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Scopa, C., Greco, A., Contalbrigo, L., Fratini, E., Lanatà, A., Scilingo, E. P., et al. (2020). Inside the Interaction: Contact With Familiar Humans Modulates Heart Rate Variability in Horses. Frontiers in Veterinary Science, 7, 998.
Abstract: A human-animal relationship can be developed through subsequent interactions, affected by the positive or negative emotional valence of the proceeding one. Horses implement a process of categorization to classify humans with whom they interact as positive, negative, or neutral stimuli by evaluating the kind of approach and the nature of the contact. In these terms, human-animal interactions are emotionally charged events, eliciting specific emotional states in both subjects involved. Although the human-horse relationship has been mainly investigated through behavioral analysis, physiological indicators are needed for a more objective assessment of the emotional responses. Heart rate variability (HRV) is a commonly used autonomic nervous system (ANS) correlate estimating the sympathovagal balance as a psychophysiological marker of emotion regulation in horses. We have assumed that long-term positive relationships with humans may have a positive and immediate impact on the emotional arousal of the horse, detectable, via ANS activity, during the interaction. We analyzed horses' heartbeat dynamics during their interaction with either familiar or unfamiliar handlers, applying a standardized experimental protocol consisting of three different conditions shifting from the absence of interaction to physical contact. The ANS signals were monitored through an innovative non-invasive wearable system, not interfering with the unconscious emotional response of the animal. We demonstrated that horses appeared to feel more relaxed while physically interacting (e.g., grooming on the right side) with some familiar handlers compared to the same task performed by someone unfamiliar. The shift of the sympathovagal balance toward a vagal predominance suggests that the horses experienced a decrease in stress response as a function not only of the handler's familiarity but also of the type of interaction they are experiencing. These results constitute the objective evidence of horses' capacity to individually recognize a familiar person, adding the crucial role of familiarity with the handler as a paramount component of human-animal interaction. Our rigorous methodological approach may provide a significant contribution to various fields such as animal welfare while further investigating the emotional side of the human-animal relationships.
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Schwenk, B. K., Fürst, A. E., & Bischhofberger, A. S. (2016). Traffic accident-related injuries in horses. Equine Med., 32(3), 192–199.
Abstract: Horses involved in road traffic accidents (RTAs) are commonly presented to veterinarians with varying types of injuries. The aim
of this study was describe the pattern and severity of traffic accident-related injuries in horses in a single hospital population. Medical
records of horses either hit by a motorized vehicle or involved in RTAs whilst being transported from 1993 to 2015 were retrospectively
reviewed and the following data was extracted: Signalement, hospitalisation time, month in which the accident happened, cause of the
accident, place of the accident and type of vehicle hitting the horse. Further the different body sites injured (head, neck, breast, fore limb,
abdomen, back and spine, pelvis and ileosacral region, hind limb, tail and genital region), the type of injury (wounds, musculoskeletal
lesions and internal lesions) and the presence of neurological signs were retrieved from the medical records. 34 horses hit by motorized
vehicles and 13 horses involved in RTAs whilst being transported were included in the study. Most of the accidents where horses were hit
by motorized vehicles occurred during December (14.7%) and October (14.7%), horses were most commonly hit by cars (85.3%) and the
majority of accidents occurred on main roads (26.5%). In 29.4% of the cases, horses had escaped from their paddock and then collided
with a motorized vehicle. Most of the accidents with horses involved in RTAs whilst being transported occurred during April (30.8%) and
June (23.1%). In 76.9% of the cases the accident happened on a freeway. In the horses hit by motorized vehicles the proximal hind limbs
were the body site most commonly affected (44.1%), followed by the proximal front limbs (38.2%) and the head (32.4%). When horses
were involved in RTAs whilst being transported the proximal fore limbs (61.5%), the proximal hind limbs (53.8%) and the distal hind limbs,
back and head (38.5% each) were the most common injured body sites. Wounds were the most common type of injury in both groups
(85.3% hit by motorized vehicle, 76.9% transported ones). In horses hit by a motorized vehicle 35.3% suffered from fractures, in 20.6%
a synovial structure was involved and in 5.9% a tendon lesion was present. 14.7% suffered from internal lesions and 14.7% showed neurologic
symptoms (40% peripheral, 60% central neurologic deficits). On the other hand, in horses involved in a RTA whilst being transported
30.8% suffered from fractures. There were no synovial structures injured and no tendon injuries were present. Furthermore there were
no internal lesions present and only one horse involved in a RTA showed central neurologic symptoms. Injuries of horses being hit by a
motorized vehicle were more severe than when horses were protected by a trailer and involved in a RTA whilst being transported. The study
has been able to identify the different injury types of traffic accident-related injuries in horses. Awareness of the nature of these injuries is
important, to avoid underestimation of their severity.
