Memory retrieval is an important memory process, and its effectiveness can vary across developmental stages. The differential maturation of hippocampal- and non-hippocampal-dependent memory systems suggests that distinct forms of memory develop along separate neurodevelopmental time points. However, it is unclear if hippocampal-dependent fear memory retrieval differs between adolescence and adulthood. We hypothesize that developmental changes in brain function contribute to differences in memory retrieval between adolescent and adult animals. Accordingly, this study examines age-dependent differences in the retrieval of contextual fear-conditioned memory by comparing adolescent and adult rats. The experiment involved three different cohorts of rats (N=32). Group A comprised adolescent rats (N=12) trained at postnatal day 30 (P30) and tested 10 days later at P40. Group B consisted of adult rats (N=10) trained at P80 and tested 24hours later at P81, while Group C included adult rats (N=10) trained at P80 but tested 10 days later at P90. Results indicated that adolescent rats had a more substantial capacity to recall contextual fear memories than adult rats. While adult rats showed a significant increase in freezing behavior 24hours after training, adolescent rats exhibited greater freezing behavior when tested 10 days post-training, highlighting the developmental changes in fear and anxiety processing associated with the maturation of the hippocampus and amygdala.
Discontinuing reinforcement for an operant response can sometimes produce a transient increase in the rate of that response (i.e., an extinction burst). Although differential reinforcement of alternative behavior (DRA) can attenuate the extinction burst, the effects of rate of alternative reinforcement on the extinction burst have never been examined. Using a within-session transition from a variable-interval (VI) 1.5-s schedule to extinction, we examined how arranging different rates of reinforcement for an alternative response during extinction affected target and alternative responding of rats. Consistent with prior findings, reinforcing an alternative behavior eliminated the extinction burst. Surprisingly, all arranged alternative reinforcement rates eliminated the extinction burst and similarly reduced target response rates, despite generating differential rates of alternative behavior. This outcome is contrary to predictions of the temporally weighted matching law, which predicts both graded suppression of target behavior and higher alternative response rates with higher alternative reinforcement rates. Early in extinction, alternative responding was elevated and initially nondifferentiated across groups, suggesting that rats required some time to discriminate the rate of alternative reinforcement. Incorporating a temporary generalization-of-value across target and alternative responses substantially improved model fits. These findings show that arranging even lean DRA schedules might prevent the extinction burst and suggest potential new avenues for studying response generalization during transitions to extinction.
The present study investigated the relationships between behavioural traits, environmental conditions, and milk production and composition in dairy cows using data obtained from an automated behavioural monitoring system. A total of 283 observations collected from 19 Holstein Friesian and Simmental cows were evaluated. Behavioural traits, including activity, eating, and rumination time, were recorded using the CowManager SensOor system, while environmental conditions were assessed using the temperature-humidity index (THI). Morning milk yield and milk composition traits were evaluated in relation to behavioural, environmental, and lactation-related factors using linear mixed-effects models. Milk yield decreased with advancing lactation stage, whereas milk protein and lactose concentrations increased. Increasing THI was negatively associated with morning milk yield in the initial analysis, but this association did not remain significant after adjustment for multiple comparisons. In contrast, THI was positively associated with milk pH, although the magnitude of this association was small. Behavioural variables showed limited associations with milk production and major milk composition traits; however, eating time was negatively associated with milk electrical conductivity after adjustment for multiple comparisons. Overall, the findings indicate that environmental conditions and lactation stage are important sources of variation in milk production and composition, whereas automated behavioural measurements may provide complementary information on selected milk quality characteristics. These results highlight the potential of sensor-based behavioural monitoring as a complementary tool for evaluating dairy cow performance under variable environmental conditions.
Extinction is not just a passive decay of behavior but an active process of reorganization. This study explored this reorganization by examining the extinction burst and its connection to changes in attentional stimulus control in human participants. In Experiment 1 (N = 64), participants responded on either a Fixed-Ratio 1 (FR1) or Fixed-Ratio 5 (FR5) schedule, followed by extinction. Both schedules triggered a significant extinction burst in the first seconds of extinction, with the burst being larger under FR5. In Experiment 2 (N = 32), response rates and eye-tracking data (gaze fixation dispersion) were measured at the same time under FR1 and FR5 schedules. Results confirmed the extinction burst, which was again more pronounced in the FR5 group. Importantly, attentional reorganization followed a different time course from the motor response: fixation dispersion stayed steady during the baseline and the peak of the burst (E1) but increased significantly in the post-burst interval (E2) as responses began to decline. These findings indicate that extinction starts a hierarchical adaptive process: a low-cost 'exploitation' phase (the motor burst) followed by a broader 'exploration' phase (attentional dispersion), occurring only after the initial strategy fails.
