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Touma, C., Sachser, N., Mostl, E., & Palme, R. (2003). Effects of sex and time of day on metabolism and excretion of corticosterone in urine and feces of mice. Gen Comp Endocrinol, 130(3), 267–278.
Abstract: Non-invasive techniques to monitor stress hormones in small animals like mice offer several advantages and are highly demanded in laboratory as well as in field research. Since knowledge about the species-specific metabolism and excretion of glucocorticoids is essential to develop such a technique, we conducted radiometabolism studies in mice (Mus musculus f. domesticus, strain C57BL/6J). Each mouse was injected intraperitoneally with 740 kBq of 3H-labelled corticosterone and all voided urine and fecal samples were collected for five days. In a first experiment 16 animals (eight of each sex) received the injection at 9 a.m., while eight mice (four of each sex) were injected at 9 p.m. in a second experiment. In both experiments radioactive metabolites were recovered predominantly in the feces, although males excreted significantly higher proportions via the feces (about 73%) than females (about 53%). Peak radioactivity in the urine was detected within about 2h after injection, while in the feces peak concentrations were observed later (depending on the time of injection: about 10h postinjection in experiment 1 and about 4h postinjection in experiment 2, thus proving an effect of the time of day). The number and relative abundance of fecal [3H]corticosterone metabolites was determined by high performance liquid chromatography (HPLC). The HPLC separations revealed that corticosterone was extensively metabolized mainly to more polar substances. Regarding the types of metabolites formed, significant differences were found between males and females, but not between the experiments. Additionally, the immunoreactivity of these metabolites was assessed by screening the HPLC fractions with four enzyme immunoassays (EIA). However, only a newly established EIA for 5alpha-pregnane-3beta,11beta,21-triol-20-one (measuring corticosterone metabolites with a 5alpha-3beta,11beta-diol structure) detected several peaks of radioactive metabolites with high intensity in both sexes, while the other EIAs showed only minor immunoreactivity. Thus, our study for the first time provides substantial information about metabolism and excretion of corticosterone in urine and feces of mice and is the first demonstrating a significant impact of the animals' sex and the time of day. Based on these data it should be possible to monitor adrenocortical activity non-invasively in this species by measuring fecal corticosterone metabolites with the newly developed EIA. Since mice are extensively used in research world-wide, this could open new perspectives in various fields from ecology to behavioral endocrinology.
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Rands, S. A., Cowlishaw, G., Pettifor, R. A., Rowcliffe, J. M., & Johnstone, R. A. (2003). Spontaneous emergence of leaders and followers in foraging pairs. Nature, 423(6938), 432–434.
Abstract: Animals that forage socially often stand to gain from coordination of their behaviour. Yet it is not known how group members reach a consensus on the timing of foraging bouts. Here we demonstrate a simple process by which this may occur. We develop a state-dependent, dynamic game model of foraging by a pair of animals, in which each individual chooses between resting or foraging during a series of consecutive periods, so as to maximize its own individual chances of survival. We find that, if there is an advantage to foraging together, the equilibrium behaviour of both individuals becomes highly synchronized. As a result of this synchronization, differences in the energetic reserves of the two players spontaneously develop, leading them to adopt different behavioural roles. The individual with lower reserves emerges as the 'pace-maker' who determines when the pair should forage, providing a straightforward resolution to the problem of group coordination. Moreover, the strategy that gives rise to this behaviour can be implemented by a simple 'rule of thumb' that requires no detailed knowledge of the state of other individuals.
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Zentall, T. R., Weaver, J. E., & Clement, T. S. (2004). Pigeons group time intervals according to their relative duration. Psychon Bull Rev, 11(1), 113–117.
