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Author |
Heitor, F.; do Mar Oom, M.; Vicente, L. |
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Title |
Social relationships in a herd of Sorraia horses Part I. Correlates of social dominance and contexts of aggression |
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Journal Article |
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Year |
2006 |
Publication |
Behavioural Processes |
Abbreviated Journal |
Behav. Process. |
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Volume |
73 |
Issue |
2 |
Pages |
170-177 |
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Keywords |
Age Factors; *Aggression; Animals; Female; *Hierarchy, Social; Horses/*psychology; Male; Sex Factors; *Social Dominance; *Social Environment; Statistics, Nonparametric |
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Abstract |
Factors related to dominance rank and the functions of aggression were studied in a herd of Sorraia horses, Equus caballus, under extensive management. Subjects were 10 adult mares 5-18 years old and a stallion introduced into the group for breeding. Dominance relationships among mares were clear, irrespective of rank difference, and remained stable after introduction of the stallion. The dominance hierarchy was significantly linear and rank was positively correlated with age and total aggressiveness. Higher-ranking mares received lower frequency and intensity of agonistic interactions. Nevertheless, higher-ranking dominants were not more likely to elicit submission from their subordinates than lower-ranking dominants. Neither close-ranking mares nor mares with less clear dominance relationships were more aggressive towards each other. Agonistic interactions seemed to be used more importantly in regulation of space than to obtain access to food or to reassert dominance relationships. Contexts of aggression were related to mare rank. The results suggest that dominance relationships based on age as a conventional criterion were established to reduce aggressiveness in a herd where the costs of aggression are likely to outweigh the benefits. |
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Centro de Biologia Ambiental, Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, Edificio C2, 1749-016 Lisboa, Portugal |
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English |
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0376-6357 |
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PMID:16815645 |
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292 |
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Author |
Cameron, E.Z. |
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Title |
Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism |
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Journal Article |
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Year |
2004 |
Publication |
Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
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Volume |
271 |
Issue |
1549 |
Pages |
1723-1728 |
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Keywords |
Age Factors; Animals; Body Constitution; *Evolution; Female; Glucose/metabolism/physiology; Litter Size; Male; Mammals/*physiology; *Models, Biological; Reproduction/physiology; Seasons; Sex Factors; *Sex Ratio; Time Factors |
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Abstract |
Evolutionary theory predicts that mothers of different condition should adjust the birth sex ratio of their offspring in relation to future reproductive benefits. Published studies addressing variation in mammalian sex ratios have produced surprisingly contradictory results. Explaining the source of such variation has been a challenge for sex-ratio theory, not least because no mechanism for sex-ratio adjustment is known. I conducted a meta-analysis of previous mammalian sex-ratio studies to determine if there are any overall patterns in sex-ratio variation. The contradictory nature of previous results was confirmed. However, studies that investigated indices of condition around conception show almost unanimous support for the prediction that mothers in good condition bias their litters towards sons. Recent research on the role of glucose in reproductive functioning have shown that excess glucose favours the development of male blastocysts, providing a potential mechanism for sex-ratio variation in relation to maternal condition around conception. Furthermore, many of the conflicting results from studies on sex-ratio adjustment would be explained if glucose levels in utero during early cell division contributed to the determination of offspring sex ratios. |
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Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za |
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0962-8452 |
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PMID:15306293 |
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413 |
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Fischer, J.; Hammerschmidt, K.; Cheney, D.L.; Seyfarth, R.M. |
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Title |
Acoustic features of male baboon loud calls: influences of context, age, and individuality |
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Journal Article |
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Year |
2002 |
Publication |
The Journal of the Acoustical Society of America |
Abbreviated Journal |
J Acoust Soc Am |
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Volume |
111 |
Issue |
3 |
Pages |
1465-1474 |
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Keywords |
Age Factors; Animal Communication; Animals; Individuality; Male; *Papio; *Social Environment; *Sound Spectrography; *Vocalization, Animal |
