Evaluating the Reaction to a Complex Rotated Object in the American Quarter Horse (Equus caballus) - MDPI
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animals Article Evaluating the Reaction to a Complex Rotated Object in the American Quarter Horse (Equus caballus) Megan Elizabeth Corgan, Temple Grandin * and Sarah Matlock Department of Animal Science, Colorado State University, Fort Collins, CO 80523, USA; email@example.com (M.E.C.); firstname.lastname@example.org (S.M.) * Correspondence: email@example.com Simple Summary: Horses are prey animals and exhibit behaviors that help them adapt and survive in their environment. These reactions are often referred to as spooking and they have the potential to be dangerous to the horse, handler and rider. Spooking consists of avoidance reactions that include suddenly moving away or running away from the perceived danger. It is dangerous for both riders and horses when a horse suddenly startles. Sometimes horses do this in familiar environments because familiar objects may look different when rotated. The purpose of this study was to determine whether horses that had been habituated to a complex object (children’s playset) would react to the object as novel when rotated 90 degrees. Twenty young horses were led past the playset 15 times by a handler. Next, the rotated group was led past the rotated playset 15 times. Each time the horse was led by the object was counted as a pass. An increasing reactivity scale was used to quantify behavioral responses. Being aware of potential reactions to changes in the orientation of previously familiar objects can help keep the handler safer. Abstract: It is dangerous for both riders and horses when a horse suddenly startles. Sometimes horses do this in familiar environments because familiar objects may look different when rotated. The Citation: Corgan, M.E.; Grandin, T.; purpose of this study was to determine whether horses that had been habituated to a complex object Matlock, S. Evaluating the Reaction to (children’s playset) would react to the object as novel when rotated 90 degrees. Twenty young horses a Complex Rotated Object in the were led past the playset 15 times by a handler. Next, the rotated group was led past the rotated American Quarter Horse (Equus caballus). Animals 2021, 11, 1383. playset 15 times. Each time the horse was led by the object was a pass. The behavioral responses https://doi.org/10.3390/ani11051383 observed and analyzed were ears focused on the object, nostril flares, neck raising, snort, avoid by stopping, avoid by moving feet sideways, and avoid by flight. An increasing reactivity scale was Academic Editor: Barbara Padalino used to quantify behavioral responses. A two-sample t-test was performed on the reactivity scores comparing the first pass by the novel object to the first pass by the rotated object. The horses in the Received: 28 March 2021 rotated group reacted to the rotated orientation similarly to the first exposure (p = 0.001, α < 0.05). Accepted: 11 May 2021 Being aware of potential reactions to changes in previously familiar environments can help keep the Published: 13 May 2021 handler safer. Publisher’s Note: MDPI stays neutral Keywords: horse; safety; training; behavior; novel object; habituation with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction Spooking was associated with 27% of horse accidents . Researchers have described “spooking” as “horse reacted in fear of something, unseating the rider” . Another study Copyright: © 2021 by the authors. showed that injuries to riders were more likely to occur “when the horse behaved in an Licensee MDPI, Basel, Switzerland. unexpected manner” . Some of the more severe injuries occur when a rider falls of a This article is an open access article horse. Data collected from hospital emergency rooms indicated that falling off a horse distributed under the terms and resulted in more injuries than injuries that occurred when the rider was not mounted . conditions of the Creative Commons Attribution (CC BY) license (https:// Another study showed that “danger to the rider increases as the horse’s speed increases” . creativecommons.org/licenses/by/ When riders fall of a horse, their head is more likely to be injured compared to other parts 4.0/). of the body . Riders have reported that sometimes they do not know what caused their Animals 2021, 11, 1383. https://doi.org/10.3390/ani11051383 https://www.mdpi.com/journal/animals
