Social buffering in horses (Equus caballus): Influence of context, companion familiarity and companion habituation

Abstract

Social buffering occurs when the presence of one animal attenuates another’s stress response during a stressful event and/or helps the subject to recover more quickly after a stressful event. Inconsistent previous results might reflect previously unrecognised contextual influences, such as the nature of the stimulus presented or social factors. We addressed these issues in a two-part study of horses paired with familiar (16 subjects) or unfamiliar (16 subjects) companions. Each subject performed 4 tests in a counterbalanced order: novel object test (static ball) – alone or with companion; and umbrella opening test – alone or with companion. Social buffering was significantly influenced by the nature of the stimulus presented, but not by companion’s habituation status or familiarity. Importantly, the stimulus used produced differential effects on behavioural and physiological measures of buffering. A companion significantly reduced behavioural response (reactivity) in the novel object test but not in the umbrella test. However, heart rate recovered more quickly for subjects with a companion in the umbrella test but not in the novel object test. We propose that circumstances which permit greater contextual processing may facilitate demonstration of behavioural effects of social buffering, whereas buffering in response to startling events may be manifest only during post-event physiological recovery.

Regulation of the stress response by social buffering: A review across species

“…The term social buffering has been coined to refer to this phenomenon Hennesy et al, 2009;Hostinar et al, 2014), which has been theoretically developed for over four decades (Cohen & McKay, 1984;Cohen & Wills, 1985;Dean & Lin, 1977). This effect has been observed in a wide variety of species, including humans (e.g., Ditzen et al, 2007;Kirschbaum, Klauer, Filipp & Hellhammer, 1995), squirrel monkeys (e.g., Hennessy, 1984), rats (e.g., Stanton et al, 1987) guinea pigs (e.g., Hennessy et al, 2006), horses (e.g., Ricci-Bonot, 2021), and fish (e.g., Culbert et al, 2019) under different situations such as mild everyday stressors (Albers et al, 2008), maternal separation (Coe et al, 1978) and public speech (Kirschbaum et al, 1993). Neurophysiological correlates of the effect have also been investigated (Einsenberger et al, 2007;Taylor et al, 2008).…”

Impact of Social Buffering and Restraint on Welfare Indicators during UK Commercial Horse Slaughter

“…As a herd and prey animal, a horse observing a conspecific being slaughtered could cause distress, but research in other social species, such as pigs and sheep, found this not to be the case, especially in comparison to the impact of social isolation [3][4][5]. In some contexts, the presence of one animal has been found to mitigate a conspecific's stress response during a stressful event, a concept referred to as social buffering [6,7]. Social buffering has been found to be predominantly influenced by the nature of the stressful stimulus presented, rather than by familiarity with the conspecific [7].…”

“…In some contexts, the presence of one animal has been found to mitigate a conspecific's stress response during a stressful event, a concept referred to as social buffering [6,7]. Social buffering has been found to be predominantly influenced by the nature of the stressful stimulus presented, rather than by familiarity with the conspecific [7].…”