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The acoustic structure of loud calls (“wahoos”) recorded from free-ranging male baboons (Papio cynocephalus ursinus) in the Moremi Game Reserve, Botswana, was examined for differences between and within contexts, using calls given in response to predators (alarm wahoos), during male contests (contest wahoos), and when a male had become separated from the group (contact wahoos). Calls were recorded from adolescent, subadult, and adult males. In addition, male alarm calls were compared with those recorded from females. Despite their superficial acoustic similarity, the analysis revealed a number of significant differences between alarm, contest, and contact wahoos. Contest wahoos are given at a much higher rate, exhibit lower frequency characteristics, have a longer “hoo” duration, and a relatively louder “hoo” portion than alarm wahoos. Contact wahoos are acoustically similar to contest wahoos, but are given at a much lower rate. Both alarm and contest wahoos also exhibit significant differences among individuals. Some of the acoustic features that vary in relation to age and sex presumably reflect differences in body size, whereas others are possibly related to male stamina and endurance. The finding that calls serving markedly different functions constitute variants of the same general call type suggests that the vocal production in nonhuman primates is evolutionarily constrained. |
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Department of Psychology, University of Pennsylvania, Philadelphia 19104, USA. fischer@eva.mpg.de |
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0001-4966 |
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PMID:11931324 |
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refbase @ user @ |
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691 |
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Author |
Harkins, J.D.; Kamerling, S.G.; Church, G. |
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Title |
Effect of competition on performance of thoroughbred racehorses |
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Journal Article |
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Year |
1992 |
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Journal of Applied Physiology (Bethesda, Md. : 1985) |
Abbreviated Journal |
J Appl Physiol |
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72 |
Issue |
3 |
Pages |
836-841 |
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Keywords |
Age Factors; Animals; Anxiety/physiopathology; Competitive Behavior/*physiology; Exertion/*physiology; Fatigue/physiopathology; Female; Heart Rate; Horses/*physiology; Lactates/blood; Lactic Acid; Male; Sex Characteristics |
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The effect of competition and the influence of age and sex on performance were examined in a study of 18 Thoroughbred racehorses. The horses performed two solo and two competitive runs at 1,200 and 1,600 m for a total of eight runs. No group ran faster during competition, which may have been a reflection of the quality of horses used for this study and their susceptibility to stress-induced impairment of performance. Males showed no significant difference between competitive and solo run times, whereas females were consistently slower during competition. Males ran significantly faster than females in all runs. There was no difference in run times due to age, which may have been due to the high mean age (5.9 yr) of the group. The slower competitive run times may have occurred because of an earlier onset of fatigue when compared with solo runs. Plasma lactate was significantly greater for the 1,200-m competitive than for the solo runs. |
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Department of Veterinary Physiology, Pharmacology, and Toxicology, School of Veterinary Medicine, Louisiana State University, Baton Rouge 70803 |
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8750-7587 |
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Notes |
PMID:1568979 |
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refbase @ user @ |
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1947 |
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Author |
Feist, J.D.; McCullough, D.R. |
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Title |
Reproduction in feral horses |
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Journal Article |
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Year |
1975 |
Publication |
Journal of Reproduction and Fertility. Supplement |
Abbreviated Journal |
J Reprod Fertil Suppl |
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Issue |
23 |
Pages |
13-18 |
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Keywords |
Age Factors; Animals; Female; Horses/*physiology; Leadership; Male; Maternal Behavior; Population; Reproduction; *Sexual Behavior, Animal; Social Dominance; Sucking Behavior |
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Abstract |
A behavioural study of feral horses was conducted on the Pryor Mountain Wild Horse Range in the western United States. All 270 horses on the Range were identified individually. The sex ratio was nearly balanced. Foal to adult female ratio was 43-2:100. Morality was concentrated among foals and old horses. Horses were organized as forty-four harem groups each with a dominant stallion, one to two immature stallions, one to three immature mares, one to three adult mares and their yearling and foal offspring, and 23 bachelor groups of one to eight stallions. Harem groups were quite stable year-round because of dominance and leadership by the stallions and group fidelity by mares and their offsring. Most changes occurred during the breeding season and involved immature females. Defeat of dominant stallions was infrequent. Immature males were tolerated because of their submissive behaviour. Bachelor stallion groups were inherently unstable. Mares came into heat after foaling in May/June, and were mated by harem stallions only. |
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English |
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0449-3087 |
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PMID:1060766 |
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refbase @ user @ |
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1964 |
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