Animals 2021, 11, 1383 2 of 9 horse to spook. Experienced horse trainers know that it is important to habituate young horses to new things in their environment. One study showed that gradually desensitizing horses to stimuli such as a moving white nylon bag had fewer flight responses than horses where it was suddenly introduced . Several studies have also indicated that a sudden stimuli such as an umbrella that opens suddenly can startle a horse [7–11]. A sudden novel stimulus such as a waving flag or a bell will raise a horse’s heart rate . Researchers have also reported the intensity of a horse’s reaction was influenced by horse genetics . Sudden novel stimuli will startle many different species of animals . The dangerous and usually unexpected “spook” reaction is likely to be a startle response. A review of the horse behavior literature showed that there are different ways that horses are introduced to new objects. They consist of voluntary approach in an open field, led towards the object, or ridden toward the object [15–17]. Open field tests are usually conducted in an arena. In these experiments a free moving horse is allowed to voluntarily approach novel objects . In many of these studies the horse learns to associate a particular novel object with a food reward [18,19]. These studies are extremely useful for the study of horse cognition and learning. However they do not provide information on the conditions that may cause a dangerous “spook” reaction that could seriously injure a rider. One study showed that horses that were more willing to investigate a novel object were able to learn more quickly . There may be differences in a horses reaction to a novel object when the way it is presented is changed. Research has shown that a horses reaction to a novel object is different during a voluntary approach compared to being led or ridden . The authors found that when including a rider in temperament tests and performance tests, results were more reliable and repeatable. When positive reinforcement such as food is used, horses are able to choose the correct object and be presented with a reward. This type of learning and test does not often include a handler and is referred to as discrimination . The purpose of this research was to conduct a study to identify a possible situation where a large complex novel object may have the potential to cause a serious horse accident. The object we chose was a child’s colored plastic playset with a small slide and swing. It is a large object and large objects may be more frightening stimulus compared to smaller objects . The playset is an object that a horse could possibly see during riding near residences. It is known that horses can learn to discriminate between different colors and shapes [18,22]. In our experiment, no attempt was made to control for color or shape, but a playset was chosen that had approximately the same dimensions when it was rotated. The purpose of this preliminary study was to determine if a habituated horse may react differently when the playset was rotated. Both its shape and color would change. A non-voluntary approach was used. All horses were led at a walk for both habituation and the test after the playset was rotated. For safety reasons, we conducted all experiments at a walk and measured behavioral reactions used by Leiner and Fendt . Their study may provide insights into a situation that might trigger dangerous “spooking”. If the rotated playset is associated with increased mild behavioral reactions when a horse is being led towards it, there is the possibility that it might trigger a more dangerous sudden reaction if a horse and rider was trotting towards it. A high speed study would be too dangerous and would be unethical. This study may help identify one cause of spooking when a rider is not able to identify an obvious possible trigger. It will also provide a starting point for further studies into horse perception. 2. Materials and Methods The sample population consisted of twenty-two 2 and 3-year-old American Quarter Horse horses (15 fillies and seven gelded colts) in a university horse training program. The horses had 4 months of handling training at the time of this study, all trained at the same place. The horses were taught using methods of pressure and release training to halter, lead, lunge, and acclimate to being groomed and handled. Of the twenty-two horses, one posed a safety concern for the research handlers by its continued attempt to pull away and
Animals 2021, 11, x 3 of 10 Animals 2021, 11, x 3 of 10 Animals 2021, 11, 1383 3 of 9 halter, lead, lunge, and acclimate to being groomed and handled. Of the twenty-two horses, one posed a safety concern for the research handlers by its continued attempt to halter, lead, lunge, and acclimate to being groomed and handled. Of the twenty-two pull away and was excluded from the study. Another horse was removed from the study horses, was one posed excluded a safety from concern theissues. study. for thehorse Another researchwas handlers removed by fromits continued the attempt 4to on pull day away 4 for and soundness was excluded Twenty from the horses study. continued Another horse through was thestudy removed entire from on day (n study the study for = 20). soundness All horses issues. were Twenty housed at horses the continued Colorado Statethrough the University entire Equine study (n = Teaching 20). All and horses Research onwere day housed 4 for soundness issues. Twenty at the Colorado State