Abstract Accumulating evidence has shown that neonatal oxytocin (OT) exposure (NOE) influences the physiology and behaviour of offspring. The present study aimed to evaluate the impact of NOE on the oestrous cycle, central OT and oestrogen receptor-alpha (ERα) expression, and cocaine-induced behavioural responses of adult female mice offspring. After receiving OT injections from postnatal day (PND) 4 to PND 10, the oestrous cycle and expression of OT- and ERα-immunoreactive (IR) neurons in specific brain regions of adult females during dioestrus were assessed, and acute cocaine-induced locomotion, anxiety levels, and social behaviour were examined. The data indicated that NOE prolonged oestrus, while OT-IR expression in the paraventricular nucleus, ERα-IR expression in the bed nucleus of the stria terminalis, medial preoptic area, arcuate nucleus, and ventromedial hypothalamic nucleus were increased. Moreover, NOE and cocaine had interaction effects on behavioural response. Compared to saline exposure, NOE resulted in greater locomotion and affiliative behaviour, and attenuated cocaine-induced locomotion rather than anxiety levels. These results indicate that NOE might affect oestrus cycles, enhance sociality in adulthood, and inhibit cocaine-induced motivity. Such effects may be associated with NOE-induced developmental changes in OT and ERα expression in relevant brain regions. This finding provides certain insights into mechanisms underlying the effects of NOE on cocaine-induced behavioural changes in female animals.

Abstract Caffeine, a xanthine alkaloid present in many foods and beverages, is widely consumed for its stimulating effects on the nervous system. This study employs Drosophila melanogaster larvae as a model organism to investigate the effects of varying caffeine concentrations on locomotor behaviour. Videos of larvae crawling on agar plates were recorded with an industrial camera, and locomotor parameters, including speed, angular velocity, and time to reach the edge, were quantified using the deep learning tool SLEAP to analyse larval trajectories. The results demonstrated that low caffeine concentrations significantly increased larval locomotor speed, reduced angular velocity, and shortened the time to reach the edge, with the most pronounced effects observed at a concentration of 0.5 g/l. Higher caffeine concentrations had a diminished effect on enhancing locomotor activity. The study suggests that continuous exposure to low concentrations of caffeine during development enhances the locomotor activity of Drosophila larvae.

Abstract To date, leaf consumption in bats has not been considered ‘true folivory’ because bats chew bits of leaves, extract and swallow their juices, and discard their fibre. The term ‘leaf fractionation’ is used to distinguish this behaviour from true folivory, or the consumption of full leaves, such as exhibited by herbivores. For over three decades, it has been posited that the consumption of entire leaves — leaf fibre included — would require a digestive system incompatible with bats’ ability to fly. Natural history observations can amend long-accepted assumptions, however. We observed a common Neotropical frugivorous bat consuming mature leaves in their entirety, without discarding any part. This anecdotal observation begs further investigation, opening the possibility for a shift in our current understanding of bat feeding behaviour. Because the consumption and digestion of whole leaves leave no readily observable trace (i.e., no dropped remains below the roost), this behaviour may be more prevalent than previously appreciated. While feeding exclusively on leaves remains unlikely in bats, our anecdotal observation reveals that true folivory does indeed take place. Our objective in publishing this observation is to invite research on the role of whole leaves in the diets of bats and their physiological implications. Exploring the effect of leaf consumption on potential self-medication is also paramount. Bats, long recognized for their spectacular dietary diversity, may now be known to feed not only on insects, fruit, nectar, pollen, vertebrates, and blood, but also on entire leaves.

Abstract Personality traits have been identified in many animals but species that are hard to observe in the wild present unique challenges. We aimed to determine an appropriate method for identifying docility in a crevice-nesting seabird (razorbill, Alca torda ) by conducting three tests associated with this trait. Two tests used quantitative behavioural coding (crevice extraction, restraint), while the other used qualitative observer ratings (routine handling). Chick-rearing razorbills ( ) in Newfoundland, Canada were tested across two years (2021, 2022), with 16 tested in both years. Observer ratings during routine handling had the highest repeatability ( , 95% CI = 0.007–0.831), compared to quantified scores during extraction ( , 95% CI = 0–0.399) and restraint ( , 95% CI = 0–0.294) tests. Overall, findings suggest that observer ratings may be a good method to quantify personality traits in species that are hard to observe in the wild.

