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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 |
Lee, R.D. |
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Title |
Rethinking the evolutionary theory of aging: transfers, not births, shape senescence in social species |
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Journal Article |
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Year |
2003 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc Natl Acad Sci U S A |
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Volume |
100 |
Issue |
16 |
Pages |
9637-9642 |
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Keywords |
Adaptation, Physiological; *Aging; Animals; *Biological Evolution; Demography; Economics; Environment; Fertility; Humans; Life Expectancy; Longevity; Models, Theoretical; Parturition; Population Dynamics; Population Growth; Reproduction |
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Abstract |
The classic evolutionary theory of aging explains why mortality rises with age: as individuals grow older, less lifetime fertility remains, so continued survival contributes less to reproductive fitness. However, successful reproduction often involves intergenerational transfers as well as fertility. In the formal theory offered here, age-specific selective pressure on mortality depends on a weighted average of remaining fertility (the classic effect) and remaining intergenerational transfers to be made to others. For species at the optimal quantity-investment tradeoff for offspring, only the transfer effect shapes mortality, explaining postreproductive survival and why juvenile mortality declines with age. It also explains the evolution of lower fertility, longer life, and increased investments in offspring. |
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Department of Demography, University of California, 2232 Piedmont Avenue, Berkeley, CA 94720-2120, USA. rlee@demog.berkeley.edu |
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0027-8424 |
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PMID:12878733 |
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Equine Behaviour @ team @ |
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5465 |
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Author |
Nelson, W.A.; Keirans, J.E.; Bell, J.F.; Clifford, C.M. |
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Title |
Host-ectoparasite relationships |
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Journal Article |
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Year |
1975 |
Publication |
Journal of Medical Entomology |
Abbreviated Journal |
J Med Entomol |
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Volume |
12 |
Issue |
2 |
Pages |
143-166 |
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Keywords |
Animal Nutrition Physiology; Animals; Anoplura/physiology; *Arthropods; Birds/parasitology; Chickens/parasitology; Dermacentor/parasitology; Diptera; Ecology; Feeding Behavior; Female; Horses/parasitology; Humans; Male; Mallophaga/physiology; Mice/parasitology; Mites/physiology; Reproduction; Sarcoptes scabiei/physiology; Sheep/parasitology; Skin/parasitology; Ticks/physiology; Toxins, Biological/toxicity; Trombiculidae/physiology |
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0022-2585 |
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PMID:808617 |
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Call Number |
Equine Behaviour @ team @ |
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2704 |
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Author |
Ogbourne, C.P. |
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Title |
Variations in the fecundity of strongylid worms of the horse |
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Journal Article |
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Year |
1971 |
Publication |
Parasitology |
Abbreviated Journal |
Parasitology |
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63 |
Issue |
2 |
Pages |
289-298 |
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Keywords |
Animals; Animals, Newborn; Ecology; Feces; Female; Horses; Larva/growth & development; Male; Ovum; Parasite Egg Count; Reproduction; Seasons; Strongyle Infections, Equine/*etiology; Strongyloides/*growth & development; Time Factors |
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0031-1820 |
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PMID:5129804 |
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no |
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Equine Behaviour @ team @ |
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2727 |
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Author |
Ganswindt, A.; Palme, R.; Heistermann, M.; Borragan, S.; Hodges, J.K. |
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Title |
Non-invasive assessment of adrenocortical function in the male African elephant (Loxodonta africana) and its relation to musth |
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Journal Article |
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Year |
2003 |
Publication |
General and Comparative Endocrinology |
Abbreviated Journal |
Gen Comp Endocrinol |
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Volume |
134 |
Issue |
2 |
Pages |
156-166 |
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Keywords |
Adrenal Cortex/*metabolism/secretion; Adrenal Cortex Function Tests/methods/*veterinary; Adrenocorticotropic Hormone/physiology; Animals; Carbon Isotopes/diagnostic use; Chromatography, High Pressure Liquid/veterinary; Elephants/*metabolism/urine; Feces/*chemistry; Glucocorticoids/analysis/urine; Hydrocortisone/*analysis/diagnostic use/urine; Immunoenzyme Techniques/methods/veterinary; Male; Reproduction/physiology; Sexual Behavior, Animal/physiology; Stress, Psychological/diagnosis/*physiopathology; Testosterone/*analysis/diagnostic use/urine |
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Abstract |
Adult male elephants periodically show the phenomenon of musth, a condition associated with increased aggressiveness, restlessness, significant weight reduction and markedly elevated androgen levels. It has been suggested that musth-related behaviours are costly and that therefore musth may represent a form of physiological stress. In order to provide data on this largely unanswered question, the first aim of this study was to evaluate different assays for non-invasive assessment of adrenocortical function in the male African elephant by (i) characterizing the metabolism and excretion of [3H]cortisol (3H-C) and [14C]testosterone (14C-T) and (ii) using this information to evaluate the specificity of four antibodies for determination of excreted cortisol metabolites, particularly with respect to possible cross-reactions with androgen metabolites, and to assess their biological validity using an ACTH challenge test. Based on the methodology established, the second objective was to provide data on fecal cortisol metabolite concentrations in bulls during the musth and non-musth condition. 