Antipredator Responses Research Articles

Little to fear: largest lizard predator induces weak defense responses in ungulate prey

Nonconsumptive effects can strongly influence apex predator ecological function. These effects arise because prey often induce costly phenotypic responses to mitigate predation risk. Yet because predator–prey interactions are complex, prey defenses may vary considerably. We investigated if the Komodo dragon (Varanus komodoensis), a reptile apex predator, induced multiscale antipredator responses in key prey, the Rusa deer (Cervus timorensis) and the wild pig (Sus scrofa). To this end, we examined the temporal and spatial partitioning of habitats by predator and prey, determined the size of ungulate groups as a function of risk, and assessed changes in individual behavior of prey individuals exposed to predator kairomones at feeding stations. Komodo dragon, deer, and pig populations exhibited significant, but subtle differences in 3 habitat preferences that otherwise indicated high niche overlap. Komodo dragon predation risk, alongside other commonly considered predictor variables, did not affect deer or pig group size. With the exception of one individual-based vigilance-type behavior in pigs, no other antipredator behavior, including reduced food consumption, significantly varied in the presence of predator odor cue at feeding stations. Overall, our results indicated limited evidence for antipredator behavior and suggested Komodo dragons exert weak nonconsumptive effects of predation in ungulates. However, weak predatory interactions could be beneficial in island ecosystems as it could promote predator–prey coexistence that reduces extinction risk.

Plasticity in the antipredator behavior of the orange-footed sea cucumber under shifting hydrodynamic forces.

Marine invertebrates that move too slowly to evade unfavorable environmental change may instead exhibit phenotypic plasticity, allowing them to adjust to varying conditions. The orange-footed sea cucumber Cucumaria frondosa is a slow-moving suspension feeder that is preyed on by the purple sunstar Solaster endeca. The sea cucumber’s antipredator behavior involves changing shape and detaching from the substratum, which might increase its probability of being displaced by water motion into an unsuitable environment. We hypothesized that sea cucumbers’ antipredator responses would be diminished under stronger hydrodynamic forces, and that behavioral strategies would be flexible so that individuals could adjust to frequent changes in water flows. In a natural orange-footed sea cucumber habitat, individuals lived along a pronounced hydrodynamic gradient, allowing us to measure antipredator behavior under different water flow strengths. We placed purple sunstars in physical contact with sea cucumbers living at various points along the gradient to elicit antipredator responses. We then repeated this procedure in a laboratory mesocosm that generated weak and strong hydrodynamic forces similar to those observed at the field site. Subjects in the mesocosm experiment were tested in both wave conditions to determine if their antipredator behavior would change in response to sudden environmental change, as would be experienced under deteriorating sea conditions. Antipredator responses did not covary with hydrodynamic forces in the field. However, antipredator responses in the mesocosm experiment increased when individuals were transplanted from strong to weak forces and decreased when transplanted from weak to strong forces. Overall, our results indicate environmentally induced plasticity in the antipredator behavior of the orange-footed sea cucumber.

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.

Repeated stimulation of the pituitary-adrenal axis alters offspring phenotype of a wild passerine.

Prolonged stress can have long-lasting effects on an individual's physiology and growth. However, the impact of chronically elevated glucocorticoids on the expression of early antipredator responses is still poorly documented. In this study, I simulated the effect of repeated acute stress on offspring phenotype in free-living pied flycatchers (Ficedula hypoleuca) by administering adrenocorticotropic hormone (ACTH) to nestlings for 6 days. The results showed that frequent induction of stress responses by ACTH injections, independent of parental care, adversely affected offspring final body size, wing length and baseline corticosterone levels. Nestling behavioural activity did not differ between ACTH- and saline-treated groups during exposure to control sounds, whereas behavioural activity during exposure to alarm calls was reduced in manipulated offspring only. I conclude that prolonged physiological stress may have short-term benefits to nest-bound offspring, such as more effective antipredator behaviour, but at the expense of negative effects on body size and developmental speed.

Differences in flight initiation distance (FID) between rural and urban populations of two species of Australian birds

Abstract Although flight initiation distance (FID) has been shown to be shorter in urban compared to rural populations of birds, less is known about how the characteristics of the urban environment, such as the population size and age of the city influences the FID and other aspects of anti-predator behaviour. Urban willie wagtails and magpie larks in a relatively small and new town had shorter FID than rural conspecifics. Both species were more likely to show a short, rather than long, escape flight if the experimenter started walking towards the bird from further away. There was some indication that urban birds may be more likely to show a short escape flight than rural birds. We conclude that anti-predator responses of birds can be influenced by a relatively small, recently established and sparsely-populated town. Additionally, the possibility of the characteristics of the urban centre influencing variation in the FID response is discussed.

