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Cheney, D. L., & Seyfarth, R. M. (1999). Recognition of other individuals' social relationships by female baboons. Anim. Behav., 58(1), 67–75.
Abstract: We describe a series of playback experiments designed to test whether free-ranging baboons, Papio cynocephalus ursinus, recognize the calls of other group members and also associate signallers with their close genetic relatives. Pairs of unrelated females were played sequences of calls that mimicked a fight between their relatives. As controls, the same females heard sequences that involved either (1) only the more dominant female's relative or (2) neither of the females' relatives. When call sequences involved their relatives, subjects looked towards the speaker for a longer duration than when the sequences involved nonkin. When the sequences involved the other female's relative, they also looked towards that female. Subjects did not look towards one another when call sequences involved nonkin. Dominant subjects were more likely to supplant their subordinate partners following playbacks of sequences that mimicked a dispute between their relatives than following the two control trials. In contrast, both subjects were more likely to approach one another and to interact in a friendly manner following the two control trials than following the test trial. Results indicate that female baboons recognize the screams and threat grunts not only of their own close relatives but also of unrelated individuals. They also replicate previous studies in suggesting that female monkeys recognize the close associates of other individuals and adjust their interactions with others according to recent events involving individuals other than themselves. Copyright 1999 The Association for the Study of Animal Behaviour.
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Rendall, D., Seyfarth, R. M., Cheney, D. L., & Owren, M. J. (1999). The meaning and function of grunt variants in baboons. Anim. Behav., 57(3), 583–592.
Abstract: Wild baboons Papio cynocephalus ursinus, give tonal, harmonically rich vocalizations, termed grunts, in at least two distinct, behavioural contexts: when about to embark on a move across an open area ('move' grunts); and when approaching mothers and attempting to inspect or handle their young infants ('infant' grunts). Grunts in these two contexts elicit different responses from receivers and appear to be acoustically distinct (Owren et al. 1997 Journal of the Acoustical Society of America101 2951-2963). Differences in responses to grunts in the two contexts may, then, be due to acoustic differences, reflecting at least a rudimentary capacity for referential signalling. Alternatively, responses may differ simply due to differences in the contexts in which the grunts are being produced. We conducted playback experiments to test between these hypotheses. Experiments were designed to control systematically the effects of both context and acoustic features so as to evaluate the role of each in determining responses to grunts. In playback trials, subjects differentiated between putative move and infant grunts. Their responses based only on the acoustic features of grunts were functionally distinct and mirrored their behaviour to naturally occurring move and infant grunts. However, subjects' responses were in some cases also affected by the context in which grunts were presented, and by an interaction between the context and the acoustic features of the grunts. Furthermore, responses to grunts were affected by the relative rank difference between the caller and the subject. These results indicate that baboon grunts can function in rudimentary referential fashion, but that the context in which grunts are produced and the social identity of callers can also affect recipients' responses. Copyright 1999 The Association for the Study of Animal Behaviour.
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Giraldeau, L. A., & Beauchamp, G. (1999). Food exploitation: searching for the optimal joining policy. Trends In Ecology And Evolution, 14(3), 102–106.
Abstract: Commonly invoked foraging advantages of group membership include increased mean food intake rates and/or reduced variance in foraging success. These foraging advantages rely on the occurrence of 'joining': feeding from food discovered or captured by others. Joining occurs in most social species but the assumptions underlying its analysis have been clarified only recently, giving rise to two classes of model: information-sharing and producer-scrounger models. Recent experimental evidence suggests that joining in ground-feeding birds might be best analysed as a producer-scrounger game, with some intriguing consequences for the spatial distribution of foragers and patch exploitation.
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Cowell, P. E., Fitch, R. H., & Denenberg, V. H. (1999). Laterality in animals: relevance to schizophrenia. Schizophr Bull, 25(1), 41–62.
