Phenotypic plasticity in oysters (Crassostrea virginica) mediated by chemical signals from predators and injured prey

Prey organisms reduce predation risk by altering their behavior, morphology, or life history. Avoiding or deterring predators often incurs costs, such as reductions in growth or fecundity. Prey minimize costs by limiting predator avoidance or deterrence to situations that pose significant risk of injury or death, requiring them to gather information regarding the relative threat potential predators pose. Chemical cues are often used for risk evaluation, and we investigated morphological responses of oysters (Crassostrea virginica) to chemical cues from injured conspecifics, from heterospecifics, and from predatory blue crabs (Callinectes sapidus) reared on different diets. Previous studies found newly settled oysters reacted to crab predators by growing heavier, stronger shells, but that adult oysters did not. We exposed oysters at two size classes (newly settled oyster spat and juveniles ~2.0 cm) to predation risk cue treatments including predator or injured prey exudates and to seawater controls. Since both of the size classes tested can be eaten by blue crabs, we hypothesized that both would react to crab exudates by producing heavier, stronger shells. Oyster spat grew heavier shells that required significantly more force to break, an effective measure against predatory crabs, when exposed to chemical exudates from blue crabs as compared to controls. When exposed to chemical cues from injured conspecifics or from injured clams (Mercenaria mercenaria), a sympatric bivalve, shell mass and force were intermediate between predator treatments and controls, indicating that oysters react to injured prey cues but not as strongly as to cues released by predators. Juvenile oysters of ~ 2.0 cm did not significantly alter their shell morphology in any of the treatments. Thus, newly settled oysters can differentiate between predatory threats and adjust their responses accordingly, with the strongest responses being to exudates released by predators, but oysters of 2.0 cm and larger do not react morphologically to predatory threats.     

Interactive effects of episodic hypoxia and cannibalism on juvenile blue crab mortality

We hypothesized that as the spatial extent of hypoxic bottom water increased, (1) adult blue crab predator densities would increase in shallow habitats as they avoided hypoxia, and that (2) juvenile blue crabs, which use shallow unvegetated habitat as a predation refuge from adult conspecifics, would experience increased mortality rates during crowding by cannibalistic adult blue crabs. These hypotheses were tested along a depth gradient of sandy-mud shoreline in the Neuse River Estuary (NRE), North Carolina, USA using a combination of (1) hydrographic measurements to characterize the spatial extent of hypoxia, (2) beach seines to quantify the density of adult blue crab predators in relatively shallow water as a function of 1, and (3) tethering experiments to quantify relative rates of predation on juvenile blue crabs as a function of 1 and 2. During our seven tethering experiments, the NRE study site experienced a range of DO scenarios including normoxia, chronic hypoxia, and hypoxic upwelling. No known predators of juvenile blue crabs, other than adult conspecifics, were collected in any of our shallow-water seines. During the transition from normoxia to chronic hypoxia, blue crab predator densities in shallow refuge habitats increased 4-fold, and relative mortality rates of juvenile blue crabs in shallow habitats increased exponentially with the density of adult conspecifics. Conversely, during hypoxic upwelling events, the density of adult blue crabs in shallow water declined, which may explain why the relative mortality of juvenile crabs did not increase significantly with the increasing spatial extent of hypoxia. Thus, juvenile blue crabs may be relatively safe from adult conspecifics during hypoxic upwelling events, but not during chronic hypoxia. These experimental results highlight the need to consider the effects of dynamic water quality on mobile consumers emigrating from degraded habitats when considering indirect trophic impacts beyond the immediate area of impact.     

Is It Worth the Risk? Food Deprivation Effects on Tadpole Anti-Predatory Responses

Predation risk affects foraging behavior and, particularly, the amount of time devoted to the search for food. When exposed to predation risk, food deprived animals should be risk prone and relax behavioral defenses to a wider extent than well fed individuals. To test for this prediction, we used a 2?×?2 factorial design experiment, manipulating both the energetic state (fed vs. fasted) and exposure to an attack-released cue (injured vs. uninjured conspecifics) of common water frog tadpoles (Pelophylax kl. esculentus). Contrary to expectations, food deprivation significantly lowered the activity level of predator-exposed tadpoles. As in this experiment no food resource was added to test containers, energy conserving behavior might have both delayed starvation and lowered the probability of encountering the potential predator. To test for the effect of food availability on behavioral responses, we performed a second experiment, using the same protocol and procedures, except for adding food to all test containers. All tadpoles showed similar levels of activity, while fed tadpoles exposed to alarm cues tended to swim farther from the cage containing the stimulus than in the first experiment. As many anuran larvae can feed on dead conspecifics, prey-borne cues may have been interpreted as the potential presence of both a food source and a predator, fed tadpoles possibly being more confident than fasted tadpoles in their ability to escape predation in case an actual attack occurs.     

