Proximity Of Predator Research Articles

Adaptive plasticity in calling site selection in grey treefrogs (Hyla versicolor)

Calling behaviour is an essential component of gaining access to mates, and calling site selection may be an important component of effective communication. Environmental factors like microclimate, or the presence of competitors and predators often show seasonal or spatial variation, and behavioural plasticity that allows the caller to adjust to this variation may be adaptive. Prompted by the observation of across-season variation in elevated calling site use in our grey treefrog population, we formulated three hypotheses about their calling site choice and tested them using field observations and behavioural trials in the lab. We found that calling site selection is largely determined by local temperature regimes, and suggest that this temperature-based plasticity in calling site selection is adaptive because it allows males to increase their metabolic efficiency and mate attraction effectiveness. The mere presence of heterospecific competitors and predators did not affect calling site selection at the pond, but close proximity to a predator during behavioural trials did reduce calling activity. This suggests that grey treefrog males attend to the presence of predators, that they can assess the degree of risk associated with predator proximity, and that they can adjust calling behaviour adaptively to reduce the chances of being detected by a predator.

Kairomones - important substances in interspecific communication in vertebrates: a review

Interspecies chemical communication is widespread among many groups of organisms, including vertebrates. Kairomones belong to a group of intensively researched substances, represent means for interspecific chemical communication in animals and bring benefit to the acceptor of the chemical signal. Important and often studied is the chemical communication between hosts and their ectoparasites such as ticks and other parasitic mite species. Uric acid is a host stimulus of the kairomone type, which is a product of bird metabolism, or secretions of blood-fed (ingested) ticks. Secretion of volatile substances with kairomone effect may depend on the health of the host organism. Another examined group is the haematophagous ectoparasite insects of the order Diptera, where in addition to the attractiveness of CO<sub>2</sub> a number of other attractants have been described. Specificity of substances in chemical communication can also be determined by their enantiomers. Detailed study of the biology of these ectoparasites is very important from a practical point of view: these parasites play an important role as vectors in a number of infectious diseases. Another area of interspecific chemical communication is the predator-prey relationship, or rather the ability to detect the proximity of predator and induce anti-predator behaviour in the prey. This relationship has been demonstrated in aquatic vertebrates (otter Lutra lutra – salmon Salmo salar) as well as in rodents and their predators. The substances produced by carnivores that induce behavioural response in mice have already been identified. The knowledge of interspecies communication (e.g., between host and parasite) is becoming a prerequisite in successful animal breeding and care.

Chick-a-dee call variation in the context of “flying” avian predator stimuli: a field study of Carolina chickadees (Poecile carolinensis)

Chick-a-dee calls function in social organization in Poecile (chickadee) species. Recent field and aviary studies have found that variation in chick-a-dee calls relates to the type or proximity of avian predator, or level of threat. Earlier studies on calls in the context of predator stimuli have typically used stationary and perched predator models. For chickadees and other small songbirds, more frequently detected and more dangerous avian predatory stimuli are flying predators. In the present study, we tested whether simulated flying avian predator and control models influenced chick-a-dee calling behavior of wild Carolina chickadees, Poecile carolinensis. At 20 independent field sites, chickadee subjects were presented with wooden models that were painted to resemble either a predatory sharp-shinned hawk (Accipiter striatus) or a blue jay (Cyanocitta cristata) and that were made to “fly” down a zip line near a feeding station chickadees were using. The note composition of chick-a-dee calls was affected by both the flight of stimuli and type of model. Call variation in this flying predator context suggests interesting similarities and differences with experimental findings with congeners. Finally, increased production of certain notes to the flying of both model types provides support for a “Better Safe than Sorry” strategy. When costs of alarm calling are low but costs of discriminating potentially serious threats may be extremely high, individuals should err on the side of caution, and alarm call to any potentially threatening stimulus.

Uso de perchas para dormir por la lagartija Anolis uniformis (Squamata: Polychrotidae) en el bosque tropical fragmentado de Los Tuxtlas, México

The use of nocturnal perches by the lizard Anolis uniformis is described. Bimonthly surveys were made throughout a year in small fragments and continuous tropical rainforest areas at Los Tuxtlas, Mexico. Twenty three juvenile individuals and 7 adults were recorded sleeping during the sampling time (18:00 - 23:00 h.). All individuals were found on leaves of plants of 14 species. Perch height ranged from 41.0 to 140.5 cm (mean: 90.1 cm juveniles; 80.6 cm adults) and the most frequent sleeping position observed was with the body oriented along the longitudinal axis of the leaf and the head facing the stem of the plant. This apparently vulnerable position can permit the perception of external stimuli such as proximity of predators; although, eco-physiological factors may also influence selection of sleeping perch sites.