Social immunity in eusocial insects involves collective behavioural mechanisms that reduce pathogen transmission within colonies. In ants, necrophoric behaviour plays an important role in colony hygiene; however, the relationship between caste-specific morphology, sensory structures, and hygienic performance remains poorly understood in Oecophylla smaragdina. This study investigated caste differences in necrophoric behaviour, morphometric traits, and antennal sensilla morphology in major and minor workers of O. smaragdina using behavioural assays, morphometric analysis, and scanning electron microscopy (SEM). Linear mixed-effects model analysis revealed significant caste-dependent differences in corpse detection latency, colony included as a random effect. Minor workers detected corpses significantly faster than major workers across all five colonies, exhibiting mean detection latencies of 40.20 ± 13.32 s to 50.60 ± 9.13 s, compared to 122.40 ± 14.03 s to 143.80 ± 17.78 s in major workers. Morphometric analyses showed that major workers possessed significantly larger body dimensions than minor workers across all measured traits. SEM examination revealed distinct caste-specific variation in antennal and mandibular structures. Minor workers exhibited higher total antennal sensillar counts (117) compared to major workers (94), whereas sensilla in majors appeared comparatively larger. These findings suggest that sensory and morphological specialization may contribute to caste-specific hygienic roles and division of labour in O. smaragdina.
In addition to the light-dark cycle, non-photic cues oscillating every 24 h can entrain central and peripheral circadian oscillators. When rodents receive a daily palatable food, they exhibit a pre-feeding increase in locomotor activity known as anticipatory activity (AA). The emergence of AA requires multiple conditioning cycles and persists following stimulus withdrawal, implicating learning and memory processes in its regulation. Environmental enrichment enhances neuroplasticity, learning, and memory capacities; however, its effects on non-photic circadian entrainment remain unexplored. For this purpose, male Wistar rats were reared from weaning under standard or enriched housing conditions for 60 days. Subsequently, locomotor activity was continuously recorded to assess AA to a daily chocolate piece administered during the light phase for 12 consecutive days. Anxiety-like behavior (elevated plus-maze and open field tests), chocolate consumption and motivation (chocolate binge and motivation for enclosed chocolate tests), and preference for other rewarding stimuli (sucrose preference test) were also assessed to determine whether differences in AA expression were attributed to these features. Both groups exhibited robust AA after repeated chocolate exposure; however, enriched rats developed AA approximately two days earlier than standard rats. Additionally, enriched animals displayed enhanced temporal precision of anticipatory onset and shorter post-chocolate activity. No differences were found between housing conditions in anxiety-like behavior, chocolate consumption, motivation to obtain chocolate, or sucrose preference. Our findings suggest that an enriched environment may influence specific temporal features of anticipatory activity induced by a palatable stimulus, without altering hedonic or motivational responses.
Dogs often use their keen olfactory abilities in laboratory settings to support scent detection research. In cognitively demanding tasks, pre-feeding appears to influence engagement and performance, but the effects of hunger state on dogs’ frustration-related behaviour during scent-detection work has not previously been examined. We analysed overall behaviour patterns observed during a laboratory-based scent detection task and evaluated whether dogs exhibited frustration-related behaviour changes as a function of having had breakfast before the task. We expected to see an increase in frustration-related behaviours when dogs were working prior to eating breakfast. Behavioural observations were extracted from video recordings of six dogs participating in the scent-detection task. During the sessions, dogs spent the greatest proportion of time with the tail held low (85%) and still (73%). Whining and engagement with the feeder and scent detection apparatus was higher when dogs had not eaten before the task, consistent with mild frustration, although behaviours varied between dogs and these differences were primarily driven by one or two dogs. Regardless of condition, lip licking and ground sniffing occurred more frequently earlier in the day, with lip licking also increasing over the course of the study. These findings suggest that working prior to a meal may have a mild effect, increasing frustration-related behaviours in some dogs, but additional research is required to clarify potential mechanisms underlying this effect. The low levels of frustration-related behaviours more generally suggest that laboratory scent-detection tasks, similar to the present task, do not reliably evoke such behaviours.
