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Nuñez, C. M. V., Adelman, J. S., Smith, J., Gesquiere, L. R., & Rubenstein, D. I. (2014). Linking social environment and stress physiology in feral mares (Equus caballus): Group transfers elevate fecal cortisol levels. General and Comparative Endocrinology, 196, 26–33.
Abstract: Abstract Feral horses (Equus caballus) have a complex social structure, the stability of which is important to their overall health. Behavioral and demographic research has shown that decreases in group (or band) stability reduce female fitness, but the potential effects on the physiological stress response have not been demonstrated. To fully understand how band stability affects group-member fitness, we need to understand not only behavioral and demographic, but also physiological consequences of decreases to that stability. We studied group changes in feral mares (an activity that induces instability, including both male and female aggression) on Shackleford Banks, NC. We found that mares in the midst of changing groups exhibit increased fecal cortisol levels. In addition, mares making more group transfers show higher levels of cortisol two weeks post-behavior. These results offer insights into how social instability is integrated into an animal’s physiological phenotype. In addition, our results have important implications for feral horse management. On Shackleford Banks, mares contracepted with porcine zona pellucida (PZP) make approximately 10 times as many group changes as do untreated mares. Such animals may therefore be at higher risk of chronic stress. These results support the growing consensus that links between behavior and physiological stress must be taken into account when managing for healthy, functional populations.
Keywords: Equus caballus; Fecal cortisol; Feral mare; Group transfer; Stress; Social instability
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R. A. Hopkins. CALIFORNIA WILDLIFE HABITAT RELATIONSHIPS SYSTEM (Vol. M174).
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Lansade, L., & Simon, F. (2010). Horses' learning performances are under the influence of several temperamental dimensions. Appl. Anim. Behav. Sci., 125(1-2), 30–37.
Abstract: Learning performances are influenced by many factors, not only breed, age and sex, but also temperament. The purpose of this study was to understand how different temperamental dimensions affect the learning performance of horses, Equus caballus. First, we carried out a series of behavioural tests on 36 Welsh ponies aged 5-7 years to measure five temperamental dimensions: fearfulness (novel area test and surprise test), gregariousness (social isolation test), reactivity to humans (passive human test), tactile sensitivity (von Frey filament test) and activity level (evaluation of locomotor activity during all the tests). We then presented them with two learning tasks (avoidance and backwards-forwards tasks). In the avoidance task they had to learn to jump over a fence when they heard a sound associated with an aversive stimulus (puff of air). In the backwards-forwards task they had to walk forwards or move backwards in response to a tactile or vocal command to obtain a food reward. There was no correlation between performances on the two learning tasks, indicating that learning ability is task-dependent. However, correlations were found between temperamental data and learning performance (Spearman correlations). The ponies that performed the avoidance task best were the most fearful and the most active ones. For instance, the number of trials required to perform 5 consecutive correct responses (learning criterion) was correlated with the variables aimed at measuring fearfulness (way of crossing a novel area: rs = -0.41, P = 0.01 and time to start eating again after a surprise effect: rs = -0.33, P = 0.05) and activity level (frequency of trotting during all the tests: rs = -0.40, P = 0.02). The animals that performed the backwards-forwards task best were the ones that were the least fearful and the most sensitive. For instance, the learning criterion (corresponding to the number of trials taken to achieve five consecutive correct responses) was correlated with the variables aimed at measuring fearfulness (latency to put one foot on the area: rs = 0.43, P = 0.01; way of crossing a novel area: rs = 0.31, P = 0.06; and time to start eating again after a surprise effect: rs = 0.43, P = 0.009) and tactile sensitivity (response to von Frey filaments: rs = -0.44, P = 0.008). This study revealed significant links between temperament and learning abilities that are highly task-dependent.
Keywords: Avoidance task; Equus caballus; Fearfulness; Learning; Personality; Temperament
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Ransom, J. I., Cade, B. S., & Hobbs, N. T. (2010). Influences of immunocontraception on time budgets, social behavior, and body condition in feral horses. Appl. Anim. Behav. Sci., 124(1-2), 51–60.
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.
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Nuñez, C. M. V., Adelman, J. S., Mason, C., & Rubenstein, D. I. (2009). Immunocontraception decreases group fidelity in a feral horse population during the non-breeding season. Appl. Anim. Behav. Sci., 117(1-2), 74–83.
Abstract: The behavioral effects of the immunocontraceptive agent porcine zona pellucida (PZP) have not been adequately studied. Important managerial decisions for several species, including the wild horse (Equus caballus), have been based on this limited research. We studied 30 horses on Shackleford Banks, North Carolina, USA to determine the effects of PZP contraception on female fidelity to the harem male. We examined two classes of females: contracepts, recipients of the PZP vaccine (n = 22); and controls, females that have never received PZP (n = 8). We conducted the study during the non-breeding season from December 2005 to February 2006, totaling 102.2 h of observation. Contracepted mares changed groups more often than control mares (P = 0.04). Contracepts also visited more harem groups than did control mares (P = 0.02) and exhibited more reproductive interest (P = 0.05). For both contracepted and control females, the number of group changes (P = 0.01) and number of groups visited (P = 0.003) decreased with the proportion of years mares were pregnant. Our study shows that the application of PZP has significant consequences for the social behavior of Shackleford Banks horses. In gregarious species such as the horse, PZP application may disrupt social ties among individuals and inhibit normal social functioning at the population level.
