Conspecific Cues Research Articles

Social facilitation for conservation planning: understanding fairy tern behavior and site selection in response to conspecific audio-visual cues

Simulated social facilitation techniques (e.g. decoys and call playbacks) are commonly used to attract seabirds to restored and artificially created nesting habitats. However, a lack of social stimuli and conspecific cueing at these habitats may limit the use of these sites, at least in the short term. Therefore, testing the effectiveness of simulated audio-visual cues for attracting gregarious birds is important for conservation planning. In this study, we (1) assessed whether call playback and decoys were associated with an increased likelihood of Australian fairy terns Sternula nereis nereis visiting potentially suitable nesting habitats; (2) tested their behavioral response to different cues; and (3) documented whether social facilitation had the potential to encourage colony establishment. A full cross-over study design consisting of all possible pairings of decoy and call playback treatments (control [no attractants], decoys, call playback, both decoys and playback), allocated as part of a random block design, was undertaken at 2 sites. Linear modeling suggested that call playback was important in explaining the time spent aerial prospecting as well as the maximum number of fairy terns aerial prospecting, although this only appeared to be the case for 1 of the 2 sites. Decoys, on the other hand, did not appear to have any effect on time spent aerial prospecting. The results from this study suggest that audio cues have the potential to encourage site selection by increasing social stimuli, but attractants may be required over several breeding seasons before colonies are established.

Basking aggregations in the adder (Vipera berus): attraction to conspecific cues or to scarce suitable microhabitats?

Snakes live a predominantly solitary and secretive life, and are most often considered to be “non-social”. We here provide quantitative information on the occurrence of basking aggregations, i.e., gatherings of two or more adders having clear physical contact with each other, in the adder (Vipera berus). Overall, approximately 1 out of 10 observed adders was seen in groups that consisted predominantly of two individuals and rarely of 3 up to 7 adders. The incidence of aggregations was higher in the adults than in the younger age classes, and in the adult males than in the adult females. Males and especially females were found much more than expected in single-sex clusters, whereas male–female groups were seen much less frequently. Aggregations of adult males were seen almost exclusively during early spring, and groups with only adult females were mainly noticed during mid-summer. For both sexes, aggregated adders were seen most often during periods when the observation frequency of solitary adders was also highest. Hence, the seasonal variation of adder groupings is not induced by varying levels of the tendency to actively associate with conspecifics. There were no indications that adders actively aggregate in large groups and individual snakes did not exhibit a stronger tendency toward gregariousness than others. Overall, our analyses indicate that the observed aggregations are mainly non-social, but rather reflect the tendency of individual adders to simultaneously select scarce thermally suitable microhabitats.

Effect of Potential Sea Lamprey (Petromyzon marinus) Repellents on the Distribution of Juvenile Rainbow Trout (Oncorhynchus mykiss) in a Laboratory Environment

Recent studies have begun to consider the use of chemosensory alarm cues as potential repellents of invasive Sea Lamprey (Petromyzon marinus Linnaeus, 1758) in the Great Lakes Basin. An important factor in determining the efficacy of potential P. marinus repellents is whether they are species-specific. To that end, using laboratory stream channels, this study investigated whether a non-target species, the Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792), would change their distribution in response to damage-released P. marinus alarm cues, potential mammalian predator cues, and damage-released conspecific cues. In groups of 10 individuals per replicate, with 10 replicates per stimulus type, subjects were exposed to one of the following treatment types: deionized water (control), P. marinus extract (heterospecific alarm cue), O. mykiss extract (conspecific alarm cue), 2-phenylethylamine hydrochloride (potential predator cue), and human saliva (potential predator cue). None of the stimuli induced a significant avoidance response during the stimulus observation period as compared to the control. These findings provide preliminary support for the species-specific nature of these proposed alternative P. marinus control measures.

Regulatory Role of Sugars on the Settlement Inducing Activity of a Conspecific Cue in Pacific Oyster Crassostrea gigas.