Abstract: In the present research, we asked whether pigeons tended to judge time intervals not only in terms of their absolute value but also relative to a duration from which they must be discriminated (i.e., longer or shorter). Pigeons were trained on two independent temporal discriminations. In one discrimination, sample durations of 2 and 8 sec were associated with, for example, red and green hue comparisons, respectively, and in the other discrimination, sample durations of 4 and 16 sec were associated with vertical and horizontal line comparisons, respectively. If pigeons are trained on a temporal discrimination and tested with intermediate durations, the subjective midpoint typically occurs close to the geometric mean of the two trained values. The 4- and 8-sec values were selected to be the geometric mean of the two values in the other discrimination. When a 4-sec test sample was presented with the comparisons from the 2- and 8-sec discrimination, the pigeons preferred the comparison associated with the shorter sample. Similarly, when an 8-sec test sample was presented with the comparisons from the 4- and 16-sec discrimination, the pigeons preferred the comparison associated with the longer sample. Thus, a relative grouping effect was found. That is, durations that should have produced indifferent choice were influenced by their relative durations (shorter than or longer than the alternative) during training.
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Zentall, T. R., Klein, E. D., & Singer, R. A. (2004). Evidence for detection of one duration sample and default responding to other duration samples by pigeons may result from an artifact of retention-test ambiguity. J Exp Psychol Anim Behav Process, 30(2), 129–134.
Abstract: S. C. Gaitan and J. T. Wixted (2000) proposed that when pigeons are trained on a conditional discrimination to associate 1 duration sample with 1 comparison and 2 other duration samples with a 2nd comparison, they detect only the single duration, and on trials involving either of the 2 other duration samples, they respond to the other comparison by default. In 2 experiments, the authors show instead that pigeons lend to treat the retention intervals (such as those used by Gaitan and Wixted) as intertrial intervals, and thus, they tend to treat all trials with a delay as 0-s sample trials. The authors tested this hypothesis by showing that divergent retention functions do not appear when the retention interval is discriminably different from the intertrial interval.
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Cameron, E. Z. (2004). Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism. Proc Biol Sci, 271(1549), 1723–1728.
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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Beran, M. J. (2004). Long-term retention of the differential values of Arabic numerals by chimpanzees (Pan troglodytes). Anim. Cogn., 7(2), 86–92.
Abstract: As previously reported (Beran and Rumbaugh, 2001), two chimpanzees used a joystick to collect dots, one-at-a-time, on a computer monitor, and then ended a trial when the number of dots collected was equal to the Arabic numeral presented for the trial. Here, the chimpanzees were presented with the task again after an interval of 6 months and then again after an additional interval of 3.25 years. During each interval, the chimpanzees were not presented with the task, and this allowed an assessment of the extent to which both animals retained the values of each Arabic numeral. Despite lower performance at each retention interval compared to the original study, both chimpanzees performed above chance levels in collecting a quantity of dots equal to the target numeral, one chimpanzee for the numerals 1-7, and the second chimpanzee for the numerals 1-6. For the 3.25-year retention, errors were more dispersed around each target numeral than in the original study, but the chimpanzees' performances again appeared to be based on a continuous representation of magnitude rather than a discrete representation of number. These data provide an experimental demonstration of long-term retention of the differential values of Arabic numerals by chimpanzees.
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Cerutti, D. T., & Staddon, J. E. R. (2004). Immediacy versus anticipated delay in the time-left experiment: a test of the cognitive hypothesis. J Exp Psychol Anim Behav Process, 30(1), 45–57.
Abstract: In the time-left experiment (J. Gibbon & R. M. Church, 1981), animals are said to compare an expectation of a fixed delay to food, for one choice, with a decreasing delay expectation for the other, mentally representing both upcoming time to food and the difference between current time and upcoming time (the cognitive hypothesis). The results of 2 experiments support a simpler view: that animals choose according to the immediacies of reinforcement for each response at a time signaled by available time markers (the temporal control hypothesis). It is not necessary to assume that animals can either represent or subtract representations of times to food to explain the results of the time-left experiment.
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Palagi, E., Paoli, T., & Tarli, S. B. (2004). Reconciliation and consolation in captive bonobos (Pan paniscus). Am. J. Primatol., 62(1), 15–30.