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Kavar, T., & Dovc, P. (2008). Domestication of the horse: Genetic relationships between domestic and wild horses. Livestock Science, 116(1-3), 1–14.
Abstract: To date, a large amount of equine genetic data has been obtained regarding (i) extant domestic horses of various breeds from all over the world, (ii) ancient domestic horses, (iii) the extant Przewalski's wild horse, and (iv) the late Pleistocene wild horse from Eurasia and North America. Here, a review of mtDNA and Y chromosome marker analyses is presented in the context of horse domestication. High matrilineal (mtDNA) diversity, which can be found in both extant and ancient (domestic and wild) horses, has suggested that a high number of wild (and tamed) mares were domesticated. Alternatively, Y chromosome marker analysis revealed a single haplotype in all domestic horses analyzed; interestingly even a small population of extant Przewalski's wild horses showed two different Y chromosome haplotypes. It seems that an extreme male population bottleneck occurred due to domestication, while reduction in the female population was only moderate, leaving about 100 distinct haplotypes. For this reason, we speculate that domestication might have started when the appropriate stallion was found or was obtained by selection. Perhaps it had some unusual but special characteristics which could have accelerated the process of domestication. We doubt that only a single Y chromosome haplotype will be found in present-day domestic horses if there are no important differences between the founder stallion/s and the other stallions that were not included in the domestication. In the Eneolithic, tamed and wild mares have probably been spread all over Eurasia, although the number of animals was most likely very low and the populations were limited to a restricted area (e.g., taming centers). Only two subspecies of wild horses (Tarpan and Przewalski's wild horse) have survived up to recently. During the further process of domestication, mares (tamed or wild) were preferentially crossed to stallions having more desirable characteristics. We assume that mares from different regions varied in their morphology due to adaptation to their local environmental conditions. These data might explain rapid expansion of horse populations, as well as their rapid differentiation into various phenotypes during the early phase of domestication.
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Lansade, L., & Bouissou, M. - F. (2008). Reactivity to humans: A temperament trait of horses which is stable across time and situations. Appl. Anim. Behav. Sci., 114(3-4), 492–508.
Abstract: The aim of this study was to test the existence of a “reactivity-to-humans” trait which is stable over time and across situations. For this purpose, four test situations were repeated on the same animals at 8 months, 1.5 years (N = 110 horses) and 2.5 years of age (N = 54 horses). These situations involved a “familiar passive human test” during which a familiar person stayed motionless in the test pen, a “familiar active human test” and an “unfamiliar active human test” during which a familiar or unfamiliar person attempted to touch the horse, and a “halter-fitting and heart-rate measurement test”, during which the horse was haltered and equipped with a surcingle and then had its heart-rate measured. Many behavioural variables were recorded during the tests, and correlations between ages and variables measured during other situations were investigated. When correlations were found, we concluded that the variables corresponded to temperament traits which are stable over time and across situations. The horses tested were divided into four groups according to breed (Anglo-Arab and Welsh) and year of birth (2001 and 2002). Data for each group were analysed separately with Spearman rank correlations. Regarding stability over time, there was a strong correlation between ages in the frequency of licking/nibbling the passive human, the time taken by a familiar or unfamiliar person to touch the horse, and the time taken to fit a halter (e.g. the time taken to touch the horse's muzzle was significantly correlated between ages in 7 out of the 8 possible cases: 0.40 <= R <= 0.67). Regarding stability across situations, results indicate that the more frequently a horse sniffed, licked or nibbled a passive human, the easier it was for either a familiar or unfamiliar active human to touch and halter it. Moreover, a horse which could be touched easily by a familiar human could also be touched and haltered easily by an unfamiliar human. These behaviours, which are linked directly to humans, therefore indicate good stability over time and across situations. In conclusion, this stability suggests the existence of a “reactivity-to-humans” temperament trait, whether the human is passive or active, familiar or unfamiliar. When the animals do not have frequent contact with humans, this reactivity is stable over time and can be measured as early as 8 months of age using the behavioural variables cited above.
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Lansade, L., Pichard, G., & Leconte, M. (2008). Sensory sensitivities: Components of a horse's temperament dimension. Appl. Anim. Behav. Sci., 114(3-4), 534–553.