Influence of Risk on Hiding Time by Balearic Lizards (Podarcis lilfordi): Predator Approach Speed, Directness, Persistence, and Proximity

Cost–benefit models predict that hiding time in refuge increases with predation risk. Studies of diverse prey confirm this prediction for various single risk factors, but much less is known regarding joint effects of variation in multiple factors. For single risk factors, we predicted that Balearic lizards (Podarcis lilfordi) hide longer after faster and more direct approaches by predators and when predators attack persistently or remain close to the refuge. We predicted that effects of approach speed on hiding time would interact with those of directness of approach and predator proximity to the refuge. We simulated attacking predators by approaching lizards ourselves. Predictions for all single risk factors were confirmed: hiding time was greater after faster and more direct approaches, second than first attacks, and when an investigator stood closer to the refuge. These findings agree with those for other prey that are ecologically and phylogenetically diverse, suggesting that optimality theory is broadly applicable to refuge use. The predictions of interaction of approach speed were confirmed for both directness of approach and predator proximity, but the interaction between approach speed and predator proximity was opposite that predicted. Knowledge of the shapes of curves relating joint risks to hiding time are needed to use optimality theory to predict joint effects of multiple risk factors, but these shapes are unknown. Comparative studies are needed to detect quantitative effects of ecological and phylogenetic differences on hiding time.

Predator proximity as a stressor in breeding flycatchers: mass loss, stress protein induction, and elevated provisioning

We investigated the physiological and behavioral consequences for prey breeding at different distances from a nesting predator. In a natural setting, Pied Flycatchers (Ficedula hypoleuca) made territory location decisions relative to established Sparrowhawk (Accipiter nisus) nests. From female flycatchers attending nests at different distances from Sparrowhawk nests, we measured body mass, blood stress protein (HSP60 and HSP70), and plasma immunoglobulin levels at the beginning (initial) and end (final) of the flycatcher breeding cycle, and provisioning rates during the nestling phase. We found that individuals breeding in closer proximity to Sparrowhawk nests, under higher perceived predation risk, showed significantly lower body mass, higher stress protein and immunoglobulin levels, and higher nestling provisioning rates compared to those individuals breeding farther away. Across the range of distances investigated (30-610 m), final stress protein levels decreased linearly with distance, whereas the final measures of the other variables showed unimodal trends, increasing or decreasing until an intermediate distance (approximately 350 m) and reversing the direction of the trend. Within 300 m, however, all measures showed significant linear associations with distance from the Sparrowhawk nest. Body mass and stress protein associations with distance from Sparrowhawk nests were only present during late breeding, and not in early incubation. Spatial proximity to Sparrowhawk nests consistently explained significant variation in both physiological and behavioral measures, despite the multitude of potential sources of variation for these measures in a natural setting. This suggests that predictable spatial patterns in these measures in avian communities are determined by the sites of breeding predators. Habitat selection decisions of migrant prey that vary only slightly spatially have consequences even at the cellular level, which plausibly have impacts on individual survival. In addition, this study suggests that predation risk is an important factor affecting physiological condition of prey, including stress protein induction in terrestrial vertebrates.

Chemically-Mediated Predator Inspection Behavior by Fathead Minnow (Pimephales promelas)

ABSTRACT In the absence of visual cues, information gained from chemically-mediated inspection behavior may serve to reduce predation risk by informing minnow shoals of the proximity of potential predators. Behavioral inspection of predator chemical cues implies that sensory modes other than visual detection may be important for assessing predation risk in shoaling fishes. To assess the potential for inspection behavior by fathead minnow (Pimephales promelas; FHM), we quantified the responses of FHM to chemical cues of a natural predator, northern pike, and chemical cues of conspecifics. The presence of northern pike odor elicited inspection-like behavior among FHM. In control treatments, FHM remained within vegetated cover, and no differences were observed in the number of individuals in open water areas. When northern pike odor was added, significantly more FHM were observed in the open water habitat, although FHM activity was similar to that of controls. This suggests that FHM respond to northern pike chemical cues via directional movement into the open water habitats. These results indicate that FHM acquire information about potential predation risk in the absence of visual cues and engage in seemingly high risk investigating activity.

