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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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refbase @ user @ |
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413 |
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Author |
Hemelrijk, C.K.; Wantia, J. |
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Title |
Individual variation by self-organisation |
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Journal Article |
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Year |
2005 |
Publication |
Neuroscience and biobehavioral reviews |
Abbreviated Journal |
Neurosci Biobehav Rev |
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Volume |
29 |
Issue |
1 |
Pages |
125-136 |
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Keywords |
Aggression; Animals; Behavior, Animal/*physiology; Competitive Behavior/*physiology; Female; Humans; *Individuality; Male; Models, Psychological; Sex Characteristics; *Social Dominance; Time Factors |
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Abstract |
In this paper, we show that differences in dominance and spatial centrality of individuals in a group may arise through self-organisation. Our instrument is a model, called DomWorld, that represents two traits that are often found in animals, namely grouping and competing. In this model individual differences grow under the following conditions: (1) when the intensity of aggression increases and grouping becomes denser, (2) when the degree of sexual dimorphism in fighting power increases. In this case the differences among females compared to males grow too, (3) when, upon encountering another individual, the tendency to attack is 'obligate' and not conditional, namely 'sensitive to risks'. Results resemble phenomena described for societies of primates, mice, birds and pigs. |
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Theoretical Biology, University of Groningen, NN Haren, The Netherlands. hemelrij@ifi.unizh.ch |
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0149-7634 |
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PMID:15652260 |
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refbase @ user @ |
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443 |
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Author |
Boyd, L. |
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Title |
Behavior problems of equids in zoos |
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Journal Article |
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Year |
1986 |
Publication |
The Veterinary clinics of North America. Equine practice |
Abbreviated Journal |
Vet Clin North Am Equine Pract |
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2 |
Issue |
3 |
Pages |
653-664 |
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Keywords |
Aerophagy/veterinary; Aggression/psychology; Animals; *Animals, Zoo; *Behavior, Animal; Coprophagia/psychology; Female; *Horses; Impotence/veterinary; Male; Mastication; Motor Activity; *Perissodactyla; Pregnancy; Sexual Behavior, Animal; Social Environment |
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Behavior problems in zoo equids commonly result from a failure to provide for needs basic to equine nature. Equids are gregarious, and failure to provide companions may result in pacing. Wild equids spend 60 to 70 per cent of their time grazing, and failure to provide ad libitum roughage contributes to the problems of pacing, cribbing, wood chewing, and coprophagia. Mimicking the normal processes of juvenile dispersal, bachelor-herd formation, and mate acquisition reduces the likelihood of agonistic and reproductive behavior problems. Infanticide can be avoided by introducing new stallions to herds containing only nonpregnant mares and older foals. |
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0749-0739 |
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Notes |
PMID:3492252 |
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no |
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Call Number |
refbase @ user @ |
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660 |
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Author |
Keiper, R.; Houpt, K. |
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Title |
Reproduction in feral horses: an eight-year study |
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Journal Article |
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Year |
1984 |
Publication |
American journal of veterinary research |
Abbreviated Journal |
Am J Vet Res |
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Volume |
45 |
Issue |
5 |
Pages |
991-995 |
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Keywords |
Abortion, Veterinary/epidemiology; Anestrus; Animal Population Groups/*physiology; Animals; Animals, Wild/*physiology; Birth Rate; Female; Fertility; Horse Diseases/epidemiology; Horses/*physiology; Lactation; Male; Maryland; Pregnancy; *Reproduction; Seasons; Sex Ratio; Virginia |
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The reproductive rate and foal survival of the free-ranging ponies on Assateague Island National Seashore were studied for 8 years, 1975 to 1982. Most (52%) of the 86 foals were born in May, 13% were born in April, 22.6% in June, 10.4% in July, and less than 1% in August and September. The mean foaling rate was 57.1 +/- 3.9% and the survival rate was 88.3 +/- 3.6%. Forty-eight colts and 55 fillies were born (sex ratio 53% female). Mares less than 3 years old did not foal and the foaling rate of 3-year-old mares was only 23%, that of 4-year-old mares was 46%, that of 5-year-old mares was 53%, and 6-year-old mares was 69%. The relatively poor reproduction rate was believed to be a consequence of the stress of lactating while carrying a foal when forage quality on the island was low. The hypothesis was supported by the higher reproductive rate (74.4 +/- 2.4%) of the ponies in the Chincoteague National Wildlife Refuge on the southern part of the island. Their foals are weaned and sold in July each year. Despite the low reproductive rate on Assateague Island National Seashore , the number of ponies increased from 43 to 80, a 90% increase in the 8-year period or greater than 10%/yr. There were 24 deaths and 8 dispersals from the study area. |
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ISSN |
0002-9645 |
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Notes |
PMID:6732036 |
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no |
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Call Number |
refbase @ user @ |
Serial |
665 |
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Author |
Cancedda, M. |
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Title |
[Social and behavioral organization of horses on the Giara (Sardinia): distribution and aggregation] |
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Journal Article |
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Year |
1990 |
Publication |
Bollettino della Societa italiana di biologia sperimentale |
Abbreviated Journal |
Boll Soc Ital Biol Sper |
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Volume |
66 |
Issue |
11 |
Pages |
1089-1096 |
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Keywords |
Animals; *Animals, Wild/physiology/psychology; Environment; Female; *Horses/physiology/psychology; Italy; Male; Population Density; Sexual Behavior, Animal; *Social Behavior; Social Dominance; Water |
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In this paper some considerations on the environment of the 42 Kmq of the volcanic-basaltic Giara tableland are discussed. Conditioning by the environment and its effect on the distribution of a population of 712 horses is illustrated in view of their social and behavioural organization. |
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Istituto di Fisiologia Generale e Speciale, Universita di Sassari |
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Italian |