Current energy state interacts with the developmental environment to influence behavioural plasticity

There is increasing evidence that among-individual differences in behaviour are, in part, generated by environmental effects. For example, diet quality can have drastically different effects on behavioural variation depending on whether it acts primarily during ontogeny (i.e. as a permanent environmental effect) or has an immediate effect on trait expression as a consequence of energy intake (i.e. temporary source of variation). Moreover, whether diet quality has a stronger effect on a trait's average expression, its variance or its covariance with other traits, remains unclear. We used a 2 × 2 factorial design crossing life stage (juvenile and adult) and diet quality (low- or high-energy content) to disentangle the effects of developmental and adult diets on the expression of behavioural differences. We tested 281 crickets for their activity levels, responses to predator cues and body mass. Neither developmental diet nor adulthood diet had any effect on population means or on the expression of an activity–antipredator response syndrome, suggesting a genetic basis for this syndrome. We did find evidence for increases in the within-individual variance as a result of exposure to a high-quality diet. However, these increases were only found for antipredator response and body mass. This indicates that diets with higher energy content can increase the potential for behavioural plasticity in antipredator response. In addition to changes in within-individual variation in behaviour, diet quality during development also mediated the links between maturation time and exploratory behaviours. More exploratory crickets matured faster when exposed to the low-quality developmental diet, but this relation was absent in the high-quality diet treatment. Our results show that changes in developmental diet quality can mediate the relationship between life history and behavioural traits later in life.

Predator Cues Increase Silkmoth Mortality

While prey responses to predators reduce the threat of consumption, the physiological costs of these responses can be considerable. This is especially true for organisms that lack effective anti-predator defenses and must rely on camouflage or mimicry for protection. The luna moth, Actias luna, is a large saturniid native to Eastern North America that is preyed on by a wide variety of predators and parasitoids. We report the results of two separate experiments assessing the responses of Actias larvae to predatory wasps (Vespula maculifrons) that were rendered non-lethal but remained able to move freely, as well as in a control (wasp-free) treatment. We determined whether these responses were predator-specific by also testing the response of Actias larvae to a similarly-sized but harmless scavenging fly. In both experiments, A) Actias larvae in the wasp treatment died at a higher rate than those in the control treatments; and B) larval survival in the fly and control treatments did not differ. Despite similar Actias survival in the fly and control treatments, fly-treatment larvae that died appeared to respond similarly to flies as other larvae did to wasps. In both years, larvae that died in the fly and wasp treatments gained virtually no weight between the start of the experiment and their death, suggesting that they may have succumbed to starvation. Our results, replicated over two years, illustrate the high cost of anti-predator responses and are the first report of lethal risk effects in caterpillars.

Olfactorily-mediated cortisol response to chemical alarm cues in zebrafish Danio rerio.

Chemical cues released as a by-product of predation mediate antipredator behaviour, but little is known about the physiological responses to olfactory detection of predation risk. In this study, zebrafish Danio rerio were exposed to either chemical alarm cues from conspecifics, or water (control). Compared with water controls, D. rerio exposed to alarm cues responded behaviourally with antipredator behaviours such as erratic dashing and an increase in time spent near the bottom of the test aquarium. Danio rerio were sacrificed 5 min after exposure to test cues (alarm cues or water). Enzyme-linked immunosorbent assay (ELISA) revealed whole-body levels of cortisol that were significantly higher for fish exposed to alarm cues (mean ± SE, 11.9 ± 3.4 ng g-1 ) than control fish (1.5 ± 0.7 ng g-1 ). These data provide a benchmark for future studies of the proximate mechanisms of olfactorily mediated antipredator responses, modelling effects on aquatic life in a changing climate and, as a model organism, Danio rerio can further our understanding of anxiety in humans.

Chemical predator signals induce metabolic suppression in rock goby (Gobius paganellus).