This study evaluated the larval settlement inducing effect of sugars and a conspecific cue from adult shell extract of Crassostrea gigas. To understand how the presence of different chemical cues regulate settlement behavior, oyster larvae were exposed to 12 types of sugars, shell extract-coated and non-coated surfaces, and under varied sugar exposure times. Lectin-glycan interaction effects on settlement and its localization on oyster larval tissues were investigated. The results showed that the conspecific cue elicited a positive concentration dependent settlement inducing trend. Sugars in the absence of a conspecific cue, C. gigas adult shell extract, did not promote settlement. Whereas, in the presence of the cue, showed varied effects, most of which were found inhibitory at different concentrations. Sugar treated larvae exposed for 2 h showed significant settlement inhibition in the presence of a conspecific cue. Neu5Ac, as well as GlcNAc sugars, showed a similar interaction trend with wheat germ agglutinin (WGA) lectin. WGA-FITC conjugate showed positive binding on the foot, velum, and mantle when exposed to GlcNAc sugars. This study suggests that a WGA lectin-like receptor and its endogenous ligand are both found in the larval chemoreceptors and the shell Ethylenediaminetetraacetic acid (EDTA) extract that may complementarily work together to allow the oyster larva greater selectivity during site selection.

Maternal and personal information mediates the use of social cues about predation risk

Abstract Organisms can gain information about predation risks from their parents, their own personal experience, and their conspecifics and adjust their behavior to alleviate these risks. These different sources of information can, however, provide conflicting information due to spatial and temporal variation of the environment. This raises the question of how these cues are integrated to produce adaptive antipredator behavior. We investigated how common lizards (Zootoca vivipara) adjust the use of conspecific cues about predation risk depending on whether the information is maternally or personally acquired. We experimentally manipulated the presence of predator scent in gestating mothers and their offspring in a full-crossed design. We then tested the consequences for social information use by monitoring offspring social response to conspecifics previously exposed to predator cues or not. Lizards were more attracted to the scent of conspecifics having experienced predation cues when they had themselves no personal information about predation risk. In contrast, they were more repulsed by conspecific scent when they had personally obtained information about predation risk. However, the addition of maternal information about predation risk canceled out this interactive effect between personal and social information: lizards were slightly more attracted to conspecific scent when these two sources of information about predation risk were in agreement. A chemical analysis of lizard scent revealed that exposure to predator cues modified the chemical composition of lizard scents, a change that might underlie lizards’ use of social information. Our results highlight the importance of considering multiple sources of information while studying antipredator defenses.

Associations of observer\u2019s gender, Body Mass Index and internalization of societal beauty ideals to visual body processing

We examined whether visual processing mechanisms of the body of conspecifics are different in women and men and whether these rely on westernised socio-cultural ideals and body image concerns. Twenty-four women and 24 men performed a visual discrimination task of upright or inverted images of female or male bodies and faces (Experiment 1) and objects (Experiment 2). In Experiment 1, both groups of women and men showed comparable abilities in the discrimination of upright and inverted bodies and faces. However, the gender of the human stimuli yielded different effects on participants’ performance, so that female faces, and male bodies appeared to be processed less configurally than female bodies and male faces, respectively. Interestingly, the reduction of configural processing for male bodies was significantly predicted by participants’ Body Mass Index (BMI) and their level of internalization of muscularity. Our findings suggest that configural visual processing of bodies and faces in women and men may be linked to a selective attention to detail needed for discriminating salient physical (perhaps sexual) cues of conspecifics. Importantly, BMI and muscularity internalization of beauty ideals may also play a crucial role in this mechanism.

A review of conspecific attraction for habitat selection across taxa.

Many species across taxa select habitat based on conspecific presence, known as conspecific attraction. Studies that document conspecific attraction typically provide social information (i.e., cues that indicate the presence of a given species) and then determine if a given species is more likely to settle at locations where the social information is provided compared to those locations that do not. Although the number of studies examining conspecific attraction has grown in recent years, a comprehensive review has not yet been undertaken. Here, we conducted a review of the literature and found 151 studies investigating conspecific attraction across eight taxa. We found that conspecific attraction is widespread with between 80% and 100% of studies, depending on taxa, documenting positive associations between habitat selection and the presence of conspecific cues. Conspecific attraction has been documented more frequently in bird and fish species with less attention given to invertebrate and mammal species. We use the patterns we found to (a) provide an overview of the current state of research on conspecific attraction and (b) discuss how important factors, such as cue characteristics and life history traits, may play a role in shaping conspecific attraction patterns within and across taxa.

