Grief-like distress responses in horses after the death of a conspecific

Abstract

As a social species, it would be anticipated that horses may display altered behaviours toward dying or dead conspecifics. However, there is remarkably little literature on this subject. The aim of this study was to identify behavioural changes in horses who have experienced the loss of a companion equid. An online survey was used to collect data on the housing and management of the equids, information on the surviving and deceased equid (including relationship), the passing of the deceased equid, and the type and duration of immediate and sustained behavioural changes in the surviving horse. The survey was completed for 325 surviving horses. Horse owners reported multiple changes in behaviour in the surviving horse within 24 h of the companion’s death; most often related to arousal (88.96 %), behaviour directed towards other equids (77.67 %) and people (77.64 %), alertness to stimuli (72.92 %) and vocalisation (68.63 %). Multiple logistic regression models indicate that horses who had shared an affectionate relationship, rather than simply tolerated each other, were more likely to change their excitement to interact with others or at feeding time (parental-dependant vs. mutual tolerance: p = 0.006; friendly vs. mutual tolerance: p = 0.023) and behaviour towards humans (parental-dependant vs. mutual tolerance: p = 0.026; friendly vs. mutual tolerance: p = 0.029). These behavioural changes often persisted for 6 months after the death of their companion. Horses who had witnessed the death of their companion were more likely to show alterations in time spent sleeping (p = 0.028) and feeding (p = 0.030) within 24 h of death, compared to before companion death. These surviving horses were also more likely to have a change in excitement towards interacting with others and/or around feeding time (p = 0.004) and vigilance (p = 0.016). Whether or not the surviving horse had spent time with the dead body did not affect its behaviour in the first 24 h of loss. However, within 6 months after the death of the companion, horses who could spend time with the body had no change in vocalisation (p = 0.005) and excitement to interact with others and/or to feed time (p = 0.022). Conversely, horses who could not spend time with the body were more likely to show a change in arousal (p = 0.038) and vigilance (p = 0.033). These findings indicate that horses may express grief-related behaviours, but further independent empirical evidence is required. The death of a companion can have negative consequences for the survivor’s welfare. This study may help owners manage emotional welfare better during this difficult time.