Human emotional odours influence horses' behaviour and physiology

Area of Science:

• Ethology
• Olfactory Communication
• Interspecies Interactions

Background:

• Olfaction is a primary sensory modality for animal communication, crucial for intraspecific interactions and reproduction.
• Emerging evidence suggests chemosignals play a role in interspecific communication and emotional signaling.
• The influence of human olfactory signals on equine behavior remains largely unexplored.

Purpose of the Study:

• To investigate the role of human-derived olfactory signals in modulating equine behavior during human-horse interactions.
• To determine if horses can perceive and respond to human emotional states conveyed through scent.
• To assess the impact of fear and joy odors on horses' responses in controlled tests.

Main Methods:

• Forty-three horses were exposed to cotton pads containing human odors from fear and joy contexts, alongside control pads.
• Horses' responses were evaluated during fear tests (suddenness, novelty) and human interaction tests (grooming, approach).
• Statistical analysis, including Principal Component Analysis and effect size calculations, was used to interpret behavioral and physiological data.

Main Results:

• Exposure to fear-related human odors significantly heightened horses' fear responses compared to joy-related and control odors.
• Horses exhibited reduced interaction with humans when exposed to fear odors, touching humans less during approach tests.
• Fear odors led to increased gazing at novel objects, greater startle responses, and elevated maximum heart rates.

Conclusions:

• Chemosignals play a significant role in interspecific interactions, particularly in human-horse communication.
• Horses can detect and react to human emotional states transmitted through olfactory cues.
• Handlers' emotional states can influence equine behavior via scent transmission, with practical implications for animal welfare and training.