Abstract: Although reconciliation in bonobos (Pan paniscus) has previously been described, it has not been analyzed heretofore by the postconflict (PC) match-control (MC) method. Furthermore, although reconciliation has been investigated before in this species, consolation has not. In this study we analyzed agonistic and affiliative contacts in all sex-class combinations to clarify and reevaluate the occurrence of reconciliation in bonobos via the PC-MC method. We also investigated the occurrence of consolation by analyzing the victims' triadic contact tendency (TCT), the influence of the sex of victims, and the relative occurrence of consolation and reconciliation. We collected 167 pairs of PC-MC observations in a captive group of bonobos (in Apeldoorn, The Netherlands). The conciliatory tendency (CCT) we obtained was tendentially lower than the mean value previously found for Yerkes captive chimpanzees. Close relationships, which were present in all female-female (FF) and some male-female (MF) dyads, positively affected reconciliation rates. When only adult PC-MC pairs (157) were considered, the mean TCTs and CCTs did not differ significantly. When we focused on types of PC affiliative contact, in the case of consolation we found a striking preference for sociosexual patterns. As to the relative occurrence of consolation and reconciliation, the highest level of the former was found in the absence of the latter. When reconciliation took place, consolation generally preceded it, suggesting that consolation may be a substitutive behavior. Our findings suggest that even if reconciliation remains the best option, consolation may be an alternative substitute for reconciliation that is used to buffer the tension originating from an unresolved conflict. Reconciliation and consolation are complex phenomena that are probably related to the life history of a group. Given that few studies have been conducted on this subject, we can not at this time make any generalizations regarding conflict resolution in certain species by comparing results among studies.
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Kutsukake, N., & Castles, D. L. (2004). Reconciliation and post-conflict third-party affiliation among wild chimpanzees in the Mahale Mountains, Tanzania. Primates, 45(3), 157–165.
Abstract: This study investigated post-conflict (PC) behavior among wild chimpanzees (Pan troglodytes) of the M-group in the Mahale Mountains, Tanzania, and examined what types of behavior characterize the PC situation in this group, and the factors that influence the occurrence of PC affiliation between opponents soon after the end of an aggressive conflict (i.e., reconciliation). We found that the opponents affiliated selectively soon after the end of aggression, suggesting that reconciliation occurred in this group. The mean individual corrected conciliatory tendency (CCT) (Veenema et al. 1994 in Behav Proc 31:29-38) was 14.4%, which is similar to or lower than frequencies observed in studies of captive and wild chimpanzees. The valuable relationship hypothesis predicts that the CCT is higher among individuals who share valuable relationships (e.g., males or affiliative dyads) than among individuals who do not (e.g., females or less-associative dyads). However, the analysis based on data for aggression between unrelated individuals (including one incident between an adult and non-adult) and aggression between unrelated adults, did not uncover this difference. Affiliation by a previously uninvolved individual with the victim (“consolation”) and with the aggressor (“appeasement”) occurred more frequently following aggression than in the control condition. The results are compared with previous studies of captive and wild chimpanzees.
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Gruter, C. C. (2004). Conflict and postconflict behaviour in captive black-and-white snub-nosed monkeys (Rhinopithecus bieti). Primates, 45(3), 197–200.
Abstract: Black-and-white snub-nosed monkeys (Rhinopithecus bieti) have almost never been the subject of any behavioural observations in captivity. This study was aimed at providing preliminary information about agonistic and reconciliation behaviour in a group kept at the Kunming Institute of Zoology in China. Established procedures were used for this investigation (i.e., the postconflict/matched-control method and the time-rule method). Intra-group aggression rates were quite low. Postconflict affiliation as well as selective attraction of former opponents to each other following conflicts was demonstrated. Former opponents contacted each other earlier in postconflict periods than in matched-control periods. The average conciliatory tendency of all focal individuals combined was 54.5%. After an agonistic interaction, the first affiliative contact between former aggressors usually took place within the first minute. The behaviours most often shown as first affiliations after a conflict were body contact, mount, touch, and “hold-lumbar”, of which the latter is an explicit reconciliatory gesture. Furthermore, the adult male intervened non-aggressively in 84% of all conflicts (n=25) among the adult females. Overall, the patterns of aggression and reconciliation observed in R. bieti bear many of the traits that characterise tolerant primate species.
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