It is well known that domestic cats (Felis catus) have the potential to impact local vulnerable wildlife, and that individual cats differ in their ecological impact due to predation. However, less is known about how individual cats may differ in their behaviours with similar motivational involvement, such as in response to a moving, feathered object toy. Using an online questionnaire, we recruited participants in the United States to expose their cat (N = 87) to standardised behavioural assay trials using a feather wand toy, aiming to capture individual variation in response to the toy and the consistency of the individuals' responses over time. We collected caretaker recorded videos capturing cats' interaction with the object toy, and found high repeatability of all behaviours measured across trials (mean R = 0.467). We then consolidated the data using Principal Component Analysis to obtain a composite cat interest score for further analysis. Overall, we found significant trial effects (p = 0.002), and consistent individual variation in the cats' composite interest score (ICC = 0.650). Interestingly, we did not find any significant connections between the cats' interest score and factors such as their outdoor access, history of hunting, frequency of play in the home, or rated playfulness by their caretakers. Our study presents the first recorded use of citizen science as a method of quantifying consistent individual differences in play behaviour of cats, and highlights the importance of assessing individual variation when studying cat behaviour.
Offspring may use various sensory modalities to learn from the mother, but this has in pigs received relatively little research attention. The objective of this study was to investigate social cues between sow and piglet during a learning scenario related to foraging. We hypothesized that 1) the sow and piglet make frequent visual, auditory and tactile contact, 2) that their behaviour is related, and 3) that frequent sow-piglet communication translates to health benefits for the offspring. Four-week old piglets (n = 95) were tested individually with their mother (n = 11 sows) in a 3-min foraging paradigm. Two food types were available which were known to the sow but unfamiliar to the piglet. Foraging, social behaviour and vocalisations were recorded. In the test, the sow and piglet interacted frequently, but mostly through visual and auditory contact rather than physical contact. Food-related and social behaviour of the sow positively related to the piglets' behaviour. There was no significant relationship between the weight gain of the litter and the sows' food-related or social behaviour. In conclusion, sows and piglets showed a bidirectional communication in a learning scenario, whereby the sow mainly has a demonstrator role.
Testosterone (T) modulates male sexual behavior, partly through actions in the medial preoptic area (mPOA) of the anterior hypothalamus. Although gonadectomy (GDX) rapidly depletes circulating T, the decline in sexual behavior is gradual, taking weeks or months. In some species, prior sexual experience delays this behavioral decay; however, whether this occurs in rats remains unclear. Here, we examined the effects of GDX and prior sexual experience on serum T levels, sexual behavior, and mPOA cellular density in male Wistar rats. Males were assigned to one of two groups: sexually experienced (Stud; n = 6) or naïve (Naïve; n = 6). Stud males underwent five 90-min copulatory sessions with receptive females at 4-day intervals, whereas naïve males were exposed to the chamber alone. All males were then gonadectomized and tested for T levels and sexual behavior at multiple time points from GDX: -1, + 1, + 7, + 30, + 45, and + 110. Sexual motivation was assessed using an olfactory preference test (urine from receptive vs. non-receptive females), and copulatory behavior was evaluated during encounters with receptive females. On GDX + 111, brains were collected for Nissl staining, and mPOA cell counts were quantified. Serum T decreased from approximately 10 ng/mL on GDX -1 to undetectable levels by GDX + 1 in all animals. Olfactory preference for receptive urine was decreased by GDX + 1, but not by + 7. On GDX + 45, stud males showed more genital investigations, mounts, and intromissions, as well as shorter latencies to mount and intromit, than naïve males; however, these differences were no longer evident by GDX + 110. Importantly, mPOA cell density was significantly higher in stud compared to naïve males. Thus, although GDX rapidly eliminates circulating T, prior sexual experience delays the decline of sexual motivation and behavior and is associated with increased cellular density in the mPOA. These findings contribute to understand that sexual experience induces neuroplastic changes in the mPOA that confer resilience to hormonal depletion.