Variation in Escape Behavior among Individuals of the Striped Plateau Lizard Sceloporus virgatus May Reflect Differences in Boldness

Individual differences may affect risk taking (boldness) in antipredatory behavior. I examined individual differences of the lizard Sceloporus virgatus in flight initiation distance (predator-prey distance when escape begins), distance fled, and hiding time (refuge entry until emergence). Positive correlations between repeated measures of flight initiation distance and distance fled showed that individuals differed reliably in each variable, demonstrating individual differences in boldness over intervals of a few minutes to a day or longer, but correlations of hiding times between trials were context-specific. Hiding times were correlated for different speeds and directnesses of approach and predator proximity but not for identical approaches or trials differing in presence of food outside refuge. Independence of repeated hiding times might indicate that assessed risk varied between trials because of uncontrolled differences in approaches that elicited immergence or costs of hiding. Independence of hiding times with food present or absent suggests that differences in nutritional state affected hiding differently when food was present or that boldness is context-specific. Contrary to previous findings for S. virgatus, distance fled and flight initiation distance were unrelated, presumably because the relationship is weak, and possibly because sample sizes were small and uncontrolled distance to refuge and direction fled obscured a relationship.

Innate abilities to distinguish between predator species and cue concentration in Atlantic salmon

Atlantic salmon, Salmo salar, increase their ventilation rate in response to predator odour cues. We measured the ventilation response of newly hatched Atlantic salmon to odours of high- and low-risk predators at five concentrations (10–200%). Concentration may be interpreted as predator proximity and/or number of predators present and thus represents a gradation of predation risk. Predator species (pike, Esox lucius, and minnow, Phoxinus phoxinus) and predator odour concentration affected the number of individuals responding and the strength of individual response. Fewer individuals responded to minnow odour than pike odour, and the proportion of individuals responding also declined with odour concentration. Salmon responded more strongly to high-risk predator (pike) odour than the low-risk (minnow) odour for a given concentration, and ventilation rate generally increased with increasing concentrations of both odours. This study shows that Atlantic salmon have the innate ability to evaluate risk in terms of odour concentration and predator species.

The nose knows: minnows determine predator proximity and density through detection of predator odours

Prey often face a behavioural trade-off between fitness-related activities and costly predator avoidance. Individuals that are able to assess their level of risk should maximize their fitness by allocating appropriate amounts of time and energy to avoid predators. The threat-sensitive predator avoidance hypothesis states that prey should respond to a given threat with an intensity that matches their level of risk. Prey fish are known to assess predation risk using predator odours. However, the level of sophistication of risk assessment based on predator odours is not well understood. We conducted two experiments to investigate whether fathead minnows, Pimephales promelas, assess proximity and density of pike, Esox lucius, predators based on pike odours. In experiment 1, we exposed pike-experienced minnows to either 60 ml of pike odour from 12 pike (i.e. 5 ml/pike), 60 ml of pike odour from two pike (i.e. 30 ml/pike) or a control of 60 ml of water. Minnows exposed to odours from two pike showed a more intense antipredator response than did minnows exposed to odours from 12 pike, demonstrating that minnows can detect individual pike in a mixture of odours from several pike. The fact that minnows responded with a greater intensity as the per-pike concentration increased while the overall concentration of pike odour remained constant, indicates that minnows can use odours to determine their relative proximity to predators. In experiment 2, we exposed pike-experienced minnows to either 5 ml/pike from each of 12 pike, 5 ml/pike from each of two pike or a water control. Minnows in the 12-pike treatment showed a stronger antipredator response than did minnows in the two-pike treatment, demonstrating that minnows can assess the relative density of predators using predator odours. These results demonstrate an amazing level of sophistication of predator odour assessment; they are the first to show that prey fish can use odours to determine predator proximity and relative density to respond to predators in a threat-sensitive manner.