horses continued University Equine throughand the Research entire study (n = (CSU 20). Center All horses(CSUwere ETRC) housed in at outdoor the pens Colorado with State libitumTeaching adUniversity water Equine and access to Teaching and Center shelter. ResearchHorses ETRC) in outdoor pens with ad libitum water and access to shelter. Horses were fed a mix were fed Center a mix (CSU of grass and alfalfa hay once per day on a feed bunk. of grass andETRC) alfalfainhayoutdoor once perpensdaywith on aad libitum feed bunk.water and access to shelter. Horses were fedThe test a mix environment was an alley (4.57 meters wide) feedinbunk. an indoor horse barn in front The test of grass and alfalfa environment was an hayalley once(4.57 per day on awide) meters in an indoor horse barn in offront empty The stalls oftest empty with environment the doors stalls withwasthean closed. The alleyclosed. doors barn (4.57 meters had wide) The barn concrete in an had flooring indoor concrete horse and flooring barn electric lights andinelectric front above of empty lights the abovealleyway. stalls with the Thedoors the alleyway. horses were The Theclosed. horses led were in barnthrough led had in the entrance, concrete through theflooring walked entrance, and down electric walked the the lights down alley- way, above past the the novel alleyway. object The and horses led were out led inof the through testthearea through entrance, the walked alleyway, past the novel object and led out of the test area through the exit (Figure 1). Two exit down (Figure the 1). alley- Two Hero way, Hero 55video pastvideo cameras the novel cameras (GoPro, object and led (GoPro, Sanout San Mateo, of the Mateo, CA, CA, testUSA) were areawere USA) through placed placed in thethe theinexit test (Figure test environment 1). Two environment Hero for 5 video forlater later cameras of observation observation (GoPro, San Mateo, of behavioral behavioral CA, USA) were placed in the test environment responses. responses. for later observation of behavioral responses. Figure Figure Figure 1.1.1. TheThe The test test test areaconsisted area consisted consisted ofofGoPros of GoPros GoPros ( (( ) and) the novel andthe ) and the object novel novel placed object object during placed placed habituation during during to the habituation habituation novel theobject to novel to the novel and object object and and rotation rotation rotation days. days. days. Thenovel The The novelobject novel objectwas object wasa aachildren’s was children’s children’s plastic plastic plasticplayset playset playset (Little (Little Tikes Tikes (Little Hide Hide Tikes and and Hide Seek Seek and Climber Climber Seek Climber and and Swing-Brown Swing-Brown and and Tan) Tan) (Table (Table 1). 1). The The object object was was 134.62 134.62 l l × and Swing-Brown and Tan) (Table 1). The object was 134.62 l × 132.08 w × 104.14 × 132.08 132.08 ww× × 104.14 104.14 hh cm. cm.h cm. This This object was used because, in both orientations, its outer dimensions are similar. The This object objectwas wasused usedbecause, because,ininbothboth orientations, orientations,its its outer dimensions outer dimensionsare similar. The The are similar. playset hada adifferent playset different shapewhen whenrotated rotatedninety ninetydegrees. degrees.RopeRopehalters halterswith with2 2mmlead lead playset had had a differentshape shape when rotated ninety degrees. Rope halters with 2 m lead ropes ropes were used to lead the young horses past the playset. ropeswere wereused usedtotolead leadthe theyoung young horses horses past thethe past playset. playset. On day 1–3 of the study (habituation to the test area) (Table 1), the horses were led through the test area five passes each day without the novel object to habituate the horses to the test area. Each time a horse was led past the object was counted as a pass. The horses were given 15 total passes through the test area based on Christensen et al. . The authors found that horses needed 4–13 exposures before meeting habituation criterion. On day 4, the novel object was placed in the test area in the original position. Days 4–6 of the study (habituation to the novel object) consisted of the same procedure for the first three days with the novel object in its original position (Table 1). Each horse passed the original position of the object fifteen times over three days. To assess the effect of object rotation on the horses’ behavior, the horses were random- ized into a control group and a rotated group. On days 7–9 (test days), the control group had five passes each day through the test area, with the novel object in the original position (Table 1). The control group passed the original position of the object fifteen times over the three days. The rotated group was led through the test environment for five passes each day with the novel object rotated 90 degrees clockwise (Table 1). The rotated group passed the rotated position of the object fifteen times over the three days.