In nature, a multitude of both abiotic and biotic stressors influence organisms with regard to their overall fitness. Stress responses that finally impair normal biological functions may ultimately result in consequences for whole populations. This study focused on the metabolic response of the intertidal rock pool fish Gobius paganellus towards simulated predation risk. Individuals were exposed to a mixture of skin extracts from conspecifics and chemical alarm cues from a top predator, Octopus vulgaris. Oxygen consumption rates of single fish were measured to establish standard (SMR) and routine metabolic rates (RMR) of G. paganellus, and to address the direct response towards simulated predation risk, compared to handling and light stress. The SMR of G. paganellus (0.0301 ± 0.0081 mg O2 h-1 g-1 WW) was significantly lower than the RMR (0.0409 ± 0.0078 mg O2 h-1 g-1 WW). In contrast to increased respiration due to handling and light stress, the exposure to chemical predation cues induced a significant reduction in oxygen consumption rates (0.0297 ± 0.0077 mg O2 h-1 g-1 WW). This metabolic suppression was interpreted as a result of the stereotypic freezing behaviour as antipredator response of gobiid fish. Results underline the importance of biotic interactions in environmental stress assessments and predation as a biotic factor that will provide more realistic scenarios when addressing stress impacts in tidal rock pool organisms.

Improving the reliability and ecological validity of pharmaceutical risk assessment: Turquoise killifish (Nothobranchius furzeri) as a model in behavioral ecotoxicology.

Pharmaceuticals are essential for human well-being, but their increasing and continuous use pollutes the environment. Although behavioral ecotoxicology is increasingly advocated to assess the effects of pharmaceutical pollution on wildlife and ecosystems, a consensus on the actual environmental risks is lacking for most compounds. The main limitation is the lack of standardized reproducible tests that are based on sensitive behavioral endpoints and that accommodate a high ecological relevance. In the present study, we assessed the impact of a 3-wk exposure to the antidepressant fluoxetine on multiple behavioral traits in the promising new model organism Nothobranchius furzeri (turquoise killifish). Overall, our study shows that fluoxetine can impact feeding behavior, habitat choice in a novel environment, and antipredator response of N. furzeri individuals; effects on spontaneous activity and exploration tendency were less pronounced. However, effects became only apparent when individuals were exposed to fluoxetine concentrations that were 10 times higher than typical concentrations in natural aquatic environments. Ecotoxicologists are challenged to maximize both the reliability and ecological validity of risk assessments of pollutants. Our study contributes to the development of a time- and cost-efficient, standardized ecotoxicological test based on sensitive, ecologically relevant behavioral endpoints in N. furzeri. Environ Toxicol Chem 2019;38:262-270. © 2018 SETAC.

Habitat use of sympatric prey suggests divergent anti-predator responses to recolonizing gray wolves.

The non-consumptive effects of predators on prey are now widely recognized, but the need remains for studies identifying the factors that determine how particular prey species respond behaviorally when threatened with predation. We took advantage of ongoing gray wolf (Canis lupus) recolonization in eastern Washington, USA, to contrast habitat use of two sympatric prey species-mule (Odocoileus hemionus) and white-tailed (O. virginianus) deer-at sites with and without established wolf packs. Under the hypothesis that the nature and scale of responses by these ungulates to wolf predation risk depend on their divergent flight tactics (i.e., modes of fleeing from an approaching predator), we predicted that (1) mule deer would respond to wolves with coarse-scale spatial shifts to rugged terrain favoring their stotting tactic; (2) white-tailed deer would manage wolf risk with fine-scale shifts toward gentle terrain facilitating their galloping tactic within their current home range. Resource selection functions based on 61 mule deer and 59 white-tailed deer equipped with GPS radio-collars from 2013 to 2016 revealed that habitat use for each species was altered by wolf presence, but in divergent ways that supported our predictions. Our findings add to a growing literature highlighting flight behavior as a viable predictor of prey responses to predation risk across multiple ecosystem types. Consequently, they suggest that predators could initiate multiple indirect non-consumptive effects in the same ecosystem that are transmitted by divergent responses of sympatric prey with different flight tactics.

