02/19/2026
Horses need stable social groups to live with for good welfare, and it makes sense for them to worry when separated from their friends.
If we insist on it anyway, we owe them ethical, evidence-based training that helps them tolerate being alone.
A multinational research collaboration led by Claire Ricci-Bonot and Daniel Simon Mills from the University of Lincoln's Animal Behaviour, Cognition and Welfare Group has established the first consensus definition of separation anxiety in horses.
The research team brought together specialists from Cornell University, the University of Milan, Ghent University, Charles Sturt University, the RSPCA, and The Horse Trust, with funding from the Morris Animal Foundation.
The study filled a significant gap in equine behavioural science: despite separation anxiety being common in both management settings and clinical practice, no standardised definition existed.
Researchers used a two-phase approach, combining survey data from 88 horse owners with expert validation from seven international equine behavioural specialists.
The research revealed eight distinct contexts for separation anxiety, defined by two key factors: whether the horse is leaving or being left behind, and the stage of separation (from preparation through active departure), initial barrier to contact, and complete loss of contact.
This framework shows that separation anxiety is not one condition but a collection of responses that depend on specific circumstances.
Horses display a wide range of behavioral signs spanning from hyperarousal (increased movement, vocalisation, and heightened alertness) to depressive responses including apathy and stopping normal activities like grazing and resting.
This spectrum confirms that horses may experience different emotional states during separation, from panic and grief to learned helplessness.
The consensus definition describes separation anxiety as a behavioral syndrome involving negative emotional responses when horses are separated from other horses or bonded companions of any species, including mare-foal pairs.
These responses can occur before, during, or after separation, even when other horses are present.
As a highly social species with strong social bonds and limited natural adaptation to isolation, horses benefit significantly from this research.
The findings provide an evidence-based framework for clinical assessment and welfare management, allowing for better identification of individual stress patterns, more targeted interventions, and a foundation for future research into risk factors and treatment approaches.
📑 Development of a consensus definition of “separation anxiety” for horses, Applied Animal Behaviour Science. Authors: Claire Ricci-Bonot, Emanuela Dalla Costa, Katherine Houpt, Milly Jones, V. Wensley Koch, Gemma Pearson, Hayley Randle, Machteld van Dierendonck, Daniel Simon Mills.