Table 1. TestingTable Procedure: 1. Testing Outline Procedure: of testing Outline procedure of testing to provide procedure details to provide of the Control detailsand of the Ro-Control and Ro- nimals 2021, 11, x tated group procedures. tated group procedures. 4 of 10 Control and Rotated Controlgroups and Rotated groups Animals 2021, 11, 1383 Habituation to test Habituation area to test area 5 passes each day 5 passes each day 4 of 9 DaysTable 1–3 1. Testing Days 1–3 Procedure: Outline of testing procedure to provide details of the Control and Ro- (novel object absent) (novel object absent) 15 total passes 15 total passes tated group procedures. test area (Figuretest1) without area (Figure novel1)object without novel object ControlControl and Rotated Controlgroups and Rotated and Rotated groups groups Table 1. Testing Procedure: Outline ofHabituation testing procedure to provide details to test area of 5the 5 passes eachControl day passes 5each and dayRotated passes each daygroup procedures. Days 1–3 (novel object absent) 15 total 15passes total 15 total passes passes Control and Rotated groups test area (Figure test test 1) with area area novel (Figure (Figure 1) object 1) with withoutin novel original novelobject object in original Habituation to test area 5 passes eachposition day Days 1–3 position Control and Rotated groups (novel object absent) 15 total passes 5 passes each day test area (Figure 1) without novel object Habituation to the Habituation novel to the novel Control15and total passes Rotated groupsin original Days 4–6 Days 4–6 test area (Figure 1) with novel object object object position 5 passes each day 15 total passes test area (Figure 1) with novel object in original position Habituation to the novel Days 4–6 Days 4–6 Habituation to the novel object object Days 7–9 Days 7–9Test days Test daysControl group Control group Rotated group Rotated group 5 passes each day 5 passes each day each day 5 passes 5 passes each day test area (Figuretest 1) with area (Figure test area1)(Figure with test 1) with area (Figure 1) with Days 7–9 Test days Control object group in originalobject posi-in original object inposi- rotatedobjectRotated posi- group in rotated posi- Days 7–9 Test days 5 passes each tion day Control group tion tion 5 passes Rotated group each tion day test area (Figure5 1) with each passes objectday in 5test area each passes (Figure day1) with object in original position rotated test area (Figure 1) with test area (Figure 1) with position object in original posi- object in rotated posi- tion tion Two handlers were used and both led the horses at a slow walk. Each handler had On day 1–3 an ofOn the day equal study1–3(habituation number of the studyto(habituation of horses the test area) randomly to (Table assignedthe test 1),area) from the both horses (Table 1), were the control theled horses and were group. rotated led through the test through area Eachfive thepasses horse test was areaeach ledfive atday apasses without walk eachthe through day novel thewithout testobject areathetobynovel habituateobjectthe the same to horses habituate handler for thethe horses entire study. to the test area.toEach the test time area. a horse Each was time leda horse past thewas object led past was the counted object The handlers wore the same clothes every day (black overalls, jacket, hat and black boots). aswas a pass. countedThe horses as a pass. The horses were given 15were total The given passes handlers15through total were passes the test instructedthrough area tobased the test walk onarea the Christensen horse based with on a etChristensen leadal. rope . through Theetau-al. the . The au- center of the thors foundOn thatday thors horses1–3 found of the needed that study horses 4–13 (habituation exposures needed 4–13 to before the exposures test meeting area) before (Table habituation alley (1 m away from the object), and move with the horse, only stopping or turning when meeting 1), the horses criterion. habituation were led criterion. Onthrough day 4, thethethe test On novel area day horse 4,five object stopped passes thewas novel each orplaced object turned day in thewithout was towards test placed area the the in novel inthe object.thetest object Iforiginal thearea to habituate inposition. horse the original stopped, the Days the horses position. handlerDays waited to the 4–6 of the study test area. 4–6(habituation 3ofsecondsEach the study time a horse to(habituation before thegently was novelencouragingled object) past to theconsisted the novelthe object object) of the horse was counted consisted same procedure forward as of the by a pass. same walking The forforward horses procedure the andforslightly the were first three daysgiven first with 15the three pulling totalonpasses days