Abstract: Behavioural observations suggest that smell is important in social discriminations between horses but balanced studies of this capacity are lacking. We used a habituation-discrimination procedure to investigate the ability of horses to distinguish between pairs of odour samples from different individuals. In Study 1, separate tests were conducted for urine, faeces or fleece fabric previously rubbed on the coat (to pick up body odour samples (BOS)) and donor pairs differed in sex, and age. 10 pregnant mares each underwent three tests, one per sample type. A test consisted of three successive 2-min presentations of a sample from Individual A with a simultaneous presentation of a sample from Individual B during the final presentation. Doubly repeated measures ANOVA indicated a main effect of sample type on investigative response (df = 2, f = 7.98, P = 0.004): durations were longer for BOS than for urine or faeces but habituation across trials was most consistent for urine. In the final presentation, mares demonstrated discrimination by investigating the novel urine sample (B) more than the repeated sample (novel: median 8.0 s, IQR = 10; repeated: median 2.5 s, IQR = 6; z = -2.558, P = 0.008). In Study 2, urine samples from castrated male donors were used and neither mares nor their 4-month-old foals discriminated between samples from different individuals in the final presentation. The findings suggest that urine odour may contain some information that horses can use to discriminate between conspecifics. This may be limited to the level of broad categories such as sex or reproductive status; further investigation is needed to reveal what functional information can be transmitted and what compounds are involved.

Abstract: Managers concerned with shrinking habitats and limited resources for wildlife seek effective tools for limiting population growth in some species. Fertility control is one such tool, yet little is known about its impacts on the behavioral ecology of wild, free-roaming animals. We investigated influences of the immunocontraceptive porcine zona pellucida (PZP) on individual and social behavior in bands of feral horses (Equus caballus) in three discrete populations and used 14 hierarchical mixed effect models to gain insight into the influences of PZP treatment on feral horse behavior. A model of body condition was the strongest predictor of feeding, resting, maintenance, and social behaviors, with treated females allocating their time similarly to control females. Time spent feeding declined 11.4% from low condition to high condition females (F1,154 = 26.427, P < 0.001) and was partially reciprocated by a 6.0% increase in resting (F1,154 = 7.629, P = 0.006), 0.9% increase in maintenance (F1,154 = 7.028, P = 0.009), and 1.8% increase in social behavior (F1,154 = 15.064, P < 0.001). There was no difference detected in body condition of treated versus control females (F1,154 = 0.033, P = 0.856), but females with a dependent foal had lower body condition than those without a foal (F1,154 = 4.512, P = 0.038). Herding behavior was best explained by a model of treatment and the interaction of band fidelity and foal presence (AICc weight = 0.660) which estimated no difference in rate of herding behavior directed toward control versus treated females (F1,102 = 0.196, P = 0.659), but resident females without a dependent foal were herded 50.9% more than resident females with a foal (F3,102 = 8.269, P < 0.001). Treated females received 54.5% more reproductive behaviors from stallions than control mares (F1,105 = 5.155, P = 0.025), with the model containing only treatment being the most-supported (AICc weight = 0.530). Treated and control females received harem-tending behaviors from stallions equally (F1,105 = 0.001, P = 0.969) and agonistic behaviors from stallions equally (F1,105 < 0.001, P = 0.986). Direct effects of PZP treatment on the behavior of feral horses appear to be limited primarily to reproductive behaviors and most other differences detected were attributed to the effects of body condition, band fidelity, or foal presence. PZP is a promising alternative to traditional hormone-based contraceptives and appears to contribute few short-term behavioral modifications in feral horses.