Hypoxia‐based habitat compression of tropical pelagic fishes

AbstractLarge areas of cold hypoxic water occur as distinct strata in the eastern tropical Pacific (ETP) and Atlantic oceans as a result of high productivity initiated by intense nutrient upwelling. We show that this stratum restricts the depth distribution of tropical pelagic marlins, sailfish, and tunas by compressing the acceptable physical habitat into a narrow surface layer. This layer extends downward to a variable boundary defined by a shallow thermocline, often at 25 m, above a barrier of cold hypoxic water. The depth distributions of marlin and sailfish monitored with electronic tags and average dissolved oxygen (DO) and temperature profiles show that this cold hypoxic environment constitutes a lower habitat boundary in the ETP, but not in the western North Atlantic (WNA), where DO is not limiting. Eastern Pacific and eastern Atlantic sailfish are larger than those in WNA, where the hypoxic zone is much deeper or absent. Larger sizes may reflect enhanced foraging opportunities afforded by the closer proximity of predator and prey in compressed habitat, as well as by the higher productivity. The shallow band of acceptable habitat restricts these fishes to a very narrow surface layer and makes them more vulnerable to over‐exploitation by surface gears. Predictably, the long‐term landings of tropical pelagic tunas from areas of habitat compression have been far greater than in surrounding areas. Many tropical pelagic species in the Atlantic Ocean are currently either fully exploited or overfished and their future status could be quite sensitive to increased fishing pressures, particularly in areas of habitat compression.

Temporal variation in predation risk: stage‐dependency, graded responses and fitness costs in tadpole antipredator defences

Temporal variation in predation risk may be an important determinant of prey antipredator behaviours. According to the risk allocation hypothesis, the strongest antipredator behaviours are expected when periods of high risk are short and infrequent. We tested this prediction in a laboratory experiment where common frog Rana temporaria tadpoles were raised form early larval stages until metamorphosis. We manipulated the time a predatory Aeshna dragonfly larva was present and recorded behavioural responses (activity) of the tadpoles at three different time points during the tadpoles’ development. We also investigated how tadpole shape, size and age at metamorphosis were affected by temporal variation in predation risk. We found that during the two first time points activity was always lowest in the constant high‐risk situation. However, antipredator response in the two treatments with brief high‐risk situation increased as tadpoles developed, and by the third time point, when the tadpoles were close to metamorphosis, activity was as low as in the constant high‐risk situation. Exposure to chemical cues of a predation event tended to reduce activity during the first time period, but caused no response later on. Induced morphological changes (deeper tail and shorter relative body length) were graded the response being stronger as the time spent in the proximity of predator increased. Tadpoles in the brief risk and chemical cue treatments showed intermediate responses. Modification of life history was only found in the constant high‐risk treatment in which tadpoles had longer larval period and larger metamorphic size. Our results indicate that both behavioural and morphological defences were sensitive to temporal variation in predation risk, but behaviour did not respond in the manner predicted by the risk allocation model. We discuss the roles of concentration of predator chemical cues and prey stage‐dependency in determining these responses.

Changes in the vertical distribution of capelin (Mallotus villosus) off Newfoundland

Vertical distribution patterns of capelin were examined using data from spring and autumn acoustic surveys off northeastern Newfoundland in the years 1988–2000. Until 1991, capelin typically underwent diel vertical migrations from 50 to 150 m. Since 1991, vertical migrations have been reduced or have become erratic, with capelin commonly located deeper in the water column (200+m) and closer to the seabed. Changes in vertical distribution initially coincided with the onset of a severe cold period, but distributions failed to return to normal as waters warmed. Vertical distribution was examined with regard to potential habitat-selection factors, including capelin density, water temperature, fish size, maturity stage, and proximity of predators. Of these, only fish density and predator (Atlantic cod) presence were significant. Capelin occupied more of the water column when their density was high than when it was low, and they were found farther from the seabed in areas with cod than without. Results indicate that, during the 1990s, capelin should have been able to optimize vertical distribution and feeding. This is not consistent with reports of poorer capelin condition and size-at-age in the 1990s, suggesting that vertical distributions are likely a result of changes in other factors, such as prey availability.