novelthe with leadthrough object therope. its the innovel To test area original object facilitate in position itsbased original on Christensen (Table habituation, position 1). if aEach (Table horse et horse al. 1).. passed stopped Each The when au- horse passed it was either thorsposition the original found that theapproaching original horses of the position objectorneeded fifteen of the passing 4–13 times exposures object the over novel fifteenthree object, before times days. it was meeting over threehabituation allowed to stop for criterion. days. a period of 3 seconds. If To assessOn the daytheTo4,horse effect theofnovel assess object did thenotobject stop,was effect rotationofthe placed object on the handler incontinued rotation the on horses' test area behavior, the inthe tohorses' lead the original it behavior, horses past thewereposition. theran- novel horses object.Days were ran- domized 4–6into of the study domized a control (habituation into group a control and ato the rotated group novel and group. object) a rotated On consisted days group. 7–9 The horses’ behavioral responses to the object exposure was analyzed based of (test On thedayssame days), 7–9 procedure the(test control days),for the the control on the first three group had fivegroup days passes video had with eachfive the day recordings. novel passes through One object each the in daytest observer its through original area, recorded with the eightposition test the area, novel (Table with different object 1). Each theinnovel horse the original behavioral object signs inpassed the original during each pass positionthe original (Table position 1).on position The eachcontrol (Table day. of1). the group The Theobject control passed behavioralfifteen the group times original over passed responses three position the recorded days. original ofwere theposition object fifteen of thetimes ears focused object on thefifteen object,times nostril over the three Toover assess days. flares, the theThe neckeffect threerotated of group days. raising, object The snorting,rotation rotated was avoid on ledgroup the through stop, was horses' the avoid ledtestbehavior, through side, environment avoid thethetest back, horses for were flight environment and five avoid ran-for(Table five 2). passes domized each day into passes with athe Behavioral eachcontrol novel day group responses with object theand were rotated novel a adapted rotated object 90 degrees group. fromclockwise rotated On . days(Table 90 degrees 7–9 (test clockwise days), 1). The the 1). (Table rotated control The rotated group had group passed group five the rotated Apasses passedreaction each position the day scale rotated of thethrough was created position object the fifteentesttimes offrom the area, the object with behaviors over fifteenthetimes the novelover observed three object days. theain on the from scale three original days.0–3 (Table 3). position Two handlers(Table ThisTwo were 1).handlers The control reaction used scale andwere group was both led passed adapted used the from andhorses theChristensen both original led at athe slow position horses et al. walk. of  at Each the a slow object walk.fifteen tohandler evaluate times reactivity Each had handler based had on over an equal number the three an behaviors equal days. of horsesnumber The observed randomly rotated of horses group inassigned this study. randomly was from The led assigned both through reactivity thefromcontrolthe scores both test and environment increase therotated with control for a bigger group. and five rotated response group. to passes Each horse was each Each ledtheday at horse with object, a walkwas the lednovel score through 3 showing at a theobject walk test rotated the through area biggest bythe 90test the degrees response. same area clockwise handler by the forsame the(Table entire1).study. handler The for therotated entire study. group passed the rotated position of the object fifteen times over the three days. Two handlers were used and both led the horses at a slow walk. Each handler had an equal number of horses randomly assigned from both the control and rotated group. Each horse was led at a walk through the test area by the same handler for the entire study.
