The flehmen response is most commonly associated with stallion behavior. This behavior will be presented when the stallion smells urine and feces from mares and other stallions alike. The flehmen response actually draws air into the vomeronasal organ found at the base of the nasal cavity. This organ is used for perception of scents and pheromones. When scents are transferred to the vomeronasal organ, signals from the brain trigger various reactions varying with individual scents. A mare's urine or just the presence of a mare in estrus has been seen to signal the flehmen response in stallions. It is believed that the stallion is also able to determine if a mare is in estrus or not from the flehmen response. This is still under debate in research studies.
One research article that I have looked at delves further into explaining the flehmen response in stallions and their connection to reproductive behavior. I have summarized it below:
One research article that I have looked at delves further into explaining the flehmen response in stallions and their connection to reproductive behavior. I have summarized it below:
In the article titled "The Role of the Flehmen Response in the Behavioral Repertoire of the Stallion" Stahlbaum and Houpt investigate the occurrence of the flehmen response in response to different substances or circumstances. Focal observations were made on five stallions and behaviors including nasal investigatory, sexual, marking, and maintenance and other behavior patterns were recorded for given periods of time.
The first experiment studied the occurrence of the flehmen response in a semi-naturalistic situation. The occurrence of the flehmen response most noticeably increased during times when surrounding mares were in estrus and decreased significantly as more and more mares in the group became pregnant and discontinued their estrous cycle. The flehmen was noted to occur most frequently on the day of copulation which is expected when correlating the response to the sexual repertoire of the stallion. It was also noted that the flehmen was frequently initiated after nasal investigation from the stallion which is most likely in reference to the function of detecting estrus in mares. The flehmen was then followed by a change in orientation including approaching and mounting a mare. Although the flehmen occurs frequently during the courtship sequence from the stallion, it is important to note that it is not exclusively a part of courtship and was also seen in other contexts. The flehmen response was a large tool in investigative areas when presented with urine or other substances especially in foals.
The second experiment consisted of multiple sub experiments that each tested the response of different test substances including urine and feces. Experiment 2a recorded the responses to estrous mare urine versus water. As expected, the reaction to water was significantly reduced and none of the stallions urine marked the water. Experiment 2b looked at the responses to estrus and nonestrus urine and feces. Surprisingly a differing response was not seen between the estrus and nonestrus mare urine. Experiment 2c observed the responses to variations in volume and frequency of urination. This was decided due to the occurance of mares in estrus frequently urinating in small quantities compared to the infrequent large volume urination of a non estrus mare. It was interesting to see that the initial reaction from the stallion was similar to both volumes but after the initial exposure the stallions interest and reaction decreased to the large volume but stayed relatively consistent to the multiple small volumes of urine. Experiment 2d looked at the differences in response to urine from a pregnant mare, an ovariectomized mare and a gelding. No significant difference was observed. Experiment 2e recorded the responses to own and other urine and feces. A significant difference to mares feces compared to their own was exhibited with both an increase in flehmen and sniffing. The last experiment 2f looked for any difference in furosemide-induced urine when presented to the stallion. This was tested to see if furosemide-induced urine could be used for testing behavioral responses. No significant difference was recorded. All of these findings suggest that the production of multiple urine depositions from a mare in estrus can aid in the ability of the stallion to determine the cyclicity of a mare. It was also concluded that the stallion has the ability to determine the sexual identity of individuals from their fecal marks.
The first experiment studied the occurrence of the flehmen response in a semi-naturalistic situation. The occurrence of the flehmen response most noticeably increased during times when surrounding mares were in estrus and decreased significantly as more and more mares in the group became pregnant and discontinued their estrous cycle. The flehmen was noted to occur most frequently on the day of copulation which is expected when correlating the response to the sexual repertoire of the stallion. It was also noted that the flehmen was frequently initiated after nasal investigation from the stallion which is most likely in reference to the function of detecting estrus in mares. The flehmen was then followed by a change in orientation including approaching and mounting a mare. Although the flehmen occurs frequently during the courtship sequence from the stallion, it is important to note that it is not exclusively a part of courtship and was also seen in other contexts. The flehmen response was a large tool in investigative areas when presented with urine or other substances especially in foals.
The second experiment consisted of multiple sub experiments that each tested the response of different test substances including urine and feces. Experiment 2a recorded the responses to estrous mare urine versus water. As expected, the reaction to water was significantly reduced and none of the stallions urine marked the water. Experiment 2b looked at the responses to estrus and nonestrus urine and feces. Surprisingly a differing response was not seen between the estrus and nonestrus mare urine. Experiment 2c observed the responses to variations in volume and frequency of urination. This was decided due to the occurance of mares in estrus frequently urinating in small quantities compared to the infrequent large volume urination of a non estrus mare. It was interesting to see that the initial reaction from the stallion was similar to both volumes but after the initial exposure the stallions interest and reaction decreased to the large volume but stayed relatively consistent to the multiple small volumes of urine. Experiment 2d looked at the differences in response to urine from a pregnant mare, an ovariectomized mare and a gelding. No significant difference was observed. Experiment 2e recorded the responses to own and other urine and feces. A significant difference to mares feces compared to their own was exhibited with both an increase in flehmen and sniffing. The last experiment 2f looked for any difference in furosemide-induced urine when presented to the stallion. This was tested to see if furosemide-induced urine could be used for testing behavioral responses. No significant difference was recorded. All of these findings suggest that the production of multiple urine depositions from a mare in estrus can aid in the ability of the stallion to determine the cyclicity of a mare. It was also concluded that the stallion has the ability to determine the sexual identity of individuals from their fecal marks.