ABSTRACT Colour polymorphisms may result from frequency dependent selection, different lighting environments, genetic drift or heterozygote advantage, or may simply be under relaxed selection. Nocturnal coconut crabs have a sex and age independent red/blue colour polymorphism, live in the same habitat and have few predators. To determine whether coloration is involved in intraspecific communication, I performed field choice experiments using photographs of crabs of different colour and size to test whether crabs use these cues in decision making. Neither the colour nor size of crabs in photographs influenced coconut crabs' behaviour, but separate observations of live crabs showed that disputes over food were settled on the basis of the relative size of live conspecifics, not their coloration. This study adds to a small body of literature suggesting that the coloration of certain crustacea is under relaxed predator and conspecific selection and may have little adaptive significance.

Correction to "Video evidence of mountings by female

ABSTRACT Facilitative interactions between invertebrates and vertebrates are rarely documented, especially those involving trophic mechanisms. Here, we report a novel case of facilitation between the stingless bee Trigona spinipes and the nectarivorous bat Glossophaga soricina , observed in an urban coastal area in southeastern Brazil. Bees were seen wounding pedicels of Senna macranthera trees during the day, inducing sap exudation. At night, bats visited these sap sources, licking the exudate without creating wounds themselves. This observation represents a rare case of indirect trophic facilitation involving distantly related taxa and expands our understanding of cross‐taxon interactions in urban ecological contexts.

Animal cognition is concerned with the mental capacities of non-human animals. For many years cognition research has continued to be a thriving field of animal behaviour. The interest in this topic seems unabated, as the recent Behaviour conference—held in Kolkata in August 2025—has shown, with a total of six symposia on animal cognition. At times, I could get the impression of attending a cognition conference rather than a general one on animal behaviour. Unsurprisingly, most of the current studies demonstrate that cognition and intelligence comprise a spectrum rather than a sharp divide between humans and other animals. Even invertebrates such as insects with relatively small brains show surprising mental capabilities, thereby challenging the myth of human exceptionalism. A few years ago, I asked Redouan Bshary, who studies cognition mostly in fish, what he considers special about humans. His slightly disappointing answer was that humans may be the only species that uses contraceptives to prevent reproduction. I expected a more sophisticated response from someone working in the field, but—admittedly—the use of contraceptives certainly requires advanced cognitive abilities. But is contraception really exceptional for humans? Many social insects and even mammals are capable of suppressing the reproduction of other group members, female birds can eject unwanted sperm, rodents can abort embryos, etc. Again, there seems to be some sort of continuum with regard to human exceptionalism, and I would not be surprised to learn if some animals may have discovered medical plants that prevent reproduction. So, what else could make us humans special and distinguish us from other species on Earth? Maybe we are the first species to cause a mass extinction of species on Earth? This may not be a very flattering distinction, but it could set us really apart from all other creatures. So far, there have been five big mass extinctions caused by rapid and dramatic changes in climate. Three of these mass extinctions likely occurred due to tectonic and volcanic activities of our planet—so we can blame Gaia. The most famous mass extinction, the one that killed off most of the dinosaurs, was likely caused by the impact of an asteroid—so we can blame the Universe. However, one mass extinction in the late Devonian about 360 million years ago seems to have been caused by organisms. The rapid growth and diversification of land plants may have led to a rapid cooling of the climate, thereby causing the extinction of a large proportion of species on Earth (Barnosky et al. 2011). And even earlier, about 2.7 billion years ago, the first oxygenic photosynthesizers produced a toxic poison that probably killed off most of the species that relied on an oxygen-free Archaean world (Lenton and Watson 2011). There goes human exceptionalism—once again. But—and here cognition comes into play again—for sure we are the first organism with a brain and the cognitive abilities that may cause a mass extinction knowingly with eyes wide open. And this extinction could possibly include ourselves—very unlike the oxygenic photosynthesizers which were smart enough to dominate the planet ever since they came into existence billions of years ago. So, in terms of cognitive abilities perhaps we are both the smartest and the dumbest creature planet Earth has ever seen! I could end here, but maybe science offers some hope. In his autobiography, Max Planck—one of the most famous physicists—formulated the Planck principle, stating “An important scientific innovation rarely makes its way by gradually winning over and converting its opponents: it rarely happens that Saul becomes Paul. What does happen is that its opponents gradually die out, and that the growing generation is familiarized with the ideas from the beginning: another instance of the fact that the future lies with the youth” (Planck 1949). Planck's principle seems to hold for science (Azoulay et al. 2019), and if it can be applied to world politics there may be some hope. Most of the world leaders responsible for the detrimental path of the planet in terms of preventing or solving the climate crisis and biodiversity loss are beyond their 70s. And some of their super-rich supporters plan to escape to Mars. Let's hope they do so, soon! So perhaps there is a chance that the smartest and the dumbest of all creatures on Earth may use some of its (younger) brains to work for the better. Imagine, all the billions of Dollars, Euros, Roubles, and Renminbis that are currently spent on producing arms and weapons could be spent on solving the climate and biodiversity crisis, instead. All of humanity's major problems would be solved in no time—what a no-brainer! The author declares no conflicts of interest. The author has nothing to report.