Responses of larval dragonflies to conspecific and heterospecific predator cues

Abstract.  1. In cannibalistic populations, smaller individuals are subject to predation by larger conspecifics, and small individuals commonly alter their behaviour in response to cannibals. Little is known, however, about the underlying cues that trigger such responses and how the behavioural responses to conspecific cannibals differ from heterospecific predators.
2. This study tests which cues are used for the detection of conspecific predators in the larva of the dragonfly Plathemis lydia and how the behavioural response to cannibals differed from the response to heterospecific predators.
3. Individuals were exposed to chemical cues, visual cues, and a combination of both cues from conspecifics as well as no predator and heterospecific predator controls during which their activity and feeding rates were observed.
4. Individuals increased their activity, spatial movement and feeding behaviour in response to either visual or chemical cues from conspecific predators, which was opposite to responses displayed with cues from heterospecific predators. Interestingly, the responses to visual and chemical cues from conspecifics combined were weaker than to either cue in isolation and similar to the no cue control.
5. The results clearly indicate that individuals are able to use chemical and visual cues to detect even very subtle differences in phenotype of conspecific predators.
6. The opposite response in behaviour when exposed to conspecific cannibals vs. heterospecific predators suggests that the presence of cannibals will increase the mortality risk of small individuals due to heterospecific predation. This risk-enhancement is likely to have important consequences for the dynamics of predator–prey interactions.     

Effect of the presence of predatory cues and hunger on cannibalistic behaviour of ladybird beetle,Menochilus sexmaculatus Fabricius (Coleoptera: Coccinellidae)

1. Cannibalism and its role in population dynamics, along with various factors influencing the rate of cannibalism, have been widely studied across taxa.
2. The effects of predatory cue concentrations and starvation on cannibalistic tendencies and other life-history traits in cannibalistic and non-cannibalistic adults of Menochilus sexmaculatus were investigated.
3. Egg cannibalism increased with increasing predatory cue concentration and was maximum in high predatory cue treatment; increased with starvation irrespective of their diet history.
4. Latency to cannibalise eggs was shorter for cannibalistic adults as compared to non-cannibalistic adults irrespective of their hunger status and concentration of conspecific cues.
5. Non-cannibalistic females have higher fecundity than cannibalistic females.
6. In conclusion, both cannibalistic and non-cannibalistic individuals respond differently to intrinsic (hunger) and extrinsic cues (predatory cue concentrations). Cannibalistic individuals cannibalise more than non-cannibalistic ones at low levels of starvation and predatory cues.
7. Our finding suggests that cannibalistic individuals are better at assessing the risk and removing future competitors, which might favour these individuals over non-cannibalistic ones in adverse conditions and increased competition.

     

Hydrodynamic mediation of predator-prey interactions: differential patterns of prey susceptibility and predator success explained by variation in water flow

In most shallow water marine systems, fluid movements vary on scales that may influence local community dynamics both directly, through changes in the abundance of species, and indirectly, by modifying important behaviors of organisms. We examined how differences in current speed affect the outcome of predator-prey interactions for two species of marine benthic predators (knobbed whelks, Busycon carica, and blue crabs, Callinectes sapidus) foraging on two common prey species (bay scallops, Argopecten irradians, and hard clams, Mercenaria mercenaria). The predators differ in their foraging strategies and prey in their potential escape responses. Predation by blue crabs, highly mobile predators/scavengers that rely upon chemical odors transported in the water column to locate prey, could be strongly affected by changes in current speed and turbulent mixing because their foraging strategy relies on a high degree of spatial integration of prey odor plumes. Whelks, slow moving, predatory gastropods that often forage with their bodies buried in the sediment, may be less susceptible to flow-induced distortion of prey odor plumes because their sluggish movements result in a high degree of temporal integration of prey odors. Bay scallops, relatively mobile bivalves capable of rapid short-distance swimming burst, and hard clams, sedentary bivalves, have been shown to respond to varying degrees to predator odors that are dispersed in the water column. Flow regime for the predator-prey experiments was manipulated in situ using large channels. Predation by blue crabs on both juvenile hard clams and bay scallops decreased with increases in water flow (0-12 vs. 0-30 cm s⁻¹). Whelk predation on bay scallops increased with increases in water flow, whereas predation by whelks on hard clams did not differ between flow regimes. For blue crabs movement decreased at periods of high water flow. Because blue crabs locate prey through chemolocation of water-borne cues, which are diluted rapidly at higher flows, decreases in foraging may result from the inability to successfully detect prey at enhanced flows. Differences in predation by whelks could not be explained by a similar mechanism. Visual observations of foraging whelks revealed no differences in whelk behavior between the two flow regimes. The pattern of higher whelk predation on scallops at enhanced flow is likely to be related to a flow-inhibiting ability of scallops to detect predator approach. Thus, flow enhancement interferes with three of the predator-prey systems but the effect on predator success depends on whether the predator or prey is most affected.     

