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Author |
Brunner, D.; Kacelnik, A.; Gibbon, J. |
Title |
Optimal foraging and timing processes in the starling, Sturnus vulgaris: effect of inter-capture interval |
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Journal Article |
Year |
1992 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
Volume |
44 |
Issue |
4 |
Pages |
597-613 |
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Laboratory experiments with starlings, Sturnus vulgaris, were conducted to investigate the interaction between timing and cost-benefit considerations. The design simulated an environment in which food was distributed in patches. Patches contained a random number of food items (N=0-4) separated by a fixed inter-capture interval or fixed interval. All patches ended with sudden depletion. The time elapsed since the last prey capture was the only way to detect the depletion of the patch. Once the patch was depleted a new patch could be reached by travelling between two perches. Three measures of timing were taken: (1) rate of working for food as function of `waiting' time in a patch, (2) the time of the last response in a patch or `giving-in' time, and (3) the time at which travel was initiated or `moving-on' time. The fixed interval that characterized patches was varied between conditions. The mean time of the peak in working rate was consistently centred around the fixed interval, while the other two measures of timing kept a roughly linear relation to the fixed interval, with slope greater than one. In accordance with Scalar Expectancy Theory, variability in the three forms of timing was proportional to the magnitude of the fixed interval. The birds seemed to take account of this increase in variability as shown by the mean value of their giving-up criterion. These results imply that information-processing constraints are important for modelling behavioural optimality. |
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2112 |
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Author |
Caraco, T.; Kacelnik, A.; Mesnick, N.; Smulewitz, M. |
Title |
Short-term rate maximization when rewards and delays covary |
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Journal Article |
Year |
1992 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
Volume |
44 |
Issue |
Part 3 |
Pages |
441-447 |
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In nature foragers must exploit resources that vary randomly in both the energy acquired per item (reward) and the time required to pursue, capture and process an item (delay). Furthermore, rewards and delays associated with particular resources may often covary significantly. An analytical model asks how variance-covariance levels for rewards and delays could influence choice of resources when lack of information or cognitive limitation implies that a consumer attempts to maximize its short-term rate of energy gain. Both greater expected reward and reduced expected delay clearly should enhance preference for a resource. The model predicts that increased delay variance and reduced reward-delay covariance should increase a forager's preference for a resource. A forager should be risk-averse towards reward variance when the reward-delay covariance is positive, but should become risk-prone towards reward variance when the reward-delay covariance is negative. |
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2113 |
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Author |
Kacelnik, A.; Todd, I.A. |
Title |
Psychological mechanisms and the Marginal Value Theorem: effect of variability in travel time on patch exploitation |
Type |
Journal Article |
Year |
1992 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
Volume |
43 |
Issue |
2 |
Pages |
313-322 |
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The Marginal Value Theorem (MVT) describes the behaviour that maximizes the ratio of expected gain over expected foraging time in a patchy environment. When travel time is variable, the MVT rationale and its predictions are sensitive only to the mean travel time and not to the spread or skew of the distribution. Two mechanistic arguments contradict these predictions. First, tests of the MVT have previously shown that there is a disproportionate influence of the last travel time, and second, psychological models of information processing suggest that memory for time intervals is strongly dependent on the scatter of the distribution experienced. These mechanistic concepts, combined with Jensen's inequality, suggest that patch exploitation should decrease as the scatter of the travel distribution increases. In a Skinner box experiment with pigeons, Columba livia, the problem was examined by simulating three environments with identical patches and the same mean travel time, but different travel time variability. Patch exploitation decreased with increasing variance in travel time. The results are used to argue in favour of the inclusion of realistic psychological properties as constraints in functional models of behaviour. Although both the MVT and the mechanistic models account for some features of the results, none of them can explain all the findings. |
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2114 |
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Pruett-Jones, S. |
Title |
Independent Versus Nonindependent Mate Choice: Do Females Copy Each Other? |
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Journal Article |
Year |
1992 |
Publication |
The American Naturalist |
Abbreviated Journal |
Am Nat |
Volume |
