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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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refbase @ user @ |
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413 |
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Author |
Johnston, C.; Holm, K.R.; Erichsen, C.; Eksell, P.; Drevemo, S. |
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Title |
Kinematic evaluation of the back in fully functioning riding horses |
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Journal Article |
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Year |
2004 |
Publication |
Equine Veterinary Journal |
Abbreviated Journal |
Equine Vet J |
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Volume |
36 |
Issue |
6 |
Pages |
495-498 |
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Keywords |
Age Factors; Animals; Back/*physiology; Back Pain/diagnosis/veterinary; Biomechanics; Exercise Test/*veterinary; Female; Gait/*physiology; Horse Diseases/diagnosis; Horses/*physiology; Male; Movement/physiology; Sex Factors |
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Abstract |
REASONS FOR PERFORMING STUDY: Clinical history and examination are important features in diagnosis of equine back dysfunction. However, interpretation is subjective and therefore may vary substantially. OBJECTIVES: To establish a clinical tool to objectively evaluate the function of the equine back, in the form of a database on the kinematics of the back at the walk and trot in fully functioning riding horses. METHODS: Thirty-three fully functioning riding horses walked and trotted on a treadmill. Morphometrics and kinematics were tested for correlations to age, height, weight and stride length, and differences between gender (geldings and mares) and use (dressage and showjumping). RESULTS: A database for range of movement and symmetry of movement for extension and flexion, lateral bending, lateral excursion and axial rotation was presented. Symmetry values were very high for all variables. Significant differences were observed in use and gender. Age was negatively correlated to extension and flexion of the thoracolumbar junction. CONCLUSIONS: Interrelationships between use, gender and age to conformation and movement were established. POTENTIAL RELEVANCE: The database provides a basis for objective reference for diagnosis, therapy and rehabilitation of clinical cases of back dysfunction. |
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Departments of Anatomy and Histology, 75007 Uppsala, Sweden |
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0425-1644 |
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PMID:15460073 |
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Equine Behaviour @ team @ |
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3716 |
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Author |
Brosnan, S.F.; de Waal, F.B.M. |
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Title |
A concept of value during experimental exchange in brown capuchin monkeys, Cebus apella |
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Journal Article |
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Year |
2004 |
Publication |
Folia primatologica; international journal of primatology |
Abbreviated Journal |
Folia Primatol (Basel) |
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Volume |
75 |
Issue |
5 |
Pages |
317-330 |
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Keywords |
Animals; Cebus/*psychology; *Choice Behavior; Female; Food Preferences; *Learning; Male; Sex Factors; Statistics, Nonparametric; *Token Economy; Video Recording |
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Abstract |
We evaluated the response of brown capuchin monkeys to two differentially valued tokens in an experimental exchange situation akin to a simple barter. Monkeys were given a series of three tests to evaluate their ability to associate tokens with food, then their responses were examined in a barter situation in which tokens were either limited or unlimited. Capuchins did not perform barter in the typical sense, returning the tokens which were associated with the reward. However, females, but not males, showed a different response, preferring the higher-value token. This may indicate that they learned to prefer one token over the other rather than to associate the tokens with their specific rewards. This sex difference parallels previous findings of greater reciprocity in female brown capuchins than in males. |
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Living Links Center, Emory University, Yerkes National Primate Research Center, 954 N. Gatewood Drive, Atlanta, GA 30329, USA. sbrosna@emory.edu |
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0015-5713 |
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PMID:15486443 |
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no |
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refbase @ user @ |
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170 |
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Author |
Ferkin, M.H.; Pierce, A.A.; Sealand, R.O.; Delbarco-Trillo, J. |
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Title |
Meadow voles, Microtus pennsylvanicus, can distinguish more over-marks from fewer over-marks |
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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 |
3 |
Pages |
182-189 |
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Keywords |
Animals; Arvicolinae/*psychology; *Discrimination Learning; Female; Intermediate Filament Proteins; Male; Mathematics; Sex Factors; *Smell |
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Abstract |
Is it possible that voles have a sense of number? To address this question, we determined whether voles discriminate between two different scent-marking individuals and identify the individual whose scent marks was on top more often than the other individual. We tested whether voles show a preference for the individual whose scent marks was on top most often. If so, the simplest explanation was that voles can make a relative size judgement-such as distinguishing an area containing more of one individual's over-marks as compared to less of another individual's over-marks. We found that voles respond preferentially to the donor that provided a greater number of over-marks as compared to the donor that provided a lesser number of over-marks. Thus, we concluded that voles might display the capacity for relative numerousness. Interestingly, female voles were better able than male voles to distinguish between small differences in the relative number of over-marks by the two scent donors. |
