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Potts, R. (1998). Variability selection in hominid evolution. Evol. Anthropol., 7(3), 81–96.
Abstract: Variability selection (abbreviated as VS) is a process considered to link adaptive change to large degrees of environment variability. Its application to hominid evolution is based, in part, on the pronounced rise in environmental remodeling that took place over the past several million years. The VS hypothesis differs from prior views of hominid evolution, which stress the consistent selective effects associated with specific habitats or directional trends (e.g., woodland, savanna expansion, cooling). According to the VS hypothesis, wide fluctuations over time created a growing disparity in adaptive conditions. Inconsistency in selection eventually caused habitat-specific adaptations to be replaced by structures and behaviors responsive to complex environmental change. Key hominid adaptations, in fact, emerged during times of heightened variability. Early bipedality, encephalized brains, and complex human sociality appear to signify a sequence of VS adaptations—i.e., a ratcheting up of versatility and responsiveness to novel environments experienced over the past 6 million years. The adaptive results of VS cannot be extrapolated from selection within a single environmental shift or relatively stable habitat. If some complex traits indeed require disparities in adaptive setting (and relative fitness) in order to evolve, the VS idea counters the prevailing view that adaptive change necessitates long-term, directional consistency in selection. © 1998 Wiley-Liss, Inc.
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Aureli, F., & de Waal, F. B. (1997). Inhibition of social behavior in chimpanzees under high-density conditions. Am. J. Primatol., 41(3), 213–228.
Abstract: This is the first study to investigate the short-term effects of high population density on captive chimpanzees (Pan troglodytes). Subjects of the study were 45 chimpanzees living in five different groups at the Yerkes Regional Primate Research Center. The groups were observed under two conditions: 1) when they had access to both the indoor and outdoor sections of their enclosures; 2) during cold days when they were locked into the indoor runs, which reduced the available space by more than half. Under the high-density condition, allogrooming and submissive greetings decreased, but juvenile play increased. Remarkably, the rate of various forms of agonistic behavior, such as aggression, bluff charge, bluff display, and hooting, occurred less frequently under the high-density condition. This general decrease in adult social activity, including agonistic behavior, can be interpreted as an inhibition strategy to reduce opportunities for conflict when interindividual distances are reduced. This strategy is probably effective only in the short run, however. Behavioral indicators of anxiety, such as rough scratching and yawning, showed elevated rates, suggesting increased social tension under the high-density condition.
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Broom, M. (2002). A unified model of dominance hierarchy formation and maintenance. J. Theor. Biol., 219(1), 63–72.
Abstract: In many different species it is common for animals to spend large portions of their lives in groups. Such groups need to divide available resources amongst the individuals they contain and this is often achieved by means of a dominance hierarchy. Sometimes hierarchies are stable over a long period of time and new individuals slot into pre-determined positions, but there are many situations where this is not so and a hierarchy is formed out of a group of individuals meeting for the first time. There are several different models both of the formation of such dominance hierarchies and of already existing hierarchies. These models often treat the two phases as entirely separate, whereas in reality, if there is a genuine formation phase to the hierarchy, behaviour in this phase will be governed by the rewards available, which in turn depends upon how the hierarchy operates once it has been formed. This paper describes a method of unifying models of these two distinct phases, assuming that the hierarchy formed is stable. In particular a framework is introduced which allows a variety of different models of each of the two parts to be used in conjunction with each other, thus enabling a wide range of situations to be modelled. Some examples are given to show how this works in practice.
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Boyd, L. (1986). Behavior problems of equids in zoos. Vet Clin North Am Equine Pract, 2(3), 653–664.
Abstract: Behavior problems in zoo equids commonly result from a failure to provide for needs basic to equine nature. Equids are gregarious, and failure to provide companions may result in pacing. Wild equids spend 60 to 70 per cent of their time grazing, and failure to provide ad libitum roughage contributes to the problems of pacing, cribbing, wood chewing, and coprophagia. Mimicking the normal processes of juvenile dispersal, bachelor-herd formation, and mate acquisition reduces the likelihood of agonistic and reproductive behavior problems. Infanticide can be avoided by introducing new stallions to herds containing only nonpregnant mares and older foals.
