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Webster, M. M., & Laland, K. N. (2008). Social learning strategies and predation risk: minnows copy only when using private information would be costly. Proc. R. Soc. Lond. B, 275(1653), 2869–2876.
Abstract: Animals can acquire information from the environment privately, by sampling it directly, or socially, through learning from others. Generally, private information is more accurate, but expensive to acquire, while social information is cheaper but less reliable. Accordingly, the 'costly information hypothesis' predicts that individuals will use private information when the costs associated with doing so are low, but that they should increasingly use social information as the costs of using private information rise. While consistent with considerable data, this theory has yet to be directly tested in a satisfactory manner. We tested this hypothesis by giving minnows (Phoxinus phoxinus) a choice between socially demonstrated and non-demonstrated prey patches under conditions of low, indirect and high simulated predation risk. Subjects had no experience (experiment 1) or prior private information that conflicted with the social information provided by the demonstrators (experiment 2). In both experiments, subjects spent more time in the demonstrated patch than in the non-demonstrated patch, and in experiment 1 made fewer switches between patches, when risk was high compared with when it was low. These findings are consistent with the predictions of the costly information hypothesis, and imply that minnows adopt a 'copy-when-asocial-learning-is-costly' learning strategy.
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Knolle, F., Goncalves, R. P., & Morton, A. J. (2017). Sheep recognize familiar and unfamiliar human faces from two-dimensional images. Royal Society Open Science, 4(11).
Abstract: One of the most important human social skills is the ability to recognize faces. Humans recognize familiar faces easily, and can learn to identify unfamiliar faces from repeatedly presented images. Sheep are social animals that can recognize other sheep as well as familiar humans. Little is known, however, about their holistic face-processing abilities. In this study, we trained eight sheep (Ovis aries) to recognize the faces of four celebrities from photographic portraits displayed on computer screens. After training, the sheep chose the 'learned-familiar' faces rather than the unfamiliar faces significantly above chance. We then tested whether the sheep could recognize the four celebrity faces if they were presented in different perspectives. This ability has previously been shown only in humans. Sheep successfully recognized the four celebrity faces from tilted images. Interestingly, there was a drop in performance with the tilted images (from 79.22 ± 7.5% to 66.5 ± 4.1%) of a magnitude similar to that seen when humans perform this task. Finally, we asked whether sheep could recognize a very familiar handler from photographs. Sheep identified the handler in 71.8 ± 2.3% of the trials without pretraining. Together these data show that sheep have advanced face-recognition abilities, comparable with those of humans and non-human primates.
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Smolla, M., Alem, S., Chittka, L., & Shultz, S. (2016). Copy-when-uncertain: bumblebees rely on social information when rewards are highly variable. Biol. Lett., 12(6).
Abstract: To understand the relative benefits of social and personal information use in foraging decisions, we developed an agent-based model of social learning that predicts social information should be more adaptive where resources are highly variable and personal information where resources vary little. We tested our predictions with bumblebees and found that foragers relied more on social information when resources were variable than when they were not. We then investigated whether socially salient cues are used preferentially over non-social ones in variable environments. Although bees clearly used social cues in highly variable environments, under the same conditions they did not use non-social cues. These results suggest that bumblebees use a 'copy-when-uncertain' strategy.
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Pongrácz.
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Kaczensky, P., & Huber, K. (2010). The Use of High Frequency GPS Data to Classify Main Behavioural Categories in a Przewalski’s Horse in the Mongolian Gobi. DigitalCommons@University of Nebraska – Lincoln, .
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Valenchon, M., Lévy, F., Moussu, C., & Lansade, L. (2017). Stress affects instrumental learning based on positive or negative reinforcement in interaction with personality in domestic horses. Plos One, 12(5), e0170783.
Abstract: The present study investigated how stress affects instrumental learning performance in horses (Equus caballus) depending on the type of reinforcement. Horses were assigned to four groups (N = 15 per group); each group received training with negative or positive reinforcement in the presence or absence of stressors unrelated to the learning task. The instrumental learning task consisted of the horse entering one of two compartments at the appearance of a visual signal given by the experimenter. In the absence of stressors unrelated to the task, learning performance did not differ between negative and positive reinforcements. The presence of stressors unrelated to the task (exposure to novel and sudden stimuli) impaired learning performance. Interestingly, this learning deficit was smaller when the negative reinforcement was used. The negative reinforcement, considered as a stressor related to the task, could have counterbalanced the impact of the extrinsic stressor by focusing attention toward the learning task. In addition, learning performance appears to differ between certain dimensions of personality depending on the presence of stressors and the type of reinforcement. These results suggest that when negative reinforcement is used (i.e. stressor related to the task), the most fearful horses may be the best performers in the absence of stressors but the worst performers when stressors are present. On the contrary, when positive reinforcement is used, the most fearful horses appear to be consistently the worst performers, with and without exposure to stressors unrelated to the learning task. This study is the first to demonstrate in ungulates that stress affects learning performance differentially according to the type of reinforcement and in interaction with personality. It provides fundamental and applied perspectives in the understanding of the relationships between personality and training abilities.
