Eva Ringler

Reliable individual identification is fundamental to ecological and behavioural studies, yet many marking techniques are invasive and may affect animal behaviour or survival. Biometric identification approaches offer a non-invasive alternative for individual recognition using phenotypic traits. In amphibians, body patterns, especially colouration, have been used to identify individuals, but species lacking permanent body patterns require alternative traits. This study evaluated whether iris patterns could serve as a marker for individual recognition in the treefrog Osteocephalus oophagus . A capture-recapture study was conducted over three breeding seasons (2021–2023) in French Guiana. At each encounter, eye photographs were compared with an image library to identify individuals without handling. Manual identifications were independently verified using Wild-ID software. Across 392 capture events involving 103 individuals, iris patterns were highly distinctive among individuals and enabled repeated identification across encounters. Within-season recapture rates ranged from 56% to 80%, indicating that iris patterns remained sufficiently stable for short-term monitoring. However, only three individuals were re-identified across years, preventing a robust assessment of long-term pattern stability. As these individuals showed no substantial alteration in iris patterns, the low interannual recapture rate was more likely explained by population turnover or emigration than by changes in iris morphology. The findings suggest that iris recognition provides an effective, non-invasive method for short-term individual identification in O. oophagus , reducing the need for repeated handling and supporting ethical wildlife research. Further studies are needed to assess the long-term stability of iris patterns and evaluate the applicability of this method to other amphibian species.

Multimodal communication, in which multiple signal modalities are combined to produce a single compound signal, is employed by many species and can mediate a wide range of fitness-relevant behaviours. While the form and function of multimodal signals have been extensively studied, we know little about how individual traits such as personality and experience influence receivers’ responses to these signals. We investigated how aggressiveness and experience affect the behavioural responses to bimodal signals in the brilliant-thighed poison frog Allobates femoralis . In this species, male advertisement calls constitute a fixed bimodal signal, as the production of sound is coupled with the inflation of the vocal sac, which adds a visual cue. We presented territorial males with a synthetic advertisement call (acoustic cue) and a model frog with a pulsating vocal sac (visual cue), and manipulated signal ambiguity by varying the spatial distance between the two components. We predicted personality and experience would affect how males responded to the bimodal signal depending on its level of ambiguity, and expected younger and/or more aggressive males to respond faster and to attack the visual cue more frequently than older or less aggressive males, especially under high signal ambiguity. Contrary to our predictions, neither aggressiveness nor experience influenced response latency or attack likelihood. Instead, all males displayed a consistent population-level pattern: as the spatial separation between the visual and acoustic signal components increased, they were less likely to attack the model, and their initial and overall interactions shifted from the visual model to the sound source. These findings suggest that the fixed bimodal signals in A. femoralis selected for robust and uniform receiver responses to maintain reliable communication during high-stakes social interactions such as territorial defence. Aggressive receiver responses seem to be dual-staged, consisting of far-field phonotaxis to the acoustic signal component and visual and multimodal signals only becoming relevant during near-field aggression. Future studies should compare how ecological and social factors shape receivers’ responses across species with varying degrees of coupling between the signal components in order to better understand the evolution of multimodal signalling and of the diversity of receiver strategies.

Parental care can have pervasive effects on offspring’s neurodevelopment. Parent-offspring interactions are often modulated by the neuropeptide oxytocin, which is responsible for the development of social bonds. The development of the oxytocinergic system is dependent on the quality of parental care during the post-natal phase. However, it is yet unknown how post-natal direct interactions can influence the development of the oxytocinergic pathway. Here we tested how an obligate parental care behaviour, tadpole transport in poison frogs, influences the development of the oxytocinergic pathway. To this end, we quantified whole brain expression of oxytocin receptor and oxytocin precursor throughout three developmental stages of A. femoralis tadpoles, before, during and after tadpole transport. Our results show an overall downregulation during tadpole transport, which indicates that during transport tadpoles enter a dormant state to slow down development until they are placed in water. Interestingly, the expression of oxytocin precursor did not vary between the three developmental stages. This might indicate that oxytocin is being recruited during transport, but does not lead to neurodevelopmental changes. In sum, here we present the first evidence of a dormant state during tadpole transport which might be an adaptive response to the terrestrial reproduction in poison frogs.

