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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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no |
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Call Number |
refbase @ user @ |
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413 |
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Author |
Witte, T.H.; Knill, K.; Wilson, A.M. |
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Title |
Determination of peak vertical ground reaction force from duty factor in the horse (Equus caballus) |
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Journal Article |
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Year |
2004 |
Publication |
The Journal of Experimental Biology |
Abbreviated Journal |
J Exp Biol |
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Volume |
207 |
Issue |
Pt 21 |
Pages |
3639-3648 |
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Keywords |
*Acceleration; Animals; Biomechanics; Forelimb/physiology; *Gait; Hindlimb/physiology; Horses/*physiology; Locomotion/*physiology; Telemetry; Time Factors |
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Abstract |
Measurement of peak vertical ground reaction force (GRFz) from multiple limbs simultaneously during high-speed, over-ground locomotion would enhance our understanding of the locomotor mechanics of cursorial animals. Here, we evaluate the accuracy of predicting peak GRFz from duty factor (the proportion of the stride for which the limb is in contact with the ground). Foot-mounted uniaxial accelerometers, combined with UHF FM telemetry, are shown to be practical and accurate for the field measurement of stride timing variables, including duty factor. Direct comparison with the force plate produces a mean error of 2.3 ms and 3.5 ms for the timing of foot on and foot off, respectively, across all gaits. Predictions of peak GRFz from duty factor show mean errors (with positive values indicating an overestimate) of 0.8+/-0.04 N kg(-1) (13%; N=42; mean +/- S.E.M.) at walk, -0.3+/-0.06 N kg(-1) (3%; N=75) at trot, -2.3+/-0.27 N kg(-1) (16%; N=18) for the non-lead limb at canter and +2.1+/-0.7 N kg(-1) (19%; N=9) for the lead limb at canter. The substantial over- and underestimate seen at canter, in the lead and non-lead limbs, respectively, is attributed to the different functions performed by the two limbs in the asymmetrical gaits. The difference in load experienced by the lead and non-lead limbs decreased with increasing speed. |
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Structure and Motion Lab, The Royal Veterinary College, Hawkshead Lane, Hatfield, Hertfordshire, AL9 7TA, UK |
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0022-0949 |
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PMID:15371472 |
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Equine Behaviour @ team @ |
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3658 |
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Author |
Bobbert, M.F.; Santamaria, S. |
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Title |
Contribution of the forelimbs and hindlimbs of the horse to mechanical energy changes in jumping |
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Journal Article |
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Year |
2005 |
Publication |
The Journal of Experimental Biology |
Abbreviated Journal |
J Exp Biol |
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Volume |
208 |
Issue |
2 |
Pages |
249-260 |
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Keywords |
Animals; Biomechanics; Forelimb/*physiology; Hindlimb/*physiology; Horses/*physiology; Locomotion/*physiology; Muscle, Skeletal/*physiology; Time Factors |
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The purpose of the present study was to gain more insight into the contribution of the forelimbs and hindlimbs of the horse to energy changes during the push-off for a jump. For this purpose, we collected kinematic data at 240 Hz from 23 5-year-old Warmbloods (average mass: 595 kg) performing free jumps over a 1.15 m high fence. From these data, we calculated the changes in mechanical energy and the changes in limb length and joint angles. The force carried by the forelimbs and the amount of energy stored was estimated from the distance between elbow and hoof, assuming that this part of the leg behaved as a linear spring. During the forelimb push, the total energy first decreased by 3.2 J kg(-1) and then increased again by 4.2 J kg(-1) to the end of the forelimb push. At the end of the forelimb push, the kinetic energy due to horizontal velocity of the centre of mass was 1.6 J kg(-1) less than at the start, while the effective energy (energy contributing to jump height) was 2.3 J kg(-1) greater. It was investigated to what extent these changes could involve passive spring-like behaviour of the forelimbs. The amount of energy stored and re-utilized in the distal tendons during the forelimb push was estimated to be on average 0.4 J kg(-1) in the trailing forelimb and 0.23 J kg(-1) in the leading forelimb. This means that a considerable amount of energy was first dissipated and subsequently regenerated by muscles, with triceps brachii probably being the most important contributor. During the hindlimb push, the muscles of the leg were primarily producing energy. The total increase in energy was 2.5 J kg(-1) and the peak power output amounted to 71 W kg(-1). |
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Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, van der Boechorstraat 9, NL-1081 BT Amsterdam, The Netherlands. MFBobbert@fbw.vu.nl |
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0022-0949 |
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PMID:15634844 |
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no |
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Serial |
1895 |
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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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Notes |
PMID:15652260 |
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no |
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Call Number |
refbase @ user @ |
Serial |
443 |
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Author |
Lewis, K.P.; Jaffe, S.; Brannon, E.M. |
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Title |
Analog number representations in mongoose lemurs (Eulemur mongoz): evidence from a search task |
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Journal Article |
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Year |
2005 |
Publication |
Animal Cognition |
Abbreviated Journal |
Anim. Cogn. |
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Volume |
8 |
Issue |
4 |
Pages |
247-252 |
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Keywords |