Observational learning does not explain improvement in predation tactics by cuttlefish (Mollusca: Cephalopoda)

When first presented with live crab prey, naive cuttlefish typically approached from the front and were often pinched. In subsequent trials, this initial group rapidly improved their prey capture techniques and attacked from above or behind the crab. Naive cuttlefish that first watched experienced conspecifics prey on crabs captured crabs without getting pinched. However, naive cuttlefish that first watched non-attacking cuttlefish in the same tank with crabs also avoided pinches, as did naive cuttlefish that were exposed only to crab odor. All three experimental groups were as successful on their first predation as the initial group was on its second predation, but the attack techniques they used were not as well developed as those of the initial group on their fifth trial. Results suggest that odor may serve as a primer for cuttlefish predatory attack behavior, perhaps by enhancing food arousal and improving attention. Practice was required for further improvements in predation techniques. We found no evidence that cuttlefish improved their predation techniques by observing conspecifics.     

The effects of interspecific competition and prey odor on foraging behavior in the rock crab, Cancer irroratus (Say)

The effects of competitor pressure and prey odor on foraging behavior of the rock crab, Cancer irroratus (Say), were investigated. The Jonah crab, Cancer borealis (Stimpson), was chosen as the interspecific competitor because it shares resources with C. irroratus. Four treatments were tested for their effect on foraging: the presence or absence of a competitor and two types of prey odor; body odor (living mussel) and tissue extract (dead mussel tissue). The presence of Jonah crabs did not influence location time, search time, prey size selected, or handling time of the rock crabs. However, rock crabs responded differently to the presence of body odor and tissue extract cues. The presence of extract odor decreased the time to locate prey while increasing the number of prey manipulated and prey size selected. When prey body odor was present, rock crabs displayed less investigative behaviors than in the presence of extract odor, illustrated by reduced location time. Extract odor provided a stronger and more attractive cue than body odor, but increased prey manipulation and search time. Extract odor induced increases in manipulation and searching for prey but canceled out the benefits of decreased location time, resulting in crabs from both treatments displaying similar search times. These elevated behaviors may be associated with foraging for injured and cracked prey or may indicate an area of conspecific feeding.     

Effects of odor flux and pulse rate on chemosensory tracking in turbulent odor plumes by the blue crab, Callinectes sapidus

The ability of animals to track through chemical plumes is often related to properties of evanescent odor bursts and to small-scale mixing process that determine burst properties. However, odor plumes contain variation over a range of scales, and little is known about how variation in the properties of the odor signal on the scale of one to several seconds affects foraging performance. We examined how flux and pulse rate interact to modulate the search behavior of blue crabs, Callinectes sapidus, locating odor sources in controlled flume flows. Experimental treatments consisted of continuous plumes and plumes with discrete odor pulses at intervals of 2.5 s and 4 s at two fluxes. Crabs experienced diminished search success and reduced search efficiency as flux decreased and the inter-pulse interval lengthened. There often were significant interactions between flux and pulse length, and neither property completely determined search behavior. Thus, over the time span of several seconds, the blue crab chemosensory system is not a simple flux detector. The sensitivity of blue crabs to inter-pulse intervals in the range of several seconds indicates that larger-scale mixing processes, which create odor variation on comparable scales, may exert a significant impact on foraging success in nature.     