Environmental conditions during early development can considerably shape individual behavior, and laboratory studies suggest that predator presence is an important factor influencing both within- and among-individual behavioral variation. To test this under natural conditions, we studied neotropical poison frog (Allobates femoralis) tadpoles from pools with and without dragonfly larvae (tadpole predators) under naturally varying environmental conditions. We measured 2 behavioral traits, distance moved in a novel environment and time to emerge from a shelter, across 4 repeated trials in predator-exposed (n = 48) and predator-naïve (n = 169) tadpoles. Predator-exposed tadpoles moved less, emerged later in their first trial and were more unpredictable in emergence time than predator-naïve individuals. Moreover, among-individual variation in both behaviors was higher in predator-exposed tadpoles, although behavioral repeatability did not differ significantly between predator-exposed and predator-naïve groups. Predator-naïve individuals exhibited behavioral and predictability syndromes, individuals that moved more also emerged sooner, and individuals more predictable in 1 behavior were more predictable in the other. Despite only being significant in predator-naïve individuals, these correlations did not differ between predator-exposed and predator-naïve groups. A personality–plasticity association occurred only in predator-exposed tadpoles: individuals that initially moved less showed less behavioral change across trials. These findings demonstrate that even in naturally variable environments, predation risk shapes behavioral variation at multiple levels, thereby contributing to the emergence and maintenance of “animal personality”.

Parental care is a well-established mechanism for the vertical transfer of gut microbiota, yet its role in shaping offspring skin microbial communities remains largely unexplored. Using a cross-fostering experiment in a Neotropical poison frog, we demonstrate that paternal tadpole transport is a critical vector for the transmission of skin microbiota. Tadpoles transported by both biological and foster fathers acquired microbial communities that persisted through metamorphosis, maintaining a stable membership despite shifts in relative abundance. Notably, the paternal contribution included multiple bacterial genera known to inhibit the lethal pathogen Batrachochytrium dendrobatidis (Bd). In contrast, tadpoles deprived of paternal transport and manually transferred to water bodies exhibited depauperate communities with a significantly lower prevalence of these protective bacteria. Our findings reveal that parental care is a multifaceted behaviour that not only ensures offspring survival but also actively provisions them with a tailored, protective skin microbiome, highlighting a novel mechanism by which parental care influences offspring fitness and resilience to disease.

Background: Parental care is costly for the caregiver. Therefore, parents should be able to discriminate between their own and conspecific offspring to avoid costly misdirected care. Infanticide, the intentional killing of conspecific young by adult individuals, occurs in many animal taxa. It has been shown to have several benefits for the perpetrator, such as increasing mating opportunities, ensuring dominance, or reducing a competitor’s fitness; but infanticide may also minimise risks of misdirected parental care. Previous studies in Allobates femoralis, a poison frog with parental care, have shown that males transport all tadpoles present in their territory to water bodies, regardless of whether they have sired the clutch or not. However, when taking over a new territory, males cannibalise clutches from the previous territory holder. These findings raise the question as to which factors actually shape parental care and infanticidal behaviour in male A. femoralis after territory takeover. To answer this question, we designed a laboratory experiment, in which we tested males with different territorial status and recent mating activity. We recorded tadpole transport and cannibalism and compared the occurrence of these two behaviours across our different experimental conditions. Results: We found that territory ownership, relatedness to clutches, and possibly also recent mating activity influenced parental behaviours. However, we were unable to clearly disentangle the factors influencing cannibalistic behaviours. Our results also confirmed that males use territorial recognition to discriminate between their own and unrelated offspring, and that they commit infanticide likely to avoid misdirected parental care. Conclusions: Transport and cannibalism appear to be impacted by several factors in different ways. We found that the territorial status and relatedness to the clutch both influence parental behaviours in male poison frogs, whereas the factors influencing infanticidal behaviours remain unclear. Therefore, transport and cannibalism appear to be two independent processes, and factors influencing one behaviour do not necessarily affect the other. Further studies should investigate associated neuroendocrine changes, to better understand the mechanisms underlying parental and infanticidal behaviour in poison frogs. Our findings suggest that the decision-making processes involved in tadpole transport and clutch cannibalism appear to be more complex than previously thought.

