Abstract: With their vertically elongated body form, giraffes generally feed above the level of other browsers within the savanna browsing guild, despite having access to foliage at lower levels. They ingest more leaf mass per bite when foraging high in the tree, perhaps because smaller, more selective browsers deplete shoots at lower levels or because trees differentially allocate resources to promote shoot growth in the upper canopy. We erected exclosures around individual Acacia nigrescens trees in the greater Kruger ecosystem, South Africa. After a complete growing season, we found no differences in leaf biomass per shoot across height zones in excluded trees but significant differences in control trees. We conclude that giraffes preferentially browse at high levels in the canopy to avoid competition with smaller browsers. Our findings are analogous with those from studies of grazing guilds and demonstrate that resource partitioning can be driven by competition when smaller foragers displace larger foragers from shared resources. This provides the first experimental support for the classic evolutionary hypothesis that vertical elongation of the giraffe body is an outcome of competition within the browsing ungulate guild.

Abstract: Breeding groups with multiple stallions occur sympatrically with single-stallion breeding groups in feral horse, Equus caballus, populations. Mutualism and reciprocal altruism between stallions have been proposed to explain the origin and functioning of multistallion bands. However, empirical support for these hypotheses is contradictory and incomplete. Furthermore, there are no explicit tests of the predictions that each hypothesis makes about stallion behaviour and social structure. We compared nine multistallion and 18 single-stallion bands in the Kaimanawa Ranges, New Zealand. Compared with agonistic behaviours, affiliative behaviours were relatively unimportant in the relationships between stallions within bands. The number of stallions in the band did not have a positive influence on mare group size, stability, home range quality or reproductive success in bands. Furthermore, there was a positive relationship between aggression ('intolerance') by the dominant towards subordinate stallions and the subordinates' effort in mare group defence ('helping') but a negative relationship between helping effort by subordinates and their proximity to, and mating with, the bands' mares. Therefore, the predictions of the mutualism and reciprocal altruism hypotheses were not supported. Indeed, for some of the predictions we found the opposite outcomes to be true. Multistallion bands had significantly poorer reproductive success, and dominant stallions were less tolerant of subordinates that helped most and reduced their access to mares. Nevertheless, in all other respects Kaimanawa stallions in multistallion bands behaved like those described elsewhere. Thus, we reject cooperative hypotheses for multimale breeding groups in horses and discuss the mate parasitism and consort hypotheses as better alternatives. Copyright 2000 The Association for the Study of Animal Behaviour.

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.

Abstract: In studies on mammalian parental investment, time spent suckling is often used as a predictor of the milk transferred from mother to infant. It is assumed that the rate of milk transfer is positively correlated with the time spent suckling. However, this assumption has not been tested and empirical studies show conflicting results. Nevertheless, in species in which suckling can readily be observed, time spent suckling is still used to measure milk transfer, although an increasing number of workers recognize that the measure is potentially inaccurate. A meta-analysis on studies that have correlated measures of time spent suckling with milk intake estimates based on weight gain revealed a weak positive relationship and significant heterogeneity between studies. Isotope-labelling techniques for the measurement of milk transfer independent of behaviour have been in use since the 1970s, particularly in studies of species in which suckling is difficult to observe. Only one study has attempted to correlate behavioural measures with independent isotope measures, and it found no relationship between the two measures. I suggest that researchers have avoided such a test as it is unlikely that a strong relationship will be found between milk transfer and suckling behaviour, and I discuss the various factors that confound the relationship and contribute to high heterogeneity between studies. Consequently, the assumption that milk transfer can be measured by time spent suckling has inadequate empirical foundation, and needs to be tested using isotope-labelling methods. Copyright 1998 The Association for the Study of Animal Behaviour

Abstract: Zusammenfassung
Mit dem Beitrag “Die Bewegungen von Pferderumpf und -rücken aus der Sicht des Reiters” (TU 59, 327-334, 2004) wurde um universitäre Forschung zur Ermittlung gemessener Werte für diese Begleiter der Fortbewegung geworben.
Die Entdeckung des Ranges der Rumpf-Rücken-Bewegungen für pferdgerechtes und kultiviertes, feinfühliges Reiten ist mit der Entwicklung des Balancesitzes und der Technik des vom Pferd Zeitvorgaben Empfangens und ihm Signale Sendens (Reiter sagen: des Fühlens und Einwirkens) eng verbunden. Ihre Geschichte läßt sich über viereinhalb Jahrhunderte verfolgen. Ein kurzer Abriß wird hier nachgeliefert.
Er mündet erneut in ein Plädoyer für interdisziplinäres universitäres Forschen, weil auch bei Sitz und Hilfengebung, weiteren Grundlagen des Reitens – im Interesse effektiveren Unterrichts an der Basis unseres “Sports” – dringender Klärungsbedarf besteht.