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Bailey, D. (2016). Dominance Hierarchies in Horses: Comparing and Contrasting Different Methods for Assessing Hierarchies. Ursidae: The Undergraduate Research Journal at the University of Northern Colorado, 5(3).
Abstract: Understanding animal social structures is imperative when it comes to the care, housing and handling of large herd animals. Knowing how hierarchies are structured, along with environmental and physiological aspects that may affect them, will allow owners and breeders to house and care for their animals. The aim of my study was to better understand two methods used to assess dominance hierarchies in horses, Equus caballus, and to predict which method would be more useful for owners housing domestic horses. I designed an experiment where I compared a structured method, the paired feeding test, with behavioral observations from the horses’ natural setting. I hypothesized that the structured method would not conclude the same dominance hierarchy as the natural observations. I also hypothesized that traits of the horses, such as size or age, would correlate with the hierarchy ranking within a herd. A herd of six individual horses from a small ranch east of Platteville, Colorado was used to test the two methods. I found that the two methods measured different hierarchies. The paired feeding test showed no correlations to any of the physical measurements, as well as did not provide a hierarchy that was similar to the natural dominance observations of the horses. Natural observations established a more linear hierarchy and had significant correlations with weight and overall body size. The results indicate that the paired feeding test may not be a valid method for establishing dominance hierarchies within domestic horses housed in a small range.
I recommend use of natural observations over paired feeding tests for ranchers, breeders or owners trying to understand the dominance hierarchies among their herds.
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Leiner, L. (2006). Vergleich verschiedener Methoden zur Angstextinktion bei Pferden. Diploma thesis, , .
Abstract: Pferde sind Fluchttiere. Ihr Fluchtinstinkt bewirkt, dass sie sich leicht erschrecken und auch in
diversen Situationen mit Flucht reagieren. Diese Tatsache ist den meisten Reitern bekannt,
nur ist es für den Menschen teilweise schwer, mit dieser Eigenschaft auszukommen und sie zu
verstehen oder gar nachzuvollziehen. So kommt es häufig zu Unfällen, die aus der Angst der
Pferde resultieren, jedoch vermeidbar gewesen wären, hätte man ankündigende Signale früher
erkannt. Des Weiteren kann die Angst eines Pferdes auch durch eine (Ver-) Weigerung,
bestimmte Dinge zu tun, sichtbar werden. Diese Weigerung wird in der Reiterei gerne als
„Bockigkeit“ und „Ungehorsam“ des Pferdes interpretiert und führt nicht selten zu einer
Bestrafung. Insgesamt kann man sagen, dass angstauslösende Reize und die Reaktionen des
Pferdes darauf oft falsch eingeschätzt oder falsch interpretiert werden und in der Folge auch
falsch damit umgegangen wird. Ein Grund dafür ist sicher das fehlende Wissen über das
Verhalten des Pferdes. Mit der vorliegenden Diplomarbeit soll ein Beitrag geleistet werden,
das Pferd in seinem Angstverhalten besser zu verstehen. Ziel der Arbeit war es, das Verhalten
des Pferdes bei verschiedenen Intensitäten von Angst zu untersuchen. Des Weiteren wurden
Methoden untersucht, mit denen man die Angst von Pferden vor bestimmten Reizen und
Situationen potentiell lindern kann, was letztendlich auch der Unfallvorbeugung dient.
Die vorliegende Diplomarbeit wurde am Haupt- und Landesgestüt Marbach durchgeführt; 24
Junghengste standen hierfür zur Verfügung. Darunter waren 18 Deutsche Warmblüter, 3
Vollblutaraber und 3 Schwarzwälder Füchse (Kaltblüter), somit war auch ein Rassenvergleich
möglich.
In einem ersten Teil der Arbeit wurde untersucht, wie sich Angst bei Pferden äußert. Hierfür
wurde ausgenutzt, dass Pferde ganz generell vor unbekannten, neuen Gegenständen Angst
haben (= Neophobie). Zur Angstauslösung dienten als Konfrontationsgegenstände ein
Sonnenschirm und eine Plastikplane. Beide Gegenstände waren für die Testpferde unbekannt.
Das Verhalten sowie die Herzrate der Tiere wurden während aller Versuche beobachtet und
quantifiziert. Nacheiner ersten Konfrontation wurden die Pferde an die Objekte gewöhnt
(Extinktionstraining = Angstlöschung) und beobachtet welche Verhaltensymptome sich
während dieser Gewöhnung (= Verlust der Neophobie) verändern. Die Hypothese war, dass
tatsächliche Angstsymptome während der Gewöhnung immer seltener zu beobachten sind.