Site fidelity and movement decisions in territorial species are often shaped by reproductive success and social context. These factors likely influence the motivation of an individual to return to a site where they have had previous mating success. We tested if reproductive behavior shapes movement decisions in the glassfrog Hyalinobatrachium valerioi, a species where males exhibit parental care by guarding clutches at oviposition sites until just before hatching. We hypothesized that recent mating success (i.e. presence of a clutch) would impact homing behavior. We expected males with clutches present at their site to home more reliably and faster, as they are likely more motivated to return to or remain at sites where they recently had mating success and/or should resume caring duties. Males with clutches homed more often, while males without clutches often remained in novel environments, supporting the reproductive performance hypothesis. Homing duration was affected by translocation distance and the presence of other males at release sites, with quicker returns observed under socially competitive conditions. These findings suggest that reproductive investments and social settings can shape movement decisions in H. valerioi, shedding light on the behavioral mechanisms underlying homing behavior in amphibians.

The drivers of differences in cognitive ability, within as well as across species, remain a debated “hot‐topic” in animal cognition. Current hypotheses link variation in sociality, ecology, and more generally, environmental challenges to differences in cognition. Research supporting the social intelligence hypothesis, which states that cognition evolved to deal with the challenges of interacting with conspecifics, is largely focused on highly social mammal and bird species, limiting our ability to evaluate the general applicability of the hypothesis. Furthermore, it is unclear whether the social environment facilitates cognitive development or if selection acts against individuals with low cognitive abilities in social groups. Unfortunately, developmental studies which can reveal the causal link between early life experiences and cognitive development are scarce. Therefore, we aimed to test the effect of the early post‐natal social environment on the development of behavior and cognition in a social lizard, the tokay gecko ( Gekko gecko ). Our results show that the early social environment influenced the development of boldness and the variation in space neophobia and associative learning. We discuss our findings in the light of the social intelligence hypothesis, taking into account the facultative social nature of our study system.

The identification of genetic mating systems in a variety of species has challenged the previous view on animal mating patterns over the past decade, resulting in the identification of multiple paternity across all vertebrate classes. In crocodylians, all species that have been investigated demonstrate multiple paternity, which may represent the ancestral state of the clade. The smooth‐fronted caiman, Paleosuchus trigonatus, is one of the last species whose genetic mating system has yet to be investigated. In this study, we analyzed genetic samples of the smooth‐fronted caiman in French Guiana, a secretive species that is difficult to observe in the wild. Scute samples were taken from three populations and five groups of neonates that hatched shortly before. Microsatellite markers were used to infer the minimum number of fathers that sired each clutch. Our results clearly show that multiple paternity was common, with 60% of the sampled group of neonates showing a minimum of two sires. The potential ecological and behavioral implications of this finding are discussed, as well as recommendations for future research avenues to elucidate this cryptic species' mating behavior and environmental constraints.

The choice of where to breed can have fundamental consequences for offspring development and survival. Among amphibians, desiccation is one of the biggest threats to offspring survival, especially in species that deposit their clutches in terrestrial habitats. In several species, hydration of the clutch is ensured by a caregiving parent, but in species without prolonged care, site selection becomes critically important for securing constant external sources of hydration. We used the Spiny Cochran frog (Teratohyla spinosa), a Neotropical glassfrog in which females perform only short-term brooding to clutches, but then both parents leave the offspring, to test the effect of oviposition site selection within leaves on offspring development and survival. Previous observations have revealed that this species preferentially deposits eggs on the underside of leaves close to their margins. We hypothesized that T. spinosa strategically chooses this position to ensure clutch hydration during embryonic development, as water drops will slide from the edges to the tip of the leaves before dripping. To this end, we performed a clutch translocation experiment where we manipulated the location of clutches by placing them away from the leaf margin and compared their level of hydration, hatching time, and mortality rate to clutches that were kept on the leaf margins. Contrary to our expectations, we found that clutch hydration and mortality were not affected by the location on the leaf. These findings suggest that the observed clutch deposition on the edges of leaves in this species is not enhancing hydration conditions – at least under high humidity conditions.