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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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Year |
2004 |
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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 |
Hall, C.A.; Cassaday, H.J.; Derrington, A.M. |
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Title |
The effect of stimulus height on visual discrimination in horses |
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Journal Article |
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Year |
2003 |
Publication |
Journal of Animal Science |
Abbreviated Journal |
J. Anim Sci. |
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Volume |
81 |
Issue |
7 |
Pages |
1715-1720 |
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Keywords |
Animals; *Discrimination Learning/physiology; Female; Horses/physiology/*psychology; Male; Orientation; *Photic Stimulation; Vision/*physiology |
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Abstract |
This study investigated the effect of stimulus height on the ability of horses to learn a simple visual discrimination task. Eight horses were trained to perform a two-choice, black/white discrimination with stimuli presented at one of two heights: ground level or at a height of 70 cm from the ground. The height at which the stimuli were presented was alternated from one session to the next. All trials within a single session were presented at the same height. The criterion for learning was four consecutive sessions of 70% correct responses. Performance was found to be better when stimuli were presented at ground level with respect to the number of trials taken to reach the criterion (P < 0.05), percentage of correct first choices (P < 0.01), and repeated errors made (P < 0.01). Thus, training horses to carry out tasks of visual discrimination could be enhanced by placing the stimuli on the ground. In addition, the results of the present study suggest that the visual appearance of ground surfaces is an important factor in both horse management and training. |
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School of Land-based Studies, Nottingham Trent University, Brackenhurst College Campus, Southwell, Nottinghamshire, England NG25 0QF. carol.hall@ntu.ac.uk |
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0021-8812 |
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PMID:12854807 |
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refbase @ user @ |
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835 |
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Honeyman, M.S.; Miller, G.S. |
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The effect of teaching approaches on achievement and satisfaction of field-dependent and field-independent learners in animal science |
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1998 |
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Journal of Animal Science |
Abbreviated Journal |
J. Anim Sci. |
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76 |
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6 |
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1710-1715 |
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Equine Behaviour @ team @ |
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2941 |
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Hamilton, C.R.; Vermeire, B.A. |
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Title |
Complementary hemispheric specialization in monkeys |
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Journal Article |
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Year |
1988 |
Publication |
Science |
Abbreviated Journal |
Science |
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Volume |
242 |
Issue |
4886 |
Pages |
1691-1694 |
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Twenty-five split-brain monkeys were taught to discriminate two types of visual stimuli that engage lateralized cerebral processing in human subjects. Differential lateralization for the two kinds of discriminations was found; the left hemisphere was better at distinguishing between tilted lines and the right hemisphere was better at discriminating faces. These results indicate that lateralization of cognitive processing appeared in primates independently of language or handedness. In addition, cerebral lateralization in monkeys may provide an appropriate model for studying the biological basis of hemispheric specialization. |
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Equine Behaviour @ team @ |
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5342 |
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Kaminski, J.; Call, J.; Fischer, J. |
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Title |
Word Learning in a Domestic Dog: Evidence for “Fast Mapping” |
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Journal Article |
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Year |
2004 |
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Science |
Abbreviated Journal |
Science |
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304 |
Issue |
5677 |
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1682-1683 |
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During speech acquisition, children form quick and rough hypotheses about the meaning of a new word after only a single exposure--a process dubbed “fast mapping.” Here we provide evidence that a border collie, Rico, is able to fast map. Rico knew the labels of over 200 different items. He inferred the names of novel items by exclusion learning and correctly retrieved those items right away as well as 4 weeks after the initial exposure. Fast mapping thus appears to be mediated by general learning and memory mechanisms also found in other animals and not by a language acquisition device that is special to humans. |
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10.1126/science.1097859 |
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Equine Behaviour @ team @ |
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4678 |
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Author |
Walter, G.; Reisner, A. |
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Title |
Student opinion formation on animal agriculture issues |
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Journal Article |
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Year |
1994 |
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Journal of Animal Science |
Abbreviated Journal |
J. Anim Sci. |
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72 |
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6 |
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1654-1658 |
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N1 - |
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Equine Behaviour @ team @ |
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2935 |
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Horváth, G.; Blahó, M.; Kriska, G.; Hegedüs, R.; Gerics, B.; Farkas, R.; Åkesson, S. |
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Title |
An unexpected advantage of whiteness in horses: the most horsefly-proof horse has a depolarizing white coat |
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Journal Article |
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2010 |
