatory aphelenchoidid nematode, Seinura caverna, and assessed correlations between cuticle thickness and survival rate. The cuticles of P. oxycercus and P. regenfussi were significantly thicker than those of P. floridensis and P. carsiops. In addition, P. oxycercus and P. regenfussi had an osmophilic zone in their cuticle structure, which was not observed in P. floridensis and P. carsiops. Both thickness of specific cuticle zones and total cuticle thickness were positively correlated with survival in the presence of a predator, with the strongest correlation observed with the thickness of the osmophilic zone. We suggest that P. oxycercus and P. regenfussi have uniquely evolved cuticles among members of Poikilolaimus in terms of thickness and structure that play an important role in reducing predation.

Tone deaf: Association of an auditory stimulus with predation risk by zebrafish Danio rerio does not generalize to another auditory stimulus

Predator recognition by small fishes can be acquired when chemical alarm cues released from damaged skin (by a predator attack) are paired with a novel stimulus, such as the appearance or odor of a predator. Once learned, fish can extend recognition of risk by generalizing to associate risk with additional stimuli that are similar to the conditioned novel stimulus. Here, we trained zebrafish to associate a novel auditory stimulus with predation risk, and then tested to see if they generalize risk to all sound stimuli or whether the conditioned response is limited to the sound frequency of the conditioning stimulus. We found that zebrafish Danio rerio readily associated risk of predation with Tone 1 (285 Hz), as evidenced by reduction in activity, increased time spent near the substratum and increased shelter use, but fish conditioned to fear Tone 1 completely ignored presentation of a second tone of 762 Hz. These data suggest that generalization does not occur as easily for auditory cues as they do for olfactory and visual cues, perhaps due to differences in the properties of sensory biology or the cognitive mechanisms that process information in different sensory modalities.

How to Stick the Landing: Kangaroo Rats Use Their Tails to Reorient during Evasive Jumps Away from Predators.

Tails are widespread in the animal world and play important roles in locomotor tasks, such as propulsion, maneuvering, stability, and manipulation of objects. Kangaroo rats, bipedal hopping rodents, use their tail for balancing during hopping, but the role of their tail during the vertical evasive escape jumps they perform when attacked by predators is yet to be determined. Because we observed kangaroo rats swinging their tails around their bodies while airborne following escape jumps, we hypothesized that kangaroo rats use their tails to not only stabilize their bodies while airborne, but also to perform aerial re-orientations. We collected video data from free-ranging desert kangaroo rats (Dipodomys deserti) performing escape jumps in response to a simulated predator attack and analyzed the rotation of their bodies and tails in the yaw plane (about the vertical-axis). Kangaroo rat escape responses were highly variable. The magnitude of body re-orientation in yaw was independent of jump height, jump distance, and aerial time. Kangaroo rats exhibited a stepwise re-orientation while airborne, in which slower turning periods corresponded with the tail center of mass being aligned close to the vertical rotation axis of the body. To examine the effect of tail motion on body re-orientation during a jump, we compared average rate of change in angular momentum. Rate of change in tail angular momentum was nearly proportional to that of the body, indicating that the tail reorients the body in the yaw plane during aerial escape leaps by kangaroo rats. Although kangaroo rats make dynamic 3D movements during their escape leaps, our data suggest that kangaroo rats use their tails to control orientation in the yaw plane. Additionally, we show that kangaroo rats rarely use their tail length at full potential in yaw, suggesting the importance of tail movement through multiple planes simultaneously.

Context-dependent use of visual cues in the shell selection behaviour of the hermit crab Pagurus bernhardus

Animals avoid predator attack in different ways; some carry defensive structures to reduce predation, with the classic example being hermit crabs and their use of a mollusc shell as a portable refugium. During shell selection, various shell characteristics are investigated by the crab to determine their suitability. Here we consider the role of visual cues. Previous research suggests that some hermit crabs are more likely to initially choose a conspicuous shell but also to move to backgrounds against which they are less conspicuous, suggesting a short-term/long-term trade-off. Across experiments in which we manipulated shell and background colour, we show initially that Pagurus bernhardus prefer black shells over white but this preference was lost in the absence of visual cues. We then show that the strength of preference was dependent on background colour. We repeated this last experiment with red and yellow shells against red or yellow backgrounds to investigate whether this preference extended to chromatic hues. A preference for darker (red) shells was expressed, but preference alteration with background was not observed. P. bernhardus therefore discriminate between shells in terms of shell and background colour, and discrimination may be rooted in a preference for darker shaded shells.