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Department of Biology, The University of Memphis, Ellington Hall, Memphis, TN 38152, USA. mhferkin@memphis.edu |
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ISSN |
1435-9448 |
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Notes |
PMID:15580367 |
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no |
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Call Number |
Equine Behaviour @ team @ |
Serial |
2501 |
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Author |
Hodgson, Z.G.; Healy, S.D. |
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Title |
Preference for spatial cues in a non-storing songbird species |
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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 |
3 |
Pages |
211-214 |
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Keywords |
Animals; Association Learning/*physiology; *Cues; Feeding Behavior/physiology; Female; Male; Memory/*physiology; Sex Factors; Songbirds/*physiology; Space Perception/*physiology; Spatial Behavior/*physiology |
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Abstract |
Male mammals typically outperform their conspecific females on spatial tasks. A sex difference in cues used to solve the task could underlie this performance difference as spatial ability is reliant on appropriate cue use. Although comparative studies of memory in food-storing and non-storing birds have examined species differences in cue preference, few studies have investigated differences in cue use within a species. In this study, we used a one-trial associative food-finding task to test for sex differences in cue use in the great tit, Parus major. Birds were trained to locate a food reward hidden in a well covered by a coloured cloth. To determine whether the colour of the cloth or the location of the well was learned during training, the birds were presented with three wells in the test phase: one in the original location, but covered by a cloth of a novel colour, a second in a new location covered with the original cloth and a third in a new location covered by a differently coloured cloth. Both sexes preferentially visited the well in the training location rather than either alternative. As great tits prefer colour cues over spatial cues in one-trial associative conditioning tasks, cue preference appears to be related to the task type rather than being species dependent. |
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Ashworth Laboratories, Institute of Evolutionary Biology, University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh, EH9 3JT, UK. s.healy@ed.ac.uk |
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1435-9448 |
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Notes |
PMID:15611879 |
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no |
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Call Number |
Equine Behaviour @ team @ |
Serial |
2499 |
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Author |
Cooper, M.A.; Berntein, I.S.; Hemelrijk, C.K. |
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Title |
Reconciliation and relationship quality in Assamese macaques (Macaca assamensis) |
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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 |
269-282 |
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Keywords |
Aggression; Animals; Female; Macaca/*psychology; Male; Sex Factors; *Social Behavior |
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Abstract |
A consistent conclusion in reconciliation research is that animals that reconcile are likely to have strong social bonds. This has led to the hypothesis that reconciliation occurs most often between valuable social partners. We tested this hypothesis in a group of Assamese macaques (Macaca assamensis) living near a temple in Assam, India. Using focal sample and ad libitum data collection, we recorded the occurrence of reconciliation, grooming, and agonistic aiding, and the outcomes of approach. We used matrix association methods (TauKr correlation) to correlate reconciliation with grooming, aiding, and approach outcome. Females reconciled more often with females with which they had stronger grooming and aiding relationships. The correlation between reconciliation and aiding was significant for support to the aggressor and the victim. In contrast, no such correlations with reconciliation were found for males. This study provides evidence that females reconcile most often with valuable and compatible social partners. The results do not support the relationship-quality hypothesis for males, and we suggest that future studies give more consideration to the possibility that males reconcile for reasons other than to repair relationships with valuable partners. |
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Department of Psychology, Georgia State University, Atlanta, Georgia 30302-3966, USA. biomcc@langate.gsu.edu |
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ISSN |
0275-2565 |
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Notes |
PMID:15772987 |
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no |
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Call Number |
refbase @ user @ |
Serial |
2875 |
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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) |
Type |
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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no |
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Call Number |
refbase @ user @ |
Serial |
2874 |
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Author |
Brosnan, S.F.; de Waal, F.B.M. |
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Title |
Responses to a simple barter task in chimpanzees, Pan troglodytes |
Type |
Journal Article |
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Year |
2005 |
Publication |
Primates |
Abbreviated Journal |
Primates |
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Volume |
46 |
Issue |
3 |
Pages |
173-182 |
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Keywords |
Analysis of Variance; Animals; Choice Behavior/*physiology; Conditioning (Psychology)/physiology; Learning/*physiology; Pan troglodytes/*physiology; Reward; Sex Factors; *Social Behavior; *Token Economy |
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Abstract |
