Ethology

Behavior is often linked to gonadal sex; however, ecological or social environments can induce plasticity in sex-biased behaviors. In biparental species, pairs may divide offspring care into two parental roles, in which one parent specializes in territory defense and the other in nest care. The African cichlid fish Julidochromis marlieri displays plasticity in sex-biased behaviors. In Lake Tanganyika, J. marlieri form female-larger pairs in which the female is more aggressive than the male who performs more nest care, but under laboratory conditions, male-larger pairs can be formed in which these sex-biased behaviors are reversed. We investigated the influence of social environment on behavior by observing how individuals in both pair-types respond to conspecific intruders of either sex. We examined behavioral responses to three factors: sex of the subject, relative size of the subject, and the sex of the intruder. We confirm that relative size is a factor in behavior. The larger fish in the pair is more aggressive than the smaller fish is towards an intruder. While neither fish in the female-larger pairs varied their behaviors in response to the sex of the intruder, both members of the male-larger pairs were sensitive to intruder sex. Both individuals in the male-larger pairs engaged in more biting behaviors towards the intruder. Intruder biting behaviors strongly correlated with the biting behavior of the larger individual in the pair and occurred more frequently when encountering pairs with same sex as the larger fish when compared to pairs with the same sex as the smaller fish. Our results support the role of the social environment as a contributor in the expression of sex-biased behavior.

Sexually dimorphic behaviors are common across taxa, particularly in the contexts of parental care and territorial aggression. The false clown anemonefish Amphiprion ocellaris is unique among animals for its combination of female behavioral dominance and territoriality, protandrous sex change, and mutualistic symbiosis with sea anemones. Several laboratory studies have begun characterizing sex differences in parental care and aggression in this species, but aggression assays have mostly focused on intra-specific aggression where individual differences are large. The goals of this study were to expand the repertoire of behavioral assays available for A. ocellaris, establish repeatability of individual differences, identify assays that produce the most robust sex differences, and explore whether individual differences in correlated behaviors can be detected consistently across experimental contexts (i.e., whether behavioral syndromes can be detected). To this end, we measured 39 behaviors across 7 behavioral assays (parental care, large intruder aggression, small intruder aggression, male-oriented aggression, female-oriented aggression, immediate reaction to a threat, and nest maintenance) in 9 reproductively active A. ocellaris pairs under 3 different contexts (without eggs in the nest, with their own eggs, and with surrogate eggs). Behaviors were repeatedly measured three separate times (rounds) over repeated spawning cycles. We found 34 out of 39 behaviors were significantly individually repeatable across egg contexts and rounds, with an average intra-class correlation of 0.33. We found parental care, large intruder aggression, and female-oriented aggression assays produced the largest sex differences. Males performed 7-fold more egg care behaviors than females, while females performed 3.5-fold more aggressive behaviors toward a large interspecific intruder. Further, females bit, chased and struck the female intruder 6.5, 4.1, and 3.2 times as many times as males did. Five different behavioral syndromes were observed in males but only one was observed in females. These results expand our understanding of sex differences in behavior and the division of labor in the iconic anemonefish. Future studies can use these assays to measure the behavioral sex of fish in the middle of sex change, in the study of behavioral plasticity, or in the study of the neuroendocrine bases of aggression and parental care in this unique species.

Plasticity is a major feature of behavior and particularly important for how animals respond to predators. While animals frequently show plastic responses when directly exposed to predators, with these exposures even leading to permanent behavioral changes and transgenerational effects, whether indirect cues of predator presence can elicit similarly severe responses is unclear. We exposed banded crickets (Gryllodes siglattus) to cues of predator presence throughout development and compared their behavior--as well as the behavior of their offspring--to individuals who had not been reared in the presence of predator cues. Contrary to findings in both G. sigilattus and related species, we did not detect either developmental plasticity in the form of differences between adult behavior or differences in offspring behavior. These findings suggest that chronic exposure to cues of predator presence have a substantially different affect on behaviors than does direct exposure to predators. How habituation might interact with developmental plasticity and transgenerational effects requires further investigation. Significance StatementPrevious research has established that exposure to predators elicits behavioral plasticity, including life-long effects, as well as transgenerational effects. Here we show that chronic exposure to cues of predator presence throughout development, with a resulting potential for habituation, results in neither differences in adult behavior or transgenerational effects. This suggests an important role for habituation in how plasticity manifests within and between generations

