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Author (up) Taillon, J.; Côté, S.
Title Are faecal hormone levels linked to winter progression, diet quality and social rank in young ungulates ? An experiment with white-tailed deer ( Odocoileus virginianus ) fawns Type Journal Article
Year 2008 Publication Behavioral Ecology and Sociobiology Abbreviated Journal Behav. Ecol. Sociobiol.
Volume 62 Issue 10 Pages 675-677
Keywords Diet quality – Glucocorticoids – Social rank – Testosterone – White-tailed deer
Abstract Abstract Hormones play a central role in the physiology and behaviour of animals. The recent development of noninvasive techniques has increased information on physical and social states of individuals through hormone measurements. The relationships among hormones, life history traits and behaviours are, however, still poorly known. For the first time, we evaluated natural winter glucocorticoid and testosterone levels in young ungulates in relation to winter progression, diet quality and social rank. Overwinter, levels of glucocorticoid and testosterone decreased, possibly due to the decline of fawns" body mass. The relationships between hormone levels and diet quality were surprising: Fawns fed the control diet presented higher glucocorticoid and lower testosterone levels then fawns fed the poor diet, suggesting that control fawns faced a higher nutritional stress than those on the poor diet. Similarly to other studies on social mammals, we found no relationship between faecal glucocorticoid levels and social rank, suggesting that social stress was similar for dominant and subordinate fawns during winter. Testosterone levels were not correlated to social rank as found previously in groups of individuals forming stable social hierarchies and maintaining stable dominance relationships. The simultaneous suppression of glucocorticoid and testosterone levels suggests for the first time that young ungulates present a hormonal strategy to prevent fast depletion of limited proteins and fat resources during winter.
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Call Number Equine Behaviour @ team @ Serial 4423
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Author (up) Taillon, J.; Cote, S.D.
Title Social rank and winter forage quality affect aggressiveness in white-tailed deer fawns Type Journal Article
Year 2007 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 74 Issue 2 Pages 265-275
Keywords aggressiveness; agonistic behaviour; body mass loss; dominance status; forage intake; Odocoileus virginianus; resource competition; social behaviour; white-tailed deer; winter forage quality
Abstract Achieving a high social rank may be advantageous for individuals at high population densities, because dominance status may determine the priority of access to limited resources and reduce individual loss of body mass. The establishment of dominance relationships between individuals involves variable levels of aggressiveness that can be influenced by resource availability. The relationship between social rank and aggressiveness and the impacts of resource abundance on aggressiveness are, however, poorly understood, but may be relevant to understand the mechanisms determining dominance relationships between individuals. We experimentally simulated, in seminatural enclosures, a deterioration of winter forage quality induced by a high-density deer population and examined the effects of (1) social dominance and (2) diet quality on aggressiveness, forage intake and body mass loss of white-tailed deer, Odocoileus virginianus, fawns during two winters. Within diet-quality treatments, fawns were consistently organized into linear hierarchies and showed clear dominance relationships. Dominants initiated more interactions and showed higher aggressiveness than subordinates, but subordinates had higher forage intake than dominants throughout winter. Social rank did not influence cumulative body mass loss of fawns. During both winters, fawns fed the control diet maintained their aggressiveness level, whereas fawns fed the poor-quality diet decreased it. Our experimental approach revealed that white-tailed deer responded to a reduction in winter forage quality by modifying their aggressiveness, indicating that ungulates may show plasticity not only in their foraging behaviour in response to decreased resources but also in their social behaviour.
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Call Number Equine Behaviour @ team @ Serial 4203
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