Ecology of African Grazing and Browsing Mammals

McNaughton, S. J.; Georgiadis, Nicholas J.

doi:10.1146/annurev.es.17.110186.000351

Cited by 277 publications

(26 citation statements)

References 160 publications

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“…Because of these asymmetries in energetic and nutritional requirements male giraffe may be more affected by the loss of forage quantity due to greater dry season deciduousness in the Delta (Main et al, 1996). Studies examining resource partitioning on the basis of body size in African browsers and grazers suggest that with increased body size, individuals may expand their diets to favor greater quantities of forage species at the expense of consuming forage species of lower nutritional quality (McNaughton and Georgiadis, 1986). In the MFNP ecosystem, this body-size effect may explain the male-biased dry season shift from the diverse, highly nutritious Acacia sp., C. adansonii, and H. abyssinica savannas of the Delta to the lower quality but more abundant forage of the broad-leaf P. kotschyi, S. kunthianum, and Terminalia spp.…”

Section: Discussionmentioning

confidence: 99%

Male-Biased Partial Migration in a Giraffe Population

Brown

Bolger

2020

Front. Ecol. Evol.

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Partial migration is a common movement phenomenon in ungulates, wherein part of the population remains resident while another portion of the population transitions to spatially or ecologically distinct seasonal ranges. Although widely documented, the causes of variation in movement strategies and their potential demographic consequences are not well-understood. Here, we used GPS telemetry data and individual-based photographic surveys to describe evidence for the partial migration of giraffe (Giraffa camelopardalis) in the tropical savanna habitat of Murchison Falls National Park, Uganda. Seasonal movements in giraffe have been described but have not been systematically investigated within the framework of partial migration. We characterized movement behaviors of eight female GPS tracked giraffe across one full year using a model-driven approach of net-squared displacement metrics. To further evaluate these space use patterns at the population-level, we used closed robust design multi-state capture recapture models derived from individually based photographic surveys collected seasonally over three years. We also characterized environmental conditions associated with seasonal space use by conducting ground-based vegetation surveys and analyzing remotely sensed phenology data. Our results from both individually based telemetry models and population-level multi-state models suggest intra-population variation in seasonal space use strategies with three dominant movement classes: (1) Residents in deciduous savanna characterized by Acacia sieberiana, Acacia senegal, Harrisonia abyssinica, and Crateva adansonii in the far western end of the park. (2) Residents in the broadleaf savannas characterized by Pseudocedrela kotschyi, Stereospermum kunthianum, Termalia spp., and Combretum spp. in the central sector of the park (3) Male-biased migrants that transitioned seasonally between the acacia savanna in the wet seasons and the broadleaf savanna in the dry seasons. Our results offer insights into how giraffe navigate spatiotemporally dynamic environments at both individual and population levels, providing ecological mechanisms for the emergent population dynamics of these large-bodied topical browsers.

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Section: Discussionmentioning

confidence: 99%

Male-Biased Partial Migration in a Giraffe Population

Brown

Bolger

2020

Front. Ecol. Evol.

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“…For example, the African savannah biome supports 31 species of large (> 5 kg), herbivorous mammals [76], and competition among its members is typically alleviated via the selection of different food types, the occupation of the same habitat at different times, or the occupation of different habitats at the same time [77-79]. The ecological separation of these ungulates may also be achieved along a vertical gradient, with different species feeding at different heights within the canopy or grass cover [77-83].…”

Section: Discussionmentioning

confidence: 99%

“…With the exception of the topi, this grazing succession is reflected by the decreasing body size of the animals (but see [83]). Similarly, feeding height stratification has been said to operate among browsing ungulates [77,79,81]. This hypothesis was tested explicitly on a subset of African browsers by du Toit [82], who found that giraffe ( Giraffa camelopardalis ), kudu ( Tragelaphus strepsiceras ), impala ( Aepyceros melampus ), and steenbok ( Raphicerus campesteris ) are stratified by mean feeding-height.…”

