Same place, different time, head up: Multiple antipredator responses to a recolonizing apex predator

Prey adjust their antipredator behavioral tactics to minimize the risk of an encounter with predators.Spatiotemporal responses of prey to pred-ators have been reported,but the nature of antipredator response is not ubiquitous and it is the object of increasing interest,especially consid-ering the recent recovery of large carnivores in Europe,and the potential for behavioral antipredator responses to elicit consequences at the ecosystem level.We have tested multiple antipredator responses by fallow deer Dama dama to wolf Canis lupus in a Mediterranean protected area recently recolonized by this apex predator.Through intensive camera trapping,we tested for temporal and spatial association between predator and prey,and we have also studied deer vigilance in forest habitats where focal observations are usually impossible.Wolf detection rates were spatially associated with those of fallow deer.Accordingly,no evidence was found for fallow deer avoiding sites with higher predator detection rates.Temporal activity patterns were significantly different between the 2 species,with the wolf being mainly nocturnal whereas fallow deer was active especially during daylight.A comparison with a preliminary study strongly suggests an increase in the diurnal activity of fallow deer along with the stabilization of wolf presence in the area.Both the rate and the duration of vigilance of female fallow deer increased with the local frequency of wolf activity.We suggest an antipredator response based on temporalrather than spatialavoidance,as well as increasedvigilance.

The Relationship between Shell Morphology and Crevice Size Affecting Retreat Selection of the Keeled Box Turtle(Cuora mouhotii)

Rock crevices are important retreat sites for many reptiles.Unlike lizards and snakes,crevicedwelling turtles have rigid shells which severely limit the size and shape of crevices they are able to use.Few studies have addressed the relationship between turtle's shell morphology,behavior,and crevice size.Here,we investigate the relationship between morphology and crevice size selection in the Keeled box turtle(Cuora mouhotii).We radio tracked turtles in the field to document crevice dimensions and turtle behavior associated with crevices,and we conducted a controlled experiment in the lab to understand how a turtle's morphology influences its decision to select crevices with different dimensions.Both laboratory and field experiments demonstrate that turtles select deep and moderately wide crevices that are low enough to barely accommodate the carapace.Crevices used by turtles tend to be about 2 times as wide,1.2 times as high,and 3 times longer than the turtle's shell.Moreover,turtles tended to prefer crevices with horizontal openings in the field and position themselves head first in the crevice.We conclude that morphology,especially carapace height,influences the Keeled box turtles' decision to select specific sizes of crevice.We argue that the tendency for turtles to select crevices that come into contact with their carapace contributes to successful defense against predators,as it would be more difficult for a predator to remove a turtle when the crevice is nearly touching the turtles shell.

Differences in predator-avoidance behavior between two invasive gobies and their native competitors

Globally,fish are frequently introduced beyond their native range.Some,like Ponto-Caspian gobies,are becoming invasive,achieving high colo-nization rates and constituting frequent prey for native predators.However,little is known about the effectiveness of antipredator behaviors of the invaders,which may shape their role in the invaded community and contribute to the invasion success.We compared antipredator behaviors of invasive gobies and native fish species after their detection by the predator,when the danger becomes direct.We studied 2 fish pairs,each consisting of an invasive and native species co-occurring in the environment and belonging to the same prey guild:(1)the racer goby Babka gymnotrachelus versus European bulhead Cottus gobio,(2)the monkey goby Neogobius fluviatilis versus gudgeon Gobio gobio,facing a naive predator(the Eurasian perch Perca fluviatilis).We analyzed behaviors of single prey individuals(escaping,staying in shelter,and activity)and sin-gle predators(activity,searching,following,capturing,and latency to prey consumption).In the predator presence,the bullhead was less active and more often managed to escape after capture than the racer goby.The gudgeon escaped before the capture more often than the monkey goby.The predator succeeded later with the bullhead compared to racer goby,whereas no differences in ingestion time occurred between the gudgeon and monkey goby.The results suggest that,in terms of hunting effort of native predators,the invasive gobies are equivalent to or more profitable prey than their native analogs,which can facilitate the integration of the gobies into local food webs.