Chimpanzees (Pan troglodytes) frequently participate in social exchange involving multiple goods and services of variable value, yet they have not been tested in a formalized situation to see whether they can barter using multiple tokens and rewards. We set up a simple barter economy with two tokens and two associated rewards and tested chimpanzees on their ability to obtain rewards by returning the matching token in situations in which their access to tokens was unlimited or limited. Chimpanzees easily learned to associate value with the tokens, as expected, and did barter, but followed a simple strategy of favoring the higher-value token, regardless of the reward proffered, instead of a more complex but more effective strategy of returning the token that matched the reward. This response is similar to that shown by capuchin monkeys in our previous study. We speculate that this response, while not ideal, may be sufficient to allow for stability of the social exchange system in these primates, and that the importance of social barter to both species may have led to this convergence of strategies. |
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Living Links, Yerkes National Primate Research Center, Atlanta, GA 30322, USA. sbrosna@emory.edu |
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0032-8332 |
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PMID:15824938 |
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no |
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Call Number |
refbase @ user @ |
Serial |
167 |
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Permanent link to this record |
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Author |
Overdorff, D.J.; Erhart, E.M.; Mutschler, T. |
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Title |
Does female dominance facilitate feeding priority in black-and-white ruffed lemurs (Varecia variegata) in southeastern Madagascar? |
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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 |
66 |
Issue |
1 |
Pages |
7-22 |
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Keywords |
Agonistic Behavior; Animals; Eating/physiology; Feeding Behavior/*physiology; Female; Leadership; Lemuridae/*physiology; Madagascar; Male; Observation; Sex Factors; *Social Dominance |
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Although many Malagasy lemurs are thought to be female dominant and to have female feeding priority, to date the relationship between these behaviors has been rigorously established only in Lemur catta, and other ways that females might achieve feeding priority have not been examined closely. Erhart and Overdorff [International Journal of Primatology 20:927-940, 1999] suggested that one way female primates achieve feeding priority is to initiate and lead groups to food, thereby gaining access to the food first and positively influencing their food intake compared to other group members. Here we describe female dominance patterns and potential measures of feeding priority in two groups of black-and-white ruffed lemurs (Varecia variegata) that were observed over a 15-month period in southeastern Madagascar. We predicted that the females would 1) be consistently dominant to males, 2) lead groups to food sources more often than males, and 3) have higher feeding rates compared to males when they arrived at food sources first. The results were dissimilar between the study groups. During the study, the oldest adult female in group 1 died. There was no evidence for female dominance in this group, and the remaining (likely natal) female did not lead the group more often, nor did she have a higher food intake than males. Group 1 dispersed shortly after the time frame reported here. In contrast, the resident female in group 2 was dominant to group males (based on agonistic interactions), led the group to food sources more often, and experienced a higher food intake when she arrived first at a food source. How these patterns vary over time and are influenced by the number of females in groups, group stability, food quality, and reproductive condition will be examined in future analyses. |
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Department of Anthropology, University of Texas, Austin, Texas 78712-1086, USA. overdorff@mail.utexas.edu |
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0275-2565 |
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PMID:15898069 |
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no |
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Equine Behaviour @ team @ |
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4110 |
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Permanent link to this record |
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Author |
de Waal, F.B.M.; Dindo, M.; Freeman, C.A.; Hall, M.J. |
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Title |
The monkey in the mirror: hardly a stranger |
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Journal Article |
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Year |
2005 |
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 |
102 |
Issue |
32 |
Pages |
11140-11147 |
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Keywords |
Analysis of Variance; Animals; Cebus/*physiology; *Discrimination (Psychology); Empathy; Female; Male; Observation; *Recognition (Psychology); *Self Concept; Sex Factors |
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Abstract |
It is widely assumed that monkeys see a stranger in the mirror, whereas apes and humans recognize themselves. In this study, we question the former assumption by using a detailed comparison of how monkeys respond to mirrors versus live individuals. Eight adult female and six adult male brown capuchin monkeys (Cebus apella) were exposed twice to three conditions: (i) a familiar same-sex partner, (ii) an unfamiliar same-sex partner, and (iii) a mirror. Females showed more eye contact and friendly behavior and fewer signs of anxiety in front of a mirror than they did when exposed to an unfamiliar partner. Males showed greater ambiguity, but they too reacted differently to mirrors and strangers. Discrimination between conditions was immediate, and blind coders were able to tell the difference between monkeys under the three conditions. Capuchins thus seem to recognize their reflection in the mirror as special, and they may not confuse it with an actual conspecific. Possibly, they reach a level of self-other distinction intermediate between seeing their mirror image as other and recognizing it as self. |
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Living Links Center, Emory University, Atlanta, GA 30322, USA. dewaal@emory.edu |
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0027-8424 |
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PMID:16055557 |
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no |
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Call Number |
refbase @ user @ |
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164 |
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