Assessment of olfactory sensitivity in horses using positively conditioned scent.
Abstract: Differences in the ranges and capacities of sensory modalities cause horses to perceive their surroundings differently than humans. To date, the horses' sense of smell has been studied mainly regarding social and reproductive behaviour. The role of olfaction in horse management and use also seems to be of utmost importance. The aim of this study was to determine the response to a scent of different intensities by horses of different sexes and types (warmblood horses vs ponies). The study involved 21 adult mares and geldings, of which 15 subjects learned how to complete the required task and were ultimately able to be tested. The study used the mint scent of different concentrations measured by the number of mint drops added to water. A box containing scented cotton was placed in one crib to allow the horses to perceive the odour. In contrast, another crib, which looked identical but was odourless, was hung in the stall to determine whether horses distinguished which of the cribs contained the scent. The horses were unable to see, touch, or taste the cotton itself. They were positively conditioned to the mint odour and were then schooled to indicate the crib with mint drops. The selected horses, which were capable of indicating the scented crib, were then tested six times for each of four decreasing odour concentrations. During the 30 s observation period, the exploration time, frequency of exploration events, and prevalence of additional behaviours (licking or nibbling on the smelling crib and empty-mouth chewing) were recorded at both cribs. The mint-scented crib was explored more intensively than the empty crib at each scent concentration, and the odour recognition was manifested mainly by a longer exploration time (with decreasing concentration: 11.7 s vs 4.8 s, 12.7 s vs 4.6 s, 12.6 s vs 5.5 s, 11.3 s vs 5.4 s; P < 0.01 and 9.5 s vs 5.7 s; P < 0.05). However, interest in scent decreased with reduced odour concentration. The sex and type of horses rarely differentiated the horses' response to the positively conditioned scent. Thus, the biological traits studied do not significantly affect the olfactory sensitivity of horses. Nevertheless, the study showed that horses' olfactory sensitivity is high, and this sense may be of crucial importance for learning. These findings should be considered in horse management and use.
Copyright © 2025 The Author(s). Published by Elsevier B.V. All rights reserved.
Publication Date: 2025-10-15 PubMed ID: 41202732DOI: 10.1016/j.animal.2025.101680Google Scholar: Lookup
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- Journal Article
Summary
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Objective Overview
- This study investigates how horses of different sexes and types respond to varying intensities of a positively conditioned mint scent, aiming to assess their olfactory sensitivity and its potential importance in horse management and learning.
Background and Rationale
- Horses perceive their environment differently from humans due to variations in sensory abilities.
- Previous research on horses’ sense of smell has focused mainly on social and reproductive behaviors.
- Olfaction is believed to play a significant role in horse management and handling, yet it remains less explored in this context.
Aim of the Study
- To evaluate how horses respond to different concentrations of a scented stimulus (mint) by measuring behavioural indicators of olfactory sensitivity.
- To compare responses across different biological traits, specifically sex (mares and geldings) and type (warmblood horses versus ponies).
Methods
- Participants: 21 adult horses (mares and geldings), of which 15 successfully learned the task and were subsequently tested.
- Stimulus: Mint scent with varying concentrations created by adding different numbers of mint drops to water.
- Setup: Two identical cribs placed in the horse’s stall:
- One crib contained cotton scented with mint infusion.
- The other crib was identical but odourless.
- Constraints: Horses could neither see, touch, nor taste the cotton, relying on olfaction alone.
- Conditioning:
- Horses were positively conditioned to associate the mint scent with a task.
- They learned to indicate the scent-containing crib.
- Testing protocol:
- Each horse was tested six times for each of four progressively lower scent concentrations.
- During a 30-second observation per trial, researchers recorded:
- Exploration time of each crib.
- Frequency of exploration events.
- Additional behaviors such as licking, nibbling on the crib, and empty-mouth chewing.
Results
- Horses explored the mint-scented crib more intensively than the empty crib across all scent concentrations.
- Longer exploration times were the most notable indicator of scent recognition:
- Example times comparing mint-scented vs. empty crib (in seconds with statistical significance):
- 11.7 vs 4.8
- 12.7 vs 4.6
- 12.6 vs 5.5
- 11.3 vs 5.4
- 9.5 vs 5.7 (lowest concentration)
- Example times comparing mint-scented vs. empty crib (in seconds with statistical significance):
- Interest in the scent decreased as the concentration diminished, indicating sensitivity to scent intensity.
- Biological traits such as sex (mares vs geldings) and type (warmblood vs ponies) had little effect on the horses’ ability to detect and respond to the conditioned scent.
Conclusions and Implications
- The olfactory sensitivity of horses is high and stable across different biological groups tested.
- Olfactory cues can be effectively used in horse training and management, potentially enhancing learning processes.
- Findings suggest that horse husbandry and behavioral training practices should incorporate consideration of horses’ keen sense of smell.
- Understanding and utilizing horses’ olfactory capabilities may improve welfare, communication, and working effectiveness.
Cite This Article
APA
Wnuk E, Janicka W, Stachurska A, Owerczuk R, Łuszczyński J.
(2025).
Assessment of olfactory sensitivity in horses using positively conditioned scent.
Animal, 19(12), 101680.
https://doi.org/10.1016/j.animal.2025.101680 Publication
Researcher Affiliations
- Department of Horse Breeding and Use, Faculty of Animal Sciences and Bioeconomy, University of Life Sciences in Lublin, 13 Akademicka Street, 20-950 Lublin, Poland.
- Institute of Biological Basis of Animal Production, Faculty of Animal Sciences and Bioeconomy, University of Life Sciences in Lublin, 13 Akademicka Street, 20-950 Lublin, Poland. Electronic address: wiktoria.janicka@up.edu.pl.
- Department of Horse Breeding and Use, Faculty of Animal Sciences and Bioeconomy, University of Life Sciences in Lublin, 13 Akademicka Street, 20-950 Lublin, Poland.
- Department of Horse Breeding and Use, Faculty of Animal Sciences and Bioeconomy, University of Life Sciences in Lublin, 13 Akademicka Street, 20-950 Lublin, Poland.
- Department of Genetics, Animal Breeding and Ethology, Faculty of Animal Science, University of Agriculture in Cracow, 21 Mickiewicz Avenue, 31-120 Cracow, Poland.
MeSH Terms
- Animals
- Horses / physiology
- Odorants
- Male
- Female
- Smell / physiology
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