3H-C (1 mCi) and 14C-T (100 microCi) were injected simultaneously into a 16 year old male and all urine and feces collected for 30 and 86 h, respectively. The majority (82%) of cortisol metabolites was excreted into the urine, whereas testosterone metabolites were mainly (57%) excreted into the feces. Almost all radioactive metabolites recovered from urine were conjugated (86% 3H-C and 97% 14C-T). In contrast, 86% and >99% of the 3H-C and 14C-T metabolites recovered from feces consisted of unconjugated forms. HPLC separations indicated the presence of various metabolites of cortisol in both urine and feces, with cortisol being abundant in hydrolysed urine, but virtually absent in feces. Although all antibodies measured substantial amounts of immunoreactivity after HPLC separation of peak radioactive samples and detected an increase in glucocorticoid output following the ACTH challenge, only two (in feces against 3alpha,11-oxo-cortisol metabolites, measured by an 11-oxo-etiocholanolone-EIA and in urine against cortisol, measured by a cortisol-EIA) did not show substantial cross-reactivity with excreted 14C-T metabolites and could provide an acceptable degree of specificity for reliable assessment of glucocorticoid output from urine and feces. Based on these findings, concentrations of immunoreactive 3alpha,11-oxo-cortisol metabolites were determined in weekly fecal samples collected from four adult bulls over periods of 11-20 months to examine whether musth is associated with increased adrenal activity. Results showed that in each male levels of these cortisol metabolites were not elevated during periods of musth, suggesting that in the African elephant musth is generally not associated with marked elevations in glucocorticoid output. Given the complex nature of musth and the variety of factors that are likely to influence its manifestation, it is clear, however, that further studies, particularly on free-ranging animals, are needed before a possible relationship between musth and adrenal function can be resolved. This study also clearly illustrates the potential problems associated with cross-reacting metabolites of gonadal steroids in EIAs measuring glucocorticoid metabolites. This has to be taken into account when selecting assays and interpreting results of glucocorticoid metabolite analysis, not only for studies in the elephant but also in other species. |
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German Primate Centre, Department of Reproductive Biology, Kellnerweg 4, 37077 Gottingen, Germany. ganswindt@www.dpz.gdwg.de |
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0016-6480 |
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PMID:14511986 |
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Call Number |
Equine Behaviour @ team @ |
Serial |
4085 |
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Author |
Bermudez, J.L. |
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Title |
The moral significance of birth |
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Journal Article |
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Year |
1996 |
Publication |
Ethics |
Abbreviated Journal |
Ethics |
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Volume |
106 |
Issue |
2 |
Pages |
378-403 |
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Keywords |
Abortion, Induced; Animal Rights; Animals; Beginning of Human Life; Embryonic and Fetal Development; *Ethical Analysis; *Ethics; *Fetus; Homicide; Humans; *Individuality; *Infant, Newborn; Infant, Premature; Infanticide; *Labor, Obstetric; Life; *Personhood; Philosophy; Primates; Psychology; *Self Concept; *Value of Life; Analytical Approach; Genetics and Reproduction; Philosophical Approach |
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0014-1704 |
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PMID:11656645; KIE: 31 fn.; KIE: KIE BoB Subject Heading: fetuses; KIE: KIE BoB Subject Heading: personhood |
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Equine Behaviour @ team @ |
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4177 |
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Author |
Mech L.D. |
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Title |
Leadership in Wolf, Canis lupus, Packs. |
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Journal Article |
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Year |
2000 |
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Canadian Field-Naturalist |
Abbreviated Journal |
Can Field Nat |
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114 |
Issue |
2 |
Pages |
259-263 |
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Wolf, Canis lupus, leadership, behavior, foraging, movements, pup care, provisioning, sociality, reproduction, breeding, Northwest Territories. |
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I examine leadership in Wolf (Canis lupus) packs based on published observations and data gathered during summers from 1986 to 1998 studying a free-ranging pack of Wolves on Ellesmere Island that were habituated to my presence. The breeding male tended to initiate activities associated with foraging and travel, and the breeding female to initiate, and predominate in, pup care and protection. However, there was considerable overlap and interaction during these activities such that leadership could be considered a joint function. In packs with multiple breeders, quantitative information about leadership is needed. |
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Equine Behaviour @ team @ |
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4688 |
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Author |
Klingel, H. |
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Title |
Social organization and reproduction in equids |
Type |
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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23 |
Pages |
7-11 |
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Animals; Behavior, Animal; Female; Male; Perissodactyla/*physiology; Reproduction; *Sexual Behavior, Animal; Social Behavior; Territoriality |
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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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Equine Behaviour @ team @ |
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2303 |
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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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23 |
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13-18 |
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Age Factors; Animals; Female; Horses/*physiology; Leadership; Male; Maternal Behavior; Population; Reproduction; *Sexual Behavior, Animal; Social Dominance; Sucking Behavior |
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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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0449-3087 |
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PMID:1060766 |
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refbase @ user @ |
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1964 |
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Author |
Moehlman, P.D. |
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Title |
Endangered wild equids |
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Journal Article |
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Year |
2005 |
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Scientific American |
Abbreviated Journal |
Sci Am |
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Volume |
292 |
Issue |
3 |
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74-81 |
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Africa; Americas; Animals; *Animals, Wild/physiology; Asia; *Conservation of Energy Resources; Environment; *Equidae/physiology; Food Chain; Humans; Male; Reproduction |
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IUCN-The World Conservation Union/Species Survival Commission Equid Specialist Group |
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0036-8733 |
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PMID:15859216 |
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refbase @ user @ |
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551 |
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