Antipredator behaviour of invasive geckos in response to chemical cues from snakes

AbstractAntipredator behaviours and the ability to appropriately assess predation risk contribute to increased fitness. Predator avoidance can be costly; however, so we expect prey to most strongly avoid predators that pose the greatest risk (i.e., prey should show threat sensitivity). For invasive species, effectively assessing the relative risk posed by predators in the new environment may help them establish in new environments. We examined the antipredator behaviour of introduced Asian house geckos, Hemidactylus frenatus (Schlegel), by determining if they avoided shelters scented with the chemical cues of native predatory snakes (spotted pythons, Antaresia maculosa [Peters]; brown tree snakes, Boiga irregularis [Merrem]; common tree snakes, Dendrelaphis punctulata [Grey]; and carpet pythons, Morelia spilota [Lacépède]). We also tested if Asian house geckos collected from vegetation vs. anthropogenic substrates (buildings) responded differently to the chemical cues of predatory snakes. Asian house geckos did not show a generalised antipredator response, that is, they did not respond to the chemical cues of all snakes in the same way. Asian house geckos avoided the chemical cues of carpet pythons more strongly than those of other snake species, providing some support for the threat‐sensitivity hypothesis. There was no difference in the antipredator behaviour of Asian house geckos collected from buildings vs. natural vegetation, suggesting that individuals that have invaded natural habitats have not changed their antipredator behaviour compared to urban individuals. Overall, we found some evidence indicating Asian house geckos are threat‐sensitive to some Australian predacious snakes.

Landscape Level Effects of Lion Presence (Panthera leo) on Two Contrasting Prey Species

Due to the strong individual cost of being predated, potential prey species alter their behavior and physiology in response to predation risk. Such alterations may cause major indirect consequences on prey populations that are additive to the direct demographic effects caused by prey being killed. However, although earlier studies showed strong general effects of the presence of apex predators, recent data suggest that indirect effects may be highly context dependent and not consistently present. We combined behavioral data with data on endocrine stress and stable isotopes to assess landscape level effects of lion (Panthera leo) presence on two prey species in South Africa, impala (Aepyceros melampus) and blue wildebeest (Connochaetes taurinus). We also evaluated if there was any seasonal variation in such effects. In addition, we provide results from a physiological validation for an enzyme-linked immunoassay (EIA) that can be used for non-invasive monitoring of glucocorticoid stress metabolite concentrations in impala from fecal pellets. We did not find any significant differences in vigilance behavior, fecal glucocorticoid metabolite concentrations, 13C values or isotope niche breadth between animals living with and without lions for either species. However, wildebeest living in a reserve with lions spent more time foraging compared to wildebeest in a lion-free environment, but only during the wet season. Values of fecal 15N suggest a shift in habitat use, with impala and wildebeest living with lions potentially feeding in less productive areas compared to animals living without lions. For both species, characteristics of the social groups appeared to be more important than individual characteristics for both foraging and vigilance behavior. Our results highlight that antipredator responses may be highly dynamic and scale-dependent. We urge for further studies that quantify at what temporal and spatial scales predation risk is causing indirect effects on prey populations.

Mice exposure to haloxyfop-p-methyl ester at predicted environmentally relevant concentrations leads to anti-predatory response deficit.

Although the efficiency of haloxyfop-p-methyl ester (HPME) as selective herbicide is acknowledged, its impact on non-target organisms is poorly known. It is not known whether the short exposure of mammals to low HPME concentrations (consistent with a realistic contamination scenario) poses risks to these animals. Thus, the aim of the current study is to evaluate the effects of HPME on the anti-predatory behavior of female Swiss mice exposed to it. The animals were divided in groups: non-exposed (control) and exposed (route: i.p., for 2days) to different herbicide concentrations (2.7 × 10-4g/kg and 2.7 × 10-2g/kg of body weight), which were considered environmentally relevant predicted concentrations. The animals were subjected to the open field and elevated plus-maze tests; results showed that the HPME did not lead to anxiolytic or anxiety behavior, or to locomotive changes in the tested animals, fact that was confirmed through the Basso Mouse Scale for locomotion scores. On the other hand, animals exposed to the herbicide were incapable of recognizing the snake as potential predator. Animals in the control group, exposed to a real snake (Pantherophis guttatus) remained longer in the safety zone of the test device, presented lower frequency of self-grooming behaviors for a shorter period-of-time, besides showing longer freezing time, which was not observed in animals exposed to HPME. Therefore, our study indicates the ecotoxicological potential of the herbicide, since anti-predatory behavior disorders may affect preys' responses and population dynamics.