Analysis of Variance; Animals; *Behavior, Animal; *Feeding Behavior; Female; Lemuridae/*psychology; Male; Mathematics; Odors; Smell/physiology; Time Factors |
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Abstract |
A wealth of data demonstrating that monkeys and apes represent number have been interpreted as suggesting that sensitivity to number emerged early in primate evolution, if not before. Here we examine the numerical capacities of the mongoose lemur (Eulemur mongoz), a member of the prosimian suborder of primates that split from the common ancestor of monkeys, apes and humans approximately 47-54 million years ago. Subjects observed as an experimenter sequentially placed grapes into an opaque bucket. On half of the trials the experimenter placed a subset of the grapes into a false bottom such that they were inaccessible to the lemur. The critical question was whether lemurs would spend more time searching the bucket when food should have remained in the bucket, compared to when they had retrieved all of the food. We found that the amount of time lemurs spent searching was indicative of whether grapes should have remained in the bucket, and furthermore that lemur search time reliably differentiated numerosities that differed by a 1:2 ratio, but not those that differed by a 2:3 or 3:4 ratio. Finally, two control conditions determined that lemurs represented the number of food items, and neither the odor of the grapes, nor the amount of grape (e.g., area) in the bucket. These results suggest that mongoose lemurs have numerical representations that are modulated by Weber's Law. |
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Department of Anthropology, Washington University, St. Louis, MO 63130-4899, USA |
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ISSN |
1435-9448 |
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PMID:15660208 |
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no |
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Call Number |
Equine Behaviour @ team @ |
Serial |
2497 |
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Author |
Hodgson, D.; Howe, S.; Jeffcott, L.; Reid, S.; Mellor, D.; Higgins, A. |
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Title |
Effect of prolonged use of altrenogest on behaviour in mares |
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Year |
2005 |
Publication |
Veterinary journal (London, England : 1997) |
Abbreviated Journal |
Vet J |
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Volume |
169 |
Issue |
1 |
Pages |
113-115 |
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Keywords |
Administration, Oral; Anabolic Agents/adverse effects/*pharmacology; Animals; Behavior, Animal/*drug effects; Body Constitution/drug effects; Body Weight/drug effects; *Doping in Sports; Female; Horses/*physiology; Social Behavior; Social Dominance; Time Factors; Trenbolone/adverse effects/*analogs & derivatives/*pharmacology |
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Abstract |
Erratum in:
Vet J. 2005 May;169(3):321.
Corrected and republished in:
Vet J. 2005 May;169(3):322-5.
Oral administration of altrenogest for oestrus suppression in competition horses is believed to be widespread in some equestrian disciplines, and can be administered continuously for several months during a competition season. To examine whether altrenogest has any anabolic or other potential performance enhancing properties that may give a horse an unfair advantage, we examined the effect of oral altrenogest (0.044 mg/kg), given daily for a period of eight weeks, on social hierarchy, activity budget, body-mass and body condition score of 12 sedentary mares. We concluded that prolonged oral administration of altrenogest at recommended dose rates to sedentary mares resulted in no effect on dominance hierarchies, body mass or condition score. |
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Address |
Faculty of Veterinary Science, University of Sydney, Private Mailbag 4, Narellan Delivery Centre, Narellan, NSW 2567, Australia. davidh@camden.usyd.edu.au |
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1090-0233 |
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PMID:15683772 |
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refbase @ user @ |
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671 |
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Author |
Manson, J.H.; Perry, S.; Stahl, D. |
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Title |
Reconciliation in wild white-faced capuchins (Cebus capucinus) |
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Journal Article |
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Year |
2005 |
Publication |
American journal of primatology |
Abbreviated Journal |
Am. J. Primatol. |
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Volume |
65 |
Issue |
3 |
Pages |
205-219 |
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Aggression; Animals; Cebus/*psychology; Female; Male; Sex Factors; *Social Behavior; Social Dominance; Time Factors |
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Abstract |
The likelihood of reconciliation (defined as preferential peaceful contact among former opponents following conflicts) has been predicted to vary positively with relationship value and compatibility, and negatively with relationship security. Long-term data on wild white-faced capuchins (Cebus capucinus) indicate that dyads consisting of an adult female and an alpha male have high value and compatibility, but low security. Two studies of C. capucinus postconflict (PC) behavior were carried out at Lomas Barbudal Biological Reserve, Costa Rica. One study consisted of 30-min PC and matched control (MC) follows. The second study extracted PC and MC periods from long follows, yielding PC/MC periods averaging 105 min. In study 2, but not study 1, significantly more PC/MC pairs were attracted (former opponents affiliated with each other sooner in the PC period than in the MC period) than were dispersed (former opponents affiliated with each other sooner in the MC period than in the PC period). Reconciliation in study 2 could not be explained as a by-product of former opponents' tendency to seek affiliative contact with conspecifics generally, or of the spatial proximity of opponents following conflicts. Attempted reconciliation was less likely to be followed by renewed aggression when reconciliation attempts were delayed following conflicts. The data were insufficient for a formal test of differences in conciliatory tendency (the difference between the number of attracted and dispersed PC/MC pairs, divided by the total number of pairs) among dyad types to be conducted. |
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Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany. manson@eva.mpg.de |
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0275-2565 |