Early-life and parental predation risk shape fear acquisition in adult minnows.

Exposure to predation risk can induce a fearful baseline state, as well as fear reactions toward novel situations (i.e., neophobia). Some research indicates that risk exposure during sensitive periods makes adults more prone to acquiring long-term fearful phenotypes. However, chronic risk can also lead to ignoring threats in order to maintain other activities. We sought to assess how a relatively long period of low risk, experienced either early in life or by the previous generation, influences fear behaviour acquired from a short period of high risk as adults. We used fathead minnows as study subjects and simulated predation risk with repeated exposures to conspecific chemical alarm cues. The period of high risk experienced by adults induced typical fear behaviour (baseline freezing and neophobia), whereas the early-life low-risk period 1year prior caused only a reduction in baselineforaging. We found no evidence that the early-life risk significantly altered the fear acquired from the adult-risk period. However, in a second experiment, a low-risk period during the parental generation interacted with a high-risk period experienced by the adult offspring. The combination of both risk periods heightened baseline freezing despite parental risk having little effect independently. Hence, our study provides evidence that parental risk exposure can lead to an additive intergenerational effect on fear acquisition in minnows.

Evidence of the peptide identity of the epidermal alarm cue in tadpoles of the toad Rhinella arenarum

Chemical cues associated with predation attempts allow prey to trigger defensive behaviours. Accordingly, tadpoles of several species of anurans display strong behavioural responses to chemical cues of injured conspecifics. As part of the antipredator response, tadpoles show rapid and sustained inhibition of activity when exposed to chemical cues of predation. Although the ability to respond to cues of conspecifics has been confirmed in a wide variety of anuran species, studies about the tissue source and the chemical aspects of the molecules involved are scarce and contradictory. In the present work, we analysed the chemical characteristics, tissue source and release mechanism of the chemical alarm cue in Rhinella arenarum tadpoles. Our results support the hypothesis that a peptide of epidermal origin in mediates amphibian tadpole communication.

Conspecific chemical cues facilitate mate trailing by invasive Argentine black and white tegus.

Squamate reptiles (snakes and lizards) rely on chemical cues from conspecifics to search the environment for potential mates. How such cues are used by invasive species to facilitate reproduction, especially seasonally, is a key question that can inform management practices. The Argentine black and white tegu (Salvator merianae) is an invasive reptile species in south Florida threatening native fauna in biodiverse regions such as Everglades National Park. While some information exists on the reproductive ecology of this species in its native range in South America, the chemical ecology of S. merianae is unclear especially in its invasive range. By testing both male (n = 7) and female (n = 7) tegus in a Y-maze apparatus, we assessed if either sex follows chemical trails left by conspecifics and if behaviors were sex- or season-specific. We conducted three types of trials where conspecifics created odor trails: Male-only (male scent only in base and one arm of Y), Female-only, and Male vs. female. Males did not preferentially follow scent trails from either sex, but they did differentially investigate conspecific scent from both sexes. Seasonally, males showed increased rates of chemosensory sampling (rates of tongue-flicking) during the spring (breeding season; March-May) compared to fall (non-breeding season; September-November). Males also had reduced turning and pausing behavior while trailing in the spring. Female tegus exhibited stronger conspecific trailing abilities than males, following both male and female scent trails, and they explored the maze less before making an arm choice. Females also investigated the scent trails intensely compared to males (more passes in scented arms, more time with scent trails). Our results demonstrate for the first time that females of an invasive reptile species can follow conspecific scent trails. Given the strong female responses to odor, sex-specific targeting of tegus via application of a conspecific chemical cue in traps could enhance removal rates of females during the breeding season.