Park size and prey density limit occurrence of Eurasian Sparrowhawks in urban parks during winter

BackgroundEurasian Sparrowhawks (Accipiter nisus) increasingly represent successful city-dwellers. Thereby, a rich food supply indicated by high numbers of small birds is believed to be the key driver for this bird-eating raptor species to settle in urban environments. However, as small passerine birds show particularly strong antipredator responses, sparrowhawks may not simply focus on patches of highest prey densities, but rather respond strategically to prey behavior, raising the importance of other parameters in determining the occurrence within urban landscapes.MethodsTo deepen our knowledge on habitat requirements of urban sparrowhawks, bird surveys were carried out during winter between December 2005 and January 2017 in 36 city parks in Vienna, Austria. Besides food supply also park size, canopy heterogeneity and the connectivity with other green spaces were considered.ResultsOccurrence of sparrowhawks was positively affected by increasing park size, prey density and the interaction between both. Bird feeder density and park connectivity with other green spaces were of minor importance in explaining the presence of this species. Canopy heterogeneity didn’t affect city park occupancy by Eurasian Sparrowhawks.ConclusionsOur results suggest that large city parks, particularly when characterized by high prey densities, substantially contribute to protect and preserve ecologically important bird species such as raptors within the urban environment—a landscape already struggling with biodiversity losses and functional homogenization.

Finding Nemo's Genes: A chromosome-scale reference assembly of the genome of the orange clownfish Amphiprion percula.

The iconic orange clownfish, Amphiprion percula, is a model organism for studying the ecology and evolution of reef fishes, including patterns of population connectivity, sex change, social organization, habitat selection and adaptation to climate change. Notably, the orange clownfish is the only reef fish for which a complete larval dispersal kernel has been established and was the first fish species for which it was demonstrated that antipredator responses of reef fishes could be impaired by ocean acidification. Despite its importance, molecular resources for this species remain scarce and until now it lacked a reference genome assembly. Here, we present a de novo chromosome‐scale assembly of the genome of the orange clownfish Amphiprion percula. We utilized single‐molecule real‐time sequencing technology from Pacific Biosciences to produce an initial polished assembly comprised of 1,414 contigs, with a contig N50 length of 1.86 Mb. Using Hi‐C‐based chromatin contact maps, 98% of the genome assembly were placed into 24 chromosomes, resulting in a final assembly of 908.8 Mb in length with contig and scaffold N50s of 3.12 and 38.4 Mb, respectively. This makes it one of the most contiguous and complete fish genome assemblies currently available. The genome was annotated with 26,597 protein‐coding genes and contains 96% of the core set of conserved actinopterygian orthologs. The availability of this reference genome assembly as a community resource will further strengthen the role of the orange clownfish as a model species for research on the ecology and evolution of reef fishes.

Assessing impacts of offshore pile driving noise on the antipredator defense and shoaling behaviors of squid (Doryteuthis pealeii)

Impulsive pile driving occurs during construction of marine platforms, producing intense sounds that may adversely impact animals’ physiology and behavior. Little is known regarding how this noise impacts sound-sensitive invertebrates such as squid, which is surprising given squids’ relative abundance and key ecological role. We quantified how a commercially important squid species (Doryteuthis pealeii) behaviorally responded (in a controlled environment) to pile driving sounds recorded from an offshore windfarm installation within this species' habitat. Both sound pressure and particle motion components of the sound were quantified. Fifteen-minute portions of the recordings were played to individual squid. Body pattern changes, inking, jetting, and startle responses were observed during sound exposure and all squid exhibited at least one response. These responses occurred primarily during the first few noise impulses and diminished quickly over the first minute of playback, indicating short-term habituation. Responses returned after a 24-hr rest, indicating re-sensitization. Separate experiments investigated changes in shoaling behaviors by quantifying shoal cohesion and polarity in groups of squid during ten-minute noise exposures. Rapid habituation of antipredator alarm responses and changes in shoaling dynamics may alter squids’ susceptibility to predation. Noise exposure may also disrupt normal intraspecific communication and ecologically relevant behavioral responses to sounds.Impulsive pile driving occurs during construction of marine platforms, producing intense sounds that may adversely impact animals’ physiology and behavior. Little is known regarding how this noise impacts sound-sensitive invertebrates such as squid, which is surprising given squids’ relative abundance and key ecological role. We quantified how a commercially important squid species (Doryteuthis pealeii) behaviorally responded (in a controlled environment) to pile driving sounds recorded from an offshore windfarm installation within this species' habitat. Both sound pressure and particle motion components of the sound were quantified. Fifteen-minute portions of the recordings were played to individual squid. Body pattern changes, inking, jetting, and startle responses were observed during sound exposure and all squid exhibited at least one response. These responses occurred primarily during the first few noise impulses and diminished quickly over the first minute of playback, indicating short-term habituat...

