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Stanley, C., & Shultz, S. (2012). Mummy’s Boys: Sex Differential Maternal Offspring Relationships in Semi-feral Horses. In K. Krueger (Ed.), Proceedings of the 2. International Equine Science Meeting (Vol. in press). Wald: Xenophon Publishing.
Abstract: In polygynous species with high reproductive skew in males, mothers often show differential investment between sons and daughters; however consistent sex differential investment has not been found by previous studies in horses. We investigated sex differences in mother-offspring relationships in nutritionally independent sub-adult semi-feral Carneddau Welsh mountain ponies Equus ferus caballus. Mothers and their sub-adult sons had consistently closer relationships than mothers and daughters. Stronger affiliative bonds between mothers and sons were quantified by their maintenance of closer proximity, higher rates of affiliative interactions and more frequent suckling bouts. These measures of affiliation were temporally associated with higher aggression levels directed towards sub-adults by other band members, particularly stallions. We suggest that aggression may serve as the proximate mechanism driving male dispersal in feral horses and that the stronger mother-son bond signals an attempt to delay their dispersal, highlighting conflict within the band concerning dispersal timing. Since males become increasingly central within the band over time, with mature stallions requiring excellent social skills in order to both acquire and keep a band of mares, we propose that delaying colts' dispersal allows for further development of these skills in a relatively safe environment. This additional investment is expected to maximise their reproductive success. This study illustrates how social network theory can be used to quantify individuals' social experiences, contributing to a greater understanding of the evolution of group living. It also gives us further insight into the mechanisms underlying dispersal in wild and semi-wild horse populations and how conflict often arises when individual needs differ.
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Vieuille, C., Berger, F., Le Pape, G., & Bellanger, D. (2003). Sow behaviour involved in the crushing of piglets in outdoor farrowing huts--a brief report. Appl. Anim. Behav. Sci., 80(2), 109–115.
Abstract: This study focuses on maternal activities involved in the trapping of piglets by the sow's body in outdoor farrowing systems and examine the mother-piglet context leading either to the death of piglets or to their survival. The behaviour of six Large-WhitexLandrace sows and their litters was continuously video recorded at their first and second parity, during the 40 h following parturition. Crushing mainly occurred at evening and night, during the first 12 h of farrowing and involved changes between lying, sitting and standing positions, as well as between udder and side lying. No piglet died from savaging. Nevertheless, aggressive behaviours of sows were observed, particularly in their first maternal experience. The immediate context of trapping was related to the labour of the sow and to the feeding and resting of piglets. The immediate crushing context was related to active avoidance of restless piglets while lying down, as well as sitting and standing behaviours. These results are discussed in terms of differential reactions of the sow to suckling attempts of piglets.
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Weaver, A., & de Waal, F. B. M. (2003). The mother-offspring relationship as a template in social development: reconciliation in captive brown capuchins (Cebus apella). J Comp Psychol, 117(1), 101–110.
Abstract: Mother-offspring (MO) relationship quality was investigated to determine its influence on the development of reconciliation--affiliation between opponents shortly after a fight--because it influenceswhat distressed youngsters learn about calming down. Data were longitudinal and cross-sectional observational samples of 38 MO pairs of monkeys across 24 months. An MO relationship quality index (RQI) classified each pair as secure or insecure. Reconciliation emerged in infancy.Secure youngsters had an appeasing conciliatory style, and insecure youngsters had an agitated conciliatory style. Conclusions are that reconciliation develops from the attachment behavior system and MO RQI is related to the particular conciliatory style youngsters develop by affecting how aroused they are by conflict and the subsequent socializing they seek to calm down.
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Weaver, A., & de Waal, F. B. M. (2002). An index of relationship quality based on attachment theory. J Comp Psychol, 116(1), 93–106.
Abstract: Two measures are reported of the nature or quality of a mother-offspring (MO) relationship during development using brown capuchin monkeys (Cebus apella) as models. One is a qualitative classification of MO relationships as secure, resistant, or avoidant attachments. The other is an empirical ratio of relative affiliation to agonism called the MO relationship quality, or MORQ, Index. The two methods tapped similar relationship features so relationships high or low of a median split of MORQ values were heuristically labeled secure (n = 22) or insecure (n = 16), respectively. A comparison revealed extensive behavioral differences between secure and insecure MO relationships and suggested MORQ provided an objective, continuous measure of attachment security.
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Zhang, T. - Y., Parent, C., Weaver, I., & Meaney, M. J. (2004). Maternal programming of individual differences in defensive responses in the rat. Ann N Y Acad Sci, 1032, 85–103.
Abstract: This paper describes the results of a series of studies showing that variations in mother-pup interactions program the development of individual differences in behavioral and endocrine stress responses in the rat. These effects are associated with altered expression of genes in brain regions, such as the amygdala, hippocampus, and hypothalamus, that regulate the expression of stress responses. Studies from evolutionary biology suggest that such “maternal effects” are common and often associated with variations in the quality of the maternal environment. Together these findings suggest an epigenetic process whereby the experience of the mother alters the nature of the parent-offspring interactions and thus the phenotype of the offspring.
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