Flight initiation distance (FID) is an important behavioral metric for assessing an animal's fear level and evaluating the trade-offs in survival strategies under predation risk. Studies have shown that various characteristics of observers - such as clothing, behavior, and gaze direction - can influence avian FID, yet the effect of observer gender on FID remains underexplored. A recent study found that urban birds were less tolerant of women than of men, a consistent observer gender specific pattern in five European countries. In light of this, this study investigated whether the FID of black-headed gulls (Chroicocephalus ridibundus) wintering in tourist areas of Kunming City, Yunnan, southwest China, differed in response to human observers of different genders. Our results revealed no significant difference in the FID measured by male and female observers. The coefficients of variation within both groups were relatively high, and the intra-class correlation coefficients showed significant inter‑observer variations. Due to long‑term exposure to large numbers of tourists with diverse behavioral patterns, the salience of observer gender cues may be attenuated for black-headed gulls. Alternatively, differences among individual observers - potentially including uncontrolled subtle behaviors or appearance features - exert a greater influence on the birds' escape responses than does observer gender. Our study contributed to filling the gap in understanding the effect of observer gender on avian escape behavior.
The development of behavioral diversity in juvenile animals is closely linked to their environmental adaptability and survival rate. However, research on development of behavioral diversity in juvenile animals remain limited. From May to August 2021, we surveyed three juvenile black storks (Ciconia nigra), a Class I protected species of China, at Zhangye Heihe National Wetland Nature Reserve in Gansu Province, to explore their behavioral ontogeny. We established their behavioral repertoire, and analyzed rhythms and diversity across developmental stages. The research results revealed that behavioral frequency and diel behavioral rhythms differed significantly across months, while time of day and month both exerted notable influences on behavioral differentiation. All behavioral diversity indices presented distinct monthly changes. Behavioral frequency and behavioral counts increased obviously over time, as did the Shannon-Wiener and Simpson's diversity indices. By contrast, the Berger-Parker and Simpson's dominance indices declined significantly with time, and no obvious correlation was detected between time and Pielou's evenness index. Discriminant analysis confirmed clear behavioral differences among developmental stages, with stable and stage-specific behavioral patterns emerging at different periods. Overall, behavioral development in juvenile black storks follows a clear temporal sequence, with environment-adaptive behaviors being progressively expressed as development proceeds. Behavioral ontogeny advances from simple to complex behaviors and from single to increasingly diverse behavioral repertoires.
Octopuses are keystone species in shallow-water marine ecosystems. While research has focused on predator-prey interactions, the non-neutral interactions between octopuses and fishes have not been well characterized. These range from possible cooperation, kleptoparasitism, and scavenging to occasional predation on unwary fishes. To address this gap, we analyzed video recordings of juvenile Octopus insularis interacting with 10 fish species on Brazilian reefs, compiled an ethogram, and tracked the outcomes of interactions using Lag Sequence Analysis. We observed a total of 101 interactions between octopuses and seven non-territorial fish species and three territorial fish species. Fish territoriality significantly affected the behavior of both fishes and octopuses. The duration of interactions was significantly longer in non-territorial fishes. Interactions with territorial fishes involved faster approaches and higher rates of behavioral change for both animals and were characterized by 'Jabs' and 'Swipes' by fishes, and 'Flinches' and arm 'Arm slaps' by octopuses. Interactions with non-territorial fishes were characterized by 'Follow' and 'Circle' by fishes, and the octopuses continuing their hunt. Lag Sequence Analysis confirmed distinct and predictable behavioral sequences for each interaction type. The presence of territorial fishes also affected octopus body patterning, with the 'Half blotch' - a defensive body pattern - occurring only in interactions with territorial fishes. These results demonstrate that during foraging, octopuses need to navigate a complex set of conflicting interactions.
Recent cross-species analyses suggest that the different forms of stereotypic behaviour have heterogeneous causal mechanisms. In ungulates, there are indications that some forms of locomotor stereotypy may be linked to social factors. Using the domestic horse as a model species within this clade, we investigated whether individuals displaying the locomotor stereotypy box-walking (n = 6) demonstrated greater responses to a stable mirror, intended to mimic presence of a conspecific, than horses displaying the oral stereotypy crib-biting (n = 5) and non-stereotypic horses (n = 5). After a 24 hr baseline phase, horses were provided with a 1 × 1.5 m stable mirror for 24hrs. This was followed by a 24 hr post-mirror phase. Responses were quantified using measures of behaviour, orientation, and ear and head/neck movements. Box-walking, but not crib-biting, was reduced when the mirror was present, and box-walking remained at this lower level following mirror removal. Box-walkers and non-stereotypic horses spent a greater proportion of time orientated towards the mirror than crib-biters. Box-walkers did not, however, demonstrate increased use of ear or head/neck movements associated with affiliative social behaviours, nor did they exhibit more behaviours indicative of frustration, once the mirror was removed, than other animals. There were, however, other unexpected differences in mirror responses between the stereotypy groups. This study provides an initial indication that stereotypic horses respond differently to mirrors, however a sufficiently powered follow-up, with additional controls, is required to establish if box-walking horses are more socially motivated.
