Biology subjects

Izawa, E.-I.

Publications and source records attributed to Izawa, E.-I..

6 recordsLinked to original sources

bioRxiv2025

Dynamic adjustment of feeding behavior depending on dominant-subordinate relationship in large-billed crows.

Animals that forage socially adjust their behavior according to social status. Dominance and subordination are defined by priority of access to resources in competitive contexts. While dominant individuals can control access to resources, subordinates must obtain food through alternative strategies. In direct encounters with dominants, subordinates are expected to adjust their behavior to the partner on a moment to moment basis. However, the decision dynamics in such situations remain unclear. We tested large-billed crows in a dyadic feeding experiment to examine whether social status shapes feeding behavior. Using tracking analysis, we quantified the time series of approach velocity toward food and assessed whether its dynamics were modulated by the partners movements. Subordinates adjusted the velocity of their reaching movements. Specifically, a dominants approach increased a subordinates reaching speed, suggesting that subordinates accelerated to avoid aggression under dominance pressure. In contrast, this effect was weak or absent in dominants, indicating asymmetric social influences on foraging. Taken together, these findings suggest that subordinates fine tune the kinematics of feeding behavior in response to dominant movements, whereas dominants do not.

animal behavior and cognition↗

bioRxiv2025

Repeated environmental change mitigates inter-individual inequal food gain in a group foraging experiment of crow

Animal group foraging produces inequality of food gain among individuals due to their differences, particularly dominance rank. External environmental factors, such as the spatial distribution of food, may mitigate the influence of social features on individual food acquisition. However, the role of environmental fluctuation in social foraging inequality remains largely unexplored Here, we investigated how repeated environmental changes affect inequality in food acquisition among captive large-billed crows (Corvus macrorhynchos). By repeatedly altering the relationship between feeding sites and food quantity, we examined changes in the inequality of food gains using Gini coefficient. In the short-term, food allocation became unequal immediately after each change but subsequently recovered. Over successive fluctuations, inequality in food acquisition declined in the long-term, while group foraging efficiency increased. We observed a significant influence of sex on food acquisition, while the expected effect of dominance rank was not detected. Our findings provide the first experimental evidence that changing environments can mitigate inequalities in food gains within foraging groups, highlighting the importance of incorporating naturalistic environmental changes into experimental designs for future group-foraging studies.

animal behavior and cognition↗

bioRxiv2024

Inhibition of V1a-like receptors disrupts male-male affiliative relationships formed by triadic cohabitation inlarge-billed crows

Same-sex affiliative relationships are common in humans and some social animals, forming one of the bases of group living. The neuropeptide vasopressin (VP) and its receptors mediate these relationships and behaviours in mammals and birds with gregarious and colonial social structures. In some species, affiliative relationships between dominant and subordinate individuals can be maintained while still retaining strict dominance hierarchies where three or more individuals interact. However, it is unclear whether triadic interaction promotes these relationships, and whether the VP system is also involved in such affiliations due to the lack of suitable animal models and experimental settings. This study addresses these questions with two experiments. In Experiment 1, two-week cohabitation among three male crows facilitated affiliative relationships in particular dyads within each triad. In Experiment 2, vasopressin 1a receptor (V1aR) antagonism disrupted affiliative behaviours and led to the resurgence of agonistic behaviours in affiliated males but not in unaffiliated ones by peripherally administering a V1aR antagonist. These findings suggest that the VP system might universally mediate same-sex affiliative relationships, despite differences in inherent aggression levels among individuals. The triadic cohabitation paradigm established here could advance our understanding of animal societies and be applied across various species, sexes, and social structures. Impact statementThis study provides evidence that a triadic interactive environment facilitates the formation of affiliative relationship between specific dominant and subordinate males in large-billed crows, with crucial involvement of vasopressin 1a receptor in maintaining this affiliation.

animal behavior and cognition↗

bioRxiv2021

Individual repeatability, species differences, and the influence of socio-ecological factors on neophobia in 10 corvid species

Behavioural responses to novelty, including fear and subsequent avoidance of novel stimuli, behaviours referred to as neophobia, determine how animals interact with their environment. Neophobia aids in navigating risk and impacts on adaptability and survival. There is variation within and between individuals and species, however, lack of large-scale, comparative studies critically limits investigation of the socio-ecological drivers of neophobia. In this study, we tested responses to novel objects and food (alongside familiar food) versus a baseline (familiar food alone) in 10 corvid species (241 subjects) across 10 labs worldwide. There were species differences in the latency to touch familiar food in the novel object and food conditions relative to the baseline. Three of seven socio-ecological factors influenced object neophobia: 1) use of urban habitat (vs not), 2) territorial pair vs family group sociality and 3) large vs small flock size (whereas range, caching, hunting live animals, and genus did not); while only flock size influenced food neophobia. We found that, overall, individuals were temporally and contextually repeatable (i.e. consistent) in their novelty responses in all conditions, indicating neophobia is a stable behavioural trait. With this study, we have established a network of corvid researchers, demonstrating potential for further collaboration to explore the evolution of cognition in corvids and other bird species. These novel findings enable us, for the first time in corvids, to identify the socio-ecological correlates of neophobia and grant insight into specific elements that drive higher neophobic responses in this avian family group.

animal behavior and cognition↗

bioRxiv2020

Interceptive capturing in large-billed crows: Velocity-dependent weighing of prediction of future target location and visual feedback of current target location.

Interception of a moving target is a fundamental behaviour of predators and requires tight coupling between the sensory and motor systems. In the literature of foraging studies, feedback mechanisms based on current target position are frequently reported. However, there have also been recent reports of animals employing feedforward mechanisms, in which prediction of future target location plays an important role. In nature, coordination of these two mechanisms may contribute to intercepting evasive prey. However, how animals weigh these two mechanisms remain poorly understood. Here, we conducted a behavioural experiment involving crows (which show flexible sensorimotor coordination in various domains) capturing a moving target. We changed the velocity of the target to examine how the crows utilised prediction of the target location. The analysis of moment-to-moment head movements and computational simulations revealed that the crows used prediction of future target location when the target velocity was high. In contrast, their interception depended on the current momentary position of the target when the target velocity was slow. These results suggest that crows successfully intercept targets by weighing predictive and visual feedback mechanisms, depending on the target velocity.

animal behavior and cognition↗

bioRxiv2018

Rapid adjustment of pecking trajectory to prism-induced visual shifts in crows.

Summary statementThe mechanisms underlying birds pecking skills are not known. We examined whether pigeons and crows adjust their pecking to the visual distortion caused by prisms. We found that vision plays a role only before movement begins in pigeons, whereas crows may have more flexible visuomotor skills.\n\nABSTRACTPecking in birds is analogous to reaching and grasping movements in primates. Although pecking in pigeons is highly stereotypic, crows show dexterous pecking skills. To unveil what sensorimotor mechanisms underlie the flexibility of pecking in crows, the current study examined whether pigeons and crows adjust their pecking to the visual distortion induced by prisms. Because prisms induce visual shifts of object positions, birds were required to adjust their movements. Pecking kinematics were examined before and after attaching prisms in front of the birds eyes. As a result, crows showed faster adjustment of pecking trajectories than pigeons. Correlational analysis showed that the initial deviation of trajectory strongly influenced the subsequent deviation in pigeons, but not in crows. These results suggest that pecking in pigeons is controlled in a feedforward manner, and vision plays a role before movement initiation, although pecking in crows is under the on-line motor control, serving a possible mechanism for flexible visuomotor skills.

animal behavior and cognition↗