Pattern biases, but not positional cues, influence learning in the little brown skink, Scincella lateralis

Abstract Studies of many lizard species have established they are capable of learning to escape to one specific retreat out of several available retreats and will escape to it when subjected to a simulated predator attack. Recently, researchers have focused on the processes involved in learning, including what cues lizards use to learn to escape to a retreat. Previous work on the little brown skink lizard, Scincella lateralis, has shown that it is capable of learning to escape to a specific retreat when it has gained prior experience with its environment and that its performance is better when a retreat is associated with a vertical stripe local cue than when the retreat was associated with a horizontal stripe one. Here I report the results of two additional experiments undertaken to gain a better understanding of how little brown skinks react to cues in their environment. In Experiment 1, the positional cue test, I tested if little brown skinks could be trained to escape to a specific retreat when the only cue available was a positional cue that lizards could use to orient themselves by conducting a series of trials in which little brown skinks were trained to escape to the retreat to the left or the right of a vertical cylinder. Only 2 of the 16 (12.5%) little brown skinks met the learning criterion. This was not significantly different from what is expected if lizards chose their retreats at random suggesting little brown skinks are poor at learning when only a positional cue is available. In Experiment 2, the pattern bias test, I tested if the little brown skink’s superior performance learning to escape to a retreat with a vertical stripe cue in previous experiments was due to a bias for vertical stripes (or against horizontal stripes) through a series of trials in which little brown skinks had to choose between two escape retreats: one with a vertical stripe local cue and the other with a horizontal stripe local cue. A significant bias for the vertical stripe local cue retreat was found among 24 adults, but not among 12 neonates. These results suggest pattern bias among adult little brown skinks impacted the results of previous studies. The possibility that lizards may have biases for colours or shapes and that these biases may have an impact on learning studies is discussed.

An integrative analysis of the short-term effects of tail autotomy on thermoregulation and dehydration rates in wall lizards.

Maintaining body temperature is essential for the optimal performance of physiological functions. Ectotherms depend on external heat sources to thermoregulate. However, thermoregulation may be constrained by body condition and hydration state. Autotomy (i.e., the voluntary shed of a body part) evolved in various animal lineages and allowed surviving certain events (such as predator attacks), but it may affect body condition and volume/surface ratios, increase dehydration and constrain thermoregulation. In the framework of a general analysis of the evolution of autotomy, here we assessed the effects of tail loss on the thermal preferences and evaporative water loss rates (EWL) in the lizard Podarcis bocagei, integrating the thermal and hydric factors. We did not observe shifts in the thermal preferences of experimentally autotomized lizards when compared to the controls, which contradicted the hypothesis that they would raise preferred temperature to increase metabolic rates and accelerate regeneration. Evaporative water loss rates were also similar for tailed and tailless individuals, suggesting negligible increase of water loss through the injury and no specific ecophysiological responses after autotomy. Therefore, the changes observed in autotomized lizards in the field are to be considered primarily behavioural, rather than physiological, and thermoregulation could be secondarily affected by behavioural compensations for an increased predation risk after autotomy. Functional studies are necessary to understand how lizards' interaction with the environment is altered after autotomy, and further studies including different dehydration levels would be useful to fully understand the effect of water shortage on lizards' performance after caudal autotomy.

Common myths of glucocorticoid function in ecology and conservation.

