Dataset Information

Behavioural and Hormonal Stress Responses to Social Separation in Ravens, Corvus corax.

ABSTRACT: Social life is profitable, but it facilitates conflicts over resources and creates interdependence between individuals. Separating highly social animals triggers intense reactions aimed at re-establishing lost connections. Less is known, however, about behavioural and physiological responses to separation in socially facultative species, where individuals temporarily form groups and may subsequently leave them. Non-breeding common ravens (Corvus corax) gather in large numbers at feeding and roosting sites, but otherwise spend time seemingly solitary or in small subgroups. We here studied how ravens cope with being socially isolated, and investigated the life characteristics that might explain potential individual differences. For this, we individually separated captive subadult ravens (n = 25) and housed them in physical and visual isolation from their group members across 4 d. During the separation period, we collected behavioural data and measured the amount of immunoreactive corticosterone metabolites from bird droppings to assess the ravens' physiological stress response. We found behavioural indicators of stress at the start of the separation, when ravens showed higher levels of tension than of comfort - a pattern that reversed at the end of the separation. Furthermore, we found that the upbringing of ravens affected their behaviour during separation. Hand-raised birds produced more vocalisations in the beginning of the separation, and were less active at the end, while the reverse pattern occurred with parent-raised ravens. Contrary to our predictions, we did not find differences in hormonal responses between the beginning and end of the separation period or any link between hormonal responses and behaviours. Ravens' behavioural responses to social separation stress seem to be dependent on their arousal states, although possible links with hormonal reactions remain unclear. Our results show that behavioural reactions are not always linked with hormonal responses to stress, and further emphasise the importance of investigating effects of early-life experiences.

SUBMITTER: Munteanu AM

PROVIDER: S-EPMC5299477 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Publications

Behavioural and Hormonal Stress Responses to Social Separation in Ravens, <i>Corvus corax</i>.

Munteanu Alexandru M AM Stocker Martina M Stöwe Mareike M Massen Jorg J M JJ Bugnyar Thomas T

Ethology : formerly Zeitschrift fur Tierpsychologie 20161228 2

Social life is profitable, but it facilitates conflicts over resources and creates interdependence between individuals. Separating highly social animals triggers intense reactions aimed at re-establishing lost connections. Less is known, however, about behavioural and physiological responses to separation in socially facultative species, where individuals temporarily form groups and may subsequently leave them. Non-breeding common ravens (<i>Corvus corax</i>) gather in large numbers at feeding a ...[more]

PMID: 28239221

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Project description:Like many predatory species, humans have pronounced individual differences in their interactions with potential prey: some humans pose a lethal threat while others may provide valuable resources. Recognizing individual humans would thus allow prey species to maximize potential rewards while ensuring survival. Previous studies on corvids showed they can recognize and remember individual humans. For instance, wild American crows produced alarm calls toward specifically masked humans up to 2.7 years after those humans had caught and ringed them while wearing that mask. However, individual behavior of the crows or the impact of social features on their responses, was hardly examined. Here, we studied predator learning and social effects on responses, using a similar method, in captive common ravens (Corvus corax). We investigated learning and the impact of key social components on individual reactions to artificial predators. Human experimenters wore two types of masks while walking past two raven aviaries. In four training trials, the "dangerous" mask was presented while carrying a dead raven, whereas the "neutral" mask was presented empty-handed. Between every training trial and in all following trials, we presented both masks without dead ravens. We assessed the subjects' (i) learning speed, (ii) selective long-term response, and (iii) potential effects of social dynamics on individual alarm calling frequency. Ravens learned quickly (often based on the first trial), and some individuals distinguished the dangerous from the neutral mask for the next 4 years. Despite having received the same amount and quality of exposure to the dangerous mask, we found pronounced individual differences in alarm calling that were fairly consistent across test trials in socially stable situations: dominance, but not sex explained individual differences in alarm responses, indicating the potential use of alarm calls as "status symbols." These findings fit to those in wild bird populations and dominant individuals signaling their quality. Changes in the individuals' participation and intensity of alarm calling coincided with changes in group composition and pair formation, further supporting the role of social context on ravens' alarm calling.

Dataset Information

Behavioural and Hormonal Stress Responses to Social Separation in Ravens, Corvus corax.

Publications

Behavioural and Hormonal Stress Responses to Social Separation in Ravens, <i>Corvus corax</i>.

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