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Houpt, K. A. (1990). Ingestive behavior. Vet Clin North Am Equine Pract, 6(2), 319–337.
Abstract: In summary, horses spend 60% or more of their time eating when grazing or when feed is available free choice. Grasses are their preferred food, but they supplement the grass with herbs and woody plants. Sweetened mixtures of oats and corn are the most preferred concentrate. Horses can increase or decrease the time spent eating and amount eaten to maintain caloric intake. Their intake is stimulated by drugs such as diazepam and by the presence of other horses. Horses stop eating when gastric osmolality increases; increases in plasma osmolality, protein, and glucose accompany digestion. Foals eat several times an hour and begin sampling solid food at the same time that their dam is eating. Several areas of particular importance to the equine industry have not been investigated. These areas include the effect of exercise on short- and long-term food intake and the influence of reproductive state on the feeding of mares.
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Franke Stevens, E. (1990). Instability of harems of feral horses in relation to season and presence of subordinate stallions. Behaviour, 112(3-4), 149–161.
Abstract: Male horses (Equus caballus) defend harems of females (bands) year-round and throughout their lifetimes. A male's lifetime reproductive success depends upon the number of females in his harem. Although harems have previously been reported as remaining stable over many years, during the two years of this study 30 % of the adult females in an island population of feral horses changed harems during late winter. The seasonal differences in harem stability resulted from seasonal differences in the abundance and distribution of food. The spacing between band members was greater and the frequency of social interactions between them was lower in winter than in summer. In addition, the amount of time devoted to grazing increased in winter. These differences are attributed to the lower availability of suitable vegetation duirng winter. Harem stability did not depend on the age of females, the size of the harem, nor the age of the harem stallion, but did depend on the presence of subordinate stallions attached to the band. All of the females that changed bands left single-male bands; multi-male bands were stable throughout the study.
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Rutberg, A. T. (1990). Inter-group transfer in assateague pony mares. Anim. Behav., 40(5), 945–952.
Abstract: Between-previous termgroup transfernext term of adult female previous termponies,next term Equus caballus, was investigated for three consecutive summers on previous Assateaguenext Island, Maryland, U.S.A. Both the previous terminternext term-band movements of individual previous termmares and the marenext term turnover rates of one-male “harem” bands were examined. Long-term previous termtransfersnext term occurred at rates ranging from 0·06 to 0·18 per previous termmarenext term per month. previous termMaresnext term with foals transferred more frequently than previous termmaresnext term without foals, but neither female age, pregnancy, nearest-neighbour distances nor dominance rank affected the likelihood of transferring. Band turnover rates were uncorrelated with the average frequency of previous termmare-marenext term aggression within the band, but new previous termmaresnext term entering a band suffered a transient rise in aggression received. Thus, female aggression did not encourage, and may have discouraged, previous terminternext term-band previous termtransfers.next term Older stallions and stallions who had held bands for 2 years or more had significantly larger and more stable bands. Fewer previous termmarenext term turnovers were seen in bands whose stallions tended to face their previous termmares,next term showed a relatively high proportion of time feeding, and showed a relatively low proportion of time involved in aggression with other stallions, although at marginal levels of significance for all three variables. Thus, variability in stallion attributes, and possibly behaviour, probably plays the strongest role in determining previous termmare transfernext term patterns at previous termAssateague.next term
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Schilder, M. B. H. (1990). Interventions in a herd of semi – captive Plains zebras. Behaviour, 112(1-2), 53–83.
Abstract: n a herd of semi-captive plains zebras interventions, which occurred within the harems, were investigated in order to answer the question why zebras interfered. These interventions are of interest because they regulate the contacts between companions and because, as corrective and preventive measures, they reveal the normative principles underlying the behaviours by which animals structure their social environment. An attempt was made to deduce 1) the internal norms of the interferer; 2) his short term aims; 3) his tactis and 4) his perception of the social environment. The analysis revealed that in the case of an affiliative interaction foals, yearlings and adult mares started to interfere if a friend had an affiliative contact with another zebra. In view of the interferer's behaviours it was concluded that their aim was to break off the ongoing interaction and that zebras tended to protect friendship bonds. Foals and yearlings further interfered if their mother was being threatened, attacked or sexually approached by a stallion. In view of the interferer's behaviours its aim was to prevent iminent interactions or to break off ongoing interactions. This suggests that these interventions were of a protective nature. The interferer's behaviours in both contexts ware very much alike. Mares tended to interfere if their foal/yearling or adult daughter was threathened or aggressed or if a mare friend was being sexually approached by a stallion. This type of intervention was of a protective nature. Stallions in a multi male harem showed a high tendency to interfere in courtship interactions. From the resemblance between interventions in courtship and in aggressive interactions it is concluded that, at leat in a number of cases, the individuals have perceived courtship behaviour by the stallion as a threat towards the mare involved.