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Schwarz, S., Marr, I., Farmer, K., Graf, K., Stefanski, V., & Krueger, K. (2022). Does Carrying a Rider Change Motor and Sensory Laterality in Horses? Animals, 12(8), 992.
Abstract: Laterality in horses has been studied in recent decades. Although most horses are kept for riding purposes, there has been almost no research on how laterality may be affected by carrying a rider. In this study, 23 horses were tested for lateral preferences, both with and without a rider, in three different experiments. The rider gave minimal aids and rode on a long rein to allow the horse free choice. Firstly, motor laterality was assessed by observing forelimb preference when stepping over a pole. Secondly, sensory laterality was assessed by observing perceptual side preferences when the horse was confronted with (a) an unfamiliar person or (b) a novel object. After applying a generalised linear model, this preliminary study found that a rider increased the strength of motor laterality (p = 0.01) but did not affect sensory laterality (p = 0.8). This suggests that carrying a rider who is as passive as possible does not have an adverse effect on a horse�s stress levels and mental state.
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Schwartz, L. P., Silberberg, A., Casey, A. H., Kearns, D. N., & Slotnick, B. (2017). Does a rat release a soaked conspecific due to empathy? Anim. Cogn., 20(2), 299–308.
Abstract: In Experiment 1, rats choosing in an E maze preferred to release a rat standing in a pool of water to dry ground over a rat already standing on dry ground. Five additional experiments showed that the choosing rat's preference for releasing the wet rat was maintained by two separable outcomes: (1) the social contact offered by the released rat and (2) the reinforcing value of proximity to a pool of water. These results call into question Sato et al.'s (Anim Cogn 18:1039-1047, 2015) claim to have demonstrated that a rat's releasing of a wet rat to dry ground is empathically motivated.
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Schuetz, A., Farmer, K., & Krueger, K. (2017). Social learning across species: horses (Equus caballus) learn from humans by observation. Anim. Cogn., 20(3), 567–573.
Abstract: This study examines whether horses can learn by observing humans, given that they identify individual humans and orientate on the focus of human attention. We tested 24 horses aged between 3 and 12. Twelve horses were tested on whether they would learn to open a feeding apparatus by observing a familiar person. The other 12 were controls and received exactly the same experimental procedure, but without a demonstration of how to operate the apparatus. More horses from the group with demonstration (8/12) reached the learning criterion of opening the feeder twenty times consecutively than horses from the control group (2/12), and younger horses seemed to reach the criterion more quickly. Horses not reaching the learning criteria approached the human experimenters more often than those that did. The results demonstrate that horses learn socially across species, in this case from humans.
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Schneider, G., & Krueger, K. (2012). Third-party interventions keep social partners from exchanging affiliative interactions with others. Anim. Behav., 83(2), 377–387.
Abstract: Third-party interventions are defined as the interruption of dyadic interactions by third animals through direct physical contact, interposing or threats. Previous studies focused on the analysis of interventions against agonistic encounters. However, there have been no evaluations of interventions against affiliative behaviours, particularly in relation to the intervening animal�s social relationships and its social and spatial position. Horses, Equus caballus, are an interesting model species, as interventions against affiliative interactions occur more frequently than against agonistic interactions. In this study, 64 feral horses displayed 67 interventions in affiliative interactions and eight interventions in agonistic interactions within the observation period. We analysed the interventions in affiliative encounters, and found that it was mainly higher-ranking females that intervened in the affiliative interactions of group mates in the stable horse harems. The intervening animals took an active part in affiliative and agonistic encounters within the group, but did not occupy particular social roles or spatial positions. They intervened in affiliative interactions in which group mates with which they had social bonds interacted with other members of the group. They targeted the nonbonded animal and approached the one with which they were socially bonded. We suggest some species use third-party interventions in affiliative interactions to prevent competition for preferred social interaction partners from escalating into more costly agonistic encounters.