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Fragaszy, D., & Visalberghi, E. (2004). Socially biased learning in monkeys. Learn Behav, 32(1), 24–35.
Abstract: We review socially biased learning about food and problem solving in monkeys, relying especially on studies with tufted capuchin monkeys (Cebus apella) and callitrichid monkeys. Capuchin monkeys most effectively learn to solve a new problem when they can act jointly with an experienced partner in a socially tolerant setting and when the problem can be solved by direct action on an object or substrate, but they do not learn by imitation. Capuchin monkeys are motivated to eat foods, whether familiar or novel, when they are with others that are eating, regardless of what the others are eating. Thus, social bias in learning about foods is indirect and mediated by facilitation of feeding. In most respects, social biases in learning are similar in capuchins and callitrichids, except that callitrichids provide more specific behavioral cues to others about the availability and palatability of foods. Callitrichids generally are more tolerant toward group members and coordinate their activity in space and time more closely than capuchins do. These characteristics support stronger social biases in learning in callitrichids than in capuchins in some situations. On the other hand, callitrichids' more limited range of manipulative behaviors, greater neophobia, and greater sensitivity to the risk of predation restricts what these monkeys learn in comparison with capuchins. We suggest that socially biased learning is always the collective outcome of interacting physical, social, and individual factors, and that differences across populations and species in social bias in learning reflect variations in all these dimensions. Progress in understanding socially biased learning in nonhuman species will be aided by the development of appropriately detailed models of the richly interconnected processes affecting learning.
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[No authors listed]. (1979). International Conference on Environmental Cadmium: an overview. In Environmental Health Perspectives (Vol. 28, pp. 297–30).
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De Pasquale, A., Ingala, A., Innella, G., Luigiano, G., Malara, L., & Panzera, M. (2008). The influence of the enriched environment on the reactivity of the precociously handled foals (Equus caballus L.). In IESM 2008.
Abstract: In a preliminary study, we evaluated the effect of precocious handling (at birth, 10, 30 and 60 days) and enriched environment on foal. Two experimental groups were created:
- 3 foals not handled and stabled in semi-enriched environment (Group A).
- 6 foals handled and stabled in an enriched environment (Group B).
All nine foals were tested with a novel object test (umbrella) at three months of age, to assess the Heart Rate (HR) values measured by a telemetric heart rate monitor (Polar Horse Trainer), during opening, touching and closing of the umbrella.
The statistical analysis carried out by means of the Mann-Whitney test showed lower HR values of the foals of group B (P<0.05).
Furthermore we have investigated 10 foals born between 2006 and 2008 to study the influence of enriched environment and precocious handling on behavioural responsiveness. The foals were housed on a farm which ensured an enriched environment and made social intra and interspecific interactions easier, alias autoshaping. They were submitted to:
- Handling within 24 hours from birth.
- Handling and reactivity test (arena test) executed at 10, 30 and 60 days.
The temporal correlation was studied among ages and baseline HR values, using the
Spearman"s test, to assess the beginning of neurovegetative HR control.
In fact statistically significant differences were obtained (r = -0.431; P<0,02). Temporal values of obtained HR baseline, using the Wilcoxon test, showed lower values at 60 days. The comparison was significant among mean and max baseline HR values of 30 vs 60 and 10 vs 60 (P<0.05), while no differences were observed during the reactivity test. This shows that adequate conditions of management associated to a precocious and continuous handling allow the foals to maintain their natural investigative behaviour disappearing fear and flight reactions.
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De Giorgio, F., & Schoorl, J. M. (2012). Why isolate during training? Social learning and social cognition applied as training approach for young horses (Equus caballus). In K. Krueger (Ed.), Proceedings of the 2. International Equine Science Meeting (Vol. in press). Wald: Xenophon Publishing.