Glucocorticoids are popular hormones to measure in both biomedical and ecological studies of stress. Many assumptions used to interpret glucocorticoid results are derived from biomedical data on humans or laboratory rodents, but these assumptions often fail for wild animals under field conditions. We discuss five common assumptions often made about glucocorticoids in ecological and conservation research that are not generally supported by the literature. (1) High acute elevations of glucocorticoids indicate an animal in distress. In fact: because glucocorticoids are needed to survive stressors, elevated concentrations often reflect adequate coping. (2) Low glucocorticoid concentrations indicate a healthy animal. In fact: because glucocorticoids are important in responding to stressors, low glucocorticoid concentrations might indicate the lack of adequate coping. (3) Sustained elevated glucocorticoids indicate chronically stressed animals. In fact: glucocorticoid concentrations by themselves have no predictive value in diagnosing chronic stress. (4) Glucocorticoids mobilize energy to survive short-term stressors such as predator attacks. In fact: glucocorticoids' primary impact on energy regulation is to remove glucose transporters from cell surfaces. Not only is this process too slow to provide short-term energy, but glucocorticoid-induced increases in glucose reflect decreased, not increased, glucose utilization. (5) Glucocorticoid measurements in non-blood tissues (e.g., feces, hair, feathers, etc.) are equivalent to blood concentrations. In fact: these alternative tissues present imperfect reflections of blood concentrations, and it is blood concentrations that interact with receptors to evoke biological change. In summary, proper consideration of these common assumptions will greatly aid in interpreting glucocorticoid data from ecological and conservation studies.

Tropical Caterpillars Provide First Evidence of Mixed‐Species Processionary Behavior

Photo 1: A colony of Hylesia caterpillars lying dormant at the base of a guava tree in Trinidad. They aggregate tightly to avoid detection by predators. They also possess urticating hairs to deter predator attacks. Photograph credit: Graham L. White. Photo 2: Every evening, the caterpillars journey in a tight procession up the tree trunk (left) and along the branches (right) to feed on leaves in the canopy, then return again at dawn. If one individual in the procession stops, the caterpillar in front immediately halts as well. This leads to a domino effect causing the whole line to come to a standstill until the individual begins to move again. Photograph credit: Graham L. White. Photo 3: This mixed-species colony of Hylesia caterpillars is preparing to begin the evening procession. In situ observations and follow-up experiments describe how H. nanus individuals participated seamlessly in all the group behaviors alongside H. metabus, including the processions. Photograph credit: Graham L. White. Photo 4: One fascinating difference was observed in the behavior of sixth instar caterpillars, seen here in the canopy. In these photographs, H. metabus individuals (the hairier larvae) are poised to “jump” from the edges of the leaves and disperse along the ground. In contrast, individuals of H. nanus remained on the tree until ready to pupate. Photo credit: Graham L. White. Photo 5: A recently emerged adult H. nanus. Photograph credit: Graham L. White. These photographs illustrate the article “Where one species leads, another follows: interspecies processions in tropical caterpillars” by Stefanie A. White and Amy E. Deacon published in Ecology. https://doi.org/10.1002/ecy.3249.

Dyadic leader–follower dynamics change across situations in captive house sparrows

Abstract Individuals can behave as either leaders or followers in many taxa of collectively moving animals. Leaders initiate movements and may incur predation risks, while followers are thought to be more risk-averse. As a group encounters different challenges and ecological situations, individuals in the group may change their social role. We investigated leader and follower roles using dyads of captive house sparrow (Passer domesticus) during both exploration of a novel environment and a simulation of predator attack. During the exploration of a novel environment, individuals behaved consistently either as leaders or followers. However, in the simulated attack tests, individuals in the dyads switched their roles, with “followers” leading the escape flights and “leaders” following them. Our study provides evidence of 1) consistent differences between individuals in behavior during social escape and 2) a relationship between social roles across different situations. We suggest that such relationship hinges on individual risk-taking tendencies, which manifest through different social roles across different ecological situations. We further speculate that risk-taking individuals might gain benefits by following risk-averse individuals during an escape flight.

