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Krueger, K. (2014). Die Bedeutung der Schiefe, Händigkeit und sensorische Lateralität der Pferde. In Pferdetage Baden-Württemberg 2014. Stuttgart: Matthaes Medien.
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Benz, B., Benitz, B., Krueger, K., & Winter, D. (2013). Weniger Einstreu bei gleichem Komfort. Pferdezucht und Haltung, 1, 66–71.
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Wolter, R., Pantel, N., Stefanski, V., Möstl, E., & Krueger, K. (2014). The role of an alpha animal in changing environmental conditions. Physiol. Behav., 133, 236–243.
Abstract: Abstract The maintenance and development of conservation areas by grazing of large herbivores, such as Przewalski's horses, is common practice. Several nature conservation areas house male bachelor groups of this species. When males are needed for breeding they are removed from the groups, often without considering group compositions and individual social positions. However, alpha animals are needed for ensuring group stability and decision making in potentially dangerous situations in several species. To investigate the role of the alpha male in a bachelor group, we observed the behaviour of five Przewalski's horse males during the enlargement of their enclosure. We analyzed the group's social structure and movement orders, as well as the animals' connectedness, activity budgets, and whether they moved with preferred group members and how factors such as social rank influenced the horses' behaviour. We also investigated the excretion of glucocorticoid metabolites (GCM) via faeces of the horses while exploring a new area as a parameter of glucocorticoid production. Our results show that the alpha male is important for a bachelor group in changing environmental conditions. The alpha male had the highest level of connectedness within the group. When exploring the new environment, its position in the group changed from previously being the last to being the first. Furthermore the whole group behaviour changed when exploring the new area. The stallions showed reduced resting behavior, increased feeding and did not stay close to each other. We found that the excretion of glucocorticoid metabolites of most horses rose only marginally during the first days on the new area while only the alpha male showed a significant increased amount of glucocorticoid production during the first day of the enclosure enlargement.
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Krueger, K., Esch, L., & Byrne, R. (2019). Animal behaviour in a human world: A crowdsourcing study on horses that open door and gate mechanisms. Plos One, 14(6), e0218954.
Abstract: Anecdotal reports of horses opening fastened doors and gates are an intriguing way of exploring the possible scope of horses' problem-solving capacities. The species' natural environment has no analogues of the mechanisms involved. Scientific studies on the topic are missing, because the rate of occurrence is too low for exploration under controlled conditions. Therefore, we compiled from lay persons case reports of horses opening closed doors and gates. Additionally, we collected video documentations at the internet platform YouTube, taking care to select raw data footage of unedited, clearly described and clearly visible cases of animals with no distinct signs of training or reduced welfare. The data included individuals opening 513 doors or gates on hinges, 49 sliding doors, and 33 barred doors and gateways; mechanisms included 260 cases of horizontal and 155 vertical bars, 43 twist locks, 42 door handles, 34 electric fence handles, 40 carabiners, and 2 locks with keys. Opening was usually for escape, but also for access to food or stable-mates, or out of curiosity or playfulness. While 56 percent of the horses opened a single mechanism at one location, 44 percent opened several types of mechanism (median = 2, min. = 1, max. = 5) at different locations (median = 2, min. = 1, max. = 4). The more complex the mechanism was, the more movements were applied, varying from median 2 for door handles to 10 for carabiners. Mechanisms requiring head- or lip-twisting needed more movements, with significant variation between individuals. 74 horses reported in the questionnaire had options for observing the behaviour in stable mates, 183 did not, which indicates that the latter learned to open doors and gates either individually or from observing humans. Experience favours opening efficiency; subjects which opened several door types applied fewer movements per lock than horses which opened only one door type. We failed to identify a level of complexity of door-fastening mechanism that was beyond the learning capacity of the horse to open. Thus, all devices in frequent use, even carabiners and electric fence handles, are potentially vulnerable to opening by horses, something which needs to be considered in relation to keeping horses safely.
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Krueger, K., Esch, L., & Byrne, R. (2021). Need or opportunity? A study of innovations in equids. Plos One, 16(9), e0257730.
Abstract: Debate persists over whether animals develop innovative solutions primarily in response to needs or conversely whether they innovate more when basic needs are covered and opportunity to develop novel behaviour is offered. We sourced 746 cases of “unusual” behaviour in equids by contacting equid owners and caretakers directly and via a website (https://innovative-behaviour.org), and by searching the internet platforms YouTube and Facebook for videos. The study investigated whether differences in need or opportunity for innovation were reflected in the numbers of different types of innovations and in the frequencies of repeating a once-innovative behaviour (i) with respect to the equids' sex, age, and breed type, (ii) across behavioural categories, and whether (iii) they were affected by the equids' management (single vs group housing, access to roughage feed, access to pasture, and social contact). We found that the numbers of different types of innovation and the frequency of displaying specific innovations were not affected by individual characteristics (sex, age, breed or equid species). Few types of innovation in escape and foraging contexts were observed, whilst the comfort, play, and social contexts elicited the greatest variety of innovations. We also found higher numbers of different types of innovations in horses kept in groups rather than in individual housing, and with unlimited rather than with restricted access to pasture and roughage. Equids in permanent social contact performed high rates of once-innovative behaviour. We suggest that equids produce goal-directed innovations and repeat the behaviour at high frequency in response to urgent needs for food and free movement or when kept in conditions with social conflict. However, equids devise the greatest variety of innovations when opportunity to play and to develop comfort behaviour arises and when kept in good conditions.