European Starling (Sturnus vulgaris) reproduction undeterred by predator scent inside nest boxes

Indirect predator cues near nests have been shown to enhance perceived predation risk and associated antipredator behaviours in breeding animals across taxa and particularly with birds. We hypothesized that scent from the raccoon (Procyon lotor (Linnaeus, 1758)) inside nest boxes would, despite being an evolutionarily unique predator, enhance perceived risk to the European Starling (Sturnus vulgaris (Linnaeus, 1758)), thus reducing use of treated sites and reproduction. During early spring, starlings selected from nest boxes treated with equal volumes of predator scent, a novel odour, or water (n = 40 boxes per treatment). We evaluated effects of treatment on reproductive traits via generalized linear models. Starlings established nest bowls in 61% of nest boxes (predator scent, n = 27 boxes; novel odour, n = 24 boxes; control (water), n = 22 boxes); clutches were laid in 68 boxes. We observed no effects of treatment on the likelihood of a clutch (≥1 egg) or nest failure. Further, we found no treatment effects on date of first egg, clutch size, or hatchling number. We conclude that starling antipredator response to enhanced, indirect risk of nest predation is contingent upon a combination of predator cues, as well as direct or indirect experience with nest predation.

Captive-born collared peccary (Pecari tajacu, Tayassuidae) fails to discriminate between predator and non-predator models

Captive animals may lose the ability to recognize their natural predators, making conservation programs more susceptible to failure if such animals are released into the wild. Collared peccaries are American tayassuids that are vulnerable to local extinction in certain areas, and conservation programs are being conducted. Captive-born peccaries are intended for release into the wild in Minas Gerais state, southeastern Brazil. In this study, we tested the ability of two groups of captive-born collared peccaries to recognize their predators and if they were habituated to humans. Recognition tests were performed using models of predators (canids and felids) and non-predators animals, as well as control objects, such as a plastic chair; a human was also presented to the peccaries, and tested as a separate stimulus. Anti-predator defensive responses such as fleeing and threatening displays were not observed in response to predator models. Predator detection behaviors both from visual and olfactory cues were displayed, although they were not specifically targeted at predator models. These results indicate that collared peccaries were unable to recognize model predators. Habituation effects, particularly on anti-predator behaviors, were observed both with a 1-h model presentation and across testing days. Behavioral responses to humans did not differ from those to other models. Thus, if these animals were to be released into the wild, they should undergo anti-predator training sessions to enhance their chances of survival.

Prey naïveté and the anti-predator responses of a vulnerable marsupial prey to known and novel predators

Prey may recognize and respond to predatory cues based on a period of co-evolution or life experience with a predator. When faced with a novel predator, prey may be naive to the threat posed and/or unable to respond effectively, making them highly susceptible to predation. Burrowing bettongs (Bettongia lesueur) are one such species whose naivete towards introduced predators has contributed to their extinction from mainland Australia. Here, we asked whether bettongs that were predator-naive and bettongs which had been exposed to feral cats (Felis catus) for up to 2 years could discriminate between odors of a predator with which they shared no evolutionary history (feral cats), a predator with which they share a deep evolutionary history (Tasmanian devil—Sarcophilus harrisii), a novel herbivore (guinea pig—Cavia porcellus), and procedural control (a towel moistened with deionized water). We deployed scents at foraging trays and filmed bettongs’ behavior at the trays. Predator-naive bettongs’ latency to approach foraging trays and behavior did not differ between scents. Cat-exposed bettongs increased their latency to approach in the presence of animal scents compared with control, and approached predatory scents slowly and cautiously more often than herbivore and procedural control scents. Taken together, these results suggest that bettongs have not retained anti-predator responses to Tasmanian devils after 8000 years of isolation from mammalian predators but nevertheless show that bettongs exposed to predators are more wary and may be able to generalize predator response using olfactory cues. When prey encounter a novel predator, they are often naive to the threat posed and employ ineffective anti-predator responses, because they lack either evolutionary or ontogenetic experience with the predator. Determining how prey identify novel predators is important to improve the success of translocations and reintroductions. Here, we examine how exposure of predator-naive individual burrowing bettongs to predators influences anti-predator responses. By quantifying bettong responses to odors, we show that those experimentally exposed to cats increased their vigilance in response to odors from cats and Tasmanian devils. The results are consistent with the idea that prey generalize anti-predator responses based on non-specific compounds found in predatory odors, and that exposure to novel predators can improve anti-predator responses.