Marmots do not consistently use their left eye to respond to an approaching threat but those that did fled sooner

In many vertebrates,the brain's right hemisphere which is connected to the left visual field specializes in the processing of information about threats while the left hemisphere which is connected to the right visual field specializes in the processing of information about conspecifics.This is referred to as hemispheric lateralization.But individuals that are too predictable in their response to predators could have reduced survival and we may expect selection for somewhat unpredictable responses.We studied hemispheric lateralization in yellow-bellied marmots Marmota flaviventer,a social rodent that falls prey to a variety of terrestrial and aerial predators.We first asked if they have lateralized responses to a predatory threat.We then asked if the eye that they used to assess risk influenced their perceptions of risk.We recorded the direction marmots were initially looking and then walked toward them until they fled.We recorded the distance that they responded to our experimental approach by looking,the eye with which they looked at us,and the distance at which they fled (i.e.,flight initiation distance;FID).We found that marmots had no eye preference with which they looked at an approaching threat.Furthermore,the population was not comprised of individuals that responded in consistent ways.However,we found that marmots that looked at the approaching person with their left eye had larger FIDs suggesting that risk assessment was influenced by the eye used to monitor the threat.These findings are consistent with selection to make prey less predictable for their predators,despite underlying lateralization.

Together We Stand-Analyzing Schooling Behavior in Naive Newborn Guppies through Biorobotic Predators

A major advantage of animal aggregations concerns cooperative antipredator strategies.Schooling behavior emerges earlier in many fish species,especially in those cannibalizing their offspring.Experience is fundamental for developing schooling behavior.However,the cognitive ability of naive newborn fish to aggregate remains unclear.Herein,Poecilia reticulata,was selected as model organism to investigate how combinations of biomimetic robotic agents and adult conspecific olfactory cues affect collective responses in newborns.The role of white and brown backgrounds in evoking aggregations was also assessed.Olfactory cues were sufficient for triggering aggregations in P.reticulata newborns,although robotic agents had a higher influence on the group coalescence.The combination of robotic agents and olfactory cues increased schooling behavior duration.Notably,schooling was longer in the escape compartment when robotic agents were presented,except for the combination of the male-mimicking robotic fish plus adult guppy olfactory cues,with longer schooling behavior in the exploring compartment.Regardless of the tested cues,newborn fish aggregated preferentially on the brown areas of the arena.Overall,this research provides novel insights on the early collective cognitive ability of newborn fish,paving the way to the use of biomimetic robots in behavioral ecology experiments,as substitutes for real predators.

Ontogenetic shifts in perceptions of safety along structural complexity gradients in a territorial damselfish

Age and body size can influence predation risk and hence habitat use. Many species undergo ontogenetic shifts in habitat use as individuals grow larger and have different age-specific predation pressures. On coral reefs, a number of fish species are more tolerant of threats in structurally complex habitats that contain more refuges than in less structurally complex habitats. However, we do not know how risk perception varies with age, and whether age interacts with habitat complexity. Adults and juveniles, because of their size, may face different risks in structurally simple versus complex habitats. We used flight initiation distanee as a metric to analyze perceptions of risk in a species of damselfish Stegastes nigricans. All else being equal, fish fleeing at greater distances are inferred to perceive higher risk. We targeted juvenile and adult damselfish to assess whether there are ontogenetic shifts in perceptions of safety in relation to structural complexity, inferred based on percent coral cover and rugosity. We found that adult damselfish tolerated closer approach in more complex habitats as measured by percent coral cover, but not rugosity, whereas juvenile fish always allowed closer approach than adult fish regardless of complexity. This ontogenetic shift in habitat use may result from juvenile fish taking bigger risks to maximize growth, whereas older animals, who are closer to their maximum body size, can afford to take fewer risks and protect their assets.