Effect of fear on two predator-one prey model in deterministic and fluctuating environment

Recent ecological studies on predator-prey interactions has concentrated on determining the impacts of antipredator behavior due to fear of predators. These studies are mainly confined into one predator-one prey system. But in case of multiple predator attack on single prey species, fear mechanism is still unknown. The combined impact of multiple predator often cannot be anticipated from their independent effects. So coexistence of multiple predators and prey’s fitness becomes an important issue from an ecological point of view. Based on the above observations, we proposed and analyzed a model consisting of two competing predator sharing a common prey where prey’s reproduction rate is affected due to fear generated by the predators. We first study the boundedness, uniform persistence, stability and Hopf bifurcation of the deterministic model. Thereafter, we have investigated the existence and uniqueness of the global positive solution, boundedness, asymptotic stability of the stochastic model. Numerical examples are provided to support our obtained results.

Effects of the cranial parasite Tylodelphys sp. on the behavior and physiology of puye Galaxias maculatus (Jenyns, 1842).

Diplostomatid digeneans are well-known manipulators of the behavior of their intermediate hosts. Unencysted metacercariae of Tylodelphys sp. inhabit the cranial cavity of the fish Galaxias maculatus; however, to date they have not been documented to alter their host behavior. The goal of this study was to evaluate the potential effects of Tylodelphys sp. inhabiting the cranial cavity of Galaxias maculatus on host physiology and swimming behavior as well as its reaction to a simulated predation attempt. Blind experiments in the lab were carried out on 56 fish that were filmed individually. The Fulton condition factor (K) was used as an approximation of nutritional status and a respirometry chamber was used to evaluate oxygen consumption rates of fish. Of the 56 fish, 21 were parasitized by Tylodelphys sp. (mean intensity = 30, range from 1 to 101). Parasitized and non-parasitized fish were similar in condition factor and oxygen consumption rates. Furthermore, the oxygen consumption rate of G. maculatus was not correlated with the abundance of Tylodelphys sp. However, parasitized fish more frequently swam close to the water surface, whereas non-parasitized fish more frequently swam at intermediate depths. When faced with a simulated predator attack, unparasitized fish showed more frequent fleeing behavior as well as a more intense post-fleeing activity. Collectively, these results suggest that Tylodelphys sp. inhabiting the cranial cavity of fish may alter their behavior predisposing them to predation by birds.

Numerical bifurcation analysis for a prey-predator type interactions with a time lag and habitat complexity

In this paper, a two-component generic prey-predator system incorporated with habitat complexity in predator functional response, and with constant time delay in predator gestation is considered. Although the role of time delay on the system dynamics is widely studied in the literature, only a few researchers have addressed the effect of habitat complexity in the prey-predator type interactions. In the first part of the paper the equilibria and stability analysis of the mathematical model is mentioned. In the second part, particular attention is paid on the numerical bifurcation analysis of the prey and predator densities based on two system parameters:(i) the strength of homogeneous habitat complexity and (ii) predator attack rate with and without time delay. It is found that dynamics with time delay in predator gestation are found to be much richer compared to that without time delay. The system stability may change from stable to unstable through a Hopf bifurcation and the solution branches emanating from these Hopf points are usually stable and supercritical. However, delay driven system may lead unstable orbits arising from Hopf bifurcations. It is also found that increasing the strength of habitat complexity may lead the stability change from unstable to stable.

Growth, survivorship, and predator avoidance capability of larval shortnose sturgeon (Acipenser brevirostrum) in response to delayed feeding.