Abstract: Anomalies in the laterality of numerous neurocognitive dimensions associated with schizophrenia have been documented, but their role in the etiology and early development of the disorder remain unclear. In the study of normative neurobehavioral organization, animal models have shed much light on the mechanisms underlying and the factors affecting adult patterns of both functional and structural asymmetry. Nonhuman species have more recently been used to investigate the environmental, genetic, and neuroendocrine factors associated with developmental language disorders in humans. We propose that the animal models used to study the basis of lateralization in normative development and language disorders such as dyslexia could be modified to investigate lateralized phenomena in schizophrenia.
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Sterling, E. J., & Povinelli, D. J. (1999). Tool use, aye-ayes, and sensorimotor intelligence. Folia Primatol (Basel), 70(1), 8–16.
Abstract: Humans, chimpanzees, capuchins and aye-ayes all display an unusually high degree of encephalization and diverse omnivorous extractive foraging. It has been suggested that the high degree of encephalization in aye-ayes may be the result of their diverse, omnivorous extractive foraging behaviors. In combination with certain forms of tool use, omnivorous extractive foraging has been hypothesized to be linked to higher levels of sensorimotor intelligence (stages 5 or 6). Although free-ranging aye-ayes have not been observed to use tools directly in the context of their extractive foraging activities, they have recently been reported to use lianas as tools in a manner that independently suggests that they may possess stage 5 or 6 sensorimotor intelligence. Although other primate species which display diverse, omnivorous extractive foraging have been tested for sensorimotor intelligence, aye-ayes have not. We report a test of captive aye-ayes' comprehension of tool use in a situation designed to simulate natural conditions. The results support the view that aye-ayes do not achieve stage 6 comprehension of tool use, but rather may use trial-and-error learning to develop tool-use behaviors. Other theories for aye-aye encephalization are considered.
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Linklater, W. L., Cameron, E. Z., Minot, E. O., & Stafford, K. J. (1999). Stallion harassment and the mating system of horses. Anim. Behav., 58(2), 295–306.
Abstract: Feral horse, Equus caballus, breeding groups, called bands, usually include one but sometimes up to five stallions. We found that mares were loyal to single-stallion (SS) or multistallion (MS) bands or were social dispersers (maverick mares, Mv). The spacing and social behaviour of mares and stallions in single- and multistallion bands was measured. Indices of mare well-being were also measured including activity budgets (feeding: MS>SS=Mv; resting: MS<SS=Mv), band and mare travel (MS>SS), maternal effort in maintaining contact with foals (MS=Mv>SS), parasite levels in faeces (MS>Mv>SS), body condition (MS=Mv<SS), fecundity (Mv<MS<SS) and offspring mortality (Mv<MS<SS). We present evidence suggesting that the poorer well-being of maverick mares and multistallion band mares results from greater harassment by stallions. Stallion and mare behaviour and poor reproductive success in multistallion bands were not consistent with explanations for the existence of such bands based on cooperation or alternative mating strategies. We suggest an alternative explanation. Stable relationships between mares and a single stallion may enhance reproductive success by reducing aggression between individuals. Therefore, we propose that there is strong selection pressure for stable, long-term stallion-mare relationships, called consort relationships. We propose the consort hypothesis, that multistallion bands are an artefact of selection for stable relationships that occasionally result in more than one such relationship forming, because mares solicit more than one stallion and stallion dominance changes during band formation. Copyright 1999 The Association for the Study of Animal Behaviour.
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Cameron, E. Z., Stafford, K. J., Linklater, W. L., & Veltman, C. J. (1999). Suckling behaviour does not measure milk intake in horses, Equus caballus. Anim. Behav., 57(3), 673–678.