People expressing olfactory and visual cues of disease are less liked.

For humans, like other social animals, behaviour acts as a first line of defence against pathogens. A key component is the ability to detect subtle perceptual cues of sick conspecifics. The present study assessed the effects of endotoxin-induced olfactory and visual sickness cues on liking, as well as potential involved mechanisms. Seventy-seven participants were exposed to sick and healthy facial pictures and body odours from the same individual in a 2 × 2 factorial design while disgust-related facial electromyography (EMG) was recorded. Following exposure, participants rated their liking of the person presented. In another session, participants also answered questionnaires on perceived vulnerability to disease, disgust sensitivity and health anxiety. Lower ratings of liking were linked to both facial and body odour disease cues as main effects. Disgust, as measured by EMG, did not seem to be the mediating mechanism, but participants who perceived themselves as more prone to disgust, and as more vulnerable to disease, liked presented persons less irrespectively of their health status. Concluding, olfactory and visual sickness cues that appear already a few hours after the experimental induction of systemic inflammation have implications for human sociality and may as such be a part of a behavioural defence against disease. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.

Behavioral Responses by Adult Northern Leopard Frogs to Conspecific Chemical Cues

Chemical signaling is an important facet of vertebrate communication, and amphibians are no exception. However, very little is known about adult anuran (frog and toad) chemical communication, with the few studies that have investigated chemical sensing in adult anurans documenting species- and sex-biased behavioral responses to chemical cues. Varied life histories and reproductive pressures likely dictate these responses, but to better understand the prevalence and purpose of adult anuran olfaction across species, information on chemical sensing across a large number of species is needed. We investigated sex-biased adult Northern Leopard Frog (Lithobates pipiens) behavioral responses to familiar and unfamiliar conspecific chemical cues to determine the importance of olfaction in conspecific recognition. Our results indicate that adult females respond to conspecific cues, with females spending significantly more time investigating cue vs. control sides of the testing arena. Results for males were equivocal, with males responding much more variably. Comparisons of familiar vs. unfamiliar cues indicate that both sexes tend to spend more time near familiar cues, although this was not statistically significant. Females also responded to unfamiliar, opposite-sex conspecific cues, indicating chemical cues may be involved in mate identification for female Leopard Frogs. Unfamiliar, same-sex conspecific odors did not appear to influence behavior for either sex. Collectively, our results indicate that adult Northern Leopard Frogs utilize chemical sensing for conspecific recognition and further indicate a sex-bias in that sensing, with adult females exhibiting a stronger response than males. Future research should investigate aquatic vs. terrestrial cues and learned vs. innate odors of significance to Northern Leopard Frog adults.

American eels produce and release bile acid profiles that vary across life stage.

The American eel (Anguilla rostrata) is an imperilled fish hypothesized to use conspecific cues, in part, to coordinate long-distance migration during their multistage life history. Here, holding water and tissue from multiple American eel life stages was collected and analysed for the presence, profile and concentration of bile acids. Distinct bile acid profiles were identified in glass, elver, yellow eel and silver eel holding waters using ultraperformance liquid chromatography high-resolution mass spectrometry and principal component analysis. Taurochenodeoxycholic acid, taurodeoxycholic acid, cholic acid, deoxycholic acid, taurolithocholic acid and taurocholic acid were detected in whole tissue of American glass eels and elvers, and in liver, intestine and gallbladder samples of late-stage yellow eels. Bile acids were not a major component of silver eel washings or tissue. This study is novel because little was previously known about bile acids produced and emitted into the environment by American eels. Future behavioural studies could evaluate whether any bile acids produced by American eels influence conspecific migratory behaviour.