Larval shortnose sturgeon, reared at 17°C, were subjected to delayed feeding treatments of 0, 5, 10, 15, 18, and 23 days post-yolk absorption to examine effects of food deprivation on growth, survival, swimming activity, and escape capabilities. Starvation affected growth and survival but despite degree of starvation, larvae were able to resume growth and experience high survivorship following feeding. Specific growth rate based on larval dry weight for the period directly following first feeding was highest for the day 15 and 18 delayed feeding treatments. There were no differences in survival between the 0 and 5 day treatments, however survival was reduced to 71.2%, 45.4%, and 28.8% for 10, 15, and 18 day delayed feeding treatments, respectively. Shortnose sturgeon had a point-of-no-return (PNR; 55.7% initiated feeding) at ~19 days (or 42 days post-fertilization) following the full absorption of yolk. Mean percent swimming activity and swimming speeds showed an interaction between delayed feeding treatment and larval age, such that no differences were detected at 1 and 6 days post-yolk absorption, while these swimming behaviors generally increased or spiked as feeding was delayed for 10, 15, and 18 days post-yolk absorption. At 23 days post-yolk absorption, only swimming speed increased for larvae that were denied food for 18 days. While there was an interaction between delayed feeding treatments and age for proportion of larvae exhibiting an escape response, generally, larvae from all feeding treatments exhibited a positive escape response. There were also interactions between delayed feeding treatments and age post-yolk absorption for mean and maximum escape speeds, such that less aggressive escape responses were typically detected the longer larvae were denied food. Our research suggests that larval shortnose sturgeon increase physical activity during periods of starvation to find a food patch while remaining vigilant but maybe not as capable to defend against a predatory attack as fed individuals.

No evidence of sexual dimorphism in the tails of the swallowtail butterflies Papilio machaon gorganus and P. m. britannicus.

The European swallowtail butterfly (Papilio machaon) is so named, because of the long and narrow prominences extending from the trailing edge of their hindwings and, although not a true tail, they are referred to as such. Despite being a defining feature, an unequivocal function for the tails is yet to be determined, with predator avoidance (diverting an attack from the rest of the body), and enhancement of aerodynamic performance suggested. The swallowtail, however, is sexually size dimorphic with females larger than males, but whether the tail is also sexually dimorphic is unknown. Here, museum specimens were used to determine whether sexual selection has played a role in the evolution of the swallowtail butterfly tails in a similar way to that seen in the tail streamers of the barn swallow (Hirundo rustica), where the males have longer streamers than those of the females. Previously identified sexual dimorphism in swallowtail butterfly size was replicated, but no evidence for dimorphism in tail length was found. If evolved to mimic antennae and a head to divert a predatory attack, and if an absolute tail size was the most effective for this, then the tail would probably be invariant with butterfly hindwing size. The slope of the relationship between tail length and size, however, although close to zero, was nonetheless statistically significantly above (tail length ∝ hindwing area 0.107 ± 0.011). The slope also did not equate to that expected for geometric similarity (tail length ∝ hindwing area1/2) suggesting that tail morphology is not solely driven by aerodynamics. It seems likely then, that tail morphology is primarily determined by, and perhaps a compromise of several, factors associated with predator avoidance (e.g. false head mimicry and a startling function). Of course, experimental data are required to confirm this.

The specificity of sperm-mediated paternal effects in threespine sticklebacks.

Parental effects may help offspring respond to challenging environments, but whether parental exposure to different environmental challenges induces similar responses in offspring is largely unknown. We compared the offspring of threespine stickleback (Gasterosteus aculeatus) fathers who had been exposed to a potentially threatening stimulus (net), a native predator (sculpin), or who had been left unexposed (control). Relative to offspring of control fathers, offspring of sculpin-exposed fathers were more responsive (greater change in activity) to a simulated sculpin predator attack, while offspring of net-exposed fathers were less responsive (fewer antipredator behaviors) and showed altered stress responses compared to the control. To evaluate whether parental exposure primes offspring to respond to specific stimuli (e.g., offspring of net-exposed fathers respond most strongly to a net), we then exposed offspring of each paternal treatment to nets, native sculpin models, or non-native trout models. Paternal treatment did not influence offspring response to different stimuli; instead, offspring were generally more responsive to the native sculpin predator compared to nets or non-native trout predator, suggesting that sticklebacks have innate predator recognition of native predators. Collectively, these results underscore that, while parental exposure to non-ecologically relevant stressors elicits effects in intergenerational studies, these findings may not mirror those produced when parents encounter ecologically relevant stressors. Knowing that parental effects can be predator-specific furthers our understanding of the ways in which parental effects may evolve to be adaptive and suggests the potential for transgenerational plasticity to affect how animals respond to human induced environmental change, including non-native predators.