ABSTRACT Animal responses to risky situations are shaped by both environmental (external) cues and internal states such as body condition. Recent meta‐analyses indicate that individuals in better condition take fewer risks, consistent with the idea that they protect their assets. However, these results rely mostly on short‐term, standard laboratory assessments of threat response. Consequently, it remains unclear whether variation in condition influences risk‐taking consistently across different ecological contexts. Here, we address this by testing whether house mice from high‐ or standard‐quality food environments, and mice of different weight (used as a proxy for condition), vary in their risk‐taking behaviour across two scenarios. First, we quantified foraging behaviour in low‐ and high‐risk areas in the absence of predation cues. We then introduced predator stimuli to assess how foraging changed under increased perceived threat. Overall, we aimed to determine whether the effect of risk on foraging depended on diet quality and body mass. Mice originating from the high‐quality food environment reduced foraging in the high‐risk area under predation cues significantly more than those from standard‐quality environments. In contrast, heavier individuals, irrespective of food quality, foraged less and for shorter periods in the high‐risk area. Last, when predation cues were introduced, these heavier mice increased their foraging effort in the high‐risk area but did not spend more time there. These findings indicate condition‐dependent responses to risk and support core predictions of the asset‐protection hypothesis. Importantly, they highlight that different traits related to individual state or condition may shape different responses to ecological unpredictability, such as predation risk. This variation as a function of different variables related to state warrants further investigation.

ABSTRACT Male courtship signals are generally a product of strong selection on their capacity to attract mates and convey signaller quality to achieve mating success. Given the costly nature of courtship signals, their expression may also be influenced by the quality of the courted female. However, such effects are rarely considered. I tested how male and female nutritional conditions affect male drumming intensity, female abdomen lifting behaviour and mating success in the jumping spider Saitis barbipes , known for its elaborate drumming displays. As expected from a condition‐dependent signal, well‐fed males drummed more intensely than hungry males and thereby increased their mating success. Yet, contrary to expectations, males often reduced drumming towards well‐fed females. Well‐fed females were observed to frequently lift their abdomens, which strongly reduced male drumming and mating success. Curiously, males that achieved mating despite female abdomen lifting did so with lower drumming intensity than in nonabdomen lifting trials. These results illustrate that condition‐dependent behaviours in both sexes can interact in unexpected ways, shaping male investment and influencing courtship outcomes.

ABSTRACTTrophically transmitted parasites play a significant role in shaping food webs, especially in aquatic environments, due to their complex life cycles and transmission through predation. Helminths that use this transmission route, such as trematodes and cestodes, can manipulate host behaviour to increase the likelihood of predation by their next host. Recent research suggests that parasites may not only influence single behavioural traits but also multiple traits simultaneously, affecting both the expression and consistency of behaviours that potentially facilitate parasite transmission. To further test this hypothesis, our study examines the impact of the recently discovered brain‐encysting trematode Cardiocephaloides ovicorpus on the behaviour and repeatability of personality traits in the mottled triplefin (Forsterygion capito) in Otago Harbour, New Zealand. Naturally infected fish were tested for seven behavioural traits, including exploration, observation, predator avoidance, boldness, surfacing, activity (tank crossing), and aggressiveness, across two trial days. Of the behavioural traits investigated, surfacing was the only one that showed a significant positive correlation with C. ovicorpus infection. Furthermore, our statistical model suggested a decrease in repeatability for this trait as a function of C. ovicorpus infection. It is possible that C. ovicorpus specifically targets the brain region responsible for controlling surfacing, as the increase in surfacing may expose fish to a higher risk of detection by avian predators, the parasite's definitive hosts. Additionally, a decrease in behavioural repeatability may increase the likelihood of mismatches between behavioural responses and stimuli, such as predator cues, further elevating predation risk. Future research could aim to uncover the complete life cycle of C. ovicorpus by identifying the unknown first intermediate host, enabling experimental infections of fish to determine the causal relationship between behavioural variation and parasite infection.

