Winning by a Neck: Tall Giraffes Avoid Competing with Shorter Browsers

  title={Winning by a Neck: Tall Giraffes Avoid Competing with Shorter Browsers},
  author={Elissa Z. Cameron and Johan T du Toit},
  journal={The American Naturalist},
  pages={130 - 135}
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… 
DNA left on browsed twigs uncovers bite-scale resource use patterns in European ungulates
This approach provides a level of detail in browsing patterns across species that was previously very hard to attain, and found that all deer species largely overlapped in terms of the tree species they used.
Generalities in grazing and browsing ecology: using across-guild comparisons to control contingencies
One trophic guild is used as a “control” for the other to identify generalities that are not contingent upon specific consumer-resource interactions to resolve contingencies in community processes.
The utilisation of woody species by male and female elephants in the Serengeti National Park, a nutrient-rich savanna
It is suggested that sexual differences in forage requirements interact with forage quality and competing herbivore communities in shaping the foraging behaviour of elephants.
Foraging Ecologies of Giraffe and Camels in Northern Kenya: Effects of Habitat Structure and Possibilities for Competition?
Examining the foraging ecologies of reticulated giraffe and domestic camels in the Laikipia District of Kenya, an area where these two species have not been sympatric until very recently, indicates that domesticCamels do not overlap with giraffe in feeding heights, and differences may be driven by local habitat structure and plant densities.
Understanding selection for long necks in different taxa
The evolution of long necks across a wide range of (both living and extinct) taxa is considered and it is concluded that in most cases long necks can be explained in terms of foraging requirements, and that alternative explanations of sexual selection, thermoregulation and predation pressure are not as well supported.
The demography of giraffe deaths in a drought
ABSTRACT Darwin's theory for the evolution of the long neck of giraffes is that height confers access to browse free of competition from smaller browsers. The theory predicts that survivors of a
Giraffe Stature and Neck Elongation: Vigilance as an Evolutionary Mechanism
It is postulated that the wider panorama afforded by an increase in height and longer neck has improved survival via allowing giraffe to browse safely over wider areas, decreasing competition within groups and with other herbivores.


Winning by a Neck: Sexual Selection in the Evolution of Giraffe
It is concluded that sexual selection has been overlooked as a possible explanation for the giraffe's long neck, and on present evidence it provides a better explanation than one of natural selection via feeding competition.
Regrowth and Palatability of Acacia Shoots Following Pruning by African Savanna Browsers
It is proposed that severe pruning by browsing ungulates reduces intershoot competition for nutrients, promoting rapid shoot regrowth, which results in patches of highly palatable browse that attract further browsing, generating a browsing- regrowth feedback loop.
Vegetation modification and resource competition in grazing ungulates
The findings indicate the conditions under which each ungulate species may limit the other's use of natural pastures through interspecific competition: bite quantity competition may apply on short grazing lawns; bite quality competition is expected on differentiated swards with a limited supply of green leaf.
Sex differences in giraffe foraging behavior at two spatial scales
Overall the results agree qualitatively with the body-size hypothesis, where sex-related differences in foraging behavior led to greater estimated intake rates for males at the within-patch and within-habitat scales.
Feeding‐height stratification among African browsing ruminants
ummary This study investigated the hypothesis that the use of different feeding levels in the vegetation promotes resource partitioning among browsing ungulate species in African savannas. Focal
Bush selection along foraging pathways by sympatric impala and greater kudu
It is suggested that both kudu and impala selected bushes on the basis of the potential number of bites they can provide, and this resulted in different search strategies, which lead to a low overlap in resource use between the two browsers in this type of savanna.
Effects of plant spinescence on large mammalian herbivores
Structural features of prickles function to restrict foliage losses to large herbivores below the levels that might otherwise occur, by reducing the tissue losses incurred by plants per encounter by a large ungulate herbivore, by restricting the eating rates that the animals obtain.
The impacts of elephant, giraffe and fire upon the Acacia tortilis woodlands of the Serengeti
It is suggested that the effects of the combination of low elephant densities and high giraffe densities prevalent in the Serengeti produce a dynamic system in which the woodland structure oscillates between mature canopy and open regeneration-grassland phases.
The feeding ecology of a very small ruminant, the steenbok (Raphicerus campestris)
This study confirms that steenbok are purely browsers by preference, and not mixed feeders as has previously been assumed.
The allometry of food intake in grazing ruminants
(1) A simulation model of grazing mechanics in ruminants shows that, due to the allometric relations of bite size and metabolic requirements to body size, small animals are able to subsist on shorter