Abstract: The requirement for assessing the effects of stressor combinations in improving the welfare of animals has not been widely recognised. Knowledge of the effects of concurrent stressors is needed to improve environments such as transport, where animals are presented with many simultaneous challenges. However, no method for measuring the effects of different stressors with a common unit is currently available. A locomotor passive avoidance method was developed as a common currency measure of the aversion of domestic fowl to concurrent stressors, using vibrational and thermal stressors as an exemplar. Juvenile fowl, fasted overnight, were trained to run a raceway into a goal-box for small food rewards (FR1). When running consistently, the reinforcement schedule was superimposed with a FR5 treatment schedule (60 min confinement in the goal-box with either a control of no other stressors [N] or concurrent vibration and thermal stressors [VT]). Subsequent latency to return to the goal-box was recorded as a measure of aversion. The factors affecting bird response were addressed in a series of experiments to optimise the method and clarify interpretation of results. Pre-feeding (20% ration 2 h prior to testing) did not affect response, but increasing the number of treatment presentations facilitated learning and increased method sensitivity. Treatment responses were consistent across experiments; overall VT was avoided (P<0.001), but N was not. However, there was large individual variation in response to VT. A final experiment indicated that, given a visual discriminatory cue, birds were capable of learning the required association between entering the goal-box and receiving the treatment, suggesting that the delay responses were due to aversion rather than the immediate impact of treatment on ability to respond. Further work is required to test the singular stressors, but the method retains common currency potential for assessing aversion to multiple stressors.

Abstract: Capuchin monkeys (Cebus apella) share food even if separated by a mesh restraint. Pairs of capuchins were moved into a test chamber in which one of them received apple pieces for 20 min, and the other received carrot pieces for the next 20 min. Previous research had shown a correlation between the rate of food transfer in both directions across female-female dyads. The present study confirmed this result. Reciprocity across dyads can be explained, however, by symmetry in affiliative and tolerant tendencies between two individuals, provided these tendencies determine food sharing. The present study was designed to exclude this symmetry-based explanation by testing each pair (N=16) of adult females on six separate occasions. There existed a significant covariation across tests of sharing in both dyadic directions, a result unexplained by relationship symmetry. Moreover, control procedures (i.e. testing of a food possessor without a partner, or testing of two individuals with the same food or two different foods at the same time) indicated that behaviour during food trials is not fully explained by mutual attraction or aversion. The monkeys take the quality of their own and the partner's food into account, and possessors limit transfers of high-quality foods. Instead of a symmetry-based reciprocity explanation, a mediating role of memory is suggested, and a mirroring of social attitude between partners. Copyright 2000 The Association for the Study of Animal Behaviour.

Abstract: A popular view is that high population density promotes behavioural pathology, particularly increased aggression. In contrast, according to a coping model, some primates have behavioural mechanisms (e.g. formal displays, reconciliation and grooming) that regulate social tensions and control the negative consequences of crowding. Seven captive rhesus monkey groups, Macaca mulattawere observed over a wide range of population densities where high-density groups were over 2000 times more crowded than low-density free-ranging groups. As density increased, male rhesus monkeys increased grooming and huddling but did not increase rates of aggression. Females increased all categories of behaviour examined (heavy aggression, mild aggression, formal bared-teeth displays, grooming and huddling), but the increases were not distributed uniformly to all classes of partners. Females increased only grooming, huddling and appeasement displays to males, increased only aggression and huddling with kin and increased all categories of behaviour to non-kin adult females. There were no differences in the percentage of aggressive conflicts reconciled across density conditions. Increased density had different effects on particular relationships. Relationships between females and males were characterized by a coping pattern in which animals modified their behaviour in ways that may decrease aggression under crowded conditions. Female relationships with kin and non-kin were characterized by increases in both aggression and friendly interactions as density increased. The different patterns of response to higher density may reflect different strategies depending on the strength and stability of relationships and the potential consequences if certain relationships are disrupted.1997The Association for the Study of Animal Behaviour

Abstract: Memory for time by animals appears to undergo a systematic shortening. This so-called choose-short effect can be seen in a conditional temporal discrimination when a delay is inserted between the sample and comparison stimuli. We have proposed that this temporal shortening may result from a procedural artifact in which the delay appears similar to the intertrial interval and thus, produces an inadvertent ambiguity or 'instructional failure'. When this ambiguity is avoided by distinguishing the intertrial interval from the delay, as well as the samples from the delay, the temporal shortening effect and other asymmetries often disappear. By avoiding artifacts that can lead to a misinterpretation of results, we may understand better how animals represent time. An alternative procedure for studying temporal discriminations is with the psychophysical bisection procedure in which following conditional discrimination training, intermediate durations are presented and the point of subjective equality is determined. Research using the bisection procedure has shown that pigeons represent temporal durations not only as their absolute value but also relative to durations from which they must be discriminated. Using this procedure, we have also found that time passes subjectively slower when animals are required to respond to the to-be-timed stimulus.

Abstract: 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.