As endotherms, horses must keep their internal body temperature within a relatively narrow window despite external conditions, and must maintain homeostasis in harsh weather conditions, such as low temperatures (Temperature regulation). In harsh environmental conditions, food is usually more scarce so endotherms attempt to lower their energy expendance to adjust for the difference in food intake. Endotherms may utilise physiological and behavioral methods to in order to control their energy expendence as external conditions change (Temperature regulation). For example, free ranging Hereford cows consistently spend more time grazing and less time standing when the temperature is warm as opposed to when it is cool, and were also seen to graze for longer periods of time following atmospheric changes (Malechek).
These specific changes in behavior allow the Hereford cows to save energy that will be used to maintain body temperature, rather than waste it on needless locomotion. Similarly, the Przewalski horse, a medium sized breed of wild horse native to central Asia, was found to spend less time on locomotive activity and more time on rest in the winter, when the temperature was lower (Arnold). Another study focused on the Shetland pony, based off of the previous study on the Przewalski horse, found the same decrease in locomotive activity as the temperature was lowered, confirming results for wild horses to be the same for domesticated horses (Brinkmann).
However, both studies focused their investigation on the correlation between temperature change and differences in general behavior by grouping actions as Locomotive or Resting, which made it impossible to tell which specific behaviors within Locomotive Action were most drastically impacted. By adding new behavioral categories and narrowly defining each category, such as with the equid specific ethogram developed by Jason Ransom (Social, Locomotive, Feeding, Resting, Maitenance, and Other) for a study on the effect of contraceptives on wild horse behavior, it would be possible to determine exactly what groups of behavior are affected by changes in the temperature. With this in mind, I began this study to determine what horse behaviors are most affected by changes in temperature. Based on results from the Shetland pony and Hereford cow studies, it can be predicted that time spent with categories requiring much energy expenditure, such as Social, Lomotive, and Maitenance, will be decreased while categories that require less energy or result in gained energy, such as Feeding and Resting, will be increased.
This experiment was carried out over a period of seven months at Hidden Creek Farm in Brownsburg, Indiana with all of the observation taking place in an enclosed field, which is roughly 174,240 ft², or 4 acres. In this study, the behavior of a domesticated mustang, an 11-year-old mare of the Nokota breed, was used. To maintain consistency, she was turned out with only one other horse, a 19-year-old Trakhener gelding, for all observation periods in the study. The horses were provided with both water and hay during the observation periods, which occurred around lunch time for roughly an hour. The temperature of each trial was recorded in degrees Fahrenheit prior to observation. Upon arriving at the field, a ten minute wait period was started in order to acclimate the horses to human presence to avoid any changes in behavior as a result of human contact. A stopwatch app was used to record the times spent on each behavior.
When the horse changed behavior, the “Lap” button was pressed, and the time spent on that behavior was written down in a notebook with an abbreviation of the category of behavior. An ethogram, or a catalog of a specific animal’s behaviors, was used to quantify the behavior. Using an ethogram involves qualifying each of the behaviors displayed into separate categories. The specific ethogram used for this study was developed by Jason Ransom and was used in his paper “Quantifying Equid Behavior – A Research Ethogram for Free-Roaming Feral Horses.” Ransom developed the ethogram in order to quantify the behaviors of wild horses in order to view the effects of immunocontraceptive porcine zona pellucida (PZP) on feral horse behavior. The categories used in this experiment were Feeding, Social, Locomotion, Resting, Maitenance, and Other. The following paragraphs will further define the behavioral categories.
Feeding behaviors entail any action that directly involved in acquiring and ingesting food. Actions such as grazing, drinking water, mineral licking and pawing at hay, amongst other things, should all be considered feeding. If the horse is walking while simultaneously grazing, then it should be considered a feeding action rather than locomotion.
Social behaviors are any actions that involve more than one horse, such as mutual grooming or play fighting. In his ethogram, Ransom spent much time defining reproductive behaviors as being social, but the horses dealt with in this experiment are not able to reproduce so these qualifications do not apply. Social behaviors also include nonphysical interactions between horses, such as pinning their ears and other forms of communication between horses. Locomotive behaviors involve actions such as walking, trotting, cantering, and galloping and any means of traversing that a horse may use. Other behaviors, such as grazing or playing, in which locomotion is a necessary piece, are categorized as the respective behaviors rather than locomotive.
Resting behaviors applies to a state in which the horse is standing or laying down and is completely relaxed, possibly asleep. This action is often denoted by standing completely still with eyes shut and head slightly lowered. Maitenance behaviors includes both grooming and comfort behaviors, with behaviors such as rolling, stretching, grooming, and tail swishing. Other behavior is qualified as any behaviors that cannot be qualified within any of the other categories. The main behavior exhibited that is put in this category is when the horse is standing alert, a behavior that is usually displayed when they are observing something in the distance.
