megaherbivore - GCF Resource Library

Megaherbivores,Competition and Coexistence within the Large Herbivore Guild

A special feature of the Hluhluwe-iMfolozi Park (HiP) is the presence of an abundant ‘mega-grazer’ in the form of the white rhinoceros (Ceratotherium simum). The study of this species in HiP (Owen-Smith, 1974) led to the identification of common features shared by white rhinos with other extremely large herbivores and hence to the recognition that these ‘megaherbivores’ constitute a distinct life form (Owen-Smith, 1988, 2013a). Defined strictly, the label ‘megaherbivore’ encompasses terrestrial mammals exceeding one metric tonne (i.e., a mega-gram)

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Megaherbivore impacts on ecosystem and Earth system functioning: the current state of the science

Megaherbivores (adult body mass > 1000 kg) are suggested to disproportionately shape ecosystem and Earth system functioning. We systematically reviewed the empirical basis for this general thesis and for the more specific hypotheses that 1) megaherbivores have disproportionately larger effects on Earth system functioning than their smaller counterparts, 2) this is true for all extant megaherbivore species and 3) their effects vary along environmental gradients. We furthermore explored possible biases in our understanding of megaherbivore impacts. We found that there

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Seasonal shifts in sociosexual behaviour and reproductive phenology in giraffe

Reproductive phenology (timing) is a heritable trait that confers a range of fitness or survival advantages. Giraffe (Giraffa spp.) breed year-round; however, some studies have suggested adaptive birth pulses, where demanding stages of reproduction coincide with seasonal increases in resource availability (phenological match). Here we use 3.5 years of demographic data to investigate the sociosexual behaviour and reproductive phenology of Angolan giraffe (G. g. angolensis) in the hyper arid northern Namib Desert, Namibia. We show that, in a highly seasonal

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Interspecific interference competition at the resource patch scale: do large herbivores spatially avoid elephants while accessing water?

1. Animals may anticipate and try to avoid, at some costs, physical encounters with other competitors. This may ultimately impact their foraging distribution and intake rates. Such cryptic interference competition is difficult to measure in the field, and extremely little is known at the interspecific level. 2. We tested the hypothesis that smaller species avoid larger ones because of potential costs of interference competition and hence expected them to segregate from larger competitors at the scale of a resource patch.

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Habitat heterogeneity and social factors drive behavioral plasticity in giraffe herd-size dynamics

Behavioral plasticity, or the mechanism by which an organism can adjust its behavior in response to exogenous change, has been highlighted as a potential buffer against extinction risk. Giraffes (Giraffa spp.) are gregarious, long-lived, highly mobile megaherbivores with a large brain size, characteristics that have been associated with high levels of behavioral plasticity. However, while there has been a recent focus on genotypic variability and morphological differences among giraffe populations, there has been relatively little discussion centered on behavioral flexibility

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The diet of giraffe (Giraffa camelopardalis giraffa) on a wildlife ranch in the mosaic thicket of the southern Cape, South Africa

We studied the diet composition and preference of giraffe in mosaic thicket. Diet composition was determined by direct observations throughout the year. The Jacobs index was used to calculate dietary preference indices. Although the recorded diet consisted of 20 browse species, 17 were tree/shrubs, and only two, Acacia karroo and the invasive alien Acacia cyclops, formed the bulk of the annual giraffe diet. On a seasonal basis, the deciduous A. karroo was the main food in spring/summer/autumn when it was

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Demography of giraffe in the fragmented Tarangire Ecosystem

Documenting whether variation in demographic parameters such as births, deaths, and movement exists, and how temporal and spatial environmental variability influences demography, is critical to understanding and affecting changes in animal populations. Natural populations often exhibit variation in demographic parameters, and while the examination of temporal variation has long been a central theme in population ecology, spatial variation among or within populations of the same species has received much less attention. Although the vast majority of the world’s ungulate species

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Comparison of Two Diet Analysis Techniques for a Browsing Megaherbivore

Diet assessment of herbivores provides insight into trophic relationships, the potential for competition, and the influences herbivores may have on an ecosystem (Bookhout 1996). Thus, the determination of their food requirements is imperative prior to the implementation of any management decisions, which must be based on reliable data (Bookhout 1996). Direct observations and fecal analysis are 2 commonly employed techniques for assessing the diet of wild herbivores (Van Aarde and Skinner 1975, Field and Ross 1976, McInnes et al. 1983,

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Androgen changes and flexible rutting behaviour in male giraffes

The social organization of giraffes (Giraffa camelopardalis) imposes a high-cost reproductive strategy on bulls, which adopt a ‘roving male’ tactic. Our observations on wild giraffes confirm that bulls indeed have unsynchronized rut-like periods, not unlike another tropical megaherbivore, the elephant, but on a much shorter timescale. We found profound changes in male sexual and social activities at the scale of about two weeks. This so far undescribed rutting behaviour is closely correlated with changes in androgen concentrations and appears to

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