Animals 2021, 11, 1383 5 of 9 Table 2. Behavioral responses and definitions used for behavioral analysis. Definitions of Behavioral Responses Behavioral Responses Definition ears focused on the object ears are pointed toward the novel object nostril flares nostrils overly expanded (nose elongation) neck raising neck raised above normal headset and/or neck muscles tense snorting “short powerful exhale”  avoid stop avoiding the object by stopping, feet stop moving avoid side avoiding the object by evasive steps to the side, away from the object avoid back avoiding the object by evasive steps backwards, backing up avoid flight avoiding the object by jumping away in a sudden movement, feet moving faster a walk Table 3. Reaction Scale used to quantify behavioral responses (adapted from Christensen et al. ). Score 0–3 Behavioral Responses Observed 0 No behavioral signs observed 1 Ears focused, nostril flares, and/or neck raising 2 Snorting and/or avoid stop 3 Avoid side, avoid back, avoid flight To assess whether the horses’ behavior was affected by the object rotation we compared difference in the reaction score per individual horse using a two-sample t-test (α < 0.05) (R with R Studio, PBC, Boston, MA, USA). Christensen et al. and Tidyverse (www.tidyverse. org, accessed on 28 March 2021) was used for the figures [15,24,25]. This test was done for each pass 1–15 comparing the corresponding passes from the original position to the rotated position. Animals 2021, 11, x 3. Results 6o The control and rotated group showed significant differences between the change in reaction score from the first pass by the novel object to the first pass on the Test days (t-test p-value = 0.001) (Figure reacted 2). Horses similarly on the that first reacted pass by to thethe novel position rotated object inof the theRotated group, object as they did on reacted similarly on the first pass by the initial pass by the novel object. rotated position of the object as they did on the initial pass by the novel object. Figure 2. Boxplot of differences in Reaction Score for pass 1 by the novel object to pass 1 by the Figure 2. Boxplot of differences in Reaction Score for pass 1 by the novel object to pass 1 by the rotated object. The Control rotated object. The Control group mean (bold line) showed a decrease in reaction. The Rotated group group mean (bold line) showed a decrease in reaction. The Rotated group mean showed no change in reaction. There was mean showed no change in reaction. There was a significant difference between the means of the a significant difference between the means of the two groups. two groups. Passes 1–4 after rotation in the rotated group showed a significant difference betwe the two groups change in reaction (p-values = 0.001, 0.010, 0.004, 0.001). After pass 4 the rotated object, there was little significant difference between the rotated and cont groups (p-values > 0.05). As noted in Table 4, some later passes also showed signific differences in the change in reaction between the two groups (Passes 1–4, 8, 9, 12: p-va
Animals 2021, 11, 1383 6 of 9 Passes 1–4 after rotation in the rotated group showed a significant difference between the two groups change in reaction (p-values = 0.001, 0.010, 0.004, 0.001). After pass 4 by the rotated object, there was little significant difference between the rotated and control groups (p-values > 0.05). As noted in Table 4, some later passes also showed significant differences in the change in reaction between the two groups (Passes 1–4, 8, 9, 12: p-value > 0.05). Figures 2 and 3 show the significance in the change in reactions for the rotated group when the horses were exposed to the rotated object. Table 4. Values for differences in reaction score for corresponding passes 1–15 by the novel object to rotated object. Control Rotated Pass # Mean Min. Max. Mean Min. Max. p-Value 1 −1.75 −3 0 0.083 −2 2 0.001 2 −0.875 −2 0 0.25 −1 2 0.010 3 −0.875 −2 0 0.167 −1 1 0.004 4 −1 −2 0 0.333 −1 1 0.001 5 −0.375 −2 1 -0.083 −2 0 0.312 6 −0.375 −1 0 -0.25 −1 1 0.719 7 −0.5 −2 0 0.167 −1 1 0.062 8 −1 −2 0 0.333 −1 2 0.005 9 −0.875 −2 0 0.583 −2 2 0.002 10 −0.125 −1 1 0.167 −1 2 0.537 11 0 0 0 0.167 −2 2 0.656 12 0.125 −1 1 -0.333 −1 0 0.010 13 −0.125 −1 1 0.333 −2 1 0.226 Animals 2021, 11, x 7o 14 −0.25 −1 2 0.083 −2 2 0.554 15 0 −1 1 -0.167 −2 2 0.700 Figure 3. Graph of reaction scores from pass 1–30 for the control and rotated groups. The colored Figure 3. Graph of reaction scores from pass 1–30 for the control and rotated groups. The colored triangles indicate indi- triangles indicate individual horses’ reactivity scores. The colored lines depict mean reaction score by vidual horses’ reactivity scores. The colored lines depict mean reaction score by group over passes (control = red, rotated = blue). group over passes (control = red, rotated = blue). 4. Discussion 4. Discussion When a previously familiar complex novel object is rotated, the rotated object may When ato cause reactions similar previously the initialfamiliar exposurecomplex to the novel novel object object.is This rotated, the rotated confirms what object m handlers and riders have described anecdotally. Understanding horses’ reaction to a what h cause reactions similar to the initial exposure to the novel object. This confirms dlers and riders have described anecdotally. Understanding horses’ reaction to a rota object is important for the safety of riders and handlers. If handlers expect horses no react to subtle changes in a familiar environment, they are less prepared for a horse spo ing which could lead to an accident. Additionally, studies have shown that investigat behavior is correlated with learning . Allowing a horse to investigate and become