Larval zebrafish have become a cornerstone in neurobehavioral research. However, the reproducibility of zebrafish behavioral studies is often hindered by subtle yet significant variations in experimental parameters. This study systematically investigates how variations in experimental parameters-well geometry; area; plate opacity; genotype; holding temperature; and light intensity-influence larval zebrafish baseline activity and behavioral responses. Using automated behavioral tracking and sample sizes ranging between 73 and 192 larvae/group, we uncovered evident differences in response to changes in these conditions. When assessing geometry and area, larvae in square wells and larger well areas displayed heightened baseline and stimulus-induced behavioral responses; however, relative comparison contradicted these findings indicating smaller areas significantly exaggerated the magnitude of behavioral responses. Clear plates elicited stronger baseline activity and stimulus-driven behaviors. Wild-type fish showed higher behavioral responses than mutants. Temperatures significantly modulated baseline activity and stimulus-induced behavior, while relative comparison analysis revealed increases in stimulus-induced responses across both extremes. Lastly, intermediate light intensities elicited the strongest reactivity, indicating a non-linear relationship between illumination and visual-motor-response behaviors. Our study demonstrates that variation in experimental parameters can alter behavioral outcomes, underscoring the need for standardized zebrafish neurobehavioral assays and for accounting for methodological differences when comparing results. Developing this framework will improve the reliability and interpretability of zebrafish behavioral data.
Jellyfish of the genus Aurelia possess a decentralized nervous system and rhopalia that contain basic visual structures, providing a unique opportunity to explore light-driven behavior in the absence of a centralized brain. Despite their anatomical simplicity, little is known about how these animals modulate their motor activity in response to light or whether they exhibit consistent preferences for light or dark environments. In this study, we conducted two behavioral experiments to investigate the light-dependent behaviour in juveniles of Aurelia coerulea. In Experiment 1, we measured pulsation frequency under light and dark conditions as a proxy for motor activity. In Experiment 2, we adapted a scototaxis-based test to assess phototactic preferences in an environment divided into illuminated and dark compartments. Our results show that jellyfish increased pulsation rates under light conditions and spent significantly more time in the illuminated area, suggesting a consistent positive response to light. These findings provide evidence of light-mediated behavior in Aurelia coerulea and contribute to a deeper understanding of how complex sensory-guided behaviors can emerge in organisms without centralized nervous systems.
Conspicuous polymorphisms provide natural tests of mechanisms maintaining behavioral and underlying genetic variation. Cognition has received relatively little attention in color-polymorphic systems. We used a melanin-based polymorphism in the eastern mosquitofish (Gambusia holbrooki) to ask whether performance in a detour task differs between morphs. Melanic males (N = 38) solved the task more often than silver males (N = 37) and had a 1.59-fold higher estimated solution rate, although effect sizes were modest and statistical support was limited. These results suggest that processes associated with detour-task performance may represent an underappreciated axis of morph divergence with a potential role in the maintenance of melanin-based polymorphism.
The estrous cycle of female mammals does not only cause regular changes in steroid hormone concentrations but can also influence behavior and hence (social) life. A valuable model organism to study such effects is the guinea pig: its long 16-day estrous cycle with an active luteal phase represents a perfect opportunity to investigate the estrous cycle in detail, but information on estrous cycle effects is scarce. This study investigated the proestrus/estrus and diestrus phases of two consecutive cycles in twelve socially housed female guinea pigs. Following cycle monitoring, sociopositive and aggressive behavior, general activity patterns, anxiety-like behavior, and saliva cortisol concentrations were investigated on three days around estrus (day -1, day 0 = estrus, day 1) and in diestrus (day 7, day 8, day 9) each. Aggressive behavior significantly increased on day 0 (estrus) and the guinea pigs spent less time in the shelters and more time feeding on day 9 compared to day 7 in diestrus. Cortisol concentrations were increased around the time of estrus versus diestrus and body mass was decreased on day 0. None of the behavioral parameters affected cortisol concentrations considerably, except for a weak negative effect of the time spent feeding. This study demonstrates that the estrous cycle exerts an effect not only on physiological parameters but also on the behavior of group-living female guinea pigs. This represents an important starting point for future research and highlights stronger consideration of the estrous cycle when investigating (social) behavior and physiology in female guinea pigs.