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Schino, G., & Aureli, F. (2016). Reciprocity in group-living animals: partner control versus partner choice. Biol Rev, 92(2), 665–672.
Abstract: ABSTRACT Reciprocity is probably the most debated of the evolutionary explanations for cooperation. Part of the confusion surrounding this debate stems from a failure to note that two different processes can result in reciprocity: partner control and partner choice. We suggest that the common observation that group-living animals direct their cooperative behaviours preferentially to those individuals from which they receive most cooperation is to be interpreted as the result of the sum of the two separate processes of partner control and partner choice. We review evidence that partner choice is the prevalent process in primates and propose explanations for this pattern. We make predictions that highlight the need for studies that separate the effects of partner control and partner choice in a broader variety of group-living taxa.
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Schanz, L., Krueger, K., & Hintze, S. (2019). Sex and Age Don't Matter, but Breed Type Does--Factors Influencing Eye Wrinkle Expression in Horses. Front. Vet. Sci., 6, 154.
Abstract: Identifying valid indicators to assess animals' emotional states is a critical objective of animal welfare science. In horses, eye wrinkles above the eyeball have been shown to be affected by pain and other emotional states. From other species we know that individual characteristics, e.g. age in humans, affect facial wrinkles, but it has not yet been investigated whether eye wrinkle expression in horses is systematically affected by such characteristics. Therefore, the aim of this study was to assess how age, sex, breed type, body condition and coat colour affect the expression and/or the assessment of eye wrinkles in horses. To this end, we adapted the eye wrinkle assessment scale from Hintze et al. (2016) and assessed eye wrinkle expression in pictures taken from the left and the right eye of 181 horses in a presumably neutral situation, using five outcome measures: a qualitative first impression reflecting how worried the horse is perceived by humans, the extent to which the brow is raised, the number of wrinkles, their markedness and the angle between a line through both corners of the eye and the topmost wrinkle. All measures could be assessed highly reliable with respect to intra- and inter-observer agreement. Breed type affected the width of the angle (F2, 114 = 8.20, p < 0.001), with thoroughbreds having the narrowest angle (M = 23.80, SD = 1.60), followed by warmbloods (M = 28.00, SD = 0.60), and coldbloods (M = 31.00, SD = 0.90). None of the other characteristics affected any of the outcome measures, and eye wrinkle expression did not differ between the left and the right eye area (all p-values > 0.05). In conclusion, horses' eye wrinkle expression and its assessment in neutral situations was not systematically affected by the investigated characteristics, except for 'breed type', which accounted for some variation in 'angle'; how much eye wrinkle expression is affected by emotion or perhaps mood needs further investigation and validation.
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Saunders, F. C., McElligott, A. G., Safi, K., & Hayden, T. J. (2005). Mating tactics of male feral goats (Capra hircus): risks and benefits. Acta Ethol, 8.
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Sato, S., Sako, S., & Maeda, A. (1991). Social licking patterns in cattle (<em>Bos taurus</em>): influence of environmental and social factors. Applied Animal Behaviour Science, 32(1), 3–12.
Abstract: To investigate the functions of social licking in cattle, four calves (one heifer and one steer in each of two herds), known to exhibit frequent social licking were observed continuously for 2 h before sunset for 13 days, using the focal animal sampling method. Calves were observed under various environmental conditions. Social licking significantly decreased on rainy days and tended to increase in a dirty barn and when food was restricted. Solicitation for social licking occurred not only from dominant animals of pairs but also from subordinates. Of the licking interactions, 31% occurred following solicitation, and these accounted for 39% of the total time spent licking. Following solicitation, 78% of social licking was oriented to the head and the neck regions that were inaccessible to self-licking animals. Unsolicited licking, however, was oriented not only to the head and the neck but also to the back and the rump regions, and these two latter regions were the major ones to receive licking. The effect of social relationships on social licking was investigated using least-squares analysis of variance. Social factors investigated were the difference of dominance values, the dominance-subordinance relationship, and kinship and familiarity; the sex of calves involved was also considered. Only familiarity had a significant effect on licking; exchanges of social licking increased with length of cohabitation. We suggest that social licking may have a cleaning effect, a tension-reducing effect and a bonding effect.
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