140 |
Issue |
6 |
Pages |
1000-1009 |
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There is increasing evidence from both observational and experimental studies that females may copy each other's mating decisions. Female copying can be defined as a type of nonindependent choice in which the probability that a female chooses a given male increases if other females have chosen that male and decreases if they have not. The important characteristic of copying behavior that separates it from other similar processes is that the change in the probability of choice is strictly because of the actions of other females and not the consequences of those actions (e.g., a male's behavior changing as a result of successful matings). A gametheory model suggests that the adaptive significance of female copying may depend primarily on the ratio of the costs to the benefits of active mate choice. Copying behavior, and more generally conspecific cueing, may be important in many behavioral processes beyond mate choice. |
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Equine Behaviour @ team @ |
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2182 |
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Author |
Smith-Funk, E.D.; Crowell-Davis, S.L. |
Title |
Maternal behavior of draft mares (Equus caballus) with mule foals (Equus asinus x Equus caballus) |
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Journal Article |
Year |
1992 |
Publication |
Applied Animal Behaviour Science |
Abbreviated Journal |
Appl. Anim. Behav. Sci. |
Volume |
33 |
Issue |
2-3 |
Pages |
93-119 |
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Draft mares and their mule foals were observed from the day of birth to Week 17 of each foal's life. The rate of nursing was recorded and the duration of nursing activity to the nearest second. The rate at which foals engaged in nursing activity varied at each age. The duration of nursing bouts varied slightly as the foals matured. Aggression was recorded during both nursing and non-nursing activity for both the mares and foals. Maternal aggression was highest during nursing activity, especially during the pre-nurse nuzzling period. Maternal aggression increased as the foals matured. Mother-directed foal aggression was primarily in response to maternal aggression. Spatial relationships between each focal dyad were recorded when the foals were upright, not nursing and when they were recumbent. Spatial relationships differed based on the foal's state. The activity in which the mare engaged while her foal was recumbent was recorded. The movements of the mares were also recorded during foal recumbency. Mares approached or maintained their distance from their recumbent foal more than they left their recumbent foal in all weeks of the study, except Week 2. |
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Equine Behaviour @ team @ |
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2272 |
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Author |
Mills, M.G.L.; Shenk, M.G.L. |
Title |
Predator--Prey Relationships: The Impact of Lion Predation on Wildebeest and Zebra Populations |
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Journal Article |
Year |
1992 |
Publication |
The Journal of Animal Ecology |
Abbreviated Journal |
T. J. Anim. Ecol. |
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61 |
Issue |
3 |
Pages |
693-702 |
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1. The role of lion Panthera leo predation in the dynamics of blue wildebeest Connochaetes taurinus and zebra Equus burchelli populations was investigated through simulation models. The data used in the models were from intensive observations over 4 years in the south-east of the Kruger National Park. 2. Population estimates of wildebeest and zebra were made from aerial surveys, sex and age ratios from ground counts. Lion numbers were determined from observations of marked and radio-collared animals. Predation was studied by following lions for continuous periods of up to 336 h. 3. Two models were constructed. Model 1 ascertained the number of killing lions (adult females) that could be supported by each prey population while remaining stable. A single model was constructed for the sedentary wildebeest population. A summer and winter model was constructed for the semi-migratory zebra population. The sensitivity of the parameters in the model was tested by changing their value by 10%. In model 2, the kill age structure for each species was changed to determine the number of killing lions the altered prey selection parameters could support. 4. There was no difference in the vulnerability of either species to predation. Zebra foals (<1 year) were killed more frequently than expected. No selection for sex or by season could be found for either species. 5. Model 1 predicted that the wildebeest population stabilizes with 7.7 killing lions, close to the number in the study area. The winter zebra population stabilizes with 6.8 killing lions and the summer zebra population with 19.4. Manipulation of kill rate followed by adult fecundity rate had the greatest effect on population size of both species. In model 2, wildebeest predation was made selective towards calves and zebra predation was made non-selective for sex and age. With these parameters the wildebeest population stabilizes with 10.7 killing lions and the zebra population with 5.4 in winter and 15.1 in summer. 6. The models suggest that lion predation affected wildebeest more severely than zebra during the study. This was through the way in which lions selected their prey, and because of the sedentary behaviour of the wildebeest, as opposed to the semi-migratory behaviour of the zebra. |