Abstract: Temperament is an important factor when working with horses. Behavioural tests have already been developed to measure certain dimensions of a horse's temperament (fearfulness, gregariousness, etc.). In order to measure the temperament more precisely, our work aimed to identify a dimension which has already been described in several species but not yet in horses, namely sensory sensitivity. Our study was based on the definition of a temperament dimension as “a behavioural characteristic stable across situations and over time”. We designed several tests for each sense and then determined whether the responses observed were correlated between situations and in time. The principle of the tests was to generate two stimuli of different intensities for each sense (e.g. two different sounds) and to measure the intensity of the horse's response (N = 26). Using Spearman rank correlations, we tested whether the responses to these different stimuli were inter-correlated. We repeated the same tests 5 months later to determine whether the responses were correlated over time. Within each sense, results show that the greater the horses' response to one stimulus, the greater their response to the other. For example, the reaction to the odour of cinnamon (time spent near the source of the odour) was significantly correlated to the reaction to lavender (R = 0.53, p = 0.004). The reactions to two different sounds or to two different tactile stimuli (von Frey filaments, or contact of a brush on the body), were also significantly correlated (R = 0.59, p < 0.0001; R = 0.38, p = 0.029). Finally, the reactions to two different tastes or to two visual stimuli tended to be correlated (R = 0.27, p = 0.09; R = 0.27, p = 0.09). However, there was no significant correlation between the responses to stimuli relating to different senses. Finally, except for the responses to odour, the responses to other sensory stimuli showed stability over a 5-month period (e.g. tactile stimulation: R = 0.71, p < 0.0001). In conclusion, our study revealed characteristics which were stable across situations and over time. The absence of links between the characteristics measured for the different senses suggests that a dimension for each sense exists (e.g. tactile sensitivity) rather than a general sensory sensitivity dimension covering all the senses.
Keywords: Horse; Equus caballus; Temperament; Sensory sensitivity; Behavioural tests
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Lansade, L., Bouissou, M. - F., & Erhard, H. W. (2008). Reactivity to isolation and association with conspecifics: A temperament trait stable across time and situations. Appl. Anim. Behav. Sci., 106(2-4), 355–373.
Abstract: A temperament trait is generally defined as individual differences in behaviour that are present early in life and relatively stable across situations and over time. The aim of this study was to test the existence of a trait <<gregariousness>> in horses, by testing the stability across situations and over time of the responses to different social events. Sixty-six Welsh ponies and 44 Anglo-Arab horses were successively tested at 8 months and 1.5 years of age. Among them, 33 ponies and 21 horses were also tested at 2.5 years of age. They were submitted to four test situations: isolation and separation from, attraction towards and passing conspecifics. We carried out the analysis using each of four test groups as a unit (e.g. 33 Welsh ponies born in 2001, tested in isolation). Isolation and separation stood out as tests that showed a high consistency within test, across tests and across time. The most interesting behavioural parameter was the frequency of neighing, which was well correlated with other parameters measured in the same tests, such as defecation, locomotion and vigilance, as well as across the 3 years (e.g. for separation test: 0.41 < R < 0.61). Therefore, the behaviour of neighing observed in separation or isolation tests as early as 8 months of age appears to be a good indicator of similar behaviour in similar situations later in life, but also of other behaviours which can render the horse difficult to use. No parameter recorded during the attraction test presented stability across situations and time: the reactions to this test were not the expression of a stable characteristic of the individual and did not reflect the same characteristic as the three other tests. Of the different parameters recorded during the passing conspecifics test, the time to cross the arrival line near conspecifics showed good stability across years (0.35 < R < 0.68). This parameter was also correlated with many others recorded during the same test, and also, to a certain extent, to the frequency of neighing in the isolation and separation tests. This stability across responses expressed in various social contexts, and this stability over time, from 8 months to 2.5 years of age suggest the existence of a trait of gregariousness in the horse. From a practical point of view, that means it is possible to estimate the level of gregariousness of a horse as early as 8 months of age. Furthermore, additional analysis shows that gregariousness decreases with age.
Keywords: Horse; Equus caballus; Temperament; Trait; Isolation; Conspecific association; Stability
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h:, M., Lévy, F., Fortin, M., Leterrier, C., & LansadLansade, L. (2013). Stress and temperament affect working memory performance for disappearing food in horses, Equus caballus. Animal Behaviour, 86(6), 1233–1240.
Abstract: In the present study, we sought to determine the influence of stress and temperament on working memory for disappearing food in horses. After assessment of five dimensions of temperament, we tested working memory of horses using a delayed-response task requiring a choice between two food locations. Delays ranging from 0 to 20 s were tested. The duration of working memory for disappearing food was first characterized without stressors (N = 26). The horses were then divided into two groups and their performance was assessed under stressful (exposure to acute stressors prior to testing, N = 12) or control conditions (N = 12). Results showed that the duration of working memory for disappearing food lasted at least 20 s under nonstressful conditions, and that under stressful conditions this duration lasted less than 12 s. This stress-induced impairment confirms in a nonrodent species that working memory performance is very sensitive to exposure to stressors. In addition, working memory performance in horses is influenced by the temperamental dimension of fearfulness according to the state of stress: fearful horses showed better performance under control conditions and worse performance under stressful conditions than nonfearful horses. These findings are discussed in the context of the Yerkes–Dodson law of stress and performance.
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