Cue reliability, risk sensitivity and inducible morphological defense in a marine snail

Reliable cues that communicate current or future environmental conditions are a requirement for the evolution of adaptive phenotypic plasticity, yet we often do not know which cues are responsible for the induction of particular plastic phenotypes. I examined the single and combined effects of cues from damaged prey and predator cues on the induction of plastic shell defenses and somatic growth in the marine snail Nucella lamellosa. Snails were exposed to chemical risk cues from a factorial combination of damaged prey presented in isolation or consumed by predatory crabs (Cancer productus). Water-borne cues from damaged conspecific and heterospecific snails did not affect plastic shell defenses (shell mass, shell thickness and apertural teeth) or somatic growth in N. lamellosa. Cues released by feeding crabs, independent of prey cue, had significant effects on shell mass and somatic growth, but only crabs consuming conspecific snails induced the full suite of plastic shell defenses in N. lamellosa and induced the greatest response in all shell traits and somatic growth. Thus the relationship between risk cue and inducible morphological defense is dependent on which cues and which morphological traits are examined. Results indicate that cues from damaged conspecifics alone do not trigger a response, but, in combination with predator cues, act to signal predation risk and trigger inducible defenses in this species. This ability to “label” predators as dangerous may decrease predator avoidance costs and highlights the importance of the feeding habits of predators on the expression of inducible defenses.     

Habitat quality mediates personality through differences in social context

Assessing the stability of animal personalities has become a major goal of behavioral ecologists. Most personality studies have utilized solitary individuals, but little is known on the extent that individuals retain their personality across ecologically relevant group settings. We conducted a field survey which determined that mud crabs, Panopeus herbstii, remain scattered as isolated individuals on degraded oyster reefs while high quality reefs can sustain high crab densities (>10 m^?2). We examined the impact of these differences in social context on personality by quantifying the boldness of the same individual crabs when in isolation and in natural cohorts. Crabs were also exposed to either a treatment of predator cues or a control of no cue throughout the experiment to assess the strength of this behavioral reaction norm. Crabs were significantly bolder when in groups than as solitary individuals with predator cue treatments exhibiting severally reduced crab activity levels in comparison to corresponding treatments with no predator cues. Behavioral plasticity depended on the individual and was strongest in the presence of predator cues. While bold crabs largely maintained their personality in isolation and group settings, shy crabs would become substantially bolder when among conspecifics. These results imply that the shifts in crab boldness were a response to changes in perceived predation risk, and provide a mechanism for explaining variation in behavioral plasticity. Such findings suggest that habitat degradation may produce subpopulations with different behavioral patterns because of differing social interactions between individual animals.     

Sickness-related odor communication signals as determinants of social behavior in rat: A role for inflammatory processes

Infected animals are avoided by conspecifics, suggesting that the inflammatory cascade may play a significant role in odor communication. Injection of male rats with the bacterial mimetic, lipopolysaccharide (LPS, 100 μg/kg, i.p.), decreased investigation through a wire-mesh partition between healthy male partners. This avoidance response was observed in adult males in response to soiled bedding collected from sick rats, regardless of whether LPS was injected peripherally (100 μg/kg, i.p.) or centrally (0.25 or 2.5 μg, icv). The release of sickness-related odor cues was dose-dependently blocked by icv infusion of the anti-inflammatory cytokine, interleukin-10 (IL-10; 20 or 200 ng), and reproduced by icv infusion of pro-inflammatory cytokine, IL-1β (5 or 50 ng). Subcutaneous pretreatment with either estradiol benzoate (20 μg/kg) or testosterone propionate (50 or 500 μg/kg) to adult males that were administered LPS inhibited release of aversive odor cues, but these hormones alone did not influence odor properties. Importantly, the avoidance response to sickness-related odor was not associated with changes in plasma corticosterone, testosterone, or IL-6 levels of odor donors. However, plasma IL-1β concentrations of sick animals was in fact predictive of aversive responses in conspecifics, suggesting that the inflammatory cascade, but not plasma steroid hormones, is likely to mediate aversive properties in odor that functions to signal illness state to conspecifics.     

Crossmodal visual input for odor tracking during fly flight

Flies generate robust and high-performance olfactory and visual behaviors. Adult fruit flies can distinguish small differences in odor concentration across antennae separated by less than 1 mm [1], and a single olfactory sensory neuron is sufficient for near-normal gradient tracking in larvae [2]. During flight a male housefly chasing a female executes a corrective turn within 40 ms after a course deviation by its target [3]. The challenges imposed by flying apparently benefit from the tight integration of unimodal sensory cues. Crossmodal interactions reduce the discrimination threshold for unimodal memory retrieval by enhancing stimulus salience [4], and dynamic crossmodal processing is required for odor search during free flight because animals fail to locate an odor source in the absence of rich visual feedback [5]. The visual requirements for odor localization are unknown. We tethered a hungry fly in a magnetic field, allowing it to yaw freely, presented odor plumes, and examined how visual cues influence odor tracking. We show that flies are unable to use a small-field object or landmark to assist plume tracking, whereas odor activates wide-field optomotor course control to enable accurate orientation toward an attractive food odor.     

