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.

The role of mesotocin on social bonding in pinyon jays

“…Most studies on social history, housing style, and their effects on adult behavior focus on a few key rodent and primate species, and overall findings suggest these effects are most pronounced when the isolation occurs early in development (Lickliter, Dyer, & McBride, 1993;Carere, Welink, Drent, Koolhaas, & Groothuis, 2001;Olsson & Westlund, 2007). Among adults, social instability (e.g., removal from a pre-existing group) is broadly stressful and can impact how individuals interact in the group (Smith, Birnie, & French, 2011;Stocker, Munteanu, Stöwe, Schwab, Palme, & Bugnyar, 2016;Munteanu, Stocker, Stöwe, Massen, & Bugnyar, 2017). Despite these observations, differences in captive housing style do not always result in demonstrable changes in behavior, as compared to wild conspecifics (Gazes, Brown, Basile, & Hampton, 2013).…”

Behavioral Responses of Captive Corvids to the Presence of Visitors

“…In the present study, we did not differentiate between the different call-types uttered in response to visitor presence and therefore can only speculate about the behavioral context. Common ravens have been shown to increase vocalizations in response to social separation (Munteanu et al, 2017), which could be a response to a stressful situation, but also an attempt to establish contact with conspecifics. Vocalizations are used by animals to signal aggression (Szipl et al, 2017) or attract potential cooperation partners (Sierro et al, 2020).…”

The role of mesotocin on social bonding in pinyon jays

“…Most studies on social history, housing style, and their effects on adult behavior focus on a few key rodent and primate species, and overall findings suggest these effects are most pronounced when the isolation occurs early in development (Carere, Welink, Drent, Koolhaas, & Groothuis, 2001;Lickliter, Dyer, & McBride, 1993;Olsson & Westlund, 2007). Among adults, social instability (e.g., removal from a pre-existing group) is broadly stressful and can impact how individuals interact in the group (Munteanu, Stocker, Stöwe, Massen, & Bugnyar, 2017;Smith, Birnie, & French, 2011;Stocker et al, 2016). Despite these observations, differences in captive housing style do not always result in demonstrable changes in behavior, as compared to wild conspecifics (Gazes, Brown, Basile, & Hampton, 2013).…”