Predator classification by the sea pen Ptilosarcus gurneyi (Cnidaria): role of waterborne chemical cues and physical contact with predatory sea stars

Using laboratory and field experiments we examined the defensive behaviour of the sea pen Ptilosarcus gurneyi (Gray) towards three species of sea stars representing three levels of predatory threat. In the laboratory we first quantified the behaviour of P. gurneyi following physical contact with the sea stars Dermasterias imbricata (specialist predator), Pycnopodia helianthoides (generalist predator), and Pisaster ochraceus (nonpredator). Whereas the majority (73%) of the sea pens rapidly burrowed into the sediment following contact with D. imbricata, their response to P. helianthoides was highly variable and only 23% exhibited burrowing. In contrast, the response of P. gurneyi to P. ochraceus was weak and similar to that elicited by contact with a glass rod (control). Also, whereas the majority of sea pens displayed colony-wide bioluminescent flashes towards D. imbricata and P. helianthoides, their responses to P. ochraceus and the control were weaker and more localized. We subsequently examined whether waterborne predator chemical cues alone could trigger the defensive responses of P. gurneyi to D. imbricata and P. helianthoides, using laboratory bioassays of varying stimulus intensity. Interestingly, although exposure to chemical cues from predatory sea stars did not elicit any defensive response in P. gurneyi, subsequent physical contact with these predators triggered complete burrowing. Field bioassays using SCUBA yielded similar results, as P. gurneyi did not respond to the proximity of predators but rather delayed its response until physical contact occurred. Our study thus provides the first experimental evidence of predator-classification abilities in cnidarians and suggests that physical contact with predatory sea stars is required to trigger defensive behaviours in P. gurneyi.

Acoustic detection and communication by decapod crustaceans

This paper reviews behavioral, physiological, anatomical, and ecological aspects of sound and vibration detection by decapod crustaceans. Our intent is to demonstrate that despite very limited work in this area in the past 20 years, evidence suggests that at least some decapod crustaceans are able to detect and use sounds in ways that parallel detection and processing mechanisms in aquatic and terrestrial vertebrates. Some aquatic decapod crustaceans produce sounds, and many are able to detect substrate vibration at sensitivities sufficient to tell of the proximity of mates, competitors, or predators. Some semi-terrestrial crabs produce and use sounds for communication. These species detect acoustic stimuli as either air- or substrate-borne energies, socially interact in acoustic "choruses," and probably use "calls" to attract mates.

Fat reserves and perceived predation risk in the great tit, Parus major.

The fat reserves of small birds are built up daily as insurance against starvation. They are believed to reflect a trade-off between the risks of starvation and predation such that in situations of high predation risk birds are expected either to reduce their fat reserves in response to mass-dependent predation risk or to increase them in response to foraging interruptions. We assessed the effect on fat reserves of experimentally altering the perceived (but not the actual) risk of predation of wild great tits at a winter feeding site. The perceived predation risk was alternated between 'safe' and 'risky'. Increasing the perceived risk of predation involved 'swooping' a model sparrowhawk over the feeder at four unpredictable times each day using a remote mechanism We produce evidence that the experiment was suceessfull in altering the perceived risk of predation. As predicted from the hypothesis of mass-dependent predation risk, great tits (Parus major) carried significantly reduced fat reserves during the 'risky' treatment. Furthermore, dominant individuals were able to reduce their reserves more than subordinates. As birds returned to feeders within seconds after a predator 'attack', the reduction in fat reserves cannot be attributed to an interruption in feeding.

Perceived predation risk as a function of predator dietary cues in terrestrial salamanders

Prey often avoid predator chemical cues, and in aquatic systems, prey may even appraise predation risk via cues associated with the predator’s diet. However, this relationship has not been shown for terrestrial predator–prey systems, where the proximity of predators and prey, and the intensity of predator chemical cues in the environment, may be less than in aquatic systems. In the laboratory, we tested behavioural responses (avoidance, habituation and activity) of terrestrial red-backed salamanders,Plethodon cinereus, to chemical cues from garter snakes,Thamnophis sirtalis, fed either red-backed salamanders or earthworms (Lumbricusspp.). We placed salamanders in arenas lined with paper towels pretreated with snake chemicals, and monitored salamander movements during 120min. Salamanders avoided substrates preconditioned by earthworm-fed (avoidanceX±SE=91.1±2.5%,N=25) and salamander-fed (95.2±2.5%,N=25) snakes, when tested against untreated substrate (control). Salamanders avoided cues from salamander-fed snakes more strongly (75.2±5.5%,N=25) than earthworm-fed snakes when subjected to both treatments simultaneously, implying that salamanders were sensitive to predator diet. Salamanders tended to avoid snake substrate more strongly during the last 60min of a trial, but activity patterns were similar between salamanders exposed exclusively to control substrate versus those subject to snake cues. In another experiment, salamanders failed to avoid cues from dead conspecifics, suggesting that the stronger avoidance of salamander-fed snakes in the previous experiment was not directly due to chemical cues emitted by predator-killed salamanders. Salamanders also did not discriminate between cues from a salamander-fed snake versus a salamander-fed snake that was recently switched (i.e. <14 days) to an earthworm diet. Our results imply that terrestrial salamanders are sensitive to perceived predation risk via by-products of predator diet, and that snake predators rather than dead salamanders may be largely responsible for the release of such chemicals.

