| Records |
| Author |
Cameron, E.Z. |
| Title |
Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism |
Type |
Journal Article |
| Year |
2004 |
Publication |
Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
| Volume |
271 |
Issue |
1549 |
Pages |
1723-1728 |
| 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 |
| 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. |
| Address |
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za |
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English |
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0962-8452 |
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PMID:15306293 |
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no |
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refbase @ user @ |
Serial |
413 |
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| Author |
Hemelrijk, C.K.; Wantia, J. |
| Title |
Individual variation by self-organisation |
Type |
Journal Article |
| Year |
2005 |
Publication |
Neuroscience and biobehavioral reviews |
Abbreviated Journal |
Neurosci Biobehav Rev |
| Volume |
29 |
Issue |
1 |
Pages |
125-136 |
| Keywords |
Aggression; Animals; Behavior, Animal/*physiology; Competitive Behavior/*physiology; Female; Humans; *Individuality; Male; Models, Psychological; Sex Characteristics; *Social Dominance; Time Factors |
| 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. |
| Address |
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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no |
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refbase @ user @ |
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443 |
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| Author |
Boyd, L. |
| Title |
Behavior problems of equids in zoos |
Type |
Journal Article |
| Year |
1986 |
Publication |
The Veterinary clinics of North America. Equine practice |
Abbreviated Journal |
Vet Clin North Am Equine Pract |
| Volume |
2 |
Issue |
3 |
Pages |
653-664 |
| 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 |
| Abstract |
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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PMID:3492252 |
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no |
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refbase @ user @ |
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660 |
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| Author |
Keiper, R.; Houpt, K. |
| Title |
Reproduction in feral horses: an eight-year study |
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Journal Article |
| Year |
1984 |
Publication |
American journal of veterinary research |
Abbreviated Journal |
Am J Vet Res |
| Volume |
45 |
Issue |
5 |
Pages |
991-995 |
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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 |
| Abstract |
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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0002-9645 |
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PMID:6732036 |
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no |
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refbase @ user @ |
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665 |
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| Author |
Weeks, J.W.; Crowell-Davis, S.L.; Caudle, A.B.; Heusner, G.L. |
| Title |
Aggression and social spacing in light horse (Equus caballus) mares and foals |
Type |
Journal Article |
| Year |
2000 |
Publication |
Applied Animal Behaviour Science |
Abbreviated Journal |
Appl. Anim. Behav. Sci. |
| Volume |
68 |
Issue |
4 |
Pages |
319-337 |
| Keywords |
Dominance relationships; Horse; Sex differences; Social ontogeny; aggregation; parent-offspring interaction; social behavior |
| Abstract |
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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no |
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refbase @ user @ |
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788 |
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| Author |
Klingel, H. |
| Title |
Social organization and reproduction in equids |
Type |
Journal Article |
| Year |
1975 |
Publication |
Journal of Reproduction and Fertility. Supplement |
Abbreviated Journal |
J Reprod Fertil Suppl |
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Issue |
23 |
Pages |
7-11 |
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Animals; Behavior, Animal; Female; Male; Perissodactyla/*physiology; Reproduction; *Sexual Behavior, Animal; Social Behavior; Territoriality |
| Abstract |
There are two distinct types of social organization and, accordingly, two types of mating systems in equids. In the horse, Plains zebra and Mountain zebra, the adults live in non-territorial and cohesive one-male groups and in stallion groups. The family stallions have exclusive mating rights which are respected by all others. In Grevy's zebra and in the African and Asiatic wild asses, the stallions are permanently territorial and have exclusive mating rights within their territories. Ecological and evolutionary aspects are discussed. |
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0449-3087 |
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PMID:1060868 |
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no |
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Equine Behaviour @ team @ |
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2303 |
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| Author |
McDonnell, S.M.; Henry,M. Bristol, F. |
| Title |
Spontaneous erection and masturbation in equids Proc 35th |
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Journal Article |
| Year |
1991 |
Publication |
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Abbreviated Journal |
J. Reprod. Fert. Suppl |
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44 |
Issue |
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664-665 |
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Horse; Masturbation; Erection; Aversive conditioning; Sexual behavior; Ejaculation; Semen |
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This paper is part of the special issue entitled “Proceedings of the 4th International Symposium on Stallion Reproduction”, Guest Edited by Dr. Edward Squires. |