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Klingel, H. (1990). Kalameili – future home of the Przewalski horse? In S. Seifert (Ed.), Proceedings of the 5th International Symposium on the Preservation of the Przewalski Horse, Leipzig (pp. 221–224). Leipzig: Zoolog Garten.
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Charles T. Snowdon,. (1990). Language capacities of nonhuman animals. American Journal of Physical Anthropology, 33(S11), 215–243.
Abstract: In the last two decades, the study of language parallels in nonhuman animals has generated considerable controversy and excitement. Many have perceived demonstrations of linguistic skills in nonhuman animals as a threat to human uniqueness, whereas others have been uncritical of claims for complex cognitive skills in animals. Two different paradigms for studying linguistic parallels have appeared. One approach teaches great apes linguistic analogues of human language using signs or arbitrary symbol systems; the other seeks to decode communicative complexity in the natural languages of nonhuman animals. This paper reviews the language analogue studies with great apes and cetaceans, examining the utility of the different methods and reviewing the animals' accomplishments. Studies of ontogeny, syntax, referential communication, audience effects, and perception of vocalizations in the natural communication of birds, squirrels, and primates are evaluated. Finally, the brain mechanisms underlying human speech and language are compared with those involved in vocal communication in nonhuman primates. Although chimpanzees and bonobos have accomplished much, they do not threaten human uniqueness with respect to speech and language. Many of the claims for language paralleles in natural communication systems of nonhuman animals are weak, and many can be interpreted without recourse to cognitive constructs. Whereas there exist many similarities between subcortical controls of language and of animal vocalizations, there are no parallels to Broca's and Wernicke's areas in monkeys. However, the critical studies have not been done.
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Feh, C.,. (1990). Long-term paternity data in relation to different aspects of rank for Camargue stallions, Equus caballus. Anim. Behav., 40(5), 995–996.
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Stander, P. E., Nott, T.B., Lindeque, P.M., & Lindeque, M. (1990). Mass marking of zebras in the Etosha National Park, Namibia. Madoqua, 17(1), 47–49.
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Hemelrijk, C. K. (1990). Models of, and tests for, reciprocity, unidirectionality and other social interaction patterns at a group level. Anim. Behav., 39(6), 1013–1029.
Abstract: Research on reciprocity is impaired by confusing definitions and often wrongly used statistical tests. Here, two models of the mechanism on which reciprocity may be based are discussed and an initial step towards a new fremework for its analysis is presented. A distinction is made between reciprocity and interchange. In the case of reciprocity, for one kind of act the same kind is received in return. In interchange, however, two different kinds of acts are bartered. Three types of reciprocity/interchange in social actions among all pairs of group-members are distinguished ([`]qualitative', [`]relative' and [`]absolute') on the basis of the precision of the reciprocity/interchange. Permutation procedures for association between matrices (such as the Mantel Z and two other newly derived tests) are used as a statistical test for detecting reciprocity/interchange. A rough comparison of the power of the two new tests is included. The tests can be applied to all kinds of group-living animals and to all sorts of social behaviour. The distinction between the three types of reciprocity/interchange and the matching statistical methods are also useful for defining and detecting other patterns in social interactions, like unidirectionality and associations between different kinds of social behaviour. The influence on social interactions of variables like dominance rank, age and sex can be analysed in the three forms by testing correlations between invented matrices which represent the influence of these variables (the so-called hypothesis matrices) and social interaction matrices. These methods are extended for two categories of individuals, thus allowing the investigation of, for example, reciprocity between males and females. The methods are illustrated with examples of coalition formation and grooming behaviour among captive chimpanzees, Pan troglodytes.
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Becker, C. D., & Ginsberg, J. R. (1990). Mother-infant behaviour of wild Grevy's zebra: adaptations for survival in semidesert East Africa. Anim. Behav., 40(6), 1111–1118.
Abstract: Mother-infant interactions and patterns of foal behaviour in the Grevy's zebra, Equus grevyi, differe from those reported for other equids. Grevy's zebra foals exhibit longer intervals between suckling bouts, do not drink water until they are 3 months old, and reach independence from the mare sooner than other equids. Furthermore, Grevy's zebra foals advance their acquisition of adult feeding behaviour. A 6-week-old Grevy's zebra foal spends as much time feeding as a 5-month-old wild horse foal. From the time their foals are born until the foals reach an age of 3 months, females form small groups (three females and their foals). These groups are never found further than 2·0 km from surface water and are usually associated with a territorial male. Unlike other equids, the foals of which always follow their mares, when female Grevy's zebra go to drink, they leave their foals in “kindergartens”, which are guarded by a single adult animal, usually a territorial male. It is proposed that many of these differences in behaviour and rates of juvenile development are the result of adaptation to an arid environment. Water requirements during early lactation appear to influence strongly the social behaviour of the Grevy's zebra and should also be a strong influence on the mother-infant behaviour of other arid-living ungulates.
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