Animals that live in a social group are often organized in a hierarchy with rank determining access to resources. Maintaining a dominant position requires a high rate of energetically expensive aggressive displays and physical exertion. Lab based winnerloser studies, often conducted with individuals from non-social species, have shown that subordinates have higher stress hormone levels than dominant individuals (subordinatestress hypothesis). However, in carnivorous animals that are cooperative breeders, displays of aggression are associated with elevated stress hormone levels (dominancestress hypothesis). The effect of reproductive state on dominance and stress is not addressed within either of these hypotheses. The purpose of this study was to examine stress level in relation to dominance rank and reproductive state in a non-cooperative breeder and herbivore, the domestic horse. As rank and reproductive state can affect behavior, I examined activity budgets, behavioral patterns, and social interactions, as well as the proximity and identity of neighbors in the social group. At two facilities in Kentucky, I recorded the social interactions and measured fecal glucocorticoids in pastured, female horses that were either lactating or non-lactating. While fecal glucocorticoid level did not differ between reproductive state and rank, activity behavior demonstrated significant differences between reproductive states. Higher energetic requirements of lactation were reflected in significantly longer bouts of eating and significantly less time spent alert and socializing. The non-cooperative social nature of horses does not limit their reproduction or resource acquisition based upon rank, and therefore does not fit with the dominance-stress hypothesis or subordinate-stress hypothesis and instead offers the alternative of an independent-stress hypothesi

O objetivo do presente estudo foi avaliar os perfis de metabólitos de glicocorticóides fecais através de radioimunoensaio em cachorros-vinagre (Speothos venaticus) mantidos em cativeiro e suas possíveis implicações na função reprodutiva. Duas fêmeas e quatro machos adultos, após período de condicionamento, foram marcados e tiveram suas fezes recolhidas durante 45 dias. Estes animais recebiam diariamente marcadores (corantes e miçangas) para a devida identificação das amostras fecais. O desafio com ACTH foi realizado em uma das fêmeas e mostrou o perfil reativo esperado, validando a técnica do ponto de vista fisiológico. As concentrações de metabólitos de glicocorticóides fecais para o grupo em geral variaram de 2,32 a 65,09 μ/g de fezes secas, com média e desvio-padrão de 18,11±11,33 μ/g de fezes secas, respectivamente. Quatro animais apresentaram um pico cada um, porém aparentemente, sem relação com qualquer evento estressante em particular. Não se verificou diferença significativa nos perfis de glicocorticóides fecais entre machos e fêmeas, nem entre a fêmea dominante e os outros indivíduos. Tais resultados sugerem que os animais estão bem adaptados à condição do cativeiro e provavelmente isentos ou minimamente afetados pelo estresse. A dosagem dos glicocorticóides fecais é uma ferramenta útil no monitoramento não-invasivo para avaliar a condição de estresse do cachorrovinagre, demonstrando se aspectos de manejo e fatores ambientais interferem de modo importante ou não no bem-estar animal e no potencial reprodutivo, sendo de interesse para a manutenção e conservação da espécie. / The aim of this study was to evaluate the fecal glucocorticoid metabolite profiles by radioimmunoassay in captive bush dog (Speothos venaticus) and its possible role in the reproductive function. Six adult animals (two females and four males), after training, were marked and their fecal samples were collected during 45 days. Every day the animals received markers (dye and colored plastic beads) for the appropriate identification of each sample. One female was used to the ACTH challenge and showed the expected classical response, with a significant peak one day after stimulation, therefore confirming the physiological validation. The overall fecal glucocorticoid metabolite concentrations for the whole group, ranged from 2,32 to 65,09 μ/g of dried feces, with an average and standard deviation of 18,11±11,33 μ/g of dried feces, respectively. Four animals revealed one individual peak during the observation period, however they could not be correlated with any stressful event. The fecal glucocorticoid metabolite concentrations did not show significant differences between males and females neither between the dominant female and the other animals in the study. The results suggest that the animals are well adapted to the captive conditions and likely without or minimally affected by stress. The fecal glucocorticoid metabolite dosage is a useful non-invasive tool to evaluate the bush dog stress situation and to monitor local management and environmental factors that could possibly influence the well being and reproductive success, considered both key factors for the specie maintenance and conservation.

O objetivo do presente estudo foi avaliar os perfis de metabólitos de glicocorticóides fecais através de radioimunoensaio em cachorros-vinagre (Speothos venaticus) mantidos em cativeiro e suas possíveis implicações na função reprodutiva. Duas fêmeas e quatro machos adultos, após período de condicionamento, foram marcados e tiveram suas fezes recolhidas durante 45 dias. Estes animais recebiam diariamente marcadores (corantes e miçangas) para a devida identificação das amostras fecais. O desafio com ACTH foi realizado em uma das fêmeas e mostrou o perfil reativo esperado, validando a técnica do ponto de vista fisiológico. As concentrações de metabólitos de glicocorticóides fecais para o grupo em geral variaram de 2,32 a 65,09 μ/g de fezes secas, com média e desvio-padrão de 18,11±11,33 μ/g de fezes secas, respectivamente. Quatro animais apresentaram um pico cada um, porém aparentemente, sem relação com qualquer evento estressante em particular. Não se verificou diferença significativa nos perfis de glicocorticóides fecais entre machos e fêmeas, nem entre a fêmea dominante e os outros indivíduos. Tais resultados sugerem que os animais estão bem adaptados à condição do cativeiro e provavelmente isentos ou minimamente afetados pelo estresse. A dosagem dos glicocorticóides fecais é uma ferramenta útil no monitoramento não-invasivo para avaliar a condição de estresse do cachorrovinagre, demonstrando se aspectos de manejo e fatores ambientais interferem de modo importante ou não no bem-estar animal e no potencial reprodutivo, sendo de interesse para a manutenção e conservação da espécie. / The aim of this study was to evaluate the fecal glucocorticoid metabolite profiles by radioimmunoassay in captive bush dog (Speothos venaticus) and its possible role in the reproductive function. Six adult animals (two females and four males), after training, were marked and their fecal samples were collected during 45 days. Every day the animals received markers (dye and colored plastic beads) for the appropriate identification of each sample. One female was used to the ACTH challenge and showed the expected classical response, with a significant peak one day after stimulation, therefore confirming the physiological validation. The overall fecal glucocorticoid metabolite concentrations for the whole group, ranged from 2,32 to 65,09 μ/g of dried feces, with an average and standard deviation of 18,11±11,33 μ/g of dried feces, respectively. Four animals revealed one individual peak during the observation period, however they could not be correlated with any stressful event. The fecal glucocorticoid metabolite concentrations did not show significant differences between males and females neither between the dominant female and the other animals in the study. The results suggest that the animals are well adapted to the captive conditions and likely without or minimally affected by stress. The fecal glucocorticoid metabolite dosage is a useful non-invasive tool to evaluate the bush dog stress situation and to monitor local management and environmental factors that could possibly influence the well being and reproductive success, considered both key factors for the specie maintenance and conservation.