Conspecific cues encourage Barn Swallow (<i>Hirundo rustica erythrogaster</i>) prospecting, but not nesting, at new nesting structures

Shed-like structures are being built to provide Barn Swallow (Hirundo rustica erythrogaster) nesting habitat in response to population declines. However, Barn Swallow use of these structures is unavailable in the literature. We conducted three manipulative experiments to test if adding conspecific cues (i.e., vocalizations and decoys) to newly-built structures affected prospecting visits by Barn Swallows (1) during pre-breeding, (2) during post-breeding, and (3) during or after broadcasts of vocalizations compared to before broadcasts. Additionally, we monitored nesting following pre- and post-breeding cues. We built one nesting structure with and one without conspecific cues at each of 10 study sites in southern Ontario, Canada where nesting habitat was recently lost. We detected about twice as many Barn Swallows immediately after conspecific broadcasts compared to before. We did not find substantial differences in abundance and interactions with new nesting structures for other comparisons involving conspecific cues. Following pre-breeding cues at 10 sites, six nests were built in three of 10 structures treated with conspecific cues, compared to five nests in four of 10 structures without cues. In the subsequent breeding season following post-breeding cues at eight sites, four nests were built in two of eight structures treated with conspecific cues, compared to four nests in three of eight structures without cues. Conspecific vocalizations appeared to increase prospecting behaviour, but not the number of nests, at new nesting structures. The paucity of nests on new structures suggests that building shed-like structures may not be an effective method of mitigating loss of nesting habitat.

Nestling tree swallows (Tachycineta bicolor) alter begging behaviour in response to odour of familiar adults, but not their nests

AbstractCommunication using chemical cues is important for many taxa, including birds, but the use of olfaction for intraspecific communication has been investigated only recently in passerines and is understudied in nestlings. To address this knowledge gap, we explored whether nestling tree swallows (Tachycineta bicolor) would recognize and respond to chemical cues of conspecifics, specifically testing begging responses to familiar and unfamiliar nest and adult odours. For the nest odour experiment, nests were treated with either orange essential oil or distilled water to create scented and unscented (control) odour environments, respectively. For the adult odour experiment, adults attending the nestlings were considered “familiar adults” and adults attending a different brood in the population were considered “unfamiliar adults.” We found that begging responses of nestlings did not differ in response to orange oil odour or water, but nestlings begged significantly longer and more intensely in response to odours of a familiar than an unfamiliar adult, regardless of adult sex. This provides evidence that tree swallows use chemical cues to alter their behaviour and opens up many exciting avenues of future research.

Socializing in experimental streams: crayfish groups exposed to cues, refuges, and day-night conditions

We initiated the use of a replicated, remote-video, artificial stream system to determine the effects of conspecific cue, refuge availability, and day/night conditions on movement, aggression, dominance, downstream preference, and refuge use by the crayfish Procambarus clarkii. In line with previous research, we found that walking on the gravel substrate was greatly increased and refuge use decreased in the dark. Conspecific cue (macerated crayfish filtrate) increased walking, contrary to our prediction but consistent with cue as a signal of food availability or of risk either from cannibalism or from visual predators. Exposure to conspecific cue in the streams resulted in a reduced degree of dominance in subsequent pairwise dominance trials. We developed and implemented a new and broadly applicable way of determining the extent of linearity (consistency of dominance ranks) for incomplete dominance; for our data, this method found a lack of evidence for linear hierarchies in these stream systems. Our results suggest that streams may tend to feature weaker dominance and reduced linearity of social hierarchies, relative to standing-water systems, a hypothesis that requires further testing.

Larval newts adjust foraging rate to perceived predator and competitor proximity

Foraging is key for most animals, because their energy and matter income depend on food ingestion. However, animals may respond adaptively to perceived competitor and/or predator proximity by modifying their foraging rates. Increased foraging activity is expected to improve the chances of succeeding in competition. However, the benefits of increased foraging activity could be offset by the risks of increased conspicuousness to predators. Plus, starvation may have counteracting or additive effects on foraging behaviour. Here, we test these hypotheses in larval Iberian ribbed newts (Pleurodeles waltl). We estimated foraging rates of individuals haphazardly assigned to either a restricted or an unrestricted-feeding regime, in water with (1) self-odour as control, (2) predator Dytiscus sp. chemical cues, and (3) competitor conspecific larva chemical cues. Treatments were presented in a random sequence. Newt larvae responded to either predator or conspecific chemical cues by increasing foraging rates relative to the control. Conspecific chemical cues increased foraging rates over the other two treatments. Feeding regime did not modify larva response to perceived predator and competitor proximity. Increased foraging rates in the presence of conspecific chemical cues could simultaneously improve larval energetic status to face competition and reduce prey available for the competitor. Intermediate foraging rates in the presence of predator chemical cues suggest a trade-off between the benefits (likely improved energetic status or accelerated metamorphosis) and the costs (likely increased conspicuousness) of increased food ingestion. These results prove that larval newts adjust foraging rates to perceived predator and competitor proximity.