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no |
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1378 |
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Barry, K.J.; Crowell-Davis, S.L. |
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Gender differences in the social behavior of the neutered indoor-only domestic cat |
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Journal Article |
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1999 |
Publication |
Applied Animal Behaviour Science |
Abbreviated Journal |
Appl. Anim. Behav. Sci. |
| Volume |
64 |
Issue |
3 |
Pages |
193-211 |
| Keywords |
Sex differences; Spatial distribution; Cat; Social; Aggression; Affiliation; Felis catus |
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The domestic cat exhibits a wide variety of social behavior. The aim of this experiment was to investigate factors which influence the affiliative and aggressive behavior of the indoor-only neutered domestic cat. Some 60 households comprised of either two males, two females or a male and female cat were observed. The cats were between 6 months and 8 years old, and were always restricted to the indoors. Each pair of housemates was observed for 10 h. There were no significant differences in affiliative or aggressive behavior based on cat gender. However, females were never observed to allorub other females. The male/male households did spend more time in close proximity. The amount of time the cats had lived together was negatively correlated with the amount of aggression observed during the study. Factors such as size of the house and weight difference between the cats did not correlate with the aggression rate. Large standard deviations and the correlations of social behavior between housemates indicated the importance of individual differences in behavior. |
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no |
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Equine Behaviour @ team @ |
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2267 |
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| Author |
McComb, K.; Clutton-Brock, T. |
| Title |
Is mate choice copying or aggregation responsible for skewed distributions of females on leks? |
Type |
Journal Article |
| Year |
1994 |
Publication |
Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
| Volume |
255 |
Issue |
1342 |
Pages |
13-19 |
| Keywords |
Animals; Deer/*physiology; Estrus/physiology; Female; Male; Phenotype; Sexual Behavior, Animal/*physiology; Territoriality |
| Abstract |
In several lek-breeding populations of birds and mammals, females arriving on leks tend to join males that already have females in their territories. This might occur either because females have an evolved preference for mating with males that are attractive to other females, or because they join groups of other females to obtain greater safety from predation or dangerous harassment by males. We have previously used controlled experiments to show that oestrous fallow deer females join males with established harems because they are attracted to female groups rather than to the males themselves. Here we demonstrate that the preference for males with females over males without females is specific to oestrous females and weak or absent in anoestrous ones, and that it is not associated with a preference for mating with males that have previously been seen to mate with other females. Furthermore, oestrous females given the choice between males that do not already have females with them show no significant preference for antlered over deantlered males or for older males over younger ones. We conclude that female attraction to other females on the lek is likely to be an adaptation to avoiding harassment in mixed-sex herds. In this situation, a male's ability to maintain the cohesion of his harem may be the principal cause of variation in mating success between males. |
| Address |
Department of Zoology, University of Cambridge, U.K |
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English |
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0962-8452 |
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| Notes |
PMID:8153135 |
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no |
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1823 |
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| Author |
Uehara, T.; Yokomizo, H.; Iwasa, Y. |
| Title |
Mate-choice copying as Bayesian decision making |
Type |
Journal Article |
| Year |
2005 |
Publication |
The American naturalist |
Abbreviated Journal |
Am Nat |
| Volume |
165 |
Issue |
3 |
Pages |
403-410 |
| Keywords |
Animals; *Bayes Theorem; *Choice Behavior; Female; Male; *Models, Biological; *Sexual Behavior, Animal |
| Abstract |
Mate-choice copying by females has been reported in fishes (e.g., guppies) and lekking birds. Presumably, females assess males' quality using both information from direct observation of males and information acquired by observing other females' choices. Here, we study mathematically the conditions under which mate-choice copying is advantageous on the basis of Bayesian decision theory. A female may observe the mate choice of another female, called the model female, who has performed an optimal choice based on her own judgment. The conditions required for the focal female to choose the same mate as that chosen by the model female should depend on the male's appearance to her, the reliability of her own judgment of male quality, and the reliability of the model females. When three or more females are involved, the optimal mate choice critically depends on whether multiple model females make decisions independently or they themselves copy the choices of others. If two equally reliable females choose different males, the choice of the second female, made knowing the choice of the first, should have a stronger effect on the choice of the third (focal) female. This “last-choice precedence” should be tested experimentally. |
| Address |
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan. uehara@bio-math.biology.kyushu-u.ac.jp |
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1537-5323 |
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PMID:15729669 |
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1821 |
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