Mudskippers engage in frequent territorial interactions. Few studies of mudskipper agonistic behavioral sequences exist. The slender mudskipper (Periophthalmus gracilis) inhabits intertidal zones of mangrove forests across Southeast Asia. Here, we describe common behavioral sequences of winners and losers among unmanipulated, wild slender mudskipper interactions in Singapore. Winning mudskippers showed more approach behaviors than losers, such as "Crawl towards", and more behaviors that may indicate aggression, such as "Pectoral wave", "Flag", and "Head up". Losers showed more evasive behaviors, like "Jump" and "Crawl away". We found evidence of agonistic behavioral matching. Larger mudskippers won contests more frequently than smaller mudskippers.

An animals ability to adapt to a changing environment often requires the coordination of various traits. Across these traits, many covary with one another to generate a diversity of complex phenomes tuned to a given ecology. While many reports have documented trait covariation in populations, less is known about how plastic traits co-vary to facilitate adaptation in an individual. In African cichlids, morphology and behavior are two hallmarks driving the adaptive speciation of lineages within the East African Great Lakes. Here, we leverage social rank and body coloration as plastic model traits to understand the intersectional relationship shaping male competition in the African cichlid Astatotilapia burtoni. Addressing the need to disentangle the influence of environmental adaptation from social dynamics on color morphology, we conducted experiments rearing cichlids in visually distinct environments using blue and yellow gravel substrates to induce blue/yellow color morphs. Our results demonstrate that the visual environment significantly influences the emergence of male color morphs: yellow territorial males were more prevalent on brown gravel, whereas blue males predominantly appeared in blue backgrounds. Contrary to previous reports, we found that blue males consistently outcompete yellow males in direct contests. Furthermore, behavioral patterns changed over time, with blue males adjusting their aggression strategies based on their visual environment, while yellow males exhibited a higher propensity to flee. These findings indicate that animal coloration and behavior are intersectional plastic traits that interact to shape male competition and behavioral ecology. This study provides new insights into the dynamics of phenotypic plasticity, adaptive strategies in fluctuating environments, and trait covariation.

Conflict is one of the most critical factors affecting the behavior of animals related to their reproduction and survival, with aggressive interactions being central to acquiring resources or mating partners. This phenomenon is more common among males than females, impacting reproduction strategy and beginning of biparental care. Investigating such interactions in species closely related to social species can be illuminating, offering valuable insights into the factors that influence the emergence and maintenance of more complex social behaviors. In this context, we present a field study of male-male agonistic behavior in the wood-feeding cockroach, Panesthia angustipennis. Panesthia is the closest genus to the subsocial genus Salganea, which is known for its biparental care. Our field observations reveal a characteristic behavior where one male pushes a rival away from a female. The victorious male repeatedly returns to a specific site near the female, suggesting a strategy to minimize unnecessary conflict or protect the female. This behavior provides insights into the potential evolutionary strategies that may have evolved in the common ancestor shared by Salganea and Panesthia. Notably, the displaced males persistently reengage, highlighting the high resource value attributed to females and the consequential intensity of male competition. This study not only sheds light on the aggressive and pacifist tendencies in P. angustipennis but also contributes to understanding the evolutionary development of social structures in Salganea. Further experimental investigations into the aggressive behaviors of P. angustipennis will enhance our comprehension of the factors shaping the evolution of sociality in these species.