Urban invaders are not bold risk-takers: a study of 3 invasive lizards in Southern California

Biological invasions threaten biodiversity worldwide,and therefore,understanding the traits of successful invaders could mitigate their spread.Many comm only invasive species do well in disturbed habitats,such as urban environments,and their abilities to effectively respond to disturbarices could con tribute to their invasiveness.Yet,there are non invasive species that also do well in disturbed habitats.The question remains whether urban invaders behave differently in urban environments than noninvaders,which could suggest an"urban-exploiting"phenotype.In Southern California,the co-occurrence of in vasive Italia n wall lizards Pod arc is siculus,brown anoles Anolis sagrei,and green anoles A.carolinensis,and native western fence lizards Sceloporus occidentalis offers an opportunity to test whether invasives exhibit consistent differences in risk-taking within human-altered habitats compared with a native species.We predicted that invasive lizards would exhibit more bold behavior by having shorter flight-initiation distances(FIDs)and by being found farther from a refuge(behaviors that would presumably maximize foraging in low-risk environments).Invasive populations had similar or longer FIDs,but were consistently found at distances closer to a refuge.Collectively,invasive lizards in urban habitats were not bolder than a native species.Relianee on nearby refuges might help species successfully invade urban habitats,and if a general pattern,may pose an added challenge in detecting or eliminating them.

Anti-predator behavior along elevational and latitudinal gradients in dark-eyed juncos

Flight-initiation distance(FID),the distance between an individual and experimenter when it begins to flee,can be used to quantify risk-assessment.Among other factors,prior studies have shown that latitude explains significant variation in avian FID:at lower latitudes,individuals and species have longer FIDs than those living at higher latitudes.No prior studies have focused on the effect of elevation on FID.Given the similar patterns of seasonality,climate,and potentially predator density,that covary between latitude and elevation,birds at higher elevations might tolerate closer approaches.We asked whether elevation or latitude would explain more variation in the FID of a common passerine bird species,dark-eyed juncos(Junco hyemalis).Juncos live in a variety of habitats along both latitudinal and elevational gradients.We found that statistical models containing elevation as a variable explained more of the variation in FID than did models containing latitude.We also found,unexpectedly,that birds at higher elevation fled at greater distances.While more predators were sighted per hour at higher elevations than at lower elevations,the frequency of predator sightings did not explain a significant amount of variation in FID.This result questions whether predator density is the main driver of risk perception along elevational gradients.Nonetheless,because elevation explains more variation in FID than latitude in at least one species,these findings have direct implications on how human impacts on birds are managed.Specifically,those designing set-back zones to reduce human impact on birds may consider modifying them based on both latitude and elevation.

Nesting innovations allow population growth in an invasive population of rose-ringed parakeets

Certain traits of recipient environments,such as the availability of limiting resources,strongly determine the establishment success and spread of non-native species.These limitations may be overcome through behavioral plasticity,allowing them to exploit alternative resources.Here,we show how a secondary cavity nester bird,the rose-ringed parakeet Psittacula krameri,innovates its nesting behavior as a response to the shortage of tree cavities for nesting in its invasive range in Tenerife(Canary Islands).We observed that some breeding pairs excavated their own nest cavities in palms,thus becoming primary cavity nester,whereas others occupied nests built with wood sticks by another invasive species,the monk parakeet Myiopsitta monachus.The use of these novel nesting strategies increased the number of breeding pairs by up to 52%over 6 years,contributing to a 128.8%increase of the whole population.Innovative nests were located at greater heights above ground and were more aggregated around conspecifics but did not result in greater breeding success than natural cavities.Occupation of monk parakeet colonies by rose-ringed parakeets also benefited the former species through a protective-nesting association against nest predators.Our results show how an invasive species innovate nesting behaviors and increase nest-site availability in the recipient environment,thus facilitating its population growth and invasion process.Potential behavioral innovations in other invasive rose-ringed parakeet populations may be overlooked,and should be considered for effective management plans.

Is the propensity to emit alarm calls associated with health status?