Has predation shaped the social systems of arboreal primates

I studied antipredator behavior in two species of monkeys to elucidate the role of predation in shaping the social systems of arboreal primates. I compared the responses of monkeys to auditory and visual contact with predators to response elicited by sound playback experiments using the recorded calls of predators. Changes in vigilance and aggregation persisting up to 30 min after predator encounter occurred in both cases. Measures of vigilance shed light on individual perceptions of risk, while aggregation measures—intragroup spatial cohesion and polyspecific associations—permit direct inference about the protective benefits of grouping for the monkeys. They responded to real predator encounters and simulations in similar ways. Thus, sound playbacks of predator vocalizations are effective to simulate predator proximity. Contrary to predictions, predator encounters did not lead invariably to increased cohesion within groups or to increased time spent vigilant. Moreover, behavior in polyspecific associations was no different from that in single-species groups. Only red colobus encountering chimpanzees behaved as predicted by increasing vigilance and intragroup cohesion. The red colobus social system may have developed to protect against chimpanzee attack. In contrast, red-tailed monkey encounters with raptors and chimpanzees involved no change in time spent vigilant, coupled with decreases in intragroup cohesion. I conclude that predation is not a uniform selective pressure and patterns of social behavior within groups do not predict antipredator behavior.

Risk Factors and Emergence from Refuge in the Lizard Eumeces Laticeps

AbstractI studied effects of three risk factors, predator proximity, persistence in attacking, and speed, on latency to emerge after entering a refuge in the scincid lizard Eumeces laticeps. I simulated a predator by directly approaching a lizard until it took refuge, usually a tree hole. Costs per unit time of lost opportunities to forage or engage in other activities enhancing fitness did not vary with risk factors. Skinks remained in refuges longer when I stayed near the refuges than when I withdrew to a greater distance. At both distances, skinks monitored my presence visually from positions at or near refuge entrances. Skinks remained in refuges longer after the second of two successive similar approaches at the same speed than after the first, suggesting that they perceived increased risk due to persistence by an individual predator, but the assessment might have been based on attack rate without individual recognition. Latency to emergence increased with predator approach speed, giving another indication of response to higher risk. If lizards were approached twice in succession, latency to emergence was much greater when predator speed was faster during the second approach. When the second approach was slower, there was no significant difference in latency between trials. Risks associated with speed and persistence thus simultaneously affect risk assessment. A recent model (Sih, 1992) of emergence from refuge supposes that decisions affecting latency to emerge are based on a balance of costs of remaining in refuge (often predominantly costs of lost opportunities for feeding or mating) against risk of predation. All data are consistent with a generalized view of Sih's (1992) model, but studies are needed to assess effects of cost and limited information about predator presence.

Threat-sensitive foraging by larval threespine sticklebacks (Gasterosteus aculeatus)

The threat-sensitive predator avoidance hypothesis predicts that prey can assess the relative threat posed by a predator and adjust their behaviour to reflect the magnitude of the threat. We tested the ability of larval threespine sticklebacks to adjust their foraging in the presence of predators by exposing them to conspecific predators of various sizes and recording their foraging and predator avoidance behaviours. Larvae (<30 days post-hatch) displayed predator escape behaviours only towards attacking predators. At 3 weeks post-hatch larvae approached the predator after fleeing, a behaviour which may be the precursor to predator inspection. Larvae reduced foraging and spent less time in the proximity of large and medium-sized predators compared to small predators. The reduction in foraging was negatively correlated to the predator/larva size ratio, indicating that larvae increased their foraging as they increased in size relative to the predator. We conclude that larval sticklebacks can assess the threat of predation early in their ontogeny and adjust their behaviour accordingly.