Nuñez, C. M. V., Adelman, J. S., Smith, J., Gesquiere, L. R., & Rubenstein, D. I. (2014). Linking social environment and stress physiology in feral mares (Equus caballus): Group transfers elevate fecal cortisol levels. General and Comparative Endocrinology, 196, 26–33.
Abstract: Abstract Feral horses (Equus caballus) have a complex social structure, the stability of which is important to their overall health. Behavioral and demographic research has shown that decreases in group (or band) stability reduce female fitness, but the potential effects on the physiological stress response have not been demonstrated. To fully understand how band stability affects group-member fitness, we need to understand not only behavioral and demographic, but also physiological consequences of decreases to that stability. We studied group changes in feral mares (an activity that induces instability, including both male and female aggression) on Shackleford Banks, NC. We found that mares in the midst of changing groups exhibit increased fecal cortisol levels. In addition, mares making more group transfers show higher levels of cortisol two weeks post-behavior. These results offer insights into how social instability is integrated into an animal’s physiological phenotype. In addition, our results have important implications for feral horse management. On Shackleford Banks, mares contracepted with porcine zona pellucida (PZP) make approximately 10 times as many group changes as do untreated mares. Such animals may therefore be at higher risk of chronic stress. These results support the growing consensus that links between behavior and physiological stress must be taken into account when managing for healthy, functional populations.
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Neumann, C., Duboscq, J., Dubuc, C., Ginting, A., Irwan, A. M., Agil, M., et al. (2011). Assessing dominance hierarchies: validation and advantages of progressive evaluation with Elo-rating. Animal Behaviour, 82(4), 911–921.
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Dumont, B., Rossignol, N., Loucougaray, G., Carrère, P., Chadoeuf, J., Fleurance, G., et al. (2012). When does grazing generate stable vegetation patterns in temperate pastures? Agriculture, Ecosystems & Environment, 153, 50–56.
Abstract: The stability of grazing-induced spatial patterns of vegetation was analyzed at two spatial scales (25 m × 20 m areas and 1.6 m × 0.8 m grids) in pastures of contrasting productivity (maximum standing biomass: 130–800 gDM/m2). At both scales, the mosaic of grazed and ungrazed patches was modeled as a Boolean process, calculating cross-variograms to quantify the temporal stability of grazing patterns and its links with local floristic composition were tested. The scale at which stability of vegetation patterns took place in two successive years depended on pasture productivity. Inter-annual stability of large-scale patterns mainly occurred in extensively used fertile pastures grazed by cattle, and in pastures grazed by horses. Less-fertile grasslands were mainly characterized by a fine-scale stability of grazing patterns. Stable fine-scale patterns were often related to the local abundance of legumes and forbs. Stable large-scale patterns of grazing within lightly grazed productive grasslands could result in divergent local vegetation dynamics, which can be seen as an opportunity for restoring biodiversity in fertile grasslands.
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Gröschl, M., Wagner, R., Rauh, M., & Dörr, H. G. (2001). Stability of salivary steroids: the influences of storage, food and dental care. Steroids, 66(10), 737–741.
Abstract: We studied influences of dental care, food and storage on the reproducibility of salivary steroid levels. Cortisol (F), 17OH-progesterone (17OHP) and Progesterone (P) were measured using adapted commercial radioimmunoassays. Saliva samples of healthy adults (n = 15; m:8; f:7) were collected directly before and after dental care, and directly before and after breakfast with various foodstuffs. A second experiment investigated stability of steroids under different storage conditions. Four series of identical saliva portions (I: Native saliva; II: Centrifuged saliva; III: Saliva with trifluor acetate (TFA); IV: Saliva with 0.5% NaN3) were stored at room temperature and at 4°C for up to three weeks. To demonstrate influences of repeated thawing and re-freezing of saliva on steroid values, saliva samples (n = 15) were divided into identical portions. These portions were frozen and re-thawed up to 5 times before measurement. Neither dental care nor intake of bread or milk effected the reproducibility of F, 170HP, and P. Steroid levels decreased significantly in the course of three weeks under different storage conditions (P < 0.001). This decrease was clinically relevant from the second week onward, with exception of NaN3 treated samples. After repeated freezing and re-thawing 17OHP and P decreased slightly (about 5%). Only F decreased significantly after the third thawing (P < 0.001). The results show the usefulness of standardized handling of saliva samples for improving reproducibility and reliability of salivary steroid measurements.
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Nuñez, C. M. V., Adelman, J. S., Mason, C., & Rubenstein, D. I. (2009). Immunocontraception decreases group fidelity in a feral horse population during the non-breeding season. Appl. Anim. Behav. Sci., 117(1-2), 74–83.
Abstract: The behavioral effects of the immunocontraceptive agent porcine zona pellucida (PZP) have not been adequately studied. Important managerial decisions for several species, including the wild horse (Equus caballus), have been based on this limited research. We studied 30 horses on Shackleford Banks, North Carolina, USA to determine the effects of PZP contraception on female fidelity to the harem male. We examined two classes of females: contracepts, recipients of the PZP vaccine (n = 22); and controls, females that have never received PZP (n = 8). We conducted the study during the non-breeding season from December 2005 to February 2006, totaling 102.2 h of observation. Contracepted mares changed groups more often than control mares (P = 0.04). Contracepts also visited more harem groups than did control mares (P = 0.02) and exhibited more reproductive interest (P = 0.05). For both contracepted and control females, the number of group changes (P = 0.01) and number of groups visited (P = 0.003) decreased with the proportion of years mares were pregnant. Our study shows that the application of PZP has significant consequences for the social behavior of Shackleford Banks horses. In gregarious species such as the horse, PZP application may disrupt social ties among individuals and inhibit normal social functioning at the population level.
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