ABSTRACTBehavioral flexibility, the ability to adjust behavior in response to environmental changes, is crucial in extreme and novel urban environments. This study assessed behavioral flexibility in both immature (n = 11) and adult (n = 12) urban Kelp Gulls (Larus dominicanus). This is a generalist seabird highly associated with anthropogenic food resources, making it a valuable model to explore behavioral features that could promote this habit. We examined the relationship between a reversal learning task, which assessed the speed of acquisition and subsequent reversal of a stimulus–reward association, and a detour‐reaching task, which tested inhibitory control by assessing the ability to suppress ineffective behaviors. The results showed no significant effect of age on either task. All individuals were able to control impulsive behaviors and reverse a previously acquired response. The reversal phase was more challenging than the acquisition phase, with individuals making more errors, especially regressive ones (i.e., inability to learn and maintain a new stimulus–reward association). Although the difference was not statistically significant, two clear patterns emerged: slower individuals during the acquisition made fewer errors and adapted more quickly during the reversal task and those who made more errors in the cylinder task also tended to make more errors in the reversal learning task. Our findings suggest that individuals learned a new color‐reward association easier than they inhibited a previously learned response. This underscores the importance of inhibitory responses during the reversal phase. In conclusion, urban gulls exhibit notable cognitive abilities in adapting their behaviors and decision‐making based on environmental cues, which could be crucial when exploiting diverse and dynamic food sources. Furthermore, behavioral flexibility was found to be independent of the age of the gulls. This may be because neophobia is low at all ages in this species; its effect is not strong enough to lead to a difference between adult and juvenile gulls.

ABSTRACTComparative studies provide crucial insights on human behaviour and our evolutionary past, ranging from the roots of human culture and cognition to understanding the mechanisms behind specific phenomena such as addiction. Chimpanzees (Pan troglodytes) are the primary model species for comparative cognition research. In particular, captive chimpanzees are important comparative models due to the more controlled settings provided by captivity and the generally easier access than wild populations. This reliance on captive chimpanzees has resulted in the rise of specific research‐intensive facilities that house chimpanzees which, in some cases, are tested regularly throughout their entire lifetimes. These differences in individual research experience history may not only affect performance in tasks, but also overall cognition and motivation to participate in research. The overarching aim of the Ape Research Index (ARI) project is to assess whether research participation over time results in variation in captive chimpanzee cognition and behaviour. To do so, we must first identify whether chimpanzee research participation varies at the group and/or individual level. Accordingly, for this perspectives piece, we carried out a systematic literature review to develop the largest (to our knowledge) database on captive chimpanzee cognitive experiments between 1950 and 2024. Using this (ARI) database, we identified systematic differences in both the extent and type of accumulated research experience in captive chimpanzees within and across facilities. Based on our data, we argue that the current approach in comparative research may be biassing our understanding of ape cognition, and reducing the robustness of insights drawn from these studies. Future work will involve empirically testing these biases in order to validate any behavioural variation potentially emerging from this effect.

ABSTRACTDuetting, a cooperative vocal behaviour performed by mated pairs, is a distinctive vocal behaviour among many species in specifically primates and birds. Yet, the exact features of duets that may make them a stronger territorial signal are still not well understood. One hypothesis is that the precision of duet coordination can indicate the quality of a pair bond or dedication of a pair, and thus the degree of threat posed to a rival pair. To address the implications of duetting precision in a territorial context, we here determined to what extent the antiphonal duetting behaviour in the chirruping wedgebill (Psophodes cristatus), a territorial, socially monogamous passerine, is affected by the precision of fine‐level duet coordination. We tested this with playback experiments where we broadcast coordinated and uncoordinated duets at mated pairs, predicting that pairs would exhibit stronger responses to coordinated duets than to uncoordinated ones and sing more coordinated after the simulated intrusion. We found that neither response intensity nor coordination of either sex differed in responses to playback of coordinated and uncoordinated duets. Since chirruping wedgebills did respond consistently to playback, we suggest that either (1) fine‐level coordination of duetting does not hold a function in joint resource defence in this species, (2) playback stimuli were too threatening for them to adjust their coordination on a level we could detect or (3) they do not discriminate between our coordinated and uncoordinated playback treatments. We highlight the notion that there may be variety in functions of duetting at play within and across avian species, and that different aspects of duets such as coordination and intensity may hold different functions.