Intraspecific variation in ecologically relevant traits is critical for animal populations to survive in our rapidly changing world. This is especially true for species that suffer from intense harvesting regimes, whereby populations density is often low. Standard hatchery procedures can assist some management and conservation programs by producing large numbers of juveniles to be released into the wild. Yet we know surprisingly little on the impact that such standard, minimalistic settings have on the development of intraspecific variation in important phenotypes of the individuals, including among-individual variation in behavioural (individuality) and life-history traits, and in the plasticity of those traits in response to varying environmental conditions. Here, we fill this gap by testing whether early-life exposure to different environmental conditions alters the development of individuality and plasticity in ecologically relevant behaviours and life-history traits of the European lobster (Homarus gammarus)--one the most harvested species in the Mediterranean, which has been subjected to conservation programs for decades. By accessing one of the largest lobsters hatcheries in Italy, we used the progeny of wild-caught females and manipulated--in a full factorial design--the environmental complexity of the individual enclosures (i.e. presence/absence of substrate and/or shelter) and the level of exposure to cues from their natural predators. We repeatedly quantified behaviours (i.e. activity, refuge use, and aggressiveness) and life-history traits (i.e. carapace length and intermoult period) of the individuals throughout their early development, capturing both mean and individual-level variation across treatments. Our results offer solid evidence that effects of standard hatchery settings extend far beyond mean changes in the behaviour and life history of the animals, compromising the development of individual plasticity in those traits that are essentials for populations to survive in the wild--likely reducing the effectiveness of conservation programs.

Animals are typically expected to avoid mating with relatives due to the costs associated with incestuous matings. Yet for more than four decades, theoretical models have consistently suggested that animals should tolerate, or even prefer, mating with relatives under a broad range of conditions. However, empirical studies that evaluate inbreeding avoidance under alternative social and sexual contexts remain scarce. Here, we investigate how experimental variation in sexual and social complexity influence precopulatory inbreeding avoidance behaviors in the guppy Poecilia reticulata, a species known to experience inbreeding depression. In an integrated set of experiments, we examined if sexual and affiliative behaviors of virgin and experienced females and males were differentially directed towards either related or unrelated individuals. In simplistic social interactions, neither virgin nor experienced females or males showed a preference for related or unrelated partners. In contrast, we detected sex-specific responses to relatives in the more sexually and socially complex free-swimming arenas. Females exhibited a stronger preference towards related males regardless of mating experience, while male preference remained unchanged. Overall, these findings challenge previous reports of preference shifts between virgin and experienced female guppies and suggest that inbreeding avoidance behaviors may be less prevalent in complex social environments than previously thought.

Animal personality is characterized by consistent behavior within individuals linked to consistently variable behavior among individuals in a population across time and contexts. Genetic determination, transgenerational effects, and personal experience are major pathways shaping animal personalities. Among these pathways, little attention has been paid to environmental factors in the parental generation affecting offspring personality. Here we tested the effects of the maternal diet on offspring personality in the plant-inhabiting predatory mite Amblyseius swirskii. Mated females and males, whose mothers were fed during egg production on either cattail pollen, two-spotted spider mites, or thrips, were subjected to a battery of three to five tests each for exploration, activity, and boldness. Movement activity was assessed in the mites familiar environment. Exploration was quantified by the latency to leave and reach novel sites or objects. Boldness was evaluated by residence in risky and benign sites. Mean behaviors were analyzed by generalized estimating equations, repeatability was assessed by intraclass correlation coefficients. On average, offspring from spider mite-fed mothers were the most active and those from pollen-fed mothers were the shiest. Offspring from thrips-fed mothers were more repeatable in activity than offspring from pollen-and spider mite-fed mothers. Consistently little and highly active personalities produced more eggs than inconsistent, flexible types. Only offspring from pollen-fed mothers were repeatable in boldness. Maternal diet did not influence offspring personality in exploration. Taken together, our study suggests that the maternal diet critically influences both mean behavioral trait expression and behavioral repeatability of offspring. The ability of mothers to respond to short-term diet changes during internal egg production allows to adaptively adjust the behavior and personalities of daughters and sons within local and regional groups.