Abstract: In the last decade an increasing number of studies has been oriented towards equine social learning and their social behavior within the herd (Kruger‚ 2006-2008). In social species, social learning is important to learn and gain useful skills to move and live in their own social and environmental context. Group housing has been recognized as an important element to fulfill the physical and behavioral needs of horses, especially their need for social contact (Søndergaard‚ 2011). Still‚ when it comes to horse training, the social aspect and‚ in general‚ cognitive abilities of the horse are rarely taken into account. Although it is widely accepted that social isolation is stressful for horse (Mal et al, 1991a and 1991b) still isolating a young horse is the first step when it comes to training methods. Due to tradition and culture and our performance-oriented society it is both difficult to accept and apply a different social/cognitive training approach. Training sessions are focused on immediate results whereas in cognitive learning part of the process is latent and will not be visible immediately‚ but taking the cognitive skills into account plays an important role in avoiding tension both in the horse as in the human-horse interaction (Baragli and De Giorgio, 2011). In this study we tested the possibility to apply social learning by creating a social environment‚ favoring a cognitive learning approach‚ for the training of six young horses. The group existed in three males and three females, between two and three years old. All six showed initial difficulties and defense to human interaction. They were housed in two groups in adjacent spacious paddocks where they had ample opportunity to move and express their individual and social behavioral repertoire. Each horse had one training session per week without isolating it from the others. The training sessions were held following a cognitive-relational model defined as the equine-zooanthropologic approach (De Giorgio, 2010 – Marchesini, 2011). The learning objectives were to be able to handle each horse‚ conduct it‚ saddle and ride it within a maximum time-frame of two years. Every time a defensive or alert behavior would occur the training activity was re-arranged to not over-pressure the horse. Therefore the persons working with the horses carried out the activities without tight expectations focusing on the horses’ positive attention. After eighteen months all six horses were used to the saddle and to riding. None of the horses ever fled or showed defense behavior and in the case of unexpected events they showed no emotional reactivity/reactive behavior. Today the horses show the same calm behavior whenever worked individually. This preliminary study highlights how social learning applied to equestrian activity can be fundamental for safety and welfare and the establishment of a more problem-free relationship between horse and human. Safety as the defensive behavior seems to have been reduced and welfare as the horses have been trained in a social context without being isolated and thus without being stressed during the training experience.
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Seyfarth, R. M., & Cheney, D. L. (2003). Signalers and receivers in animal communication. Annu Rev Psychol, 54, 145–173.
Abstract: In animal communication natural selection favors callers who vocalize to affect the behavior of listeners and listeners who acquire information from vocalizations, using this information to represent their environment. The acquisition of information in the wild is similar to the learning that occurs in laboratory conditioning experiments. It also has some parallels with language. The dichotomous view that animal signals must be either referential or emotional is false, because they can easily be both: The mechanisms that cause a signaler to vocalize do not limit a listener's ability to extract information from the call. The inability of most animals to recognize the mental states of others distinguishes animal communication most clearly from human language. Whereas signalers may vocalize to change a listener's behavior, they do not call to inform others. Listeners acquire information from signalers who do not, in the human sense, intend to provide it.
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Danchin, E., Giraldeau, L. - A., Valone, T. J., & Wagner, R. H. (2004). Public information: from nosy neighbors to cultural evolution. Science, 305(5683), 487–491.
Abstract: Psychologists, economists, and advertising moguls have long known that human decision-making is strongly influenced by the behavior of others. A rapidly accumulating body of evidence suggests that the same is true in animals. Individuals can use information arising from cues inadvertently produced by the behavior of other individuals with similar requirements. Many of these cues provide public information about the quality of alternatives. The use of public information is taxonomically widespread and can enhance fitness. Public information can lead to cultural evolution, which we suggest may then affect biological evolution.
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