The production and structure of animal signals may depend on an individual's health status and may provide more than one type of information to receivers.While alarm calls are not typically viewed as health condition dependent,recent studies have suggested that their structure,and possibly their propensity to be emitted,depends on an individual,s health condition and state.We asked whether the propensity of yellow-bellied marmots(Marmota flaviventer)to emit calls is influen ced by their immuno logical or parasite status,by quantifying both trap-elicited and n atural calling rates as a function of their neutrophil-to-lymphocyte(NL)ratio,the presence of a blood borne trypanosome,and the presenee of several intestinal parasites(Eimeria sp.,Entamoeba sp.,and Ascaris sp.).We fitted mixed effects models to determine if the health measures we collected were associated with the probability of calling in a trap and with annual rates of natural alarm calling.Marmots infected with a blood-borne trypanosome were marginally more likely to call naturally and when trapped,while those infected with the intestinal parasite Ascaris were less likely to call when trapped.NL ratio was not directly associated with in-trap calling probability,but males were more likely to call when they had higher NL ratios.Thus,health conditions,such as parasite infection and immune system activation,can modulate the production of alarm signals and potentially provide in formation to both predators and prey about the caller's condition.Playback experiments are required to confirm if receivers use such information.

Acoustic and visual adaptations to predation risk: a predator affects communication in vocal female fish

Predation is an important ecological constraint that influences communication in animals.Fish respond to predators by adjusting their visual signaling behavior,but the responses in calling behavior in the presence of a visually detected predator are largely unknown.We hypothesize that fish will reduce visual and acoustic signaling including sound levels and avoid escalating fights in the presence of a predator.To test this we investigated dyadic contests in female croaking gouramis(Trichopsis vittata,Osphronemidae)in the presence and absence of a predator(Astronotus ocella-tus,Cichlidae)in an adjoining tank.Agonistic behavior in T.vittata consists of lateral(visual)displays,antiparallel circling,and production of croaking sounds and may escalate to frontal displays.We analyzed the number and duration of lateral display bouts,the number,duration,sound pressure level,and dominant frequency of croaking sounds as well as contest outcomes.The number and duration of lateral displays decreased significantly in predator when compared with nopredator trials.Total number of sounds per contest dropped in parallel but no significant changes were observed in sound characteristics.In the presence of a predator,dyadic contests were decided or terminated during lateral displays and never escalated to frontal displays.The gouramis showed approaching behavior toward the predator between lateral displays.This is the first study supporting the hypothesis that predators reduce visual and acoustic signaling in a vocal fish.Sound properties,in contrast,did not change.Decreased signaling and the lack of escalating contests reduce the fish's conspicuousness and thus predation threat.

Oviposition behavior of the mirid Macrolophus pygmaeus under risk of intraguild predation and cannibalism

Zoophytophagous mirid species,that feed and develop either on prey or plant resources,are often found simultaneously on the same host.Hence,these species can engage in both intraguild predation and cannibalism,which can pose a threat to mirid eggs.Ovipositing females may respond to such risks of predation on their eggs by reducing the number of eggs laid or selecting safer oviposition sites.We tested the oviposition behavior of Macrolophus pygmaeus(Rambur)(Hemiptera:Miridae)females under the risk of cannibalism by M.pygmaeus males and intraguild predation by Nesidiocoris tenuis(Reuter)males(Hemiptera:Miridae)under laboratory conditions.Intraguild predators and cannibals were introduced during or after the oviposition period.The number of eggs laid(using counts of newly hatched nymphs)and their proportion on each part of a tomato plant were both measured.The results reveal that only cannibalism by M.pygmaeus males after the period of oviposition significantly decreased the number of hatched eggs.Cannibalism thus represents a greater risk to mirid eggs than intraguild predation.The M.pygmaeus female responded to the presence of potential intraguild predators(or competitors)by decreasing the nu mber of eggs laid in the upper leaves.The results suggest that M.pygmaeus females avoid competition by N.tenuis,by laying fewer eggs on upper leaves.Cannibalism could regulate zoophytophagous predator populations under prey scarcity conditions and minimize the risk of crop damage associated with those biological control agents.