Predator‐Naïve Brown Trout (Salmo trutta) Show Antipredator Behaviours to Scent from an Introduced Piscivorous Mammalian Predator Fed Conspecifics

Introduced mammalian predators may pose a high risk for native and naïve prey populations, but little is known about how native fish species may recognize and respond to scents from introduced mammalian predators. We investigated the role of diet‐released chemical cues in facilitating predator recognition, hypothesizing that native brown trout (Salmo trutta) would exhibit antipredator behaviours to faeces scents from the introduced American mink (Neovision vison) fed conspecifics, but not to non‐trout diets. In treatments‐control and replicate stream tank experiments, brown trout showed significant antipredator responses to faeces scent from mink fed conspecifics, but not to faeces scent from mink fed a non‐trout diet (chicken), or the non‐predator food control, Eurasian beaver (Castor fiber). We conclude that native and naïve brown trout show relevant antipredator behaviours to an introduced mammalian predator, presumably based on diet‐released conspecific alarm cues and thereby estimate the predation risk.     

Alarm cue induces an antipredator morphological defense in juvenile Nicaragua cichlids Hypsophrys nicaraguensis

Olfactory cues that indicate predation risk elicit a number of defensive behaviors in fishes, but whether they are sufficient to also induce morphological defenses has receivedlittle attention. Cichlids are characterized by a high level of morphological plasticity during development, and the few species that have been tested do exhibit defensive behaviors when exposed to alarm cues released from the damaged skin of conspecifics. We utilized young juvenile Nicaragua cichlids Hypsophrys nicaraguensis to test if the perception of predation risk from alarm cue (conspecific skin extract) alone induces an increased relative body depth which is a defense against gape-limited predators. After two weeks of exposure, siblings that were exposed to conspecific alarm cue increased their relative body depth nearly double the amount of those exposed to distilled water (control) and zebrafish Danio rerio alarm cue. We repeated our measurements over the last two weeks (12 and 14) of cue exposure when the fish were late-stage juveniles to test if the rate of increase was sustained; there were no differences in final dimensions between the three treatments. Our results show that 1) the Nicaragua cichlid has an innate response to conspecific alarm cue which is not a generalized response to an injured fish, and 2) this innate recognition ultimately results in developing a deeper body at a stage of the life history where predation risk is high [Current Zoology 56 (1): 36-42, 2010].     

Predator Recognition and Learned Irrelevance in the Crayfish Orconectes virilis

When individuals of the crayfish Orconectes virilis detect an unlearned danger cue (alarm odor) and a novel cue (goldfish odor) at the same time, they form a learned association and behave as if the novel cue is associated with increased predation risk ( Hazlett et al. 2002 ). This study examined the potential for learned irrelevance in O. virilis and the circumstances under which blockage of the formation of a learned association could occur. If individuals experience a random pattern of alarm odor and goldfish odor over the days prior to the simultaneous detection of those two cues, no learned association is formed (= learned irrelevance). That is, there is no inhibition of responses to a food cue when goldfish odor is added if the crayfish has experienced a random pattern of the two cues. Learning was eliminated if the random pattern of cues was experienced before or after the simultaneous detection. To present the two cues (alarm and goldfish odors) to crayfish independently on separate days, the water containing goldfish odor had to be removed from the aquaria as the odor persisted at least 24 h. The importance of the learned irrelevance phenomenon on predator–prey interactions is discussed.     

Pattern of integration of conflicting stimuli by the crab Heterozius rotundifrons

When an animal receives several stimuli that could evoke conflicting behaviours they can either show a response to just one stimulus or show a gradation of responses to the multiple stimuli. It has been proposed [Hazlett BA. 2000. Responses to single and multiple sources of chemical cues by New Zealand crustaceans. Mar Freshw Behav Physiol. 34:1–20] that a graded response will be seen if the animals have an alternative response to one behavioural category of stimuli (the alternative-behaviour-gradual-change rule). The crab Heterozius rotundifrons has two alternative patterns of predation avoidance, either assumption of a rigid limb-extended posture for several minutes or a short period of limb extension and then rapid locomotion. We presented crabs with full strength input in one category (food stimulus) and one of seven intensities of input in a conflicting category (either chemical or visual cues associated with increased predation risk). In both cases, as the intensity of the danger signal gradually increased, there was a gradual increase in the duration of the limb-extended posture.     