Abstract Although hissing is a common strategy of defence used by snakes, especially of the Phytonidae and Boidae families, few studies have described in detail the acoustics components of this behaviour. Here we gathered eight recordings from six different boas from Brazil and extracted acoustic measurements from their hissing sounds. We also examined the potential of our measurements to encode individual identity using discriminant function analyses (DFAs) and to correlate with body length using linear mixed models (LMMs). Boas produce from four to 12 hisses per minute (7.13 ± 3.04) evoked by a negative stimulus, a visual looming stimulus generated by researcher’s approach. Each hiss usually has two parts (the first louder part and the second softer part) that are basically broadband white noises split by a short silent interval. The first hiss part also has more frequency modulations and narrower bandwidth than the second hiss part. The DFAs correctly assigned all hisses to their correspondent individuals in the testing data. The first discriminant function explained most of the variance (⩾84%) in the discrimination between groups for the entire hiss and for both hiss parts in the training data subset. Frequency parameters and spectral entropy (for entire hiss and hiss part 1) and the mean frequency and duration (for hiss part 2) were the strongest absolute loadings in the DFAs. Intraspecific morphological traits (e.g. sexual dimorphism and ontogenetic variations) may influence the sound parameters, as detected by individual variations and the tendency for larger individuals to produce lower frequency hisses. Further studies may investigate these aspects in detail, including anatomy of the snake’s larynx and experiments with different types of predators.

Abstract Dendrobatid frogs are famous for their amazing body design colours and poisonous skin. The male perspective is the focus of most studies, with males known as caregivers, persistent singers, and assiduous flirts. Little is known about what females do other than reproduce or very rarely be territorial and care for their tadpoles. Two interesting questions that remain to be answered are whether dendrobatid frogs can organize themselves into a complex social system and what males and females do outside of reproductive periods. We studied the multicolour species Adelphobates galactonotus in a delimited natural environment, with 11 females and 6 males with three different body colours. Over 27 months, the individuals interacted and conducted their life histories together since their metamorphosis. Continuous daily samplings revealed that females and males are organized in a female dominance hierarchy based on aggression, with resource defence: the territory. The social repertoire involved touching, visual and sound communication, fights and grouping of individuals associated with dominant females and territorial males. Herein, we describe the social repertoire, and we tested the behavioural trait that most influences successful reproduction: fighting a lot or being a popular individual in groups.

Abstract The passing of Frans de Waal marked a significant loss for the field of animal behaviour and cognition. His groundbreaking scientific work transformed our understanding of animal behaviour and influenced many scholars. De Waal’s popular science books reached millions, shaping public perception of animal minds and inspiring many young scientists. This memorial article reflects on de Waal’s profound impact on a new generation of animal behaviour scholars and the lasting legacy he leaves in the field of animal behaviour and cognition.

Abstract In iteroparous animals, it may be adaptive to adjust the amount of reproductive investment based on their current competitive ability. Male fiddler crabs use an enlarged major claw for claw-waving display in the breeding season. Males sometimes lose their claws, but they can regenerate a claw, which is an inferior weapon for male-male fights. Here, we compared the waving frequency between males with a regenerated claw (regenerated males) and with an original claw (original males) to examine the differences in the amount of reproductive investment. Regenerated males showed lower waving frequency than original males, but some regenerate males waved frequently before the optimal mating season where original males waved frequently. These results indicate that individuals with poor fighting ability that have lower chance of acquiring females invested less in waving, and may also have shifted their peak of mating period in order to avoid competition with original males.

Abstract Recently, various philosophers and ethologists have argued or hypothesised that, in addition to humans, there are also non-human animals that are capable of following rules and implementing normative behaviours. The investigation of animal normativity until now, however, has been almost exclusively focused on mammals and, in particular, non-human primates and cetaceans. In contrast, this work aims to extend this research to the world of invertebrates and, more specifically, to the world of eusocial insects. For the purpose of investigating whether there are clues of normativity in the world of eusocial insects, we will inquire into the question of whether certain behaviours of ants can be considered normatively conditioned behaviours.

Abstract Personality in non-human animals has been a popular area of research; however, it is still unknown how genetic and non-genetic factors influence the development of personality in many species. Therefore, we investigated how maternal genetic and non-genetic effects influenced adult offspring personality (exploration and anxiety) in the fawn-footed mosaic-tailed rat Melomys cervinipes. We first measured the amount of maternal care mothers provided to their offspring. Later, we assessed mothers and adult offspring over two testing sessions for exploratory behaviour using open field and novel object tests, and anxiety behaviour in a light/dark test. We calculated repeatability of behaviours and used parent–offspring regressions to assess heritability of behaviours. No measure of maternal care significantly influenced offspring personality. However, exploration of new spaces was constrained by maternal genetic effects. In contrast, anxiety and exploration of novel objects was more flexible, suggesting these behaviours may be more influenced by an individual’s experiences during development.