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Krueger, K., Gruentjens, T., & Hempel, E. (2023). Wolf contact in horses at permanent pasture in Germany. Plos One, 18(8), e0289767.
Abstract: Wolves returned to Germany in 2000, leading to fear in German horse owners that their horses could be in danger of wolf attacks or panic-like escapes from pastures when sighting wolves. However, reports from southern European countries indicate that wolf predation on horses diminishes with increasing presence of wildlife. Therefore, we conducted a long-term, filed observation between January 2015 and July 2022 on 13 non breeding riding horses, mares and geldings, kept permanently on two pastures within the range of wildlife and a stable wolf pack with annual offspring. Wildlife cameras at the fences of the pastures made 984 times recordings of wolves and 3151 times recordings of wildlife in and around the pastures. Between 1 January 2022 and 23 March 2022 we observed two stable horse groups. Pasture 1 was grazed by five horses of mixed breed, four mares and one gelding, with the median age of 8 years (min. = 6y, max. = 29y). Pasture 2 was grazed by eight heavy warmbloods and draught horses, three mares and five geldings, with the median age of 16 years (min. = 13y, max. = 22y). During this period no wolf was recorded at pasture 2, but wild boar several times, whereas at pasture 1, wolves were recorded 89 times, and for the wildlife mostly hare. Wolves may have avoided pasture 2 because of the presence of wild boar or because the large group of older, heavy breed horses may have formed a stable, protective group. The latter needs to be confirmed in a follow-up field observation, which records anti-predator behavior and welfare indicators in horses. In conclusion, wolves did not attack the mature horses on pastures with plenty of wildlife and the horses did not respond to the presence of wolves with visible signs of reduced welfare or panic. This indicates that wolves may prefer to prey on easily accessible wildlife around and at horse pastures and that Central European horses become accustom to the presence of non-hunting wolves.
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Flauger, B., Krueger, K., Gerhards, H., & Moestl, E. (2009). Measurement of glucocorticoid metabolites in horse faeces: the validation of different group specific enzymeimmunoassays and extraction methods. In S. Cremer, A. Schrempf, & J. Heinze (Eds.), Proceeding of the 102. Annual meeting of the Deutsche Zoologische Gesellschaft (DZG). (166). München: Dt. Zoologische Ges.
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Schneider, G., & Krueger, K. (2012). Third-party intervention. In Proceedings of the 2. International Equine Science Meeting (73). Wald: Xenophon Publishing.
Abstract: Third-party intervention is the interruption of a dyadic interaction by a third animal. We observed such interventions in affiliative interactions in free-ranging Esperia-ponies (Equus caballus). It is known that horses intervene in affiliative contexts especially when a preferred partner is involved, probably to protect their social bond to this preferred partner. To prove this hypothesis the present study investigated whether the preferred partner was targeted, i.e. challenged, or supported by the intervener or both randomly. Therefore we examined the social relationship between the intervener and both dyadic interacting individuals. We found that interveners usually supported individuals to which they have stronger social bonds than to other group mates, while they have no particular relationship to the targeted animals. This indicates that interveners in stable horse groups protect their social bonds to the supported animals by challenging their interaction partners. Of all observed horses only some mares showed intervention behaviour. Their social position, reflected by their position in the dominance hierarchy, social networks, and the spatial group structure were investigated. We found that interveners occupy no unique position, but they are involved in a high amount of affiliative interactions, high-ranking, and relatively aggressive. KW -
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Pick, D., & Krueger, K. (2012). Heuristics and complex decisions in man and horses. In K. Krueger (Ed.), Proceedings of the 2. International Equine Science Meeting (Vol. in press). Wald: Xenophon Publishing.
Abstract: Darwin’s claim of differences in mental abilities between man and other animals is a matter of degree rather than of kind and appears to apply nicely to a comparison of choice behaviour in humans and equine. Humans and horses make two kinds of decisions, fast reflexive decisions based on heuristics, and slower more considered decisions that require more complex cognitive processing. Heuristic use is adaptive in that decisions based on them are most often useful in helping an organism to survive while requiring little time and cognitive effort. There is considerable evidence that there is an innate basis to many heuristics in humans as well as horses. A case will be made that the investigation of heuristics specific to horses will lead to an understanding of equine behaviour that has not been possible using traditional learning theories alone. Traditional learning theories are restricted in explaining behaviour to appeals to reinforcement regimes or to the formation of associations between novel stimuli and stimuli that cause innate reflexes, but they are of no use when behaviour is controlled by stimuli that have never been reinforced or been systematically paired with other stimuli that cause reflexive responses. For example, a horse in a two-choice discrimination task may choose a familiar stimulus which has never been reinforced over a new stimulus added to the discrimination task, simply due to the use of an heuristic that usually works -- when in doubt, choose a more familiar object over an unfamiliar one. Conflict resolution strategies provide another good example of heuristic vs. slow decision making. In both humans and horses, conflict resolution strategies are used within, but not typically between social groups. Such groups can be defined as community of interest. Depending on the resource that has to be defended, groups may well be small identities, such as human families or horse harems, or large aggregations such as herds in horses, or religious groups or nations in humans. Fast and simple resolution is possible with stable social identities in simple environments, but more complicated and time consuming deliberative processes are required to resolve conflict over long-term resource acquisition, for decisions in complex conflicts situations and complex social settings.
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Krueger, K. (2012). Konfliktlösungsstrategien der Menschen und Pferde. In Proceedings of the 2. International Equine Science Meeting (Vol. in press). Wald: Xenophon Publishing.
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