Abstract: Recent studies have suggested that crib-biting in horses is associated with diminished capacity of learning or coping with stress. Such findings raise the question whether trainability, which is fundamentally important in practice, could also be affected by stereotypic behaviour. Trainability of a horse is difficult to assess in simple tests, however, it is reliably estimated by experienced riders. To assess trainability and other characteristics related to that, a questionnaire survey was conducted with the owners of 50 crib-biting and 50 control horses. Where possible, control horses were selected from the same establishment as crib-biters. Groups did not differ significantly regarding age, breed, gender, training level or usage. Principal component analysis revealed three main factors which can be labelled as [`]Anxiety', [`]Affability' and [`]Trainability'. The [`]Anxiety' factor consisted of the items [`]Nervousness', [`]Excitability', [`]Panic', [`]Inconsistent emotionality', [`]Vigilance', [`]Skittishness', and [`]Timidity'. [`]Affability' consisted of [`]Friendliness toward people', [`]Cooperation', [`]Docility' and [`]Friendliness toward horses'. [`]Trainability' involved [`]Concentration', [`]Trainability', [`]Memory', and [`]Perseverance'. Temperament traits were not affected by age, gender, breed or training level, but the usage of the horse and the presence of crib-biting behaviour had significant effects. Competition horses had lower level of [`]Anxiety' (p = 0.032) and higher level of [`]Trainability' (p = 0.068) than leisure horses. Crib-biting horses had significantly lower level of [`]Anxiety' than control horses (p < 0.001), while [`]Trainability' and [`]Affability' did not differ between groups (p = 0.823 and p = 0.543, respectively). Competition horses are more often exposed to novel environment and to frightening stimuli (e.g. colourful obstacles) than leisure horses and therefore might have also become more habituated to these types of stimuli. Coping with novel situation may be enhanced by defusing nervous behaviour by the more experienced riders of competition. Previous studies indicated crib-biting horses to be less reactive when challenged as compared to control horses. We suggest that the virtual calmness and lower nervousness of the crib-biting horses might be due to the passive coping style of these animals. [`]Affability' of horses might be more related to housing and management conditions than to crib-biting. Contrary to expectations, scores on [`]Trainability' had not coincided with the impaired learning of crib-biting horses reported in laboratory tests. However, previous behavioural tests on equine learning rarely had a direct relevance to the training abilities of the horses. Our results do not support crib-biting stereotypy to affect performance in training, which is a complex learning process involving cooperation and docility in the social environment.

Abstract: Crib-biting is a form of oral stereotypy affecting 4-5% of horses. Once fixed, crib-biting is difficult to eliminate by behaviour therapy, however, its performance can be inhibited by collar or surgery treatment (modified Forssell's procedure). Although surgical intervention is widespread, the effects on stress coping in horses have not been studied. In the present study we evaluated changes in behaviour response and heart rate variability in 9 control, 10 crib-biting, 10 collar and 11 surgically treated horses in a feeding stress-test, in which a feeding-bowl was placed in front but out of the reach of the horses, from which tidbits were given 3 times. We found that stress triggers high oral activity, mainly cribbing in crib-biting horses, elevates other forms of oral activities in the inhibited groups and does not affect oral activities of controls. Instead of performing oral activities, control horses tended to target an unavailable feeding-bowl by pawing or head-tossing. Changes in stress level were indistinguishable in controls and crib-biters as heart rate variability returned to baseline values in both groups. In contrast, horses inhibited to perform crib-biting showed elevated stress level throughout the test period. Our results suggest that crib-biting may develop to cope with stress, and such coping function diminishes when inhibited.

Abstract: The numbers of horses grazing at pasture are increasing in developed countries, so a proper understanding of their feeding selectivity and of the tactics they use for extracting nutrients from swards is essential for the management of horses and grasslands. Resource acquisition in herbivores can be optimised through the modulation of their intake and patch selection, both being strongly dependent on the characteristics of swards. However, the principles by which horses adjust their grazing behaviour in response to variations in sward features are not completely understood. The aim of this study was to determine whether the behaviour of horses conforms to optimal foraging models. We hypothesized that, faced with binary choices between vegetative swards of a good and similar quality at three different heights, horses would select the taller sward, i.e. that allowing a higher reward in terms of dry matter intake rate. Three groups of three 2-year-old saddle horses were grazed on a semi-natural pasture that was managed to produce three contrasting sward heights at 6, 11 and 17 cm, in a Latin-square design. The instantaneous intake rate was determined from bite rate measured at pasture on the three sward heights, and bite mass estimated from measurements using swards offered indoors in experimental trays. Daily dry matter intake was estimated individually by total faecal collection and an estimation of digestibility from faecal nitrogen. Short-term (first 30 min) and daily preferences were assessed from the time spent grazing each sward offered in pair-wise tests at pasture. The results show that daily voluntary intake (an average of 21 g DM kg LW-1 day-1) and total grazing time (an average of 14 h day-1) were independent of sward height and of the choice of patches offered. In choice situations, the animals spent more time grazing on the taller sward, both during the first 30 min and at the daily scale. These results show that horses choose between vegetative patches of a good and similar quality according to the predictions from optimal foraging models, and select the one that they can ingest faster. Further research will now have to explore how the horses will adapt their feeding behaviour when they face a trade-off between sward height and quality.