Mate choice has the potential to drive phenotypic evolution because it can determine traits that increase an individuals likelihood to reproduce (courtship behaviors, elaborate ornamentation). These traits, however, can also be detrimental for health or survival, often antagonizing the evolution of extreme phenotypes. Mangrove rivulus fish (Kryptolebias marmoratus) develop as self-fertilizing simultaneous hermaphrodites. Hermaphrodites overwhelmingly self-fertilize their eggs internally, but occasionally oviposit unfertilized eggs. Some individuals change sex to male after sexual maturity, essentially forgoing the reproductive assurance of selfing. In a continuing effort to understand how sex change to male is maintained this species, I designed an experiment to determine whether males act as choosers to increase their likelihood of finding unfertilized eggs for reproduction. I hypothesized that males would prefer to associate with younger hermaphrodites when given a dichotomous choice, as they lay a greater proportion of unfertilized eggs compared to older hermaphrodites. The males in this study did not show a preference for either the younger or older hermaphrodite but exhibited greater within individual variance across subtrials than among individual variation. I discuss alternative hypotheses concerning male mate choice in mangrove rivulus, which may illuminate hypotheses to be tested in this and other hermaphroditic species.

Early-life social experiences shape adult phenotype, yet the underlying behavioural mechanisms remain poorly understood. We manipulated early-life social experience in the highly social African cichlid fish Astatotilapia burtoni to investigate the effects on behaviour and neuroendocrine stress axis function. Juveniles experienced different numbers of early-life social partners in stable pairs (1 partner), stable groups (6 fish; 5 partners), and socialized pairs (a novel fish was exchanged every 5 days; 5 partners). Treatments differed in group size (groups vs. pairs) and stability (stable vs. socialized). We then measured behaviour in multiple contexts and collected water-borne cortisol. We found effects of treatment on behaviour across all assays: open field exploration, social cue investigation, dominant behaviour, and subordinate behaviour. Cortisol did not differ across treatments. Principal components (PC) analysis revealed robust co- variation of behaviour across contexts, including with cortisol, to form behavioural syndromes sensitive to early-life social experience. PC1 (25.1%) differed by numbers of social partners: juveniles with more social partners were more active during the social cue investigation, spent less time in the territory, and were more interactive as dominants. Differences in PC5 (8.5%) were based on stability: socialized pairs were more dominant, spent less time in and around the territory, were more socially investigative, and had lower cortisol than stable groups or pairs. Behaviour observations in the home tanks provided further insights into the behavioural mechanisms underlying these effects. These results contribute to our understanding of how early- life social experiences are accrued and exert strong, lasting effects on adult phenotype.

Mating strategies in species is context-dependent and driven by several ecological and demographic factors. In natural habitats, a multitude of ecological factors interact and these eventually determine mating preferences and mate choice decisions among species. While zebrafish (Danio rerio) is a widely studied biological model organism, our understanding of their mating preferences, strategies and their underlying ecological drivers are still limited. Here, we explore the role of ecological factors such as spatial variation (or patchiness) in mate density and associated vegetation cover in determining mate association tactics among males in a wild zebrafish population. We employed a multi-choice experimental design for a better representation of ecologically relevant scenarios. Our results revealed that when presented with patches with increasing female densities, males displayed only a marginal increase in preference for higher female density patches. However, when female density varied concomitantly with variation in vegetation cover, the males associated more with higher foliage density patches irrespective of the female density in that patch. Our findings throw light on the complex interaction between these two most basic ecological factors in determining mate search strategies and mate associations among these group-living fish species.

Phenotypic plasticity allows organisms to adapt to changing environments within their lifetimes. The cost of plastic adaptations may constrain the persistence of plasticity over evolutionary time. One potential cost is the possibility that phenotypic adjustment to specific environments can cause correlated responses that are not necessarily adaptive. Males in the African cichlid Astatotilapia burtoni are blue or yellow, and males are able adjust their body coloration to the color of the background, presumably to increase crypsis. To test whether background color influences fitness-related traits, we raised mix-sex groups of juvenile A. burtoni to adulthood in yellow or blue tanks. We found that fish in blue tanks were darker and more bluish, whereas fish reared in yellow tanks were paler and more yellow in body coloration. Males, but not females, from blue tanks showed earlier sexual maturation than those held in yellow tanks. However, across the duration of the experiment, there was a higher frequency of females mouthbrooding in groups housed in yellow tanks than those that were housed in blue tanks. In addition, fish in blue tanks exhibited reduced growth rate but higher survivorship relative to their yellow-reared counterparts. Our data suggests that background color affects important fitness-related traits in a color polymorphic cichlid, which may influence the evolution of phenotypic plasticity.