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Introduzione all'organizzazione sociale e comportamentale dei cavallini sulla Giara (Sardegna): distribuzione ed aggregazione |
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0037-8771 |
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PMID:2095819 |
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refbase @ user @ |
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673 |
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Author |
Beaver, B.V. |
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Title |
Aggressive behavior problems |
Type |
Journal Article |
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Year |
1986 |
Publication |
The Veterinary clinics of North America. Equine practice |
Abbreviated Journal |
Vet Clin North Am Equine Pract |
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2 |
Issue |
3 |
Pages |
635-644 |
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Keywords |
Affect; Aggression/*psychology; Animals; *Behavior, Animal; Dominance-Subordination; Fear; *Horses; Play and Playthings; Sexual Behavior, Animal; Social Environment |
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Accurate diagnosis of the cause of aggression in horses is essential to determining the appropriate course of action. The affective forms of aggression include fear-induced, pain-induced, intermale, dominance, protective, maternal, learned, and redirected aggressions. Non-affective aggression includes play and sex-related forms. Irritable aggression and hypertestosteronism in mares are medical problems, whereas genetic factors, brain dysfunction, and self-mutilation are also concerns. |
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0749-0739 |
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PMID:3492250 |
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refbase @ user @ |
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674 |
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Author |
Keiper, R.R. |
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Title |
Social structure |
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Journal Article |
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Year |
1986 |
Publication |
The Veterinary clinics of North America. Equine practice |
Abbreviated Journal |
Vet Clin North Am Equine Pract |
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2 |
Issue |
3 |
Pages |
465-484 |
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Keywords |
Animal Communication; Animals; Animals, Domestic; Animals, Wild; Dominance-Subordination; Female; *Hierarchy, Social; Homing Behavior; *Horses; Male; Sexual Behavior, Animal; *Social Behavior; *Social Dominance |
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Socially feral horses live in stable social groups characterized by one adult male, a number of adult females, and their offspring up to 2 years of age. Extra males either live by themselves or with other males in bachelor groups. The bands occupy nondefended home ranges that often overlap. Many abnormal behaviors seen in domestic horses occur because some aspect of their normal social behavior cannot be carried out in captivity. |
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0749-0739 |
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PMID:3492240 |
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refbase @ user @ |
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675 |
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Author |
Collery, L. |
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Observations of equine animals under farm and feral conditions |
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Journal Article |
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1974 |
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Equine veterinary journal |
Abbreviated Journal |
Equine Vet J |
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6 |
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4 |
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170-173 |
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Aggression; Animals; Animals, Newborn; Breeding; Circadian Rhythm; Feeding Behavior; Female; Horses/*physiology; Housing, Animal; Humans; Male; Pregnancy; Puberty; Reproduction; Sexual Behavior, Animal; Social Dominance |
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0425-1644 |
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PMID:4473340 |
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refbase @ user @ |
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680 |
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Author |
Kiley, M. |
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Title |
The vocalizations of ungulates, their causation and function |
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Journal Article |
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1972 |
Publication |
Zeitschrift für Tierpsychologie |
Abbreviated Journal |
Z. Tierpsychol. |
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31 |
Issue |
2 |
Pages |
171-222 |
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Aggression; Animals; *Artiodactyla; Cattle; Fear; Female; Frustration; Horses; Humans; Male; Pain; *Perissodactyla; Sexual Behavior, Animal; Social Behavior; Social Dominance; Swine; *Vocalization, Animal |
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0044-3573 |
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PMID:4674022 |
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681 |
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Author |
Weeks, J.W.; Crowell-Davis, S.L.; Caudle, A.B.; Heusner, G.L. |
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Title |
Aggression and social spacing in light horse (Equus caballus) mares and foals |
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Journal Article |
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2000 |
Publication |
Applied Animal Behaviour Science |
Abbreviated Journal |
Appl. Anim. Behav. Sci. |
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68 |
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4 |
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319-337 |
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Dominance relationships; Horse; Sex differences; Social ontogeny; aggregation; parent-offspring interaction; social behavior |
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Aggression and social spacing were studied in 14 light horse mares and their foals living at pasture. Focal samples were collected on each mare-foal dyad for 6 to 10.5 h from 2 months of foal age until weaning at approximately 4 months of age. Observations on foals continued until approximately 6 months of age for 7.5 to 10.5 h per foal. Every 2 min the identities of all individuals within 5 m were recorded. All occurrences of agonistic behavior, and the participants, were recorded during the focal samples. In addition, during feeding of supplemental grain, all occurrences of agonistic behavior by all subjects were recorded. Significant correlations were found between mare rank and the rank of foals both prior to and after weaning. Before weaning, the rank of the foal was significantly correlated with birth order. No significant correlation between birth order and foal rank was found for the post-weaning hierarchy. An animal's gender had no significant effect on foal rank or the choice of preferred associate. Both prior to and after weaning, foals associated preferentially with the foal of their dam's most preferred associate. In addition, significant positive correlations were found between rank of mares and foals and the rate at which they directed aggression to other herd members. (C) 2000 Elsevier Science B.V. |
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Cited By (since 1996): 7; Export Date: 21 April 2007; Source: Scopus |
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