Abstract: This simulation study explores some conditions leading to transitivity within dominance orders. Combinations of three parameters were varied to study their consequences upon hierarchy formation and upon the degree of linearity of resultant structures. The factors studied were: (1) the importance of initial resource holding potentials (RHPs); (2) changes brought in RHPs by successive victories and defeats; and (3) accuracy of RHP assessment made by opponents. Results show that initial differences in RHP always lead to perfectly transitive chains whose rank order reflects the importance of initial differences. Even when simulated animals make important errors while assessing each other during round robin tournaments, emerging dominance structures are perfectly linear and ranks obtained in the structure are highly correlated with initial values in RHPs. Moreover, accumulated experiences of victory and/or defeat alone always lead to perfectly linear hierarchies. Their combination with initial individual differences in RHP led to the same conclusion. Even when assessment was far from being perfect, not only perfect chains were formed but initial values in RHPs significantly influenced rank order when the contribution of victory and defeat to RHP was relatively unimportant. The higher the importance of victory and defeat to RHP as compared to that of initial RHP values, the lower was the correlation between initial RHP values and the ranks order reached by individuals in the resultant hierarchies. In general also, the lower the variation within initial RHPs, the lower was the correlation between initial RHPs and ranks in the hierarchy. At a given level of initial RHP dispersion, increasing the contribution of victory and defeat to RHP diminished the correlation between initial RHP values and obtained ranks. In addition, inaccurate assessment reduced the overall correlation, especially when dispersion of initial RHP values was low and the contribution of victory and defeat relatively unimportant. These results shed some light on the controversy about the respective roles of initial individual attributes and that of patterns of resolution in the formation of animal hierarchies. We present the emergence of social order within closed systems as those simulated here as a case of self-organization.

Abstract: Bird song learning is a major model system for the study of learning with many parallels to human language development. In this experiment we examined a critical but poorly understood aspect of song learning: its social context. We compared how much young song sparrows, Melospiza melodia, learned from two kinds of adult `song tutors': one with whom the subject interacted vocally, and one whom the subject only overheard singing with another young bird. We found that although subjects learned from both song models, they learned more than twice as many songs from the overheard tutor. These results provide the first evidence that young birds choose their songs by eavesdropping on interactions, and in some cases may learn more by eavesdropping than by direct interaction.

Abstract: A problem in assessing animal welfare is that collecting data in itself may be stressful to the animals. Therefore, noninvasive methods for collecting data have to be devised and tested. A first step in investigating saliva cortisol, urinary cortisol, and urinary catecholamine as noninvasive indicators of canine well-being is the validation of these hormonal measures as alternatives for those in plasma. Using a model of insulin (0.2 U/kg)-induced hypoglycemia, we report on stress-induced responses in saliva cortisol, urinary cortisol, and urinary catacholamines relative to cortisol and catecholamine responses in plasma. Hypoglycemia in six dogs induced significant (P< 0.05) increases in plasma cortisol and adrenaline but not noradrenaline. Saliva cortisol responses expressed as net area under the response curve correlated significantly with plasma cortisol responses (r> 0.92). Saliva cortisol levels measured 7 to 12% of plasma cortisol concentrations. Cortisol/creatinine ratios in urine were significantly higher when voided after insulin administeration, compared to when voided after saline treatment. Insulin-induced increments in cortisol/creatinine ratios were nonsignificant when urine samples were assayed after dichloromethane extraction. Although urinary adrenaline/creatinine (A/C) ratios were significantly correlated with maximum plasma adrenaline values after insulin administration, A/C ratios did not differ significantly between insulin and saline treatment. The present experiment provides strong support for using saliva sampling and urine collection as noninvasive methods to establish stress-induced cortisol responses. For measuring acute plasma adrenaline responses, measuring A/C ratios may not be a valid alternative.

Abstract: The aim of this study was to investigate the relationship between age, reproductive status and sire of the mare and the tendency to perform stereotypies. One hundred and fourteen purebred Arab mares, offspring of 39 sires ( offspring per sire) and aged 4-21 years () were observed from the 30th March to the 15th of May 2005 using instantaneous scan sampling. We used a multivariate logistic regression in order to study the relationship between age, reproductive status and sire of the mare and the tendency to perform stereotypies. 28% of the observed mares showed stereotypic behaviour, mostly weaving (22%). Neither age (χ2 Wald = 9.36, p = 0.89) nor sire (χ2 Wald = 4.34, p = 1.0) affected the occurrence of stereotypies whilst the reproductive status of the mare influenced significantly the occurrence (χ2 Wald = 10.75, p = 0.001) but also the type (χ2 = 12.1, p < 0.001) of stereotypic behaviour. Weaving was more frequent in non foaling mares (41.4%) than in foaling mares (1.8%) that performed mostly stall-walking.

Abstract: 1. Several aspects of the behavioral ecology of feral horses (Equus caballus) were studied in Grand Canyon, Arizona, USA. Most bands contained three to five horses that included one stallion and his harem. Males that did not obtain a harem remained solitary. Throughout the study bands remained stable in composition.
2. Home ranges for all bands decreased in size in successive warm months, probably due to increased ambient temperature and drought. This resulted in greater utilization of spring areas that led to increased interband confrontation and agonistic display.
3. Territoriality was not observed in individual horses or bands, but bands hierarchial in both inter- and intraband structures. Interband stallion dominance was reinforced through posturing and fighting. Intraband hierarchies, as determined by dominance coefficients, were independent of individual size in three of four bands.
4. Indexes of nervousness (NER), calculated while horses were drinking, showed that stallions were less nervous than mares. A low NER was correlated with individuals leading toward drinking areas, whereas a high NER existed in individuals initiating flight although no single horse acted consistently as a leader.
5. Diurnal activity patterns were correlated with ambient temperatures.