Females are traditionally presented as the choosier sex, selecting males based on the quality of their traits. Yet, there is increasing evidence that male mate choice is also important, even in species without male parental care. Social environment and learning are key factors in determining mate preference, and animals are able to use the information they gather from previous experience to potentially increase their odds of obtaining a high-quality mate. We examined how the social environment affects male mate choice in the guppy (Poecilia reticulata). We evaluated whether male guppies with previous social experience of female receptivity cues learn to prefer and adapt their behavioural repertoire towards females with higher receptiveness levels, as this represents an optimal use of time and energy and is more likely to result in insemination. For this, we measured sexual preference and behaviour for receptive females in no-choice and dichotomous choice tests using guppy males experienced or naive to female receptivity cues. Experience with receptivity cues did not change the strength of preference towards receptive females. However, male guppies that had previous experience with female receptivity cues adapted their mating tactic compared to naive males. The change in mating tactics but lack of preference towards receptive females shows that the influence of social learning is present but might be weaker than predicted in this species. Furthermore, these results provide further support to studies of female mate choice suggesting mating status is not a key factor driving the strength of sexual preferences in natural populations.

Variation in color morph behavior is an important factor in the maintenance of color polymorphism. Alternative anti-predator behaviors are often associated with morphological traits such as coloration, possibly because predator-mediated viability selection favors certain combinations of anti-predator behavior and color. The Aegean wall lizard, Podarcis erhardii, is color polymorphic and populations can have up to three monochromatic morphs: orange, yellow, and white. We investigated whether escape behaviors differ among coexisting color morphs, and if morph behaviors are repeatable across different populations with the same predator species. Specifically, we assessed color morph flight initiation distance (FID), distance to the nearest refuge (DNR), and distance to chosen refuge (DR) in two populations of Aegean wall lizards from Naxos island. We also analyzed the type of refugia color morphs selected and their re-emergence behavior following a standardized intrusion event. We found that orange morphs have different escape behaviors from white and yellow morphs, and these differences are consistent in both of the populations we sampled. Orange morphs have shorter FIDs, DNRs, and DRs, select different refuge types, and re-emerge less often after an intruder event compared to white and yellow morphs. Observed differences in color morph escape behaviors support the idea that morphs have evolved alternative behavioral strategies that may play a role in population-level morph maintenance and loss.

Appropriate hatching time is important for successful brood parasitism in some bird and insect groups. Parental burying beetles typically rear their larvae on carcasses buried in nests; however, they occasionally raise brood-parasitic larvae from eggs dumped by other females. Parasitic larvae must hatch synchronously with host larvae because the host parents indiscriminately accept any larvae during that period. However, parasites in burying beetles are assumed to have more severe restrictions on synchronous hatching than those in birds because of less predictability of reproductive sites, the necessity for ovarian development at the site, and difficulty in adjusting by oviposition. Is the hatching of parasitic larvae synchronized with that of host larvae, even if the reproductive behavior of the parasites lags behind that of the host owing to restrictions? In the burying beetle Nicrophorus quadripunctatus Kraatz, we observed the hatching of host and parasite offspring under experimental conditions in which female parasites (intruders) encountered carcasses that had been secured by female hosts (residents) two days earlier. In 14 of the 40 replicates, defeated intruders dumped eggs, residents laid 36 eggs, and intruders laid six eggs on average. The hatching of intruder offspring was synchronized with that of the resident offspring despite the two-day lag. Egg dumping is regarded as brood parasitism. Notably, the period from contact with carcasses to hatching was significantly shorter for intruders than for residents. Advances in hatching time may contribute to the success of brood parasitism.