Animals 2021, 11, 1383 7 of 9 rotated object is important for the safety of riders and handlers. If handlers expect horses not to react to subtle changes in a familiar environment, they are less prepared for a horse spooking which could lead to an accident. Additionally, studies have shown that investigative behavior is correlated with learning . Allowing a horse to investigate and become familiar with all orientations of an object can help to avoid spooking. Future studies are needed to evaluate if allowing a horse to fully investigate a novel object will help with habituation and decrease spooking. As shown in Figure 3, there was a decline in the horses’ reactions with each successive pass by the rotated object. Table 4 shows the significant decrease in the horses’ reaction to the object with each successive pass, for the first four passes. After pass 4, the changes in reactions between the rotated and non-rotated groups seem to be less consistent. This inconsistency in changes in reactions between the two groups shows the unpredictable nature of the horse . Even subtle changes to a familiar object can cause horses to react again. These subtle changes can cause the horse to need more exposure until they are habituated or until no reactions are shown again. Handlers need to be aware of this for safety of themselves and the horses. This study shows that despite findings from previous research , horses may not recognize different orientations of previously familiar objects, when being led by a handler. While assumptions cannot be made about the horse’s recognition of the rotated object from the present study, there is an obvious reaction to the rotated object. This reaction is important to note and important for anyone handling horses to be aware of. There are possible differences in personality and reactivity by breed . The traits that showed the most variability between breeds were excitability and anxiousness . This is thought to be because of the purpose each breed has been bred for over time. For example, Thoroughbreds tend to show a bigger flight response because they are bred to race and are expected to leave the gate quickly . Age has also been shown to have an effect on reactivity. In a study comparing horses ranging in age from two months to two years, younger horses were more reactive . Training methodologies are worth further exploration when researching equine percep- tion of novel objects. Humans can have an impact on how the horse reacts and behaves . There may be a difference between a voluntary approach, as compared to being led by a handler. Marsboll and Christensen  and Hartmann et al.  found that a familiar handler can have a calming effect on the horses response to a novel object as well as a change in fear response. The present study used unknown handlers to evaluate how horses will react to a rotated object with a handler. Christensen et al.  showed that fearfulness was not correlated with learning, whereas investigative behavior was correlated with learning. While their study did not use handlers, the present study allowed some investigative behavior and kept the handler involved, creating a more practical scenario. The present study did not use food or positive reinforcement when evaluating recognition or reactivity, as compared to . Using food as a reinforcement in training is similar to using latency to eat in research. It is important to note, that most trainers do not use food as reinforcement in their training. The purpose of this study was to evaluate how horses being led and habituated to a previously familiar complex object would react after it was rotated ninety degrees. This study showed that horses’ reaction to a rotated orientation of a familiar complex object was similar to its reaction when it first saw it. 5. Conclusions Horses may have a greater reaction to new orientations of previously familiar objects. This may cause accidents that lead to injury of the horse or handler. If handlers and riders can be prepared for how a horse may react, they may be able to help reduce risk by adjusting training methods to allow for investigation of all sides of an object. Additionally, while horses show a decrease in reactions to novel objects and novel orientations of familiar objects, there is the possibility for reactions during habituation. Further research needs to