Responses of incubating females to female cuckoo calls in 2 hole-nesting bird species

Acoustic signals play an important role in animal communication systems,and these signals can transfer diverse and meaningful information from a signaler to a receiver(e.g.,Yu et al.2019).Animal signals tend to be honest;however,deception can occur when it is beneficial for receivers to send dishonest signals,such as by mimicking alarm calls to steal food from other individuals(Flower et al.2014).In birds,vocal mimicry is a widespread phenomenon that has 2 major functional explanation categories:intraspecific and interspecific communications(Dalziell et al.2015).Vocal mimicry in intraspecific communication mainly involves sexual selection and social affiliation(Dalziell et al.2015).In interspecific communication,studies on vocal mimicry are mostly related to predator–prey interactions(Dalziell et al.2015).Mimics could mimic calls of predators to scare off other predators or competitors.For example,some species of hole-nesting birds produce a snakelike hissing call to drive nest predators away(e.g.,Dutour et al.2020).Receiver should be particularly sensitive to the deceptive vocals of mimics if failing to respond to an actual model sound is costly.Therefore,the mimics could derive an advantage from mimicking the calls of predators of the receivers.A recent experimental study suggested that the bubbling calls of female common cuckoo Cuculus canorus mimic those of Eurasian sparrowhawk Accipiter nisus,and they primarily serve to distract regular hosts after laying eggs(York and Davies 2017).However,Xia et al.(2019)found that female cuckoo calls have other functions,including attracting mates and repelling rivals.

Empirical studies of escape behavior find mixed support for the race for life model

Escape theory has been exceptionally successful in conceptualizing and accurately predicting effects of numerous factors that affect predation risk and explaining variation in flight initiation distance(FID;predator–prey distance when escape begins).Less explored is the relative orientation of an approaching predator,prey,and its eventual refuge.The relationship between an approaching threat and its refuge can be expressed as an angle we call the“interpath angle”or“Φ,”which describes the angle between the paths of predator and prey to the prey’s refuge and thus expresses the degree to which prey must run toward an approaching predator.In general,we might expect that prey would escape at greater distances if they must flee toward a predator to reach its burrow.The“race for life”model makes formal predictions about howΦshould affect FID.We evaluated the model by studying escape decisions in yellow-bellied marmots Marmota flaviventer,a species which flees to burrows.We found support for some of the model’s predictions,yet the relationship betweenΦand FID was less clear.Marmots may not assessΦin a continuous fashion;but we found that binning angle into 445°bins explained a similar amount of variation as models that analyzed angle continuously.Future studies ofΦ,especially those that focus on how different species perceive relative orientation,will likely enhance our understanding of its importance in flight decisions.

A test of the species confidence hypothesis in dusky damselfish

Visual cues are important in both interspecific and intraspecific communication.The species confidence hypothesis proposes that animals are more attracted to conspecific colors and repelled by colors,not on their bodies.Studies on terrestrial lizards and birds have tested the species confidence hypothesis and shown that conspecific colors elicit reduced antipredator behavior.To date,the species confidence hypothesis has not been tested in the marine environment,specifically on coral reefs where color communication is of vital importance.We addressed this knowledge gap by measuring flight initiation distance(the distance an individual moves away from an approaching threat)in dusky damselfish(Stegastes nigricans)in response to an approaching disc of 1 of 4 different color treatments:conspecific,blue,yellow,and black.If the species confidence hypothesis explained variation in damselfish flight initiation distance,then we expected individuals to tolerate closer approaches when approached by a conspecific color.In addition,we calculated the color difference between each stimulus and its corresponding back-ground as a potential alternative explanation for flight responses.Damselfish tolerated the closest approach from the conspecific color stimulus;there were no significant differences between other colors and there was no support for the alternative color difference hypothesis.As with similar terrestrial studies,these results are relevant to ecotourists'choice of swimsuit and wetsuit colors because color choice may modify naturalantipredatorbehavior.