Although much work has focused on non-social personality traits such as activity, exploration, and neophobia, there is a growing appreciation that social personality traits play an important role in group dynamics, disease transmission, and fitness, and that social personality traits may be linked to non-social personality traits. These relationships are important because behavioral syndromes, defined here as correlated behavioral phenotypes, can constrain evolutionary responses. However, the strength and direction of relationships between social and non-social personality traits remain unclear. In this project, we examine social and non-social personality traits, and the relationships between them, in the paper wasp Polistes fuscatus. With a novel assay we identify five personality traits, two non-social (exploration and activity) and three social (aggression, affiliation, and antennation) personality traits. We also find that social and non-social personality traits are phenotypically linked. We find a positive correlation between aggression and activity (rs = 0.33) and a negative correlation between affiliation and activity (rs = - 0.35). We also find a positive correlation between exploration and activity. Our work is an important step in understanding how phenotypic linkage between social and non-social behaviors may influence behavioral evolution. As a burgeoning model system for the study of genetic and neurobiological mechanisms of social behavior, Polistes fuscatus has potential to add to this work through exploring the causes and consequences of individual behavioral variation.

Many animals have the ability to learn, and some taxa have shown learned mate preference. This learning may be important for speciation in some species. The butterfly Heliconius melpomene is a model system for several areas of research, including hybridization, mate selection, and speciation, partially due to its widespread diversity of wing patterns. It remains unclear whether these butterflies can learn to prefer certain mates and if social experience shapes realized mating preferences. Here we test whether previous experience with a female influences male mate preference for two different H. melpomene subspecies, H. m. malleti and H. m. rosina. We conducted no-choice behavioral assays to determine if latency to court and whether males courted (vs no courtship) differed between naive males and males with previous exposure to a young, sexually mature, virgin female. To test whether assortative courtship preference is learned in H. melpomene, males were either paired with a female who shared their phenotype or one who did not. Naive H. m. malletti males courted assortatively, while naive H.m. rosina males did not. Experienced H. m. malleti males reduced their courting relative to naive males, suggesting that social experience with a sexually mature female that does not result in copulation may be perceived as a negative experience. In contrast, experienced H. m. rosina males exhibited similar courting rates to naive H. m. rosina males. Our results suggest that social experience can influence male mating behavior in H. melpomene and that behavioral plasticity may differ across populations in this species.

Aggression between juveniles can be unexpected, as their primary motivation is to survive until their reproductive stage. However, instances of aggression, which may escalate to cannibalism, can be vital for survival, although the factors (e.g. genetic or environmental) leading to cannibalism vary across taxa. While cannibalism can greatly accelerate individual growth, it may also reduce inclusive fitness when kin are consumed. As a solution to this problem, some cannibals demonstrate kin discrimination and preferentially attack unrelated individuals. Here, we used both experimental and modeling approaches to consider how physical traits (e.g. size in relation to opponent) and genetic relatedness mediate aggressive behavior in dyads of cannibalistic Dendrobates tinctorius tadpoles. We paired sibling, half-sibling, and non-sibling tadpoles of different sizes together in an arena and recorded their aggression and activity. We found that the interaction between size and relatedness predicts aggressive behavior: large non-siblings are significantly more aggressive than large siblings. Unexpectedly, although siblings tended to attack less overall, in size mismatched pairs they attacked faster than in non-sibling treatments. Ultimately, it appears that larval aggression reflects a balance between relatedness and size where individuals trade-off their own fitness with that of their relatives.

Individual behaviour is a combination of previous experiences and genetic factors whose interaction can be adaptively adjusted to respond to changes in the surrounding environment. Understanding the continuity of behaviours both within and among individuals can help us disentangle the ecological and evolutionary significance underlying patterns of aggression, activity, boldness, and cooperation. In this study, we examined whether there is repeatability in the activity levels of juvenile dyeing poison frogs (Dendrobates tinctorius). This tropical species, known for its striking coloration and skin toxins, changes upon metamorphosis from an aquatic to a terrestrial habitat where individuals must immediately become active foragers to acquire their chemical defences. We did not find individual behaviour to be repeatable, however, we detected repeatability in activity at the family level, suggesting that behavioural variation may be explained, at least partially, by genetic factors in addition to a common environment. The assumption that activity level is very important for the survival of individuals after metamorphosis is supported by our results in that genetic factors seem to play a role in the formation of activity level. Further experiments are needed to investigate to what extent other areas of the individuals lives are affected by the respective activity levels, and what significance this has for the survival of a population.