Abstract: Studies of parental investment in mammals have frequently used suckling behaviour to estimate energy transfer from mother to offspring, and consequently to measure maternal input. Such studies assume that the more an offspring sucks, the more milk it will receive. This assumption has been questioned, and a review of the literature found little support for it. To test if suckling behaviour provided an accurate index of milk or energy intake we used a radioactive isotope technique to label the milk of thoroughbred mares and to measure milk transfer to foals. We found no significant linear relationship between usual measures of suckling behaviour and milk or energy intake. No behaviours associated with suckling nor with characteristics of mares and foals improved the relationship; only the number of butts associated with each suck episode even approached significance. If we had used suckling behaviour to test theories on differential maternal investment our conclusions would have been in error. For example, female foals tended to suck for longer than males did but there was no difference in the amount of milk transferred. Consequently, we show that measures of suckling behaviour do not adequately predict milk intake in the domestic horse and we suggest that conclusions about differential maternal investment in mammals based on suckling behaviour are likely to be in error. Copyright 1999 The Association for the Study of Animal Behaviour.
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Rogers, C. W., Davies, A. S., Pfeiffer, D. U., & Davie, P. S. (1999). Linear and temporal stride characteristics of 3-day event horses at a CCI*** 3-day event horse inspection. N Z Vet J, 47(6), 193–197.
Abstract: AIMS: To quantify the linear and temporal characteristics of the trot of 3-day event horses during the preliminary horse inspection of an advanced grade CCI* 3-day event. METHODS: A cross sectional study was made of the kinematics of 24 3-day-event horses during the first horse inspection at a CCI* level S-day event. Video footage was digitised and linear and temporal measurements were made. RESULTS: The horses trotted for an average of 10.44+/-1.55 strides. Spatial measurements were made on an average of 5.66+/-0.92 consecutive strides when the horses were within the calibration zone. The horses increased and then obtained a constant velocity within the calibration zone. Trotting on the asphalt track did not alter the relationships between stride length, stride duration and velocity when compared with previously published values. Horse-specific differences in stance and retraction percentages were identified. CONCLUSION: Horse specific differences were identified that may contribute to each horse's unique gait or kinematic fingerprint. It is proposed that the initiation of, and completion of, stance by the hind limb first may represent engagement of the hind quarters and be a response to dressage training.
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MacFadden, B. J., Solounias, N., & Cerling, T. E. (1999). Ancient diets, ecology, and extinction of 5-million-year-Old horses from florida. Science, 283(5403), 824–827.
Abstract: Six sympatric species of 5-million-year-old (late Hemphillian) horses from Florida existed during a time of major global change and extinction in terrestrial ecosystems. Traditionally, these horses were interpreted to have fed on abrasive grasses because of their high-crowned teeth. However, carbon isotopic and tooth microwear data indicate that these horses were not all C4 grazers but also included mixed feeders and C3 browsers. The late Hemphillian Florida sister species of the modern genus Equus was principally a browser, unlike the grazing diet of modern equids. Late Hemphillian horse extinctions in Florida involved two grazing and one browsing species.
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Minero, M., Canali, E., Ferrante, V., Verga, M., & Odberg, F. O. (1999). Heart rate and behavioural responses of crib-biting horses to two acute stressors. Vet. Rec., 145(15), 430–433.
Abstract: The heart rate and behaviour of 14 adult saddle horses, eight crib-biters and six normal controls, were investigated. Initially, the relationship between crib-biting and heart rate was investigated while the horses were undisturbed. The horses were tested when restrained with a lip twitch, and assessed when they were exposed suddenly to the rapid inflation of a balloon. The heart rate of the crib-biters during crib-biting was lower than during other behaviours. The crib-biters had a higher overall mean heart rate (P<0.05) suggesting that they may have had a higher basal sympathetic activity. After the application of the twitch, all the horses had a transient increase in heart rate which returned to basal values more rapidly in the crib-biters. The crib-biters were less reactive to the lip twitch, five of the six investigated remaining calm, and after the release of the twitch, they spent more time nibbling (P<0.05) than the control horses. The crib-biters reacted more strongly to the inflation of the balloon (three of the six reacted), and after it had been inflated they spent more time walking in the box.
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