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PMID:15772989 |
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Call Number |
refbase @ user @ |
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2874 |
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Author |
Macfadden, B.J. |
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Title |
Evolution. Fossil horses--evidence for evolution |
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Journal Article |
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Year |
2005 |
Publication |
Science (New York, N.Y.) |
Abbreviated Journal |
Science |
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Volume |
307 |
Issue |
5716 |
Pages |
1728-1730 |
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Keywords |
Animals; Body Size; DNA, Mitochondrial; Diet; *Equidae/anatomy & histology/classification/genetics; *Evolution; Feeding Behavior; *Fossils; *Horses/anatomy & histology/classification/genetics; Paleodontology; Phylogeny; Time; Tooth/anatomy & histology |
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Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA. bmacfadd@flmnh.ufl.edu |
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1095-9203 |
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PMID:15774746 |
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1892 |
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Author |
Thiel, D.; Jenni-Eiermann, S.; Palme, R. |
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Title |
Measuring corticosterone metabolites in droppings of capercaillies (Tetrao urogallus) |
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Journal Article |
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Year |
2005 |
Publication |
Annals of the New York Academy of Sciences |
Abbreviated Journal |
Ann N Y Acad Sci |
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1046 |
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Pages |
96-108 |
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Adrenocorticotropic Hormone/administration & dosage/analysis/metabolism; Animals; Circadian Rhythm; Corticosterone/administration & dosage/*analysis/*metabolism; Feces/*chemistry; Female; Freezing; Galliformes/*metabolism; Male; Reproducibility of Results; Sex Factors; Temperature; Time Factors; Tritium/diagnostic use |
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The capercaillie (Tetrao urogallus), the largest grouse species in the world, is decreasing in numbers in major parts of its distribution range. Disturbances by human outdoor activities are discussed as a possible reason for this population decline. An indicator for disturbances is the increase of the glucocorticoid corticosterone, a stress hormone, which helps to cope with life-threatening situations. However, repeated disturbances might result in a long-term increase of the basal corticosterone concentration, which can result in detrimental effects like reduced fitness and survival of an animal. To measure corticosterone metabolites (CMs) noninvasively in the droppings of free-living capercaillies, first an enzyme immunoassay (EIA) in captive birds had to be selected and validated. Therefore, the excretion pattern of intravenously injected radiolabeled corticosterone was determined and 3H metabolites were characterized. High-performance liquid chromatography (HPLC) separations of the samples containing peak concentrations revealed that corticosterone was extensively metabolized. The HPLC fractions were tested in several EIAs for glucocorticoid metabolites. The physiological relevance of this method was proved after pharmacological stimulation of the adrenocortical activity. Only the recently established cortisone assay, measuring CMs with a 3,11-dione structure, detected an expressed increase of concentrations following ACTH stimulation. To set up a sampling protocol suited for the field, we examined the influence of various storage conditions and time of day on concentrations of CMs. |
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Swiss Ornithological Institute, 6204 Sempach, Switzerland. dominik.thiel@vogelwarte.ch |
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0077-8923 |
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PMID:16055846 |
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Equine Behaviour @ team @ |
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4079 |
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Author |
Zentall, T.R. |
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Title |
Timing, memory for intervals, and memory for untimed stimuli: the role of instructional ambiguity |
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Journal Article |
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Year |
2005 |
Publication |
Behavioural processes |
Abbreviated Journal |
Behav. Process. |
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Volume |
70 |
Issue |
3 |
Pages |
209-222 |
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Keywords |
Animals; *Attention; Columbidae; *Discrimination Learning; *Memory, Short-Term; Practice (Psychology); Reinforcement Schedule; *Retention (Psychology); *Time Perception |
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Theories of animal timing have had to account for findings that the memory for the duration of a timed interval appears to be dramatically shorted within a short time of its termination. This finding has led to the subjective shortening hypothesis and it has been proposed to account for the poor memory that animals appear to have for the initial portion of a timed interval when a gap is inserted in the to-be-timed signal. It has also been proposed to account for the poor memory for a relatively long interval that has been discriminated from a shorter interval. I suggest here a simpler account in which ambiguity between the gap or retention interval and the intertrial interval results in resetting the clock, rather than forgetting the interval. The ambiguity hypothesis, together with a signal salience mechanism that determines how quickly the clock is reset at the start of the intertrial interval can account for the results of the reported timing experiments that have used the peak procedure. Furthermore, instructional ambiguity rather than memory loss may account for the results of many animal memory experiments that do not involve memory for time. |
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Address |
Department of Psychology, University of Kentucky, 202B Kastle Hall, Lexington, KY 40506-0044, USA. zentall@uky.edu |
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0376-6357 |
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PMID:16095851 |
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refbase @ user @ |
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222 |
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