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Author |
Cameron, E.Z.; du Toit, J.T. |
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Title |
Winning by a neck: tall giraffes avoid competing with shorter browsers |
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Journal Article |
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Year |
2007 |
Publication |
The American naturalist |
Abbreviated Journal |
Am Nat |
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Volume |
169 |
Issue |
1 |
Pages |
130-135 |
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Keywords  |
Acacia/growth & development; Animals; Feeding Behavior/*physiology; Neck/*anatomy & histology; Plant Leaves/growth & development; Ruminants/*anatomy & histology/*physiology; South Africa |
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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. |
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Address |
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za |
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English |
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Edition |
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ISSN |
1537-5323 |
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Notes |
PMID:17206591 |
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Call Number |
refbase @ user @ |
Serial |
410 |
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Author |
Dixon, G.; Green, L.E.; Nicol, C.J. |
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Title |
Effect of diet change on the behavior of chicks of an egg-laying strain |
Type |
Journal Article |
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Year |
2006 |
Publication |
Journal of applied animal welfare science : JAAWS |
Abbreviated Journal |
J Appl Anim Welf Sci |
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Volume |
9 |
Issue |
1 |
Pages |
41-58 |
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Keywords |
*Animal Feed; *Animal Nutrition Physiology; Animals; Behavior, Animal/*physiology; Chickens/*physiology; Crowding; Feeding Behavior/*physiology; Female; Food Preferences/physiology; Oviposition; Random Allocation; Taste |
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Abstract |
Injurious pecking has serious welfare consequences in flocks of hens kept for egg laying, especially when loose-housed. Frequent diet change is a significant risk for injurious pecking; how the mechanics of diet change influence pecking behavior is unknown. This study investigated the effect of diet change on the behavior of chicks from a laying strain. The study included a 3-week familiarity phase: 18 chick pairs received unflavored feed (Experiment 1); 18 pairs received orange oil-flavored (Experiment 2). All chicks participated in a dietary preference test (P); a diet change (DC); or a control group (C), 6 scenarios. All P chicks preferred unflavored feed. In Experiment 1, DC involved change from unflavored to orange-flavored; Experiment 2, orange- flavored to unflavored. Compared with controls, Experiment 2 DC chicks exhibited few behavioral differences; Experiment 1 DC chicks exhibited increased behavioral event rates on Days 1 and 7. They pecked significantly longer at their environment; by Day 7, they showed significantly more beak activity. There was little evidence of dietary neophobia. Change from more preferred to less preferred feed led to increased activity and redirected pecking behavior. |
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Address |
School of Veterinary Science, University of Bristol, England |
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English |
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ISSN |
1088-8705 |
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Notes |
PMID:16649950 |
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Call Number |
refbase @ user @ |
Serial |
64 |
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