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Proceedings of the Royal Society B: Biological Sciences |
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277 |
Issue |
1688 |
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1643-1650 |
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White horses frequently suffer from malign skin cancer and visual deficiencies owing to their high sensitivity to the ultraviolet solar radiation. Furthermore, in the wild, white horses suffer a larger predation risk than dark individuals because they can more easily be detected. In spite of their greater vulnerability, white horses have been highly appreciated for centuries owing to their natural rarity. Here, we show that blood-sucking tabanid flies, known to transmit disease agents to mammals, are less attracted to white than dark horses. We also demonstrate that tabanids use reflected polarized light from the coat as a signal to find a host. The attraction of tabanids to mainly black and brown fur coats is explained by positive polarotaxis. As the host's colour determines its attractiveness to tabanids, this parameter has a strong influence on the parasite load of the host. Although we have studied only the tabanid–horse interaction, our results can probably be extrapolated to other host animals of polarotactic tabanids, as the reflection–polarization characteristics of the host's body surface are physically the same, and thus not species-dependent. |
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Equine Behaviour @ team @ |
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5702 |
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Hare, B.; Brown, M.; Williamson, C.; Tomasello, M. |
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The domestication of social cognition in dogs |
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Journal Article |
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2002 |
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Science (New York, N.Y.) |
Abbreviated Journal |
Science |
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Volume |
298 |
Issue |
5598 |
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1634-1636 |
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Keywords |
Animals; *Animals, Domestic; *Behavior, Animal; *Cognition; *Cues; *Dogs; Food; Humans; Memory; Pan troglodytes; *Social Behavior; Species Specificity; Vision; Wolves |
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Dogs are more skillful than great apes at a number of tasks in which they must read human communicative signals indicating the location of hidden food. In this study, we found that wolves who were raised by humans do not show these same skills, whereas domestic dog puppies only a few weeks old, even those that have had little human contact, do show these skills. These findings suggest that during the process of domestication, dogs have been selected for a set of social-cognitive abilities that enable them to communicate with humans in unique ways. |
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Department of Anthropology, Harvard University, Cambridge, MA 02138, USA. bhare@fas.harvard.edu |
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1095-9203 |
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PMID:12446914 |
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refbase @ user @ |
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595 |
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Hostikka, S.L.; Eddy, R.L.; Byers, M.G.; Hoyhtya, M.; Shows, T.B.; Tryggvason, K. |
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Title |
Identification of a distinct type IV collagen alpha chain with restricted kidney distribution and assignment of its gene to the locus of X chromosome-linked Alport syndrome |
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Journal Article |
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Year |
1990 |
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Proceedings of the National Academy of Sciences of the United States of America |
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Proc. Natl. Acad. Sci. U.S.A. |
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87 |
Issue |
4 |
Pages |
1606-1610 |
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Amino Acid Sequence; Base Sequence; Chromosome Mapping; Cloning, Molecular; Collagen/*genetics; Epitopes/analysis; Female; Fluorescent Antibody Technique; Gene Library; *Genes; Humans; Immunoblotting; Kidney/cytology/*metabolism; Macromolecular Substances; Molecular Sequence Data; Nephritis, Hereditary/*genetics; Oligopeptides/chemical synthesis/immunology; Placenta/metabolism; Pregnancy; Restriction Mapping; Sequence Homology, Nucleic Acid; *X Chromosome |
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We have identified and extensively characterized a type IV collagen alpha chain, referred to as alpha 5(IV). Four overlapping cDNA clones isolated contain an open reading frame for 543 amino acid residues of the carboxyl-terminal end of a collagenous domain, a 229-residue carboxyl-terminal noncollagenous domain, and 1201 base pairs coding for a 3' untranslated region. The collagenous Gly-Xaa-Yaa repeat sequence has five imperfections that coincide with those in the corresponding region of the alpha 1(IV) chain. The noncollagenous domain has 12 conserved cysteine residues and 83% and 63% sequence identity with the noncollagenous domains of the alpha 1(IV) and alpha 2(IV) chains, respectively. The alpha 5(IV) chain has less sequence identity with the putative bovine alpha 3(IV) and alpha 4(IV) chains. Antiserum against an alpha 5(IV) synthetic peptide stained a polypeptide chain of about 185 kDa by immunoblot analysis and immunolocalization of the chain in human kidney was almost completely restricted to the glomerulus. The gene was assigned to the Xq22 locus by somatic cell hybrids and in situ hybridization. This may be identical or close to the locus of the X chromosome-linked Alport syndrome that is believed to be a type IV collagen disease. |
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Biocenter, University of Oulu, Finland |
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0027-8424 |
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PMID:1689491 |
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Equine Behaviour @ team @ |
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5291 |
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Author |
Bloom, P. |
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Behavior. Can a dog learn a word? |
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2004 |
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Science (New York, N.Y.) |
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Science |
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304 |
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5677 |
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1605-1606 |
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Animals; Child; Child, Preschool; *Dogs; Humans; *Learning; *Memory; *Vocabulary |
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Department of Psychology, Yale University, Post Office Box 208205, New Haven, CT 06520-8205, USA. paul.bloom@yale.edu |
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1095-9203 |
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PMID:15192205 |
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