Section: Discussionmentioning

confidence: 99%

Feeding height stratification among the herbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada

et al. 2013

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BackgroundHerbivore coexistence on the Late Cretaceous island continent of Laramidia has been a topic of great interest, stemming from the paradoxically high diversity and biomass of these animals in relation to the relatively small landmass available to them. Various hypotheses have been advanced to account for these facts, of which niche partitioning is among the most frequently invoked. However, despite its wide acceptance, this hypothesis has not been rigorously tested. This study uses the fossil assemblage from the Dinosaur Park Formation of Alberta as a model to investigate whether niche partitioning facilitated herbivorous dinosaur coexistence on Laramidia. Specifically, the question of feeding height stratification is examined in light of the role it plays in facilitating modern ungulate coexistence.ResultsMost herbivorous dinosaur species from the Dinosaur Park Formation were restricted to feeding no higher than approximately 1 m above the ground. There is minimal evidence for feeding height partitioning at this level, with ceratopsids capable of feeding slightly higher than ankylosaurs, but the ecological significance of this is ambiguous. Hadrosaurids were uniquely capable of feeding up to 2 m quadrupedally, or up to 5 m bipedally. There is no evidence for either feeding height stratification within any of these clades, or for change in these ecological relationships through the approximately 1.5 Ma record of the Dinosaur Park Formation.ConclusionsAlthough we cannot reject the possibility, we find no good evidence that feeding height stratification, as revealed by reconstructed maximum feeding heights, played an important role in facilitating niche partitioning among the herbivorous dinosaurs of Laramidia. Most browsing pressure was concentrated in the herb layer, although hadrosaurids were capable of reaching shrubs and low-growing trees that were out of reach from ceratopsids, ankylosaurs, and other small herbivores, effectively dividing the herbivores in terms of relative abundance. Sympatric hadrosaurids may have avoided competing with one another by feeding differentially using bipedal and quadrupedal postures. These ecological relationships evidently proved to be evolutionarily stable because they characterize the herbivore assemblage of the Dinosaur Park Formation through time. If niche partitioning served to facilitate the rich diversity of these animals, it may have been achieved by other means in addition to feeding height stratification. Consideration of other feeding height proxies, including dental microwear and skull morphology, may help to alleviate problems of underdetermination identified here.

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“…[22], Bond (2008) [17], Staver and Levin (2012) [84], Baudena et al (2010) [11], (2014) [12], Jeffery et al (2014) [51]; Figure 2b & -c). Browsers impact, though undoubtedly pervasive in certain situations (McNaughton and Georgiadis (1986) [62], Scholes and Walker (1993) [80], Van Langevelde et al (2003) [101], Holdo et al (2009) [49]) is not systematic across the savanna biome and the generality of the disturbance hypothesis relies mainly on fire. Indeed, experimental fire suppression systematically leads to the thickening-up of the woody vegetation and to the development of dense woodlands or thickets.…”

Section: B Lines Of Thoughtsmentioning

confidence: 99%

A tribute to the use of minimalistic spatially-implicit models of savanna vegetation dynamics to address broad spatial scales in spite of scarce data

Yatat

Tchuinte²,

Dumont³

et al. 2018

BIOMATH

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The savanna biome encompasses a variety of vegetation physiognomies that traduce complex dynamical responses of plants to the rainfall gradients leading from tropical forests to hot deserts. Such responses are shaped by interactions between woody and grassy plants that can be either direct, disturbance-mediated or both. There has been increasing evidence that several vegetation physiognomies, sometimes highly contrasted, may durably coexist under similar rainfall conditions suggesting multi-stability or at least not abrupt transitions. These fascinating questions have triggered burgeoning modelling efforts which have, however, not yet delivered an integrated picture liable to furnish sensible predictions of potential vegetation at broad scales. In this paper, we will recall the key ecological processes and resulting vegetation dynamics that models should take into account. We will also present the main modelling options present in the literature and advocate the use of minimalistic models, capturing only the essential processes while retaining sufficient mathematical tractability and restricting themselves to a minimal set of parameters assessable from the overall literature.

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Ecology of African Grazing and Browsing Mammals

Cited by 277 publications

References 160 publications

Male-Biased Partial Migration in a Giraffe Population

Male-Biased Partial Migration in a Giraffe Population

Feeding height stratification among the herbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada

A tribute to the use of minimalistic spatially-implicit models of savanna vegetation dynamics to address broad spatial scales in spite of scarce data

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