Subtle cues of predation risk: starlings respond to a predator's direction of eye-gaze

For prey animals to negotiate successfully the fundamental trade-off between predation and starvation, a realistic assessment of predation risk is vital. Prey responses to conspicuous indicators of risk (such as looming predators or fleeing conspecifics) are well documented, but there should also be strong selection for the detection of more subtle cues. A predator's head orientation and eye-gaze direction are good candidates for subtle but useful indicators of risk, since many predators orient their head and eyes towards their prey as they attack. We describe the first explicit demonstration of a bird responding to a live predator's eye-gaze direction. We present wild-caught European starlings (Sturnus vulgaris) with human 'predators' whose frontal appearance and gaze direction are manipulated independently, and show that starlings are sensitive to the predator's orientation, the presence of eyes and the direction of eye-gaze. Starlings respond in a functionally significant manner: when the predator's gaze was averted, starlings resumed feeding earlier, at a higher rate and consumed more food overall. By correctly assessing lower risk and returning to feeding activity earlier (as in this study), the animal gains a competitive advantage over conspecifics that do not respond to the subtle predator cue in this way.     

Ecological Risk Aversion and Foraging Behaviors of Juvenile Squirrel Monkeys (Saimiri sciureus)

The ‘ecological risk aversion hypothesis’ [C.H. Janson and C.P. van Schaik, Juvenile Primates, Oxford Univ. Press, New York (1993), pp. 57–74] proposes that the pattern of slow growth characteristic of juvenile primates is a response to ecological risks (predation and starvation) experienced by juveniles. Juveniles are thought to avoid predation risk by positioning themselves near conspecifics, therefore experiencing high levels of feeding competition with older individuals, reduced access to resources and, consequently, high starvation risks during periods of food scarcity. The present study compared the foraging behaviors of juvenile and adult squirrel monkeys, a small neotropical primate characterized by a long juvenile period, to determine how predation and starvation risks affected juvenile behaviors. The study was conducted in Eastern Amazonia, in a seasonal environment. Due to their slow development, small body size and large group sizes, it was expected that juveniles in this species would behave in a manner consistent with the risk aversion hypothesis. However, age differences in foraging efficiency and foraging success were smaller than predicted. There was also no evidence that juveniles sacrificed access to food for predator protection. Adults did not have preferential access to fruit patches and direct competition was rare. Feeding competition for prey, the most common resource in the troop's diet, was negligible. Therefore, the slow growth and long juvenile period of squirrel monkeys do not correspond with evidence of predation or starvation risk, as predicted by the risk aversion hypothesis.     

The power of the seasons: rainfall triggers parental care in poison frogs

The quality of breeding sites is of great importance for the reproductive success and accordingly the fitness of many animal species. Hence, individuals should decide carefully where to rear their offspring. Often parents have to account for multiple characteristics of habitat quality at once, which in turn might change over time. Specimens confronted with such variability may evolve the ability to display context-dependant decision plasticity. Anuran amphibians breeding in ephemeral pools largely face two risks for their offspring: desiccation and predation. The Neotropical poison frog Ranitomeya variabilis deposits both eggs and tadpoles in phytotelmata. These small tadpole nurseries lower the risk of offspring predation. However, because most poison frog tadpoles are cannibalistic, even these pools need to be surveyed for predators, and parents tend to avoid deposition with conspecifics. We tested if this avoidance behaviour does change in parental R. variabilis depending on seasonal circumstances. Over several months we provided the frogs the option to deposit their eggs or tadpoles in pools that did and did not contain chemical cues of cannibalistic conspecifics, respectively. During the rainy season, frogs strongly avoided conspecific cues for both eggs and tadpoles. Anyway, with the change to the dry season, parental preferences changed such that parent frogs were more likely to deposit tadpoles (but not eggs) in pools containing cues of conspecific tadpoles. We suggest that R. variabilis, a species that typically isolates its cannibalistic offspring, has evolved a plastic feeding behaviour with regard to the risk of phytotelmata desiccation. We interpret that parents provide older tadpoles with younger ‘trophic’ tadpoles in order to accelerate their development and save them from impending desiccation.