Animals 2021, 11, 1383 8 of 9 be conducted to evaluate how different methods of handling and training affect the horses’ reaction to changes in their environment. Author Contributions: Conceptualization, M.E.C., T.G., and S.M.; methodology, M.E.C. and T.G.; formal analysis, M.E.C.; investigation, M.E.C. and S.M.; resources, M.E.C. and T.G.; data curation, M.E.C.; writing—original draft preparation, M.E.C.; writing—review and editing, M.E.C., T.G., and S.M.; visualization, M.E.C., T.G., and S.M.; project administration, M.E.C.; funding acquisition, T.G. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by Grandin Livestock Handling Systems, Inc., Fort Collins, CO 80523, USA. Institutional Review Board Statement: This study received ethical approved by the Colorado State University Animal Care and Use Committee [IACUC #: 1349]. Informed Consent Statement: No applicable because no human subjects were involved. Data Availability Statement: The data presented in this study are openly available in FigShare at [10.6084/m9.figshare.14256512.v1]. Acknowledgments: The authors would like to thank John Snyder and the Legends of Ranching Program for use of the horses in the study and the Equine Teaching and Research Center for use of the facility. The authors would also like to thank Ben Sharp for assistance in statistical analysis. Conflicts of Interest: The authors declare no conflict of interest. References 1. Camargo, F.; Gombeski, W.R.; Barger, P.; Jehlik, C.; Wiemers, H.; Mead, J.; Lawyer, A.; Gonzalez-Redondo, P. Horse-related injuries: Causes, preventability, and where educational efforts should be focused. Cogent Food Ag. 2018, 4, 14322168. [CrossRef] 2. Meredith, L.; Ekman, R.; Brolin, K. Epidemiology of Equestrian Accidents: A Literature Review. Internet J. Allied Health Sci. Pract. 2018, 17, 9. 3. Acton, A.S.; Gaw, C.E.; Chounthirath, T.; Smith, G.A. Nonfatal horse-related injuries treated in emergency departments in the United States, 1990–2017. Am. J. Emerg. Med. 2020, 38, 1062–1068. [CrossRef] [PubMed] 4. Hawson, L.A.; McLean, A.N.; McGreevy, P.D. The roles of equine ethology and applied learning theory in horse related human injuries. J. Vet. Behav. 2010, 5, 324–338. [CrossRef] 5. Krüger, L.; Hohberg, M.; Lehmann, W.; Dresing, K. Assesing the risk for major injuries in equestrian sports. BMJ Open Sport Exerc. Med. 2010, 4, 1–9. [CrossRef] 6. Christensen, J.W.; Rundgren, M.; Olsson, K. Training methods for horses: Habituation to a frightening stimulus. Eq. Vet. J. 2010, 38, 439–443. [CrossRef] 7. Leiner, L.; Fendt, M. Behavioural fear and heart rate responses of horses after exposure to novel objects: Effects of habituation. Appl. Anim. Behav. Sci. 2011, 131, 104–109. [CrossRef] 8. Dai, F.; Heinzl, N.H.C.E.U.I.; Costa, E.D.; Canali, E.; Minero, M. Validation of a fear test in sport horses using infrared thermogra- phy. J. Vet. Behav. 2015, 10, 128–138. [CrossRef] 9. Górecka-Bruzda, A.; Jastrzebska, E.; Sosnowska, Z.; Jaworksi, Z.; Jezierski, T.; Chruszczewski, M.H. Reactivity to humans and fearfulness tests: Field validation in Polish Cold Blood Horses. Appl. Anim. Behav. Sci. 2011, 133, 207–215. [CrossRef] 10. Scopa, C.; Palagi, E.; Sighieri, C.; Baragli, P. Physiological outcomes of calming behaviors support the resilience hypothesis in horses. Sci. Rep. 2018, 8, 1–9. [CrossRef] 11. Lansade, L.; Bouissou, M.F.; Erhard, H.W. Fearfulness in horses: A temerament trait stable across time and situation. Appl. Anim. Behav. Sci. 2008, 115, 182–200. [CrossRef] 12. Noble, G.K.; Blackshaw, K.L.; Cowling, A.; Harris, P.A.; Sillence, M.N. An objective measure of reactive behavior in horses. Appl. Anim. Behav. Sci. 2013, 144, 121–129. [CrossRef] 13. Borstel, U.K.v.; Duncan, I.J.H.; Lundin, M.C.; Keeling, L.J. Fear reactions in trained and untrained horses from dressage and show-jumping breeding lines. Appl. Anim. Behav. Sci. 2010, 125, 124–131. [CrossRef] 14. King, T.; Hemsworth, P.H.; Coleman, G.J. Fear of novel and startling stimuli in domestic dogs. Appl. Anim. Behav. Sci. 2003, 82, 45–64. [CrossRef] 15. Christensen, J.W.; Malmkvist, J.; Nielsen, B.L.; Keeling, L.J. Effects of a calm companion on fear reactions in naive test horses. Equine Vet. J. 2008, 40, 46–50. [CrossRef] 16. Visser, E.K.; van Reenen, C.G.; van der Werf, J.T.; Schilder, M.B.H.; Knaap, J.H.; Barneveld, A.; Blokuis, H.J. Heart rate and heart rate variability during a novel object test and a handling test in young horses. Physio. Behav. 2002, 76, 289–296. [CrossRef] 17. Borstel, U.K.v.; Pirsich, W.; Gauly, M.; Bruns, E. Repeatability and reliability of scores from ridden temperament tests conducted during performance tests. Appl. Anim. Behav. Sci. 2012, 139, 251–263. [CrossRef]
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