Conspecific chemical cues drive density-dependent metabolic suppression independently of resource intake.

Within species, individuals of the same size can vary substantially in their metabolic rate. One source of variation in metabolism is conspecific density - individuals in denser populations may have lower metabolism than those in sparser populations. However, the mechanisms through which conspecifics drive metabolic suppression remain unclear. Although food competition is a potential driver, other density-mediated factors could act independently or in combination to drive metabolic suppression, but these drivers have rarely been investigated. We used sessile marine invertebrates to test how food availability interacts with oxygen availability, water flow and chemical cues to affect metabolism. We show that conspecific chemical cues induce metabolic suppression independently of food and this metabolic reduction is associated with the downregulation of physiological processes rather than feeding activity. Conspecific cues should be considered when predicting metabolic variation and competitive outcomes as they are an important, but underexplored, source of variation in metabolic traits.

Response to conspecific alarm cues by larval and juvenile spotted salamanders (Ambystoma maculatum)

For many species, the highest predation rates are on the earliest life stages, favoring the early development of predator detection mechanisms. Aquatic larvae of Spotted salamanders, Ambystoma maculatum, suffer very high mortality rates and juveniles are vulnerable to a new suite of terrestrial predators after metamorphosis. In some species, adult salamanders assess predation risk via chemical cues released by damaged conspecifics and some heterospecifics (“alarm cues”), but responses of larvae and metamorphs have not been tested. Our first experiment confirmed that field-caught, experienced larvae responded with fright to chemical cues of damaged conspecifics, but not to control cues or alarm cues from toad tadpoles. Responses of sedentary hatchlings in the next experiment indicated that the alarm cue was not present in damaged tissues of hatchlings (1-day-old), but was present by the time the larvae reached the age of 1 month. The third experiment tested responses of naïve lab-reared, free-swimming larvae to alarm cue. In contrast to the other two experiments, these larvae without experience did not distinguish between conspecific alarm cues and control stimuli, suggesting that either embryonic learning or reinforcement learning as larvae may be required to develop or maintain the alarm response. In the fourth experiment, post-metamorphic juveniles raised from field-experienced larvae significantly avoided alarm cues from conspecifics but not control stimuli, indicating that the production and recognition of alarm cues can be retained after metamorphosis. Our study provides the first evidence of chemical alarm cues produced by both larval and juvenile salamanders and indicates that alarm responses may vary according to experience.

Conspecific cues that induce spore settlement in the biofouling and green tide-forming alga Ulva tepida provide a potential aggregation mechanism

Ulva, an important biofouling and green tide-forming alga, forms aggregations that have adverse economic and ecological impacts. However, little is known regarding the aggregation mechanism of Ulva. Knowledge of Ulva aggregation provides clues for controlling this alga in marine biofouling and green tides. We hypothesized Ulva contains conspecific settlement cue(s). Hexane and dichloromethane extracts of U. tepida fronds were found to induce the settlement of conspecific spores. From these extracts, two bioactive compounds that induce spore settlement in U. tepida were isolated: C16:4 at 5 μg mL−1 and di-n-butyl phthalate at 0.1–10 μg mL−1. Fatty acids with different carbon chains (C16–C18) and degrees of saturation, C16:1 and C18:2, previously reported to be present in U. tepida fronds, showed significant inducing activity for spore settlement. C16:1, C16:4, C18:2, and di-n-butyl phthalate all triggered dense settlements of U. tepida spores. The results support our hypothesis and provide insight into possible aggregation mechanisms for Ulva.