Zusammenfassung III
Als Verhaltensweisen für Angst konnten Ausweichbewegungen und Flucht, Lautäußerungen
(Prusten und Schnauben), das Anspannen der Halsmuskulatur sowie das Vordrücken der
Oberlippe identifiziert werden. Darüber hinaus wurde gezeigt, dass Abstufungen im
Angstverhalten möglich sind: Bei sehr hohem Angstlevel sind Fluchtreaktionen zu
beobachten. Bei mittlerem Angstlevel treten Ausweichbewegungen im Schritt und
Lautäußerungen (Prusten und Schnauben) auf, bei geringem Angstlevel wird die
Halsmuskulatur angespannt und die Oberlippe vorgedrückt.
Im Zweiten Teil der Arbeit sollten verschiedene Methoden zur Angst-Extinktionauf ihre
Wirksamkeit hin untersucht werden. Verwendet wurde in verschiedenen Testgruppen die
Methode der Desensibilisierung (d.h. leichte, schrittweise stärker werdende Exposition
gegenüber dem angstauslösenden Reiz), die Desensibilisierung mit Gegenkonditionierung
(positive Verstärkung) durch Streicheln bzw. Reiben des Halses und die Desensibilisierung
mit Gegenkonditionierung durch Futterbelohnung. Als Kontrollgruppe dienten Pferde, die
ohne eine Konfrontation mit dem angstauslösenden Reiz nur über den Versuchplatz geführt
wurden.
Während des Extinktionstrainings konnte beobachtet werden, dass die Desensibilisierung mit
Gegenkonditionierung zu einer schnelleren Extinktion führt als ohne Gegenkonditionierung.
Allerdings zeigte ein Vergleich mit der Kontrollgruppe, die das Extinktionstraining nicht
erfahren hatte, den gleichen Verlust an Angstverhalten wie die Gruppen mit Extinktionstraining.
Dieses Ergebnis wurde so interpretiert, dass die wiederholte Exposition gegenüber
angstauslösenden Reizen bei den durchgeführten Verhaltenstests zwar eine Rolle spielt, doch
dass auch allein die Beschäftigung mit den Tieren zu einem Verlust von Angstverhalten führt
(wahrscheinlich auch aufgrund eines wachsenden Vertrauens zur Führperson, die über das
komplette Experiment hin die Gleiche blieb).
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Petersen, J. L., Mickelson, J. R., Cothran, E. G., Andersson, L. S., Axelsson, J., Bailey, E., et al. (2013). Genetic Diversity in the Modern Horse Illustrated from Genome-Wide SNP Data. Plos One, 8(1), e54997.
Abstract: Horses were domesticated from the Eurasian steppes 5,000-6,000 years ago. Since then, the use of horses for transportation, warfare, and agriculture, as well as selection for desired traits and fitness, has resulted in diverse populations distributed across the world, many of which have become or are in the process of becoming formally organized into closed, breeding populations (breeds). This report describes the use of a genome-wide set of autosomal SNPs and 814 horses from 36 breeds to provide the first detailed description of equine breed diversity. FST calculations, parsimony, and distance analysis demonstrated relationships among the breeds that largely reflect geographic origins and known breed histories. Low levels of population divergence were observed between breeds that are relatively early on in the process of breed development, and between those with high levels of within-breed diversity, whether due to large population size, ongoing outcrossing, or large within-breed phenotypic diversity. Populations with low within-breed diversity included those which have experienced population bottlenecks, have been under intense selective pressure, or are closed populations with long breed histories. These results provide new insights into the relationships among and the diversity within breeds of horses. In addition these results will facilitate future genome-wide association studies and investigations into genomic targets of selection.
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Pirault, P., Danvy, S., Verrier, E., & Leroy, G. (2013). Genetic Structure and Gene Flows within Horses: A Genealogical Study at the French Population Scale. Plos One, 8(4), e61544.
Abstract: Since horse breeds constitute populations submitted to variable and multiple outcrossing events, we analyzed the genetic structure and gene flows considering horses raised in France. We used genealogical data, with a reference population of 547,620 horses born in France between 2002 and 2011, grouped according to 55 breed origins. On average, individuals had 6.3 equivalent generations known. Considering different population levels, fixation index decreased from an overall species FIT of 1.37%, to an average of -0.07% when considering the 55 origins, showing that most horse breeds constitute populations without genetic structure. We illustrate the complexity of gene flows existing among horse breeds, a few populations being closed to foreign influence, most, however, being submitted to various levels of introgression. In particular, Thoroughbred and Arab breeds are largely used as introgression sources, since those two populations explain together 26% of founder origins within the overall horse population. When compared with molecular data, breeds with a small level of coancestry also showed low genetic distance; the gene pool of the breeds was probably impacted by their reproducer exchanges.
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