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Equine Behaviour @ team @ |
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2376 |
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Author |
Munthali, S.M.; Banda, H.M. |
Title |
Distribution and abundance of the common ungulates of Nyika National Park |
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Journal Article |
Year |
1992 |
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Afr. J. Ecol |
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Afr. J. Ecol |
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30 |
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203-212 |
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Equine Behaviour @ team @ |
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2390 |
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Author |
Davis, H.; Balfour, D. (eds) |
Title |
The Inevitable Bond: Examining Scientist-Animal Interactions |
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1992 |
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Book Description
Although animals are widely employed as research subjects, it is only recently that we have acknowledged the bond that frequently, perhaps inevitably, develops between subject and researcher. Whatever the qualities of this relationship, an increasing body of evidence suggests that it may result in profound behavioural and physiological changes in the animal subject. Such effects are apparent in behavioural studies conducted in both laboratory and field settings. They also appear in physiological studies ranging from the biomedical (e.g. heart rate, blood pressure, immunological changes) to animal science (e.g. growth, reproduction). Such effects are not confined to obvious cases involving primates and dogs, but appear in unexpected animals like chickens, reptiles and even octopuses. Despite the fact that most researchers are trained to minimise or avoid such interactions, they continue to occur. This book, the first of its kind to address this issue systematically, describes many examples of this “inevitable bond” between scientist and animal. This discussion will allow researchers to anticipate these potentially confounding effects and take advantage of such relationships in designing more effective and humane environments for animal subjects. |
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Cambridge University Press |
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Cambridge, Massachusetts |
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Davis, H.; Balfour, D. |
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978-0521405102 |
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Equine Behaviour @ team @ |
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3595 |
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Author |
Poysa, Hannu |
Title |
Group Foraging in Patchy Environments: The Importance of Coarse-Level Local Enhancement |
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Journal Article |
Year |
1992 |
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Ornis Scandinavica |
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Ornis[ Scand[ |
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23 |
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2 |
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159-166 |
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Local enhancement is one way individuals may realize foraging advantages from grouping. A distinction between fine-level and coarse-level local enhancement is made, the latter often being neglected in theoretical research on group foraging. In the former case, an individual has a higher feeding rate as a member of a group because individuals copy other group members' foraging, whereas in the latter, groups simply attract other individuals to patches where food is particularly abundant and copying does not occur within the group. Coarse-level local enhancement may decrease the time needed to find profitable feeding patches in spatially and temporally variable environments. A review of the empirical literature indicated that coarse-level local enhancement is typical in bird species foraging in open habitats and in large groups with relatively little competition between group members whereas the opposite attributes fit the species for which fine-level local enhancement had been documented. Furthermore, species in which coarse-level local enhancement prevails usually forage in temporary groups. However, coarse-level and fine-level local enhancement are not necessarily mutually exclusive, but which one is more important in a particular case may be habitat-dependent. |
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Equine Behaviour @ team @ |
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4272 |
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Author |
Leng, V. |
Title |
Das Vielseitigkeitspferd. Der Vielseitigkeitsreiter. Ausbildung, Training, Event. |
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1992 |
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Blv Verlagsgesellschaft |
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München |
